🕷️ Crawler Inspector

URL Lookup

Direct Parameter Lookup

Raw Queries and Responses

1. Shard Calculation

Query:

Response:

Calculated Shard: 8 (from laksa140)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa008.int.ahrefs:8124/' \
  -H 'Content-Type: text/plain' \
  -H 'X-ClickHouse-Database: crawler3' \
  -H 'Authorization: Basic YXBpOg==' \
  -d 'SELECT getAhrefsURLFromUnparsed(src_unparsed) AS found_url, ifNull(toUnixTimestamp(download_stamp), 0) AS crawl_time, ifNull(toUnixTimestamp(props_url_first_seen), 0) AS first_indexed_time, download_http_code AS http_code, src_unparsed AS src_unparsed, src_root_hash AS src_root_hash, history_drop_reason AS history_drop_reason, meta_title AS meta_title, meta_descriptions AS meta_descriptions, attrs_boilerpipe_text AS attrs_boilerpipe_text, attrs_markdown AS attrs_markdown, attrs_readable_markdown AS attrs_readable_markdown, meta_canonical AS meta_canonical FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://www.space.com/17594-string-theory.html\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.space.com/17594-string-theory.html\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.space.com\/17594-string-theory.html","crawl_time":1775650402,"first_indexed_time":1497061916,"http_code":200,"src_unparsed":"com,space!www,\/17594-string-theory.html s443","src_root_hash":"7770394665477845008","history_drop_reason":null,"meta_title":"What is string theory? | Space","meta_descriptions":["String theory might be the theory of everything… or a flawed framework for theoretical physics."],"attrs_boilerpipe_text":"String theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: Tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles.\n(Image credit: PASIEKA via Getty Images)\nString theory is the idea in theoretical physics that reality is made up of infinitesimal vibrating strings, smaller than atoms, electrons or quarks. According to this theory, as the strings vibrate, twist and fold, they produce effects in many, tiny dimensions that humans interpret as everything from particle physics to large-scale phenomena like\ngravity\n. \nString theory has been held up as a possible \"theory of everything,\" a single framework that could unite\ngeneral relativity\nand\nquantum mechanics\n, two theories that underlie almost all of modern physics. While quantum mechanics does very well in describing the behavior of very small things and general relativity works well to explain how very large things happen in\nthe universe\n, they don't play nicely together. Some scientists think (or thought) that string theory could resolve the conundrums between the two, conquering one of the major remaining unsolved problems of physics. \nBut after string theory gained prominence in the late 1960s and '70s, its popularity among theoretical physicists fluctuated, according to a lecture by California Institute of Technology physicist\nJohn Schwarz\n, widely considered one of the founders of string theory. After countless papers, conferences and dry-erase markers, the breathtaking breakthrough many once hoped for seems further away than ever. \nNevertheless, the flurry of thought around the very idea of string theory has left a deep imprint on both physics and math. Like it or not (and some physicists certainly don't), string theory is here to stay.\nString theory FAQs answered by an expert\nWe asked Nick Geiser, a theoretical physicist at UCLA, a few frequently asked questions about string theory. \n Nick Geiser is a PhD candidate in theoretical physics at UCLA and will join the University of Michigan as a Leinweber and Van Loo Postdoctoral Fellow, working with Professor Henriette Elvang in the Leinweber Center for Theoretical Physics in June 2023. Geiser's research spans several areas of theoretical high-energy physics centered around scattering amplitudes. Scattering amplitudes are fundamental objects in theoretical physics that can be measured in experiments and reveal deep connections between physics and pure mathematics. Outside of research, Geiser works with a variety of organizations to support under-represented minority groups in STEM fields. \nWhat is string theory?\nString theory is a collection of ideas in theoretical physics in which the fundamental building-blocks of nature are not particles (such as the point-like electron) but instead strings. Imagine microscopic wiggling rubber bands.\nString theory is primarily a theory of\nquantum gravity\nwhich elegantly combines the theories of gravity and quantum mechanics. Physicists have been searching for a theory of quantum gravity for nearly one hundred years. Moreover, ideas from string theory have been used to solve problems in mathematics and other fields of theoretical physics.\nIn many ways, string theory is a language that can be used by theoretical physicists to solve problems and to investigate the mathematics of the universe.\nWho invented string theory?\nString theory was discovered by accident! In 1969, Italian physicist Gabriele Veneziano wrote down a formula describing the scattering of four strings, the now-famous Veneziano amplitude. Veneziano was trying to describe the physics of particles like the\nproton\nand neutron, not strings. In the following years, physicists around the world began to unravel string theory from that first formula.\nThe full picture of string theory has become clearer over the following fifty years. There were several bursts of new ideas and deep insights in the 1970s, 1980s, and 1990s, and string theory is still an active field with thousands of researchers around the world.\nHas string theory been proven?\nNo experiment has definitively proven string theory to be the fundamental theory of nature. However, the ideas of string theory have passed countless theoretical and mathematical tests over the last fifty years.\nFundamental physics is a long-game. Einstein first predicted\ngravitational waves\nin 1915, and they were first detected by the\nLIGO\nexperiment in 2015, one hundred years later! Future particle physics experiments, gravitational wave observatories, or cosmological measurements may offer definitive tests of string theory. \nHow many dimensions are there in string theory?\nString theory predicts ten total spacetime dimensions, but we clearly live in a world with four dimensions (three space and one time)! Thankfully, it is not a problem to get from ten to four. Six of the dimensions predicted by string theory could be wrapped into a small compact shape. These compactified dimensions could then only be seen by a large, precise experiment like CERN's\nLarge Hadron Collider\n.\nWhat is string theory?\nString theory is a framework that physicists use to describe how forces usually conceptualized on a gigantic level, like gravity, could affect tiny objects like electrons and protons. \nIn\nAlbert Einstein\n's theory of general relativity, gravity is a force that warps space-time around massive objects. It's one of the\nfour forces\nthat physicists use to describe nature. But unlike the other forces (electromagnetism, the strong force and the weak force), gravity is so weak that it can't be detected or observed on the scale of a particle. Instead, its effects are only noticeable and important on the scale of moons, planets, stars and galaxies. \nBreaking space news, the latest updates on rocket launches, skywatching events and more!\nGravity seems not to exist as a particle of its own, either. Theorists can predict what a gravity particle should look like, but when they try to calculate what happens when two such \"gravitons\" smash together, they get an infinite amount of energy packed into a small space — a sure sign, according to astrophysicist Paul Sutter in a\nprevious article for Space.com\n, that the math is missing something.\nOne possible solution, which theorists borrowed from nuclear physicists in the 1970s, is to get rid of the idea of problematic, point-like graviton particles. Strings, and only strings, can collide and rebound cleanly without implying physically impossible infinities.\nString theory math required six additional dimensions (for a total of 10)\nvisible only to the little strings\n, much as a powerline looks like a 1D line to birds flying far overhead but a 3D cylinder to an ant crawling on the wire.\n(Image credit: Shutterstock)\n\"A one-dimensional object — that's the thing that really tames the infinities that come up in the calculations,\" string theory expert Marika Taylor, a theoretical physicist at the University of Southampton in England, told Space.com. \nString theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles. A string of a particular length striking a particular note might gain the properties of a photon, another string folded and vibrating with a different frequency could play the role of a quark, and so on. \nIn addition to taming gravity, string theory was attractive for its potential to explain so-called fundamental constants like the mass of an electron. The next step, theorists hoped, would be to find the right way to describe the folding and movement of strings, and everything else should have followed.\nBut that initial simplicity turned out to come at the cost of unexpected complexity — string math didn't work in our familiar four dimensions (three of space and one of time). It needed a total of\n10 dimensions\n, with six visible only to the perspective of the little strings, much as a powerline looks like a 1D line to birds flying far overhead but becomes a 3D cylinder to an ant crawling on the wire. \nHow did string theory evolve?\nString theory today doesn't exactly match the string theory of the 1960s and '70s. Researchers disagree over whether, with modifications, it's still the best candidate for a \"theory of everything\" or whether theorists should abandon it in favor of other topics.\n\"By 1973–'74 there were many good reasons to stop working on string theory,\" Schwarz wrote. Physicists' attention had turned from what felt like an unfruitful exploration of tiny undetectable \"soft\" strings and instead taken up more compelling evidence of hadrons, subatomic particles made up of quarks whose actions couldn't be explained by strings. \n\"What had been a booming enterprise involving several hundred theorists rapidly came to a grinding halt,\" Schwarz wrote. \"Only a few diehards continued to pursue it.\" \nOver the next decade, a few scientists continued to pursue five different versions of string theory. Over time, the researchers began to find unexpected connections between the five ideas, which Edward Witten, a theorist at the Institute for Advanced Study in Princeton, New Jersey, gathered up and presented at a\n1995 string theory conference\nat the University of Southern California. Witten argued that the five string theories each represented an approximation of a more fundamental, 11-dimensional theory as it behaved in a particular situation, much as how Einstein's space- and time-bending theories of relativity match Newton's description of objects moving at normal speeds. That was the beginning of one string theory spin-off: M-theory.\nThe \"M\" is likely inspired by higher-dimensional objects called membranes, Taylor said, but since the theory has no concrete mathematical equations, the \"M\" remains a placeholder with no official meaning. \"It was really a parametrization of our ignorance,\" she said. \nAttempts to find those general equations that would work in every possible situation made little progress, but the alleged existence of the fundamental theory gave theorists the understanding and confidence needed to develop mathematical techniques for the five versions of string theory and apply them in the context where each theory worked. \nAn artist's interpretation of string theory.\n(Image credit: Science Photo Library via Getty Images)\nStrings are far too small to detect with any conceivable technology, but one early theoretical success was physicists' ability to describe black hole entropy in a 1996 paper published in the journal\nPhysics Letters\n.\nEntropy refers to the number of ways that you can arrange the parts of a system, but without being able to see into the impenetrable depths of a black hole, no one knows what type of particles might lie inside or what arrangements they can take. And yet, in the early 1970s,\nStephen Hawking\nand others used the laws of thermodynamics and, according to an article published in 2020 in the journal\nPhysics\n, quantum mechanics to calculate entropy inside a black hole, suggesting that black holes must have some sort of internal structure. What that structure might be, remained a mystery. \nMost attempts to describe the black hole's makeup fall short, but the configurations of hypothetical strings does the trick. \"String theory has been able to give a spot-on counting,\" Taylor said — an actual possible explanation of black hole interiors, not just a rough idea. \nThe string theory framework still faces many challenges, however: It produces an impossible number of ways to fold up the extra six dimensions. Every option seems to fit the broad features of the Standard Model that governs particle physics, with little hope of distinguishing which is the right one. Moreover, wrote astrophysicist Ethan Siegel in his blog\nStarts With a Bang\n, all of those models for managing the extra dimensions rely on an equivalence between force particles and matter particles called supersymmetry. But, just like the extra dimensions that string theory requires, we don't observe supersymmetry in our world. \nOn top of those objections, it's not clear that string theory — M-theory or not — can ever be compatible with our modern understanding of an expanding universe, replete with dark energy, reported\nQuanta Magazine\nin 2018. \nA number of physicists, such as Peter Woit of Columbia University, view these divergences from reality as fatal flaws. \"The basic problem with string theory unification research is not that progress has been slow over the past 30 years,\" he wrote on his\nblog\n, \"but that it has been negative, with everything learned showing more clearly why the idea doesn't work.\"\nTaylor, however, maintains that today's models are overly simplistic, and that features like\ncosmological expansion\nand a lack of supersymmetry may someday be built into future versions. Taylor expects that, while the new era of\ngravitational-wave astronomy\nmay bring new tidbits of information about quantum gravity, more progress will be made by continuing to follow the math deeper into string theory. \n\"I have a theoretical bias,\" she said, \"but I think the kind of breakthrough I'm describing would come from a chalkboard; from thought.\"\nWhy is string theory still important?\nRegardless of whether string theory can ever be massaged into a \"theory of everything,\" its legacy as a productive research program may be assured on mathematical merit alone. \n\"It can't be a dead end in the sense of what we've learned just from mathematics itself,\" Taylor said. \"If you told me tomorrow that the universe absolutely isn't supersymmetric and doesn't have 10 [spatial] dimensions, we've still connected whole branches of mathematics\" using the string theory framework. \nIn particular, when Witten and other researchers showed that the five-string theories were shadows of a single-parent theory, they highlighted connections called dualities, which have proven to be a major contribution to mathematics and physics. \nDualities let mathematicians translate from one branch of math to another, attacking problems untenable in one framework by using calculations done in the other, for example in geometry and number theory. Other dualities have helped overcome challenges in quantum computing, according to Taylor. \"It's not going to make your next-generation iPhone,\" she said, \"But it may make your iPhone for the 22nd century.\"\nWhether string theory's ability to illuminate the dark web connecting different areas of math turns out to be a sign of its potential or just a lucky coincidence remains a subject of debate. Witten, speaking at the\nInstitute for Advanced Study\nin 2019, acknowledged that while he no longer feels as confident as he once did that string theory will evolve into a complete physical theory, his gut tells him that the theory remains a productive field of research. \n\"To me, it's implausible that humans stumbled by accident on[to] such an incredible structure that sheds so much light on established physical theories, and also on so many different branches of mathematics,\" he told the audience. \"I have confidence that the general enterprise is on the right track, but I don't claim that the argument I've given is scientifically convincing.\"\nAdditional resources\nFind more in-depth history and explanations of current string theory science at\nWhyStringTheory.com\n, a website created by graduate students at the University of Oxford and the University of Cambridge for the \"interested layperson.\" Or, if you'd rather go right to the source, check out this\nCERN Courier\ninterview with string theory originator Gabriele Veneziano. If you're looking for a video explainer, watch these two videos entitled \"\nWhy string theory is right\n\" and \"\nWhy string theory is wrong\n,\" both from PBS Digital Studios. \nBibliography\n\"Robbert Dijkgraaf and Edward Witten in Conversation - Videos | Institute for Advanced Study,\" May 30, 2019.\nhttps:\/\/www.ias.edu\/video\/universe\/2019\/0529-DijkgraafWitten\n. \nSchwarz, John H. \"The Early History of String Theory and Supersymmetry,\" January 4, 2012.\nhttps:\/\/arxiv.org\/abs\/1201.0981v1\n. \nSiegel, Ethan. \"Why Supersymmetry May Be The Greatest Failed Prediction In Particle Physics History.\" Forbes, February 12, 2019.\nhttps:\/\/www.forbes.com\/sites\/startswithabang\/2019\/02\/12\/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history\/\n. \nStrominger, A., and C. Vafa. \"Microscopic Origin of the Bekenstein-Hawking Entropy.\"\nPhysics Letters B\n379, no. 1–4 (June 1996): 99–104.\nhttps:\/\/doi.org\/10.1016\/0370-2693(96)00345-0\n. \nWitten, Edward. \"String Theory Dynamics In Various Dimensions.\"\nNuclear Physics B\n443, no. 1–2 (June 1995): 85–126.\nhttps:\/\/doi.org\/10.1016\/0550-3213(95)00158-O\n. \nWoit, Peter. \"Frequently Asked Questions | Not Even Wrong.\"\nNot Even Wrong\n(blog). Accessed January 17, 2022.\nhttps:\/\/www.math.columbia.edu\/~woit\/wordpress\/?page_id=4338\n. \nWolchover, Natalie. \"Dark Energy May Be Incompatible With String Theory.\" Quanta Magazine, August 9, 2018.\nhttps:\/\/www.quantamagazine.org\/dark-energy-may-be-incompatible-with-string-theory-20180809\/\n. \nZayas, Leopoldo A. Pando. “A Microscopic Account of Black Hole Entropy.” \nPhysics\n 13 (May 18, 2020): 80. \nhttps:\/\/doi.org\/10.1103\/PhysRevX.10.021037\n.\nShare your thoughts\n0\n0\n0\n0\nJoin the community\nJoin the Space.com Family! The best way to keep in touch and to be informed of our latest quizzes and competitions, as well as news and offers.\nAlready have an account?\nLog in\nLog In\nForgotten your password?\nReset it\nNot got an account?\nRegister\nMy Details\nUpdate your details below...\nKeep in the Know\nWould you like to be kept informed about new quizzes and offers from Future and its partners?\nValidate Your Mobile No.\nWe have sent a code to\n. Please enter it below to verify your account.\nUpdate mobile number\nResend code\nUpdate Your Mobile No.\nYou may enter a new mobile number below. You will be sent a verification code to the phone number you provide.\nCancel\nembed-reactions.hint_heading\nembed-reactions.hint_subheading\nValidate Your Email Address\nWe have sent a code to\n. Please enter it below to verify your account.\nUpdate email address\nResend code\nUpdate Your Email Address\nYou may enter a new email address below. You will be sent a verification code to the address you provide.\nCancel\nCreate a Username\nThis will be publicly viewable so make it something you like!\nReset your password\nEnter your email address below. If it is registered with us, we will email you a code that will allow you to reset your password.\nCheck your inbox\nIf your email address was found in our system, you should receive an email in the next few minutes containing a code. Enter that code below to reset your password.\nSet new password\nPlease enter your new password below.\nLeaderboard\nRank\nPlayer\nScore\nTime\nCharlie Wood is a freelance journalist covering physical sciences both on and off this pale blue dot. He contributes to Space.com and LiveScience, as well as Popular Science, Scientific American, Quanta Magazine, and others. These days he writes from New York but in previous lives he taught physics in Mozambique and science English in Japan. Find him on Twitter @walkingthedot. ","attrs_markdown":"![](https:\/\/sb.scorecardresearch.com\/p\/?c1=2&c2=10055482&cv=4.4.0&cj=1)\n\n[Skip to main content](https:\/\/www.space.com\/17594-string-theory.html#main)\n\nOpen menu\n\n[![Space](https:\/\/www.space.com\/media\/img\/spc-logo-w.svg) Space](https:\/\/www.space.com\/)\n\n[Sign up to our newsletter Newsletter](https:\/\/www.space.com\/newsletter)\n\n[RSS](https:\/\/www.space.com\/feeds.xml)\n\nSign in\n\n- View Profile\n- Sign out\n\nSearch\n\n- [Space Exploration](https:\/\/www.space.com\/space-exploration)\n  - [Launches & Spacecraft](https:\/\/www.space.com\/space-exploration\/launches-spacecraft)\n    - [Private spaceflight](https:\/\/www.space.com\/space-exploration\/private-spaceflight)\n    - [Human spaceflight](https:\/\/www.space.com\/space-exploration\/human-spaceflight)\n    - [SpaceX](https:\/\/www.space.com\/tag\/spacex)\n    - [Blue Origin](https:\/\/www.space.com\/tag\/blue-origin)\n    - [Virgin Galactic](https:\/\/www.space.com\/tag\/virgin-galactic)\n    - 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[Astronomy](https:\/\/www.space.com\/astronomy)\n# What is string theory?\n[References](https:\/\/www.space.com\/references)\n\nBy [Vicky Stein](https:\/\/www.space.com\/author\/vicky-stein), [Charlie Wood](https:\/\/www.space.com\/author\/charlie-wood)\n\nlast updated\n\nMay 18, 2023\n\nString theory might be the theory of everything… or a flawed framework for theoretical physics.\n\nWhen you purchase through links on our site, we may earn an affiliate commission. [Here’s how it works](https:\/\/www.space.com\/41418-about-us.html#section-affiliate-advertising-disclosure).\n\nClick for next article\n\n![Artist\\&\\#039;s illustration of string theory shows numerous colored strings in an abstract configuration.](https:\/\/cdn.mos.cms.futurecdn.net\/ZUxv3mD76WxYbBwUUYJnV4.jpg)\n\nString theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: Tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles. (Image credit: PASIEKA via Getty Images)\n\nJump to:\n\n- [String theory FAQs](https:\/\/www.space.com\/17594-string-theory.html#section-string-theory-faqs-answered-by-an-expert)\n- [What is it?](https:\/\/www.space.com\/17594-string-theory.html#section-what-is-string-theory)\n- [Evolution](https:\/\/www.space.com\/17594-string-theory.html#section-how-did-string-theory-evolve)\n- [Importance](https:\/\/www.space.com\/17594-string-theory.html#section-why-is-string-theory-still-important)\n- [Additional resources](https:\/\/www.space.com\/17594-string-theory.html#section-additional-resources)\n\nShare\n\n- Copy link\n- [Facebook](https:\/\/www.facebook.com\/sharer\/sharer.php?u=https%3A%2F%2Fwww.space.com%2F17594-string-theory.html)\n- [X](https:\/\/twitter.com\/intent\/tweet?text=What+is+string+theory%3F+&url=https%3A%2F%2Fwww.space.com%2F17594-string-theory.html)\n- [Whatsapp](whatsapp:\/\/send?text=What+is+string+theory%3F++https%3A%2F%2Fwww.space.com%2F17594-string-theory.html?fwa)\n- [Reddit](https:\/\/www.reddit.com\/submit?url=https%3A%2F%2Fwww.space.com%2F17594-string-theory.html&title=What+is+string+theory%3F+)\n- [Pinterest](https:\/\/pinterest.com\/pin\/create\/button\/?url=https%3A%2F%2Fwww.space.com%2F17594-string-theory.html&media=https%3A%2F%2Fcdn.mos.cms.futurecdn.net%2FZUxv3mD76WxYbBwUUYJnV4.jpg)\n- [Flipboard](https:\/\/share.flipboard.com\/bookmarklet\/popout?title=What+is+string+theory%3F+&url=https%3A%2F%2Fwww.space.com%2F17594-string-theory.html)\n- [Email](mailto:?subject=I%20found%20this%20webpage&body=Hi,%20I%20found%20this%20webpage%20and%20thought%20you%20might%20like%20it%20https:\/\/www.space.com\/17594-string-theory.html)\n\nShare this article\n\nJoin the conversation\n\n[Follow us](https:\/\/google.com\/preferences\/source?q=space.com)\n\nAdd us as a preferred source on Google\n\nNewsletter\n\nGet the Space.com Newsletter\n\nBreaking space news, the latest updates on rocket launches, skywatching events and more\\!\n\n***\nBy signing up, you agree to our [Terms of services](https:\\\/\\\/futureplc.com\\\/terms-conditions\\\/)  and acknowledge that you have read our [Privacy Notice](https:\\\/\\\/futureplc.com\\\/privacy-policy\\\/). 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Sign up for our skywatching newsletter and explore the universe with us\\!\n\nSubscribe +\n\n![Strange New Words](https:\/\/cdn.mos.cms.futurecdn.net\/Mk2LrCm68RFHzQhNyQaH2Y.jpg)\n\nTwice a month\n\nStrange New Words\n\nSpace.com's Sci-Fi Reader's Club. Read a sci-fi short story every month and join a virtual community of fellow science fiction fans\\!\n\nSubscribe +\n\n***\nAn account already exists for this email address, please log in.\n\nSubscribe to our newsletter\n\nString theory is the idea in theoretical physics that reality is made up of infinitesimal vibrating strings, smaller than atoms, electrons or quarks. According to this theory, as the strings vibrate, twist and fold, they produce effects in many, tiny dimensions that humans interpret as everything from particle physics to large-scale phenomena like [gravity](https:\/\/www.space.com\/classical-gravity.html).\n\nString theory has been held up as a possible \"theory of everything,\" a single framework that could unite [general relativity](https:\/\/www.space.com\/17661-theory-general-relativity.html) and [quantum mechanics](https:\/\/www.livescience.com\/33816-quantum-mechanics-explanation.html), two theories that underlie almost all of modern physics. While quantum mechanics does very well in describing the behavior of very small things and general relativity works well to explain how very large things happen in [the universe](https:\/\/www.space.com\/52-the-expanding-universe-from-the-big-bang-to-today.html), they don't play nicely together. Some scientists think (or thought) that string theory could resolve the conundrums between the two, conquering one of the major remaining unsolved problems of physics.\n\nBut after string theory gained prominence in the late 1960s and '70s, its popularity among theoretical physicists fluctuated, according to a lecture by California Institute of Technology physicist [John Schwarz](https:\/\/arxiv.org\/abs\/1201.0981), widely considered one of the founders of string theory. After countless papers, conferences and dry-erase markers, the breathtaking breakthrough many once hoped for seems further away than ever.\n\nYou may like\n\n- [![A series of blue and red and green and orange analog clocks all superimposed on each other](https:\/\/cdn.mos.cms.futurecdn.net\/wECuuHE7jxzT73orWxpY5.jpg) Is time a fundamental part of reality? A quiet revolution in physics suggests not](https:\/\/www.space.com\/science\/particle-physics\/is-time-a-fundamental-part-of-reality-a-quiet-revolution-in-physics-suggests-not)\n- [![The galaxy Messier 33 according to competing models of the universe (left) with a dark matter halo (right) without a bubble of this mysterious \\&quot;stuff.\\&quot;](https:\/\/cdn.mos.cms.futurecdn.net\/ug3qTXVQFJFGSaFGH9hnzh.png) Does dark matter actually exist? New theory says it could be gravity behaving strangely](https:\/\/www.space.com\/astronomy\/dark-universe\/does-dark-matter-actually-exist-new-theory-says-it-could-be-gravity-behaving-strangely)\n- [![An illustration of matter pouring into a black hole, crossing an Einstein-Rosen bridge and emerging in another region of the universe](https:\/\/cdn.mos.cms.futurecdn.net\/QiqgvSVLR8GjPCQ4fEyjHa.png) Wormholes may not exist – we've found they reveal something deeper about time and the universe](https:\/\/www.space.com\/astronomy\/wormholes-may-not-exist-weve-found-they-reveal-something-deeper-about-time-and-the-universe)\n\nNevertheless, the flurry of thought around the very idea of string theory has left a deep imprint on both physics and math. Like it or not (and some physicists certainly don't), string theory is here to stay.\n\n[Click here for more Space.com videos...](https:\/\/videos.space.com\/m\/OXcbz76g\/string-theory-examined-with-nasas-chandra-x-ray-observatory-observations?list=9wzCTV4g)\n\n## String theory FAQs answered by an expert\nWe asked Nick Geiser, a theoretical physicist at UCLA, a few frequently asked questions about string theory.\n\n![Nick Geiser in front of a blackboard.](https:\/\/cdn.mos.cms.futurecdn.net\/ijuYubKj7AU3iL3mPmm5Rk.jpeg)\n\nNick Geiser\n\nTheoretical physicist\n\nNick Geiser is a PhD candidate in theoretical physics at UCLA and will join the University of Michigan as a Leinweber and Van Loo Postdoctoral Fellow, working with Professor Henriette Elvang in the Leinweber Center for Theoretical Physics in June 2023. Geiser's research spans several areas of theoretical high-energy physics centered around scattering amplitudes. Scattering amplitudes are fundamental objects in theoretical physics that can be measured in experiments and reveal deep connections between physics and pure mathematics. Outside of research, Geiser works with a variety of organizations to support under-represented minority groups in STEM fields.\n\n### What is string theory?\nString theory is a collection of ideas in theoretical physics in which the fundamental building-blocks of nature are not particles (such as the point-like electron) but instead strings. Imagine microscopic wiggling rubber bands.  \n   \n String theory is primarily a theory of [quantum gravity](https:\/\/www.space.com\/quantum-gravity.html) which elegantly combines the theories of gravity and quantum mechanics. Physicists have been searching for a theory of quantum gravity for nearly one hundred years. Moreover, ideas from string theory have been used to solve problems in mathematics and other fields of theoretical physics.  \n   \n In many ways, string theory is a language that can be used by theoretical physicists to solve problems and to investigate the mathematics of the universe.\n\n### Who invented string theory?\nString theory was discovered by accident! In 1969, Italian physicist Gabriele Veneziano wrote down a formula describing the scattering of four strings, the now-famous Veneziano amplitude. Veneziano was trying to describe the physics of particles like the [proton](https:\/\/www.space.com\/protons-facts-discovery-charge-mass) and neutron, not strings. In the following years, physicists around the world began to unravel string theory from that first formula.  \n   \n The full picture of string theory has become clearer over the following fifty years. There were several bursts of new ideas and deep insights in the 1970s, 1980s, and 1990s, and string theory is still an active field with thousands of researchers around the world.\n\n### Has string theory been proven?\nNo experiment has definitively proven string theory to be the fundamental theory of nature. However, the ideas of string theory have passed countless theoretical and mathematical tests over the last fifty years.  \n   \n Fundamental physics is a long-game. Einstein first predicted [gravitational waves](https:\/\/www.space.com\/25088-gravitational-waves.html) in 1915, and they were first detected by the [LIGO](https:\/\/www.space.com\/LIGO-Laser-Interferometer-Gravitational-Wave-Observatory.html) experiment in 2015, one hundred years later! Future particle physics experiments, gravitational wave observatories, or cosmological measurements may offer definitive tests of string theory.\n\n### How many dimensions are there in string theory?\nString theory predicts ten total spacetime dimensions, but we clearly live in a world with four dimensions (three space and one time)! Thankfully, it is not a problem to get from ten to four. Six of the dimensions predicted by string theory could be wrapped into a small compact shape. These compactified dimensions could then only be seen by a large, precise experiment like CERN's [Large Hadron Collider](https:\/\/www.space.com\/large-hadron-collider-particle-accelerator).\n## What is string theory?\nString theory is a framework that physicists use to describe how forces usually conceptualized on a gigantic level, like gravity, could affect tiny objects like electrons and protons.\n\nIn [Albert Einstein](https:\/\/www.space.com\/15524-albert-einstein.html)'s theory of general relativity, gravity is a force that warps space-time around massive objects. It's one of the [four forces](https:\/\/www.livescience.com\/the-fundamental-forces-of-nature.html) that physicists use to describe nature. But unlike the other forces (electromagnetism, the strong force and the weak force), gravity is so weak that it can't be detected or observed on the scale of a particle. Instead, its effects are only noticeable and important on the scale of moons, planets, stars and galaxies.\n\nGet the Space.com Newsletter\n\nBreaking space news, the latest updates on rocket launches, skywatching events and more\\!\n\nBy signing up, you agree to our [Terms of services](https:\\\/\\\/futureplc.com\\\/terms-conditions\\\/)  and acknowledge that you have read our [Privacy Notice](https:\\\/\\\/futureplc.com\\\/privacy-policy\\\/). You also agree to receive marketing emails from us that may include promotions from our trusted partners and sponsors, which you can unsubscribe from at any time.\n\nGravity seems not to exist as a particle of its own, either. Theorists can predict what a gravity particle should look like, but when they try to calculate what happens when two such \"gravitons\" smash together, they get an infinite amount of energy packed into a small space — a sure sign, according to astrophysicist Paul Sutter in a [previous article for Space.com](https:\/\/www.space.com\/32147-why-is-gravity-so-hard-to-understand.html), that the math is missing something.\n\nOne possible solution, which theorists borrowed from nuclear physicists in the 1970s, is to get rid of the idea of problematic, point-like graviton particles. Strings, and only strings, can collide and rebound cleanly without implying physically impossible infinities.\n\n[![Tangled yarn to represent the complexity of string theory.](https:\/\/cdn.mos.cms.futurecdn.net\/mCY6r3XpvQYrGyb28ENwcM.jpg)]()\n\nString theory math required six additional dimensions (for a total of 10) [visible only to the little strings](https:\/\/www.space.com\/41947-gravitational-waves-reveal-no-extra-dimensions.html), much as a powerline looks like a 1D line to birds flying far overhead but a 3D cylinder to an ant crawling on the wire. (Image credit: Shutterstock)\n\n\"A one-dimensional object — that's the thing that really tames the infinities that come up in the calculations,\" string theory expert Marika Taylor, a theoretical physicist at the University of Southampton in England, told Space.com.\n\nWhat to read next\n\n- [![A cylinder-like shape with stars within. There\\&\\#039;s a glow toward the left and a grid pattern all around it.](https:\/\/cdn.mos.cms.futurecdn.net\/SmcBfLjCAEkg9NziAM9CuH.png) How fast is the universe actually expanding? Ripples in spacetime could finally solve 'Hubble tension'](https:\/\/www.space.com\/astronomy\/how-fast-is-the-universe-actually-expanding-ripples-in-spacetime-could-finally-solve-hubble-tension)\n- [![Screenshot from a new NASA animation highlighting some of the universe\\&\\#039;s biggest black holes, including the record-holding TON 618, which is about as massive as 60 billion suns.](https:\/\/cdn.mos.cms.futurecdn.net\/LonKAe8kapjmivFoVTBLRX.jpeg) James Webb Space Telescope reveals new origin story for the universe's 1st supermassive black holes](https:\/\/www.space.com\/astronomy\/james-webb-space-telescope\/james-webb-space-telescope-data-backs-new-origin-story-for-the-universes-1st-supermassive-black-holes)\n- [![An illustration shows dark matter powering the heart of a spiral galaxy](https:\/\/cdn.mos.cms.futurecdn.net\/69kRCSZKQ5H5nddwqCTGR3.png) Could the Milky Way galaxy's supermassive black hole actually be a clump of dark matter?](https:\/\/www.space.com\/astronomy\/dark-universe\/could-the-milky-way-galaxys-supermassive-black-hole-actually-be-a-clump-of-dark-matter)\n\nString theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles. A string of a particular length striking a particular note might gain the properties of a photon, another string folded and vibrating with a different frequency could play the role of a quark, and so on.\n\nIn addition to taming gravity, string theory was attractive for its potential to explain so-called fundamental constants like the mass of an electron. The next step, theorists hoped, would be to find the right way to describe the folding and movement of strings, and everything else should have followed.\n\nBut that initial simplicity turned out to come at the cost of unexpected complexity — string math didn't work in our familiar four dimensions (three of space and one of time). It needed a total of [10 dimensions](https:\/\/www.space.com\/41947-gravitational-waves-reveal-no-extra-dimensions.html), with six visible only to the perspective of the little strings, much as a powerline looks like a 1D line to birds flying far overhead but becomes a 3D cylinder to an ant crawling on the wire.\n\n[Click here for more Space.com videos...](https:\/\/videos.space.com\/m\/jMcp2B0n\/all-quantum-gravity-theories-suck-heres-why?list=9wzCTV4g)\n\n## How did string theory evolve?\nString theory today doesn't exactly match the string theory of the 1960s and '70s. Researchers disagree over whether, with modifications, it's still the best candidate for a \"theory of everything\" or whether theorists should abandon it in favor of other topics.\n\n\"By 1973–'74 there were many good reasons to stop working on string theory,\" Schwarz wrote. Physicists' attention had turned from what felt like an unfruitful exploration of tiny undetectable \"soft\" strings and instead taken up more compelling evidence of hadrons, subatomic particles made up of quarks whose actions couldn't be explained by strings.\n\n\"What had been a booming enterprise involving several hundred theorists rapidly came to a grinding halt,\" Schwarz wrote. \"Only a few diehards continued to pursue it.\"\n\nOver the next decade, a few scientists continued to pursue five different versions of string theory. Over time, the researchers began to find unexpected connections between the five ideas, which Edward Witten, a theorist at the Institute for Advanced Study in Princeton, New Jersey, gathered up and presented at a [1995 string theory conference](https:\/\/arxiv.org\/abs\/hep-th\/9503124) at the University of Southern California. Witten argued that the five string theories each represented an approximation of a more fundamental, 11-dimensional theory as it behaved in a particular situation, much as how Einstein's space- and time-bending theories of relativity match Newton's description of objects moving at normal speeds. That was the beginning of one string theory spin-off: M-theory.\n\nThe \"M\" is likely inspired by higher-dimensional objects called membranes, Taylor said, but since the theory has no concrete mathematical equations, the \"M\" remains a placeholder with no official meaning. \"It was really a parametrization of our ignorance,\" she said.\n\nAttempts to find those general equations that would work in every possible situation made little progress, but the alleged existence of the fundamental theory gave theorists the understanding and confidence needed to develop mathematical techniques for the five versions of string theory and apply them in the context where each theory worked.\n\n[![string theory illustration shows numerous strings in an abstract shape configuration.](https:\/\/cdn.mos.cms.futurecdn.net\/3JBXDjWtgHGtY4UjFCzszS.jpg)]()\n\nAn artist's interpretation of string theory. (Image credit: Science Photo Library via Getty Images)\n\nStrings are far too small to detect with any conceivable technology, but one early theoretical success was physicists' ability to describe black hole entropy in a 1996 paper published in the journal [Physics Letters](https:\/\/arxiv.org\/abs\/hep-th\/9601029).\n\nEntropy refers to the number of ways that you can arrange the parts of a system, but without being able to see into the impenetrable depths of a black hole, no one knows what type of particles might lie inside or what arrangements they can take. And yet, in the early 1970s, [Stephen Hawking](https:\/\/www.space.com\/15923-stephen-hawking.html) and others used the laws of thermodynamics and, according to an article published in 2020 in the journal [Physics](https:\/\/physics.aps.org\/articles\/v13\/80), quantum mechanics to calculate entropy inside a black hole, suggesting that black holes must have some sort of internal structure. What that structure might be, remained a mystery.\n\nMost attempts to describe the black hole's makeup fall short, but the configurations of hypothetical strings does the trick. \"String theory has been able to give a spot-on counting,\" Taylor said — an actual possible explanation of black hole interiors, not just a rough idea.\n\nThe string theory framework still faces many challenges, however: It produces an impossible number of ways to fold up the extra six dimensions. Every option seems to fit the broad features of the Standard Model that governs particle physics, with little hope of distinguishing which is the right one. Moreover, wrote astrophysicist Ethan Siegel in his blog [Starts With a Bang](https:\/\/www.forbes.com\/sites\/startswithabang\/2019\/02\/12\/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history\/), all of those models for managing the extra dimensions rely on an equivalence between force particles and matter particles called supersymmetry. But, just like the extra dimensions that string theory requires, we don't observe supersymmetry in our world.\n\nOn top of those objections, it's not clear that string theory — M-theory or not — can ever be compatible with our modern understanding of an expanding universe, replete with dark energy, reported [Quanta Magazine](https:\/\/www.quantamagazine.org\/dark-energy-may-be-incompatible-with-string-theory-20180809\/) in 2018.\n\nA number of physicists, such as Peter Woit of Columbia University, view these divergences from reality as fatal flaws. \"The basic problem with string theory unification research is not that progress has been slow over the past 30 years,\" he wrote on his [blog](http:\/\/www.math.columbia.edu\/~woit\/wordpress\/?page_id=4338), \"but that it has been negative, with everything learned showing more clearly why the idea doesn't work.\"\n\nTaylor, however, maintains that today's models are overly simplistic, and that features like [cosmological expansion](https:\/\/www.space.com\/16042-cosmology.html) and a lack of supersymmetry may someday be built into future versions. Taylor expects that, while the new era of [gravitational-wave astronomy](https:\/\/www.space.com\/LIGO-Laser-Interferometer-Gravitational-Wave-Observatory.html) may bring new tidbits of information about quantum gravity, more progress will be made by continuing to follow the math deeper into string theory.\n\n\"I have a theoretical bias,\" she said, \"but I think the kind of breakthrough I'm describing would come from a chalkboard; from thought.\"\n\n[Click here for more Space.com videos...](https:\/\/videos.space.com\/m\/0rBxIHZF\/theory-of-everything-tested-with-perseus-galaxy-cluster-observations?list=9wzCTV4g)\n\n## Why is string theory still important?\nRegardless of whether string theory can ever be massaged into a \"theory of everything,\" its legacy as a productive research program may be assured on mathematical merit alone.\n\n\"It can't be a dead end in the sense of what we've learned just from mathematics itself,\" Taylor said. \"If you told me tomorrow that the universe absolutely isn't supersymmetric and doesn't have 10 \\[spatial\\] dimensions, we've still connected whole branches of mathematics\" using the string theory framework.\n\nIn particular, when Witten and other researchers showed that the five-string theories were shadows of a single-parent theory, they highlighted connections called dualities, which have proven to be a major contribution to mathematics and physics.\n\nDualities let mathematicians translate from one branch of math to another, attacking problems untenable in one framework by using calculations done in the other, for example in geometry and number theory. Other dualities have helped overcome challenges in quantum computing, according to Taylor. \"It's not going to make your next-generation iPhone,\" she said, \"But it may make your iPhone for the 22nd century.\"\n\nWhether string theory's ability to illuminate the dark web connecting different areas of math turns out to be a sign of its potential or just a lucky coincidence remains a subject of debate. Witten, speaking at the [Institute for Advanced Study](https:\/\/video.ias.edu\/universe\/2019\/0529-DijkgraafWitten) in 2019, acknowledged that while he no longer feels as confident as he once did that string theory will evolve into a complete physical theory, his gut tells him that the theory remains a productive field of research.\n\n\"To me, it's implausible that humans stumbled by accident on\\[to\\] such an incredible structure that sheds so much light on established physical theories, and also on so many different branches of mathematics,\" he told the audience. \"I have confidence that the general enterprise is on the right track, but I don't claim that the argument I've given is scientifically convincing.\"\n\n## Additional resources\nFind more in-depth history and explanations of current string theory science at [WhyStringTheory.com](http:\/\/whystringtheory.com\/), a website created by graduate students at the University of Oxford and the University of Cambridge for the \"interested layperson.\" Or, if you'd rather go right to the source, check out this [CERN Courier](https:\/\/cerncourier.com\/a\/the-roots-and-fruits-of-string-theory\/) interview with string theory originator Gabriele Veneziano. If you're looking for a video explainer, watch these two videos entitled \"[Why string theory is right](https:\/\/www.youtube.com\/watch?v=iTTa9YcTe1k)\" and \"[Why string theory is wrong](https:\/\/www.youtube.com\/watch?v=IhpGdumLRqs),\" both from PBS Digital Studios.\n\n### Bibliography\n- \"Robbert Dijkgraaf and Edward Witten in Conversation - Videos \\| Institute for Advanced Study,\" May 30, 2019.\n  [https:\/\/www.ias.edu\/video\/universe\/2019\/0529-DijkgraafWitten](https:\/\/www.ias.edu\/video\/universe\/2019\/0529-DijkgraafWitten)\n  .\n- Schwarz, John H. \"The Early History of String Theory and Supersymmetry,\" January 4, 2012.\n  [https:\/\/arxiv.org\/abs\/1201.0981v1](https:\/\/arxiv.org\/abs\/1201.0981v1)\n  .\n- Siegel, Ethan. \"Why Supersymmetry May Be The Greatest Failed Prediction In Particle Physics History.\" Forbes, February 12, 2019.\n  [https:\/\/www.forbes.com\/sites\/startswithabang\/2019\/02\/12\/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history\/](https:\/\/www.forbes.com\/sites\/startswithabang\/2019\/02\/12\/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history\/)\n  .\n- Strominger, A., and C. Vafa. \"Microscopic Origin of the Bekenstein-Hawking Entropy.\" *Physics Letters B* 379, no. 1–4 (June 1996): 99–104.\n  [https:\/\/doi.org\/10.1016\/0370-2693(96)00345-0](https:\/\/doi.org\/10.1016\/0370-2693\\(96\\)00345-0)\n  .\n- Witten, Edward. \"String Theory Dynamics In Various Dimensions.\" *Nuclear Physics B* 443, no. 1–2 (June 1995): 85–126.\n  [https:\/\/doi.org\/10.1016\/0550-3213(95)00158-O](https:\/\/doi.org\/10.1016\/0550-3213\\(95\\)00158-O)\n  .\n- Woit, Peter. \"Frequently Asked Questions \\| Not Even Wrong.\" *Not Even Wrong* (blog). Accessed January 17, 2022.\n  [https:\/\/www.math.columbia.edu\/~woit\/wordpress\/?page\\_id=4338](https:\/\/www.math.columbia.edu\/~woit\/wordpress\/?page_id=4338)\n  .\n- Wolchover, Natalie. \"Dark Energy May Be Incompatible With String Theory.\" Quanta Magazine, August 9, 2018.\n  [https:\/\/www.quantamagazine.org\/dark-energy-may-be-incompatible-with-string-theory-20180809\/](https:\/\/www.quantamagazine.org\/dark-energy-may-be-incompatible-with-string-theory-20180809\/)\n  .\n- Zayas, Leopoldo A. Pando. “A Microscopic Account of Black Hole Entropy.” *Physics* 13 (May 18, 2020): 80. <https:\/\/doi.org\/10.1103\/PhysRevX.10.021037>.\n\n**Share your thoughts**\n\n0\n\n0\n\n0\n\n0\n\nRandom QuizPlay a Random Quiz\n\nFilter by Category\n\nJoin the community\n\nJoin the Space.com Family! The best way to keep in touch and to be informed of our latest quizzes and competitions, as well as news and offers.\n\nI'm in\\!\n\nNot right now\n\nAlready have an account? 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These days he writes from New York but in previous lives he taught physics in Mozambique and science English in Japan. Find him on Twitter @walkingthedot.\n\nRead more\n\n[![A series of blue and red and green and orange analog clocks all superimposed on each other](https:\/\/cdn.mos.cms.futurecdn.net\/wECuuHE7jxzT73orWxpY5.jpg) Particle Physics Is time a fundamental part of reality? A quiet revolution in physics suggests not](https:\/\/www.space.com\/science\/particle-physics\/is-time-a-fundamental-part-of-reality-a-quiet-revolution-in-physics-suggests-not \"Is time a fundamental part of reality? A quiet revolution in physics suggests not\")\n\n[![The galaxy Messier 33 according to competing models of the universe (left) with a dark matter halo (right) without a bubble of this mysterious \\&quot;stuff.\\&quot;](https:\/\/cdn.mos.cms.futurecdn.net\/ug3qTXVQFJFGSaFGH9hnzh.png) Dark Universe Does dark matter actually exist? New theory says it could be gravity behaving strangely](https:\/\/www.space.com\/astronomy\/dark-universe\/does-dark-matter-actually-exist-new-theory-says-it-could-be-gravity-behaving-strangely \"Does dark matter actually exist? New theory says it could be gravity behaving strangely\")\n\n[![An illustration of matter pouring into a black hole, crossing an Einstein-Rosen bridge and emerging in another region of the universe](https:\/\/cdn.mos.cms.futurecdn.net\/QiqgvSVLR8GjPCQ4fEyjHa.png) Astronomy Wormholes may not exist – we've found they reveal something deeper about time and the universe](https:\/\/www.space.com\/astronomy\/wormholes-may-not-exist-weve-found-they-reveal-something-deeper-about-time-and-the-universe \"Wormholes may not exist – we've found they reveal something deeper about time and the universe\")\n\n[![A cylinder-like shape with stars within. There\\&\\#039;s a glow toward the left and a grid pattern all around it.](https:\/\/cdn.mos.cms.futurecdn.net\/SmcBfLjCAEkg9NziAM9CuH.png) Astronomy How fast is the universe actually expanding? Ripples in spacetime could finally solve 'Hubble tension'](https:\/\/www.space.com\/astronomy\/how-fast-is-the-universe-actually-expanding-ripples-in-spacetime-could-finally-solve-hubble-tension \"How fast is the universe actually expanding? Ripples in spacetime could finally solve 'Hubble tension'\")\n\n[![Screenshot from a new NASA animation highlighting some of the universe\\&\\#039;s biggest black holes, including the record-holding TON 618, which is about as massive as 60 billion suns.](https:\/\/cdn.mos.cms.futurecdn.net\/LonKAe8kapjmivFoVTBLRX.jpeg) James Webb Space Telescope James Webb Space Telescope reveals new origin story for the universe's 1st supermassive black holes](https:\/\/www.space.com\/astronomy\/james-webb-space-telescope\/james-webb-space-telescope-data-backs-new-origin-story-for-the-universes-1st-supermassive-black-holes \"James Webb Space Telescope reveals new origin story for the universe's 1st supermassive black holes\")\n\n[![An illustration shows dark matter powering the heart of a spiral galaxy](https:\/\/cdn.mos.cms.futurecdn.net\/69kRCSZKQ5H5nddwqCTGR3.png) Dark Universe Could the Milky Way galaxy's supermassive black hole actually be a clump of dark matter?](https:\/\/www.space.com\/astronomy\/dark-universe\/could-the-milky-way-galaxys-supermassive-black-hole-actually-be-a-clump-of-dark-matter \"Could the Milky Way galaxy's supermassive black hole actually be a clump of dark matter?\")\n\nLatest in Astronomy\n\n[![A colorful view of space with tendrils and blobs of gas. A box-out shows a bunch of glowing dots.](https:\/\/cdn.mos.cms.futurecdn.net\/NdgbDvKVdnveuQMWkeu98N.png) Galaxies This star-forming galaxy is blowing out powerful winds topping 2 million mph](https:\/\/www.space.com\/astronomy\/galaxies\/this-star-forming-galaxy-is-blowing-out-powerful-winds-topping-2-million-mph \"This star-forming galaxy is blowing out powerful winds topping 2 million mph\")\n\n[![An illustration showing Earth\\&\\#039;s uniform magnetic field and the uneven magnetic field of Saturn](https:\/\/cdn.mos.cms.futurecdn.net\/HQRfME6w8yjSh5V9qqCvMD.png) Saturn Saturn's magnetic field is curiously warped, and one of its moons may be to blame](https:\/\/www.space.com\/astronomy\/saturn\/saturns-magnetic-field-is-curiously-warped-and-one-of-its-moons-may-be-to-blame \"Saturn's magnetic field is curiously warped, and one of its moons may be to blame\")\n\n[![A white light of the comet 3I\/ATLAS is surrounded by a blue glow against a black background](https:\/\/cdn.mos.cms.futurecdn.net\/Pvmi4MNsFrESjVVcU94qGE.jpg) Comets Interstellar comet 3I\/ATLAS may be nearly 12 billion years old — so ancient its star system may no longer exist](https:\/\/www.space.com\/astronomy\/comets\/interstellar-comet-3i-atlas-may-be-nearly-12-billion-years-old-so-ancient-its-star-system-may-no-longer-exist \"Interstellar comet 3I\/ATLAS may be nearly 12 billion years old — so ancient its star system may no longer exist\")\n\n[![A diagram showing the fabric of spacetime with a boxout on the top-left with a blurry blue-white orb with jets shooting from both sides. There\\&\\#039;s a red blurry ring around the orb, but the jets are slightly jutting out from the ring.](https:\/\/cdn.mos.cms.futurecdn.net\/SXUJEe5z5TTEX6dJnju3Xb.png) Galaxies Record-breaking 'space laser' erupts from merging galaxies 8 billion light-years away](https:\/\/www.space.com\/astronomy\/galaxies\/record-breaking-space-laser-erupts-from-merging-galaxies-8-billion-light-years-away \"Record-breaking 'space laser' erupts from merging galaxies 8 billion light-years away\")\n\n[![three panel image from left to right showing the x-flare the accompanying CME and the Artemis 2 moon rocket sitting ready on the launch pad.](https:\/\/cdn.mos.cms.futurecdn.net\/cwbEMbdMx8yUXHkX2fpPoU.jpg) The Sun Powerful X-class solar flare triggers radio blackout ahead of Artemis 2 launch (video)](https:\/\/www.space.com\/astronomy\/sun\/powerful-x-class-solar-flare-triggers-radio-blackout-ahead-of-artemis-2-launch \"Powerful X-class solar flare triggers radio blackout ahead of Artemis 2 launch (video)\")\n\n[![a pale yellow planet surrounded by white concentric rings](https:\/\/cdn.mos.cms.futurecdn.net\/vqgm4zqiCKvJozzWBa98NY.jpg) Saturn Are Saturn's rings made of a lost, shattered moon? 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Left: GLaDOS from Portal, Middle: Cortana from Halo, Right: SHODAN from System Shock.](https:\/\/cdn.mos.cms.futurecdn.net\/FfxRqNtHqoEova9orXkQ4X.jpg) Space Games Best AI games… as in games about AI, not slop made by AI](https:\/\/www.space.com\/entertainment\/space-games\/best-ai-games-as-in-games-about-ai-not-slop-made-by-ai \"Best AI games… as in games about AI, not slop made by AI\")\n\n[![Screenshot from the sci-fi video game The Expanse: Osiris Reborn.](https:\/\/cdn.mos.cms.futurecdn.net\/DuKgLSxcuJm4TuMQE8gPEe.jpg) Space Games The Expanse: Osiris Reborn: Release date rumors, gameplay, & everything else we know about this sci-fi RPG](https:\/\/www.space.com\/entertainment\/space-games\/the-expanse-osiris-reborn-release-date-rumors-gameplay-and-everything-else-we-know-about-this-sci-fi-rpg \"The Expanse: Osiris Reborn: Release date rumors, gameplay, & everything else we know about this sci-fi RPG\")\n\n[![a close-up of two gloved hands holding a tube full of grey rocky dust in a clean room](https:\/\/cdn.mos.cms.futurecdn.net\/6qH6hGLT5YbqJyMkT2P4AD.jpg) Human Spaceflight Is it legal to own, buy, or sell Apollo mission moon rocks and lunar samples?](https:\/\/www.space.com\/space-exploration\/human-spaceflight\/is-it-legal-to-own-buy-or-sell-apollo-mission-moon-rocks-and-lunar-samples \"Is it legal to own, buy, or sell Apollo mission moon rocks and lunar samples? \")\n\n[![Three sci-fi couples kissing: Peter Quill \\&amp; Gamora, Han Solo \\&amp; Leia, and Nurse Chapel \\&amp; Spock](https:\/\/cdn.mos.cms.futurecdn.net\/H7cVHj3rhDjqbYimbms8PP.jpg) Space Movies & Shows The 8 best sci-fi couples to emulate this Valentine's Day](https:\/\/www.space.com\/entertainment\/space-movies-shows\/best-sci-fi-couples \"The 8 best sci-fi couples to emulate this Valentine's Day\")\n\n[![Hero art for Halo: Campaign Evolved, the remake of Halo: Combat Evolved.](https:\/\/cdn.mos.cms.futurecdn.net\/35Das3N4fRZYLKCqwiyaud.jpg) Space Games Halo: Campaign Evolved: Release date rumors, platforms, and everything else we know about the Halo remake](https:\/\/www.space.com\/entertainment\/space-games\/halo-campaign-evolved-release-date-rumors-platforms-and-everything-else-we-know-about-the-halo-remake \"Halo: Campaign Evolved: Release date rumors, platforms, and everything else we know about the Halo remake\")\n\nMORE FROM SPACE...\n\n1. [![A view of the Earth from space as seen from NASA's Orion spacecraft after launching on the Artemis 2 mission.](https:\/\/cdn.mos.cms.futurecdn.net\/DetkhQhrsGBtXGvRbrqycB.jpg)](https:\/\/www.space.com\/space-exploration\/artemis\/theres-a-bit-of-toilet-trouble-on-nasas-artemis-2-mission-to-the-moon \"There was a bit of toilet trouble on NASA's Artemis 2 mission to the moon \")\n   \n   1\n   \n   [There was a bit of toilet trouble on NASA's Artemis 2 mission to the moon](https:\/\/www.space.com\/space-exploration\/artemis\/theres-a-bit-of-toilet-trouble-on-nasas-artemis-2-mission-to-the-moon)\n2. 2\n   \n   [Why is the Artemis 2 rocket launch different from all other rocket launches?](https:\/\/www.space.com\/space-exploration\/artemis\/why-is-the-artemis-2-rocket-launch-different-from-all-other-rocket-launches)\n3. 3\n   \n   [NASA launches 4 astronauts to the moon on historic Artemis 2 voyage, a lunar leap for the 21st century](https:\/\/www.space.com\/space-exploration\/artemis\/nasa-launches-4-astronauts-to-the-moon-on-historic-artemis-2-voyage-a-lunar-leap-for-the-21st-century)\n4. 4\n   \n   ['Project Hail Mary' end credits showcase stunning nebula photos captured over 400 hours by a single astrophotographer — here's the inside story](https:\/\/www.space.com\/stargazing\/astrophotography\/project-hail-mary-end-credits-showcase-stunning-nebula-photos-captured-over-400-hours-by-a-single-astrophotographer-heres-the-inside-story)\n5. 5\n   \n   [2 bright planets light up April evenings — here's where and when to look](https:\/\/www.space.com\/stargazing\/2-bright-planets-light-up-april-evenings-heres-where-and-when-to-look)\n\nSpace is part of Future US Inc, an international media group and leading digital publisher. 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Full 7th Floor, 130 West 42nd Street, New York, NY 10036.\n\nClose\n\nPlease login or signup to comment\n\nPlease wait...\n\nLogin\n\nSign Up","attrs_readable_markdown":"![Artist\\&\\#039;s illustration of string theory shows numerous colored strings in an abstract configuration.](https:\/\/cdn.mos.cms.futurecdn.net\/ZUxv3mD76WxYbBwUUYJnV4.jpg)\n\nString theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: Tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles. (Image credit: PASIEKA via Getty Images)\n\nString theory is the idea in theoretical physics that reality is made up of infinitesimal vibrating strings, smaller than atoms, electrons or quarks. According to this theory, as the strings vibrate, twist and fold, they produce effects in many, tiny dimensions that humans interpret as everything from particle physics to large-scale phenomena like [gravity](https:\/\/www.space.com\/classical-gravity.html).\n\nString theory has been held up as a possible \"theory of everything,\" a single framework that could unite [general relativity](https:\/\/www.space.com\/17661-theory-general-relativity.html) and [quantum mechanics](https:\/\/www.livescience.com\/33816-quantum-mechanics-explanation.html), two theories that underlie almost all of modern physics. While quantum mechanics does very well in describing the behavior of very small things and general relativity works well to explain how very large things happen in [the universe](https:\/\/www.space.com\/52-the-expanding-universe-from-the-big-bang-to-today.html), they don't play nicely together. Some scientists think (or thought) that string theory could resolve the conundrums between the two, conquering one of the major remaining unsolved problems of physics.\n\nBut after string theory gained prominence in the late 1960s and '70s, its popularity among theoretical physicists fluctuated, according to a lecture by California Institute of Technology physicist [John Schwarz](https:\/\/arxiv.org\/abs\/1201.0981), widely considered one of the founders of string theory. After countless papers, conferences and dry-erase markers, the breathtaking breakthrough many once hoped for seems further away than ever.\n\nNevertheless, the flurry of thought around the very idea of string theory has left a deep imprint on both physics and math. Like it or not (and some physicists certainly don't), string theory is here to stay.\n\n## String theory FAQs answered by an expert\nWe asked Nick Geiser, a theoretical physicist at UCLA, a few frequently asked questions about string theory.\n\n![Nick Geiser in front of a blackboard.](https:\/\/cdn.mos.cms.futurecdn.net\/ijuYubKj7AU3iL3mPmm5Rk.jpeg)\n\nNick Geiser is a PhD candidate in theoretical physics at UCLA and will join the University of Michigan as a Leinweber and Van Loo Postdoctoral Fellow, working with Professor Henriette Elvang in the Leinweber Center for Theoretical Physics in June 2023. Geiser's research spans several areas of theoretical high-energy physics centered around scattering amplitudes. Scattering amplitudes are fundamental objects in theoretical physics that can be measured in experiments and reveal deep connections between physics and pure mathematics. Outside of research, Geiser works with a variety of organizations to support under-represented minority groups in STEM fields.\n\n### What is string theory?\nString theory is a collection of ideas in theoretical physics in which the fundamental building-blocks of nature are not particles (such as the point-like electron) but instead strings. Imagine microscopic wiggling rubber bands.\n\nString theory is primarily a theory of\n\n[quantum gravity](https:\/\/www.space.com\/quantum-gravity.html)\n\nwhich elegantly combines the theories of gravity and quantum mechanics. Physicists have been searching for a theory of quantum gravity for nearly one hundred years. Moreover, ideas from string theory have been used to solve problems in mathematics and other fields of theoretical physics.\n\nIn many ways, string theory is a language that can be used by theoretical physicists to solve problems and to investigate the mathematics of the universe.\n\n### Who invented string theory?\nString theory was discovered by accident! In 1969, Italian physicist Gabriele Veneziano wrote down a formula describing the scattering of four strings, the now-famous Veneziano amplitude. Veneziano was trying to describe the physics of particles like the\n\n[proton](https:\/\/www.space.com\/protons-facts-discovery-charge-mass)\n\nand neutron, not strings. In the following years, physicists around the world began to unravel string theory from that first formula.\n\nThe full picture of string theory has become clearer over the following fifty years. There were several bursts of new ideas and deep insights in the 1970s, 1980s, and 1990s, and string theory is still an active field with thousands of researchers around the world.\n\n### Has string theory been proven?\nNo experiment has definitively proven string theory to be the fundamental theory of nature. However, the ideas of string theory have passed countless theoretical and mathematical tests over the last fifty years.\n\nFundamental physics is a long-game. Einstein first predicted\n\n[gravitational waves](https:\/\/www.space.com\/25088-gravitational-waves.html)\n\nin 1915, and they were first detected by the\n\n[LIGO](https:\/\/www.space.com\/LIGO-Laser-Interferometer-Gravitational-Wave-Observatory.html)\n\nexperiment in 2015, one hundred years later! Future particle physics experiments, gravitational wave observatories, or cosmological measurements may offer definitive tests of string theory.\n\n### How many dimensions are there in string theory?\nString theory predicts ten total spacetime dimensions, but we clearly live in a world with four dimensions (three space and one time)! Thankfully, it is not a problem to get from ten to four. Six of the dimensions predicted by string theory could be wrapped into a small compact shape. These compactified dimensions could then only be seen by a large, precise experiment like CERN's [Large Hadron Collider](https:\/\/www.space.com\/large-hadron-collider-particle-accelerator).\n## What is string theory?\nString theory is a framework that physicists use to describe how forces usually conceptualized on a gigantic level, like gravity, could affect tiny objects like electrons and protons.\n\nIn [Albert Einstein](https:\/\/www.space.com\/15524-albert-einstein.html)'s theory of general relativity, gravity is a force that warps space-time around massive objects. It's one of the [four forces](https:\/\/www.livescience.com\/the-fundamental-forces-of-nature.html) that physicists use to describe nature. But unlike the other forces (electromagnetism, the strong force and the weak force), gravity is so weak that it can't be detected or observed on the scale of a particle. Instead, its effects are only noticeable and important on the scale of moons, planets, stars and galaxies.\n\nBreaking space news, the latest updates on rocket launches, skywatching events and more\\!\n\nGravity seems not to exist as a particle of its own, either. Theorists can predict what a gravity particle should look like, but when they try to calculate what happens when two such \"gravitons\" smash together, they get an infinite amount of energy packed into a small space — a sure sign, according to astrophysicist Paul Sutter in a [previous article for Space.com](https:\/\/www.space.com\/32147-why-is-gravity-so-hard-to-understand.html), that the math is missing something.\n\nOne possible solution, which theorists borrowed from nuclear physicists in the 1970s, is to get rid of the idea of problematic, point-like graviton particles. Strings, and only strings, can collide and rebound cleanly without implying physically impossible infinities.\n\n[![Tangled yarn to represent the complexity of string theory.](https:\/\/cdn.mos.cms.futurecdn.net\/mCY6r3XpvQYrGyb28ENwcM.jpg)]()\n\nString theory math required six additional dimensions (for a total of 10) [visible only to the little strings](https:\/\/www.space.com\/41947-gravitational-waves-reveal-no-extra-dimensions.html), much as a powerline looks like a 1D line to birds flying far overhead but a 3D cylinder to an ant crawling on the wire. (Image credit: Shutterstock)\n\n\"A one-dimensional object — that's the thing that really tames the infinities that come up in the calculations,\" string theory expert Marika Taylor, a theoretical physicist at the University of Southampton in England, told Space.com.\n\nString theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles. A string of a particular length striking a particular note might gain the properties of a photon, another string folded and vibrating with a different frequency could play the role of a quark, and so on.\n\nIn addition to taming gravity, string theory was attractive for its potential to explain so-called fundamental constants like the mass of an electron. The next step, theorists hoped, would be to find the right way to describe the folding and movement of strings, and everything else should have followed.\n\nBut that initial simplicity turned out to come at the cost of unexpected complexity — string math didn't work in our familiar four dimensions (three of space and one of time). It needed a total of [10 dimensions](https:\/\/www.space.com\/41947-gravitational-waves-reveal-no-extra-dimensions.html), with six visible only to the perspective of the little strings, much as a powerline looks like a 1D line to birds flying far overhead but becomes a 3D cylinder to an ant crawling on the wire.\n\n## How did string theory evolve?\nString theory today doesn't exactly match the string theory of the 1960s and '70s. Researchers disagree over whether, with modifications, it's still the best candidate for a \"theory of everything\" or whether theorists should abandon it in favor of other topics.\n\n\"By 1973–'74 there were many good reasons to stop working on string theory,\" Schwarz wrote. Physicists' attention had turned from what felt like an unfruitful exploration of tiny undetectable \"soft\" strings and instead taken up more compelling evidence of hadrons, subatomic particles made up of quarks whose actions couldn't be explained by strings.\n\n\"What had been a booming enterprise involving several hundred theorists rapidly came to a grinding halt,\" Schwarz wrote. \"Only a few diehards continued to pursue it.\"\n\nOver the next decade, a few scientists continued to pursue five different versions of string theory. Over time, the researchers began to find unexpected connections between the five ideas, which Edward Witten, a theorist at the Institute for Advanced Study in Princeton, New Jersey, gathered up and presented at a [1995 string theory conference](https:\/\/arxiv.org\/abs\/hep-th\/9503124) at the University of Southern California. Witten argued that the five string theories each represented an approximation of a more fundamental, 11-dimensional theory as it behaved in a particular situation, much as how Einstein's space- and time-bending theories of relativity match Newton's description of objects moving at normal speeds. That was the beginning of one string theory spin-off: M-theory.\n\nThe \"M\" is likely inspired by higher-dimensional objects called membranes, Taylor said, but since the theory has no concrete mathematical equations, the \"M\" remains a placeholder with no official meaning. \"It was really a parametrization of our ignorance,\" she said.\n\nAttempts to find those general equations that would work in every possible situation made little progress, but the alleged existence of the fundamental theory gave theorists the understanding and confidence needed to develop mathematical techniques for the five versions of string theory and apply them in the context where each theory worked.\n\n[![string theory illustration shows numerous strings in an abstract shape configuration.](https:\/\/cdn.mos.cms.futurecdn.net\/3JBXDjWtgHGtY4UjFCzszS.jpg)]()\n\nAn artist's interpretation of string theory. (Image credit: Science Photo Library via Getty Images)\n\nStrings are far too small to detect with any conceivable technology, but one early theoretical success was physicists' ability to describe black hole entropy in a 1996 paper published in the journal [Physics Letters](https:\/\/arxiv.org\/abs\/hep-th\/9601029).\n\nEntropy refers to the number of ways that you can arrange the parts of a system, but without being able to see into the impenetrable depths of a black hole, no one knows what type of particles might lie inside or what arrangements they can take. And yet, in the early 1970s, [Stephen Hawking](https:\/\/www.space.com\/15923-stephen-hawking.html) and others used the laws of thermodynamics and, according to an article published in 2020 in the journal [Physics](https:\/\/physics.aps.org\/articles\/v13\/80), quantum mechanics to calculate entropy inside a black hole, suggesting that black holes must have some sort of internal structure. What that structure might be, remained a mystery.\n\nMost attempts to describe the black hole's makeup fall short, but the configurations of hypothetical strings does the trick. \"String theory has been able to give a spot-on counting,\" Taylor said — an actual possible explanation of black hole interiors, not just a rough idea.\n\nThe string theory framework still faces many challenges, however: It produces an impossible number of ways to fold up the extra six dimensions. Every option seems to fit the broad features of the Standard Model that governs particle physics, with little hope of distinguishing which is the right one. Moreover, wrote astrophysicist Ethan Siegel in his blog [Starts With a Bang](https:\/\/www.forbes.com\/sites\/startswithabang\/2019\/02\/12\/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history\/), all of those models for managing the extra dimensions rely on an equivalence between force particles and matter particles called supersymmetry. But, just like the extra dimensions that string theory requires, we don't observe supersymmetry in our world.\n\nOn top of those objections, it's not clear that string theory — M-theory or not — can ever be compatible with our modern understanding of an expanding universe, replete with dark energy, reported [Quanta Magazine](https:\/\/www.quantamagazine.org\/dark-energy-may-be-incompatible-with-string-theory-20180809\/) in 2018.\n\nA number of physicists, such as Peter Woit of Columbia University, view these divergences from reality as fatal flaws. \"The basic problem with string theory unification research is not that progress has been slow over the past 30 years,\" he wrote on his [blog](http:\/\/www.math.columbia.edu\/~woit\/wordpress\/?page_id=4338), \"but that it has been negative, with everything learned showing more clearly why the idea doesn't work.\"\n\nTaylor, however, maintains that today's models are overly simplistic, and that features like [cosmological expansion](https:\/\/www.space.com\/16042-cosmology.html) and a lack of supersymmetry may someday be built into future versions. Taylor expects that, while the new era of [gravitational-wave astronomy](https:\/\/www.space.com\/LIGO-Laser-Interferometer-Gravitational-Wave-Observatory.html) may bring new tidbits of information about quantum gravity, more progress will be made by continuing to follow the math deeper into string theory.\n\n\"I have a theoretical bias,\" she said, \"but I think the kind of breakthrough I'm describing would come from a chalkboard; from thought.\"\n\n## Why is string theory still important?\nRegardless of whether string theory can ever be massaged into a \"theory of everything,\" its legacy as a productive research program may be assured on mathematical merit alone.\n\n\"It can't be a dead end in the sense of what we've learned just from mathematics itself,\" Taylor said. \"If you told me tomorrow that the universe absolutely isn't supersymmetric and doesn't have 10 \\[spatial\\] dimensions, we've still connected whole branches of mathematics\" using the string theory framework.\n\nIn particular, when Witten and other researchers showed that the five-string theories were shadows of a single-parent theory, they highlighted connections called dualities, which have proven to be a major contribution to mathematics and physics.\n\nDualities let mathematicians translate from one branch of math to another, attacking problems untenable in one framework by using calculations done in the other, for example in geometry and number theory. Other dualities have helped overcome challenges in quantum computing, according to Taylor. \"It's not going to make your next-generation iPhone,\" she said, \"But it may make your iPhone for the 22nd century.\"\n\nWhether string theory's ability to illuminate the dark web connecting different areas of math turns out to be a sign of its potential or just a lucky coincidence remains a subject of debate. Witten, speaking at the [Institute for Advanced Study](https:\/\/video.ias.edu\/universe\/2019\/0529-DijkgraafWitten) in 2019, acknowledged that while he no longer feels as confident as he once did that string theory will evolve into a complete physical theory, his gut tells him that the theory remains a productive field of research.\n\n\"To me, it's implausible that humans stumbled by accident on\\[to\\] such an incredible structure that sheds so much light on established physical theories, and also on so many different branches of mathematics,\" he told the audience. \"I have confidence that the general enterprise is on the right track, but I don't claim that the argument I've given is scientifically convincing.\"\n\n## Additional resources\nFind more in-depth history and explanations of current string theory science at [WhyStringTheory.com](http:\/\/whystringtheory.com\/), a website created by graduate students at the University of Oxford and the University of Cambridge for the \"interested layperson.\" Or, if you'd rather go right to the source, check out this [CERN Courier](https:\/\/cerncourier.com\/a\/the-roots-and-fruits-of-string-theory\/) interview with string theory originator Gabriele Veneziano. If you're looking for a video explainer, watch these two videos entitled \"[Why string theory is right](https:\/\/www.youtube.com\/watch?v=iTTa9YcTe1k)\" and \"[Why string theory is wrong](https:\/\/www.youtube.com\/watch?v=IhpGdumLRqs),\" both from PBS Digital Studios.\n\n### Bibliography\n- \"Robbert Dijkgraaf and Edward Witten in Conversation - Videos \\| Institute for Advanced Study,\" May 30, 2019.\n  [https:\/\/www.ias.edu\/video\/universe\/2019\/0529-DijkgraafWitten](https:\/\/www.ias.edu\/video\/universe\/2019\/0529-DijkgraafWitten)\n  .\n- Schwarz, John H. \"The Early History of String Theory and Supersymmetry,\" January 4, 2012.\n  [https:\/\/arxiv.org\/abs\/1201.0981v1](https:\/\/arxiv.org\/abs\/1201.0981v1)\n  .\n- Siegel, Ethan. \"Why Supersymmetry May Be The Greatest Failed Prediction In Particle Physics History.\" Forbes, February 12, 2019.\n  [https:\/\/www.forbes.com\/sites\/startswithabang\/2019\/02\/12\/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history\/](https:\/\/www.forbes.com\/sites\/startswithabang\/2019\/02\/12\/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history\/)\n  .\n- Strominger, A., and C. Vafa. \"Microscopic Origin of the Bekenstein-Hawking Entropy.\" *Physics Letters B* 379, no. 1–4 (June 1996): 99–104.\n  [https:\/\/doi.org\/10.1016\/0370-2693(96)00345-0](https:\/\/doi.org\/10.1016\/0370-2693\\(96\\)00345-0)\n  .\n- Witten, Edward. \"String Theory Dynamics In Various Dimensions.\" *Nuclear Physics B* 443, no. 1–2 (June 1995): 85–126.\n  [https:\/\/doi.org\/10.1016\/0550-3213(95)00158-O](https:\/\/doi.org\/10.1016\/0550-3213\\(95\\)00158-O)\n  .\n- Woit, Peter. \"Frequently Asked Questions \\| Not Even Wrong.\" *Not Even Wrong* (blog). Accessed January 17, 2022.\n  [https:\/\/www.math.columbia.edu\/~woit\/wordpress\/?page\\_id=4338](https:\/\/www.math.columbia.edu\/~woit\/wordpress\/?page_id=4338)\n  .\n- Wolchover, Natalie. \"Dark Energy May Be Incompatible With String Theory.\" Quanta Magazine, August 9, 2018.\n  [https:\/\/www.quantamagazine.org\/dark-energy-may-be-incompatible-with-string-theory-20180809\/](https:\/\/www.quantamagazine.org\/dark-energy-may-be-incompatible-with-string-theory-20180809\/)\n  .\n- Zayas, Leopoldo A. Pando. “A Microscopic Account of Black Hole Entropy.” *Physics* 13 (May 18, 2020): 80. <https:\/\/doi.org\/10.1103\/PhysRevX.10.021037>.\n\n**Share your thoughts**\n\n0\n\n0\n\n0\n\n0\n\nJoin the community\n\nJoin the Space.com Family! The best way to keep in touch and to be informed of our latest quizzes and competitions, as well as news and offers.\n\nAlready have an account? Log in\n\nMy Details\n\nUpdate your details below...\n\nKeep in the Know\n\nWould you like to be kept informed about new quizzes and offers from Future and its partners?\n\nValidate Your Mobile No.\n\nWe have sent a code to . Please enter it below to verify your account.\n\nUpdate Your Mobile No.\n\nYou may enter a new mobile number below. You will be sent a verification code to the phone number you provide.\n\nembed-reactions.hint\\_heading\n\nembed-reactions.hint\\_subheading\n\nValidate Your Email Address\n\nWe have sent a code to . Please enter it below to verify your account.\n\nUpdate Your Email Address\n\nYou may enter a new email address below. You will be sent a verification code to the address you provide.\n\nCreate a Username\n\nThis will be publicly viewable so make it something you like\\!\n\nReset your password\n\nEnter your email address below. 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Boilerpipe Text	String theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: Tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles. (Image credit: PASIEKA via Getty Images) String theory is the idea in theoretical physics that reality is made up of infinitesimal vibrating strings, smaller than atoms, electrons or quarks. According to this theory, as the strings vibrate, twist and fold, they produce effects in many, tiny dimensions that humans interpret as everything from particle physics to large-scale phenomena like gravity . String theory has been held up as a possible "theory of everything," a single framework that could unite general relativity and quantum mechanics , two theories that underlie almost all of modern physics. While quantum mechanics does very well in describing the behavior of very small things and general relativity works well to explain how very large things happen in the universe , they don't play nicely together. Some scientists think (or thought) that string theory could resolve the conundrums between the two, conquering one of the major remaining unsolved problems of physics. But after string theory gained prominence in the late 1960s and '70s, its popularity among theoretical physicists fluctuated, according to a lecture by California Institute of Technology physicist John Schwarz , widely considered one of the founders of string theory. After countless papers, conferences and dry-erase markers, the breathtaking breakthrough many once hoped for seems further away than ever. Nevertheless, the flurry of thought around the very idea of string theory has left a deep imprint on both physics and math. Like it or not (and some physicists certainly don't), string theory is here to stay. String theory FAQs answered by an expert We asked Nick Geiser, a theoretical physicist at UCLA, a few frequently asked questions about string theory. Nick Geiser is a PhD candidate in theoretical physics at UCLA and will join the University of Michigan as a Leinweber and Van Loo Postdoctoral Fellow, working with Professor Henriette Elvang in the Leinweber Center for Theoretical Physics in June 2023. Geiser's research spans several areas of theoretical high-energy physics centered around scattering amplitudes. Scattering amplitudes are fundamental objects in theoretical physics that can be measured in experiments and reveal deep connections between physics and pure mathematics. Outside of research, Geiser works with a variety of organizations to support under-represented minority groups in STEM fields. What is string theory? String theory is a collection of ideas in theoretical physics in which the fundamental building-blocks of nature are not particles (such as the point-like electron) but instead strings. Imagine microscopic wiggling rubber bands. String theory is primarily a theory of quantum gravity which elegantly combines the theories of gravity and quantum mechanics. Physicists have been searching for a theory of quantum gravity for nearly one hundred years. Moreover, ideas from string theory have been used to solve problems in mathematics and other fields of theoretical physics. In many ways, string theory is a language that can be used by theoretical physicists to solve problems and to investigate the mathematics of the universe. Who invented string theory? String theory was discovered by accident! In 1969, Italian physicist Gabriele Veneziano wrote down a formula describing the scattering of four strings, the now-famous Veneziano amplitude. Veneziano was trying to describe the physics of particles like the proton and neutron, not strings. In the following years, physicists around the world began to unravel string theory from that first formula. The full picture of string theory has become clearer over the following fifty years. There were several bursts of new ideas and deep insights in the 1970s, 1980s, and 1990s, and string theory is still an active field with thousands of researchers around the world. Has string theory been proven? No experiment has definitively proven string theory to be the fundamental theory of nature. However, the ideas of string theory have passed countless theoretical and mathematical tests over the last fifty years. Fundamental physics is a long-game. Einstein first predicted gravitational waves in 1915, and they were first detected by the LIGO experiment in 2015, one hundred years later! Future particle physics experiments, gravitational wave observatories, or cosmological measurements may offer definitive tests of string theory. How many dimensions are there in string theory? String theory predicts ten total spacetime dimensions, but we clearly live in a world with four dimensions (three space and one time)! Thankfully, it is not a problem to get from ten to four. Six of the dimensions predicted by string theory could be wrapped into a small compact shape. These compactified dimensions could then only be seen by a large, precise experiment like CERN's Large Hadron Collider . What is string theory? String theory is a framework that physicists use to describe how forces usually conceptualized on a gigantic level, like gravity, could affect tiny objects like electrons and protons. In Albert Einstein 's theory of general relativity, gravity is a force that warps space-time around massive objects. It's one of the four forces that physicists use to describe nature. But unlike the other forces (electromagnetism, the strong force and the weak force), gravity is so weak that it can't be detected or observed on the scale of a particle. Instead, its effects are only noticeable and important on the scale of moons, planets, stars and galaxies. Breaking space news, the latest updates on rocket launches, skywatching events and more! Gravity seems not to exist as a particle of its own, either. Theorists can predict what a gravity particle should look like, but when they try to calculate what happens when two such "gravitons" smash together, they get an infinite amount of energy packed into a small space — a sure sign, according to astrophysicist Paul Sutter in a previous article for Space.com , that the math is missing something. One possible solution, which theorists borrowed from nuclear physicists in the 1970s, is to get rid of the idea of problematic, point-like graviton particles. Strings, and only strings, can collide and rebound cleanly without implying physically impossible infinities. String theory math required six additional dimensions (for a total of 10) visible only to the little strings , much as a powerline looks like a 1D line to birds flying far overhead but a 3D cylinder to an ant crawling on the wire. (Image credit: Shutterstock) "A one-dimensional object — that's the thing that really tames the infinities that come up in the calculations," string theory expert Marika Taylor, a theoretical physicist at the University of Southampton in England, told Space.com. String theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles. A string of a particular length striking a particular note might gain the properties of a photon, another string folded and vibrating with a different frequency could play the role of a quark, and so on. In addition to taming gravity, string theory was attractive for its potential to explain so-called fundamental constants like the mass of an electron. The next step, theorists hoped, would be to find the right way to describe the folding and movement of strings, and everything else should have followed. But that initial simplicity turned out to come at the cost of unexpected complexity — string math didn't work in our familiar four dimensions (three of space and one of time). It needed a total of 10 dimensions , with six visible only to the perspective of the little strings, much as a powerline looks like a 1D line to birds flying far overhead but becomes a 3D cylinder to an ant crawling on the wire. How did string theory evolve? String theory today doesn't exactly match the string theory of the 1960s and '70s. Researchers disagree over whether, with modifications, it's still the best candidate for a "theory of everything" or whether theorists should abandon it in favor of other topics. "By 1973–'74 there were many good reasons to stop working on string theory," Schwarz wrote. Physicists' attention had turned from what felt like an unfruitful exploration of tiny undetectable "soft" strings and instead taken up more compelling evidence of hadrons, subatomic particles made up of quarks whose actions couldn't be explained by strings. "What had been a booming enterprise involving several hundred theorists rapidly came to a grinding halt," Schwarz wrote. "Only a few diehards continued to pursue it." Over the next decade, a few scientists continued to pursue five different versions of string theory. Over time, the researchers began to find unexpected connections between the five ideas, which Edward Witten, a theorist at the Institute for Advanced Study in Princeton, New Jersey, gathered up and presented at a 1995 string theory conference at the University of Southern California. Witten argued that the five string theories each represented an approximation of a more fundamental, 11-dimensional theory as it behaved in a particular situation, much as how Einstein's space- and time-bending theories of relativity match Newton's description of objects moving at normal speeds. That was the beginning of one string theory spin-off: M-theory. The "M" is likely inspired by higher-dimensional objects called membranes, Taylor said, but since the theory has no concrete mathematical equations, the "M" remains a placeholder with no official meaning. "It was really a parametrization of our ignorance," she said. Attempts to find those general equations that would work in every possible situation made little progress, but the alleged existence of the fundamental theory gave theorists the understanding and confidence needed to develop mathematical techniques for the five versions of string theory and apply them in the context where each theory worked. An artist's interpretation of string theory. (Image credit: Science Photo Library via Getty Images) Strings are far too small to detect with any conceivable technology, but one early theoretical success was physicists' ability to describe black hole entropy in a 1996 paper published in the journal Physics Letters . Entropy refers to the number of ways that you can arrange the parts of a system, but without being able to see into the impenetrable depths of a black hole, no one knows what type of particles might lie inside or what arrangements they can take. And yet, in the early 1970s, Stephen Hawking and others used the laws of thermodynamics and, according to an article published in 2020 in the journal Physics , quantum mechanics to calculate entropy inside a black hole, suggesting that black holes must have some sort of internal structure. What that structure might be, remained a mystery. Most attempts to describe the black hole's makeup fall short, but the configurations of hypothetical strings does the trick. "String theory has been able to give a spot-on counting," Taylor said — an actual possible explanation of black hole interiors, not just a rough idea. The string theory framework still faces many challenges, however: It produces an impossible number of ways to fold up the extra six dimensions. Every option seems to fit the broad features of the Standard Model that governs particle physics, with little hope of distinguishing which is the right one. Moreover, wrote astrophysicist Ethan Siegel in his blog Starts With a Bang , all of those models for managing the extra dimensions rely on an equivalence between force particles and matter particles called supersymmetry. But, just like the extra dimensions that string theory requires, we don't observe supersymmetry in our world. On top of those objections, it's not clear that string theory — M-theory or not — can ever be compatible with our modern understanding of an expanding universe, replete with dark energy, reported Quanta Magazine in 2018. A number of physicists, such as Peter Woit of Columbia University, view these divergences from reality as fatal flaws. "The basic problem with string theory unification research is not that progress has been slow over the past 30 years," he wrote on his blog , "but that it has been negative, with everything learned showing more clearly why the idea doesn't work." Taylor, however, maintains that today's models are overly simplistic, and that features like cosmological expansion and a lack of supersymmetry may someday be built into future versions. Taylor expects that, while the new era of gravitational-wave astronomy may bring new tidbits of information about quantum gravity, more progress will be made by continuing to follow the math deeper into string theory. "I have a theoretical bias," she said, "but I think the kind of breakthrough I'm describing would come from a chalkboard; from thought." Why is string theory still important? Regardless of whether string theory can ever be massaged into a "theory of everything," its legacy as a productive research program may be assured on mathematical merit alone. "It can't be a dead end in the sense of what we've learned just from mathematics itself," Taylor said. "If you told me tomorrow that the universe absolutely isn't supersymmetric and doesn't have 10 [spatial] dimensions, we've still connected whole branches of mathematics" using the string theory framework. In particular, when Witten and other researchers showed that the five-string theories were shadows of a single-parent theory, they highlighted connections called dualities, which have proven to be a major contribution to mathematics and physics. Dualities let mathematicians translate from one branch of math to another, attacking problems untenable in one framework by using calculations done in the other, for example in geometry and number theory. Other dualities have helped overcome challenges in quantum computing, according to Taylor. "It's not going to make your next-generation iPhone," she said, "But it may make your iPhone for the 22nd century." Whether string theory's ability to illuminate the dark web connecting different areas of math turns out to be a sign of its potential or just a lucky coincidence remains a subject of debate. Witten, speaking at the Institute for Advanced Study in 2019, acknowledged that while he no longer feels as confident as he once did that string theory will evolve into a complete physical theory, his gut tells him that the theory remains a productive field of research. "To me, it's implausible that humans stumbled by accident on[to] such an incredible structure that sheds so much light on established physical theories, and also on so many different branches of mathematics," he told the audience. "I have confidence that the general enterprise is on the right track, but I don't claim that the argument I've given is scientifically convincing." Additional resources Find more in-depth history and explanations of current string theory science at WhyStringTheory.com , a website created by graduate students at the University of Oxford and the University of Cambridge for the "interested layperson." Or, if you'd rather go right to the source, check out this CERN Courier interview with string theory originator Gabriele Veneziano. If you're looking for a video explainer, watch these two videos entitled " Why string theory is right " and " Why string theory is wrong ," both from PBS Digital Studios. Bibliography "Robbert Dijkgraaf and Edward Witten in Conversation - Videos \| Institute for Advanced Study," May 30, 2019. https://www.ias.edu/video/universe/2019/0529-DijkgraafWitten . Schwarz, John H. "The Early History of String Theory and Supersymmetry," January 4, 2012. https://arxiv.org/abs/1201.0981v1 . Siegel, Ethan. "Why Supersymmetry May Be The Greatest Failed Prediction In Particle Physics History." Forbes, February 12, 2019. https://www.forbes.com/sites/startswithabang/2019/02/12/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history/ . Strominger, A., and C. Vafa. "Microscopic Origin of the Bekenstein-Hawking Entropy." Physics Letters B 379, no. 1–4 (June 1996): 99–104. https://doi.org/10.1016/0370-2693(96)00345-0 . Witten, Edward. "String Theory Dynamics In Various Dimensions." Nuclear Physics B 443, no. 1–2 (June 1995): 85–126. https://doi.org/10.1016/0550-3213(95)00158-O . Woit, Peter. "Frequently Asked Questions \| Not Even Wrong." Not Even Wrong (blog). Accessed January 17, 2022. https://www.math.columbia.edu/~woit/wordpress/?page_id=4338 . Wolchover, Natalie. "Dark Energy May Be Incompatible With String Theory." Quanta Magazine, August 9, 2018. https://www.quantamagazine.org/dark-energy-may-be-incompatible-with-string-theory-20180809/ . Zayas, Leopoldo A. Pando. “A Microscopic Account of Black Hole Entropy.” Physics 13 (May 18, 2020): 80. https://doi.org/10.1103/PhysRevX.10.021037 . Share your thoughts 0 0 0 0 Join the community Join the Space.com Family! The best way to keep in touch and to be informed of our latest quizzes and competitions, as well as news and offers. Already have an account? Log in Log In Forgotten your password? Reset it Not got an account? Register My Details Update your details below... Keep in the Know Would you like to be kept informed about new quizzes and offers from Future and its partners? Validate Your Mobile No. We have sent a code to . Please enter it below to verify your account. Update mobile number Resend code Update Your Mobile No. You may enter a new mobile number below. You will be sent a verification code to the phone number you provide. Cancel embed-reactions.hint_heading embed-reactions.hint_subheading Validate Your Email Address We have sent a code to . Please enter it below to verify your account. Update email address Resend code Update Your Email Address You may enter a new email address below. You will be sent a verification code to the address you provide. Cancel Create a Username This will be publicly viewable so make it something you like! Reset your password Enter your email address below. If it is registered with us, we will email you a code that will allow you to reset your password. Check your inbox If your email address was found in our system, you should receive an email in the next few minutes containing a code. Enter that code below to reset your password. Set new password Please enter your new password below. Leaderboard Rank Player Score Time Charlie Wood is a freelance journalist covering physical sciences both on and off this pale blue dot. He contributes to Space.com and LiveScience, as well as Popular Science, Scientific American, Quanta Magazine, and others. These days he writes from New York but in previous lives he taught physics in Mozambique and science English in Japan. Find him on Twitter @walkingthedot.
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Physics behind the temperature of the universe ") [![Stargate\_MGM](https://cdn.mos.cms.futurecdn.net/Gy5YY89HNsbmqL53asZhg5.jpg) Space Movies & Shows Amazon's new 'Stargate' show raises big questions for the beloved sci-fi universe](https://www.space.com/entertainment/space-movies-shows/amazons-new-stargate-show-raises-big-questions-for-the-beloved-sci-fi-universe "Amazon's new 'Stargate' show raises big questions for the beloved sci-fi universe") [![An illustration shows the JWST in space next to its observations of some of the earliest galaxies ever seen, the so-called \"little red dots.\"](https://cdn.mos.cms.futurecdn.net/ExCZSbHLLaztex8gVgeUhE.png) Galaxies Are mysterious 'Little Red Dots' discovered by the James Webb Space Telescope actually baby galaxies under construction?](https://www.space.com/astronomy/galaxies/are-mysterious-little-red-dots-discovered-by-the-james-webb-space-telescope-actually-baby-galaxies-under-construction "Are mysterious 'Little Red Dots' discovered by the James Webb Space Telescope actually baby galaxies under construction?") [![The SETI Institute\&\#039;s Allen Telescope Array in Northern California searches for radio signals that could have been generated by intelligent alien life.](https://cdn.mos.cms.futurecdn.net/zjDgGzk64iR5Wu9fbZebEh.jpg) Search for Life Where are all the aliens? Maybe space weather is scrambling their transmissions](https://www.space.com/space-exploration/search-for-life/where-are-all-the-aliens-maybe-space-weather-is-scrambling-their-transmissions "Where are all the aliens? Maybe space weather is scrambling their transmissions") [![(Main) the galaxy Centaurus A as seen by the the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile (Inset) The velocities of galaxies in groups versus distance](https://cdn.mos.cms.futurecdn.net/5EaSWNDJ6VF5oFzJM74YJL.png) Astronomy How fast is the universe expanding? Astronomers may be one step closer to resolving 'Hubble trouble'](https://www.space.com/astronomy/how-fast-is-the-universe-expanding-astronomers-may-be-one-step-closer-to-resolving-hubble-trouble "How fast is the universe expanding? Astronomers may be one step closer to resolving 'Hubble trouble'") [![Pink structures looks like dots all across the image. There\&\#039;s a boxout that shows a magnified view of one section. 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How AI is revolutionizing our study of the cosmos") [![Screenshot from a new NASA animation highlighting some of the universe\&\#039;s biggest black holes, including the record-holding TON 618, which is about as massive as 60 billion suns.](https://cdn.mos.cms.futurecdn.net/LonKAe8kapjmivFoVTBLRX.jpeg) James Webb Space Telescope James Webb Space Telescope reveals new origin story for the universe's 1st supermassive black holes](https://www.space.com/astronomy/james-webb-space-telescope/james-webb-space-telescope-data-backs-new-origin-story-for-the-universes-1st-supermassive-black-holes "James Webb Space Telescope reveals new origin story for the universe's 1st supermassive black holes") [![Disney+ artwork from the 1979 sci-fi movie \"The Black Hole\"](https://cdn.mos.cms.futurecdn.net/NYGZnfUsBP6s3mFs2TW52i.jpg) Space Movies & Shows 'The Black Hole' was Disney's original response to 'Star Wars'. What the hell were they thinking?](https://www.space.com/entertainment/space-movies-shows/the-black-hole-was-disneys-original-response-to-star-wars-what-the-hell-were-they-thinking "'The Black Hole' was Disney's original response to 'Star Wars'. What the hell were they thinking?") [![A speculative illustration of tiny primordial black holes. Have physicists just seen one explode?](https://cdn.mos.cms.futurecdn.net/2zwJQfcoh55WtPyoSDqgc5.jpg) Black Holes Did astronomers see a black hole explode? An 'impossible' particle that hit Earth in 2023 may tell us](https://www.space.com/astronomy/black-holes/did-astronomers-see-a-black-hole-explode-an-impossible-particle-that-hit-earth-in-2023-may-tell-us "Did astronomers see a black hole explode? An 'impossible' particle that hit Earth in 2023 may tell us") [![An illustration shows two neutron stars colliding and merging](https://cdn.mos.cms.futurecdn.net/EhXSVTSQNkAoScgqAjASgG.png) Stars A state of matter last seen just after the Big Bang may exist inside neutron stars — and scientists think they can prove it](https://www.space.com/astronomy/stars/a-state-of-matter-last-seen-just-after-the-big-bang-may-exist-inside-neutron-stars-and-scientists-think-they-can-prove-it "A state of matter last seen just after the Big Bang may exist inside neutron stars — and scientists think they can prove it") [![bright white and blue dots of light on a black background, with clouds of faint light surrounding them](https://cdn.mos.cms.futurecdn.net/aywrqAGfthnXdftVScfVCf.jpg) Comets Could the remains of a 'dead' comet still be in the solar system? 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[Astronomy](https://www.space.com/astronomy) # What is string theory? [References](https://www.space.com/references) By [Vicky Stein](https://www.space.com/author/vicky-stein), [Charlie Wood](https://www.space.com/author/charlie-wood) last updated May 18, 2023 String theory might be the theory of everything… or a flawed framework for theoretical physics. When you purchase through links on our site, we may earn an affiliate commission. [Here’s how it works](https://www.space.com/41418-about-us.html#section-affiliate-advertising-disclosure). Click for next article ![Artist\&\#039;s illustration of string theory shows numerous colored strings in an abstract configuration.](https://cdn.mos.cms.futurecdn.net/ZUxv3mD76WxYbBwUUYJnV4.jpg) String theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: Tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles. (Image credit: PASIEKA via Getty Images) Jump to: - [String theory FAQs](https://www.space.com/17594-string-theory.html#section-string-theory-faqs-answered-by-an-expert) - [What is it?](https://www.space.com/17594-string-theory.html#section-what-is-string-theory) - [Evolution](https://www.space.com/17594-string-theory.html#section-how-did-string-theory-evolve) - [Importance](https://www.space.com/17594-string-theory.html#section-why-is-string-theory-still-important) - [Additional resources](https://www.space.com/17594-string-theory.html#section-additional-resources) Share - Copy link - [Facebook](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.space.com%2F17594-string-theory.html) - [X](https://twitter.com/intent/tweet?text=What+is+string+theory%3F+&url=https%3A%2F%2Fwww.space.com%2F17594-string-theory.html) - [Whatsapp](whatsapp://send?text=What+is+string+theory%3F++https%3A%2F%2Fwww.space.com%2F17594-string-theory.html?fwa) - [Reddit](https://www.reddit.com/submit?url=https%3A%2F%2Fwww.space.com%2F17594-string-theory.html&title=What+is+string+theory%3F+) - [Pinterest](https://pinterest.com/pin/create/button/?url=https%3A%2F%2Fwww.space.com%2F17594-string-theory.html&media=https%3A%2F%2Fcdn.mos.cms.futurecdn.net%2FZUxv3mD76WxYbBwUUYJnV4.jpg) - [Flipboard](https://share.flipboard.com/bookmarklet/popout?title=What+is+string+theory%3F+&url=https%3A%2F%2Fwww.space.com%2F17594-string-theory.html) - [Email](mailto:?subject=I%20found%20this%20webpage&body=Hi,%20I%20found%20this%20webpage%20and%20thought%20you%20might%20like%20it%20https://www.space.com/17594-string-theory.html) Share this article Join the conversation [Follow us](https://google.com/preferences/source?q=space.com) Add us as a preferred source on Google Newsletter Get the Space.com Newsletter Breaking space news, the latest updates on rocket launches, skywatching events and more\! * By signing up, you agree to our [Terms of services](https:\/\/futureplc.com\/terms-conditions\/) and acknowledge that you have read our [Privacy Notice](https:\/\/futureplc.com\/privacy-policy\/). You also agree to receive marketing emails from us that may include promotions from our trusted partners and sponsors, which you can unsubscribe from at any time. You are now subscribed Your newsletter sign-up was successful * Want to add more newsletters? ![Daily Newsletter](https://cdn.mos.cms.futurecdn.net/vfpcxVDrtfCysGSjzYjeSg.png) Delivered daily Daily Newsletter Breaking space news, the latest updates on rocket launches, skywatching events and more\! Subscribe + ![Watch This Space](https://cdn.mos.cms.futurecdn.net/tjzmFi262iKuxrcCtSghKg.jpg) Once a month Watch This Space Sign up to our monthly entertainment newsletter to keep up with all our coverage of the latest sci-fi and space movies, tv shows, games and books. Subscribe + ![Night Sky This Week](https://cdn.mos.cms.futurecdn.net/qsHaEcQ6H695rhBoNZdK5g.jpg) Once a week Night Sky This Week Discover this week's must-see night sky events, moon phases, and stunning astrophotos. Sign up for our skywatching newsletter and explore the universe with us\! Subscribe + ![Strange New Words](https://cdn.mos.cms.futurecdn.net/Mk2LrCm68RFHzQhNyQaH2Y.jpg) Twice a month Strange New Words Space.com's Sci-Fi Reader's Club. Read a sci-fi short story every month and join a virtual community of fellow science fiction fans\! Subscribe + *** An account already exists for this email address, please log in. Subscribe to our newsletter String theory is the idea in theoretical physics that reality is made up of infinitesimal vibrating strings, smaller than atoms, electrons or quarks. According to this theory, as the strings vibrate, twist and fold, they produce effects in many, tiny dimensions that humans interpret as everything from particle physics to large-scale phenomena like [gravity](https://www.space.com/classical-gravity.html). String theory has been held up as a possible "theory of everything," a single framework that could unite [general relativity](https://www.space.com/17661-theory-general-relativity.html) and [quantum mechanics](https://www.livescience.com/33816-quantum-mechanics-explanation.html), two theories that underlie almost all of modern physics. While quantum mechanics does very well in describing the behavior of very small things and general relativity works well to explain how very large things happen in [the universe](https://www.space.com/52-the-expanding-universe-from-the-big-bang-to-today.html), they don't play nicely together. Some scientists think (or thought) that string theory could resolve the conundrums between the two, conquering one of the major remaining unsolved problems of physics. But after string theory gained prominence in the late 1960s and '70s, its popularity among theoretical physicists fluctuated, according to a lecture by California Institute of Technology physicist [John Schwarz](https://arxiv.org/abs/1201.0981), widely considered one of the founders of string theory. After countless papers, conferences and dry-erase markers, the breathtaking breakthrough many once hoped for seems further away than ever. You may like - [![A series of blue and red and green and orange analog clocks all superimposed on each other](https://cdn.mos.cms.futurecdn.net/wECuuHE7jxzT73orWxpY5.jpg) Is time a fundamental part of reality? A quiet revolution in physics suggests not](https://www.space.com/science/particle-physics/is-time-a-fundamental-part-of-reality-a-quiet-revolution-in-physics-suggests-not) - [![The galaxy Messier 33 according to competing models of the universe (left) with a dark matter halo (right) without a bubble of this mysterious \"stuff.\"](https://cdn.mos.cms.futurecdn.net/ug3qTXVQFJFGSaFGH9hnzh.png) Does dark matter actually exist? New theory says it could be gravity behaving strangely](https://www.space.com/astronomy/dark-universe/does-dark-matter-actually-exist-new-theory-says-it-could-be-gravity-behaving-strangely) - [![An illustration of matter pouring into a black hole, crossing an Einstein-Rosen bridge and emerging in another region of the universe](https://cdn.mos.cms.futurecdn.net/QiqgvSVLR8GjPCQ4fEyjHa.png) Wormholes may not exist – we've found they reveal something deeper about time and the universe](https://www.space.com/astronomy/wormholes-may-not-exist-weve-found-they-reveal-something-deeper-about-time-and-the-universe) Nevertheless, the flurry of thought around the very idea of string theory has left a deep imprint on both physics and math. Like it or not (and some physicists certainly don't), string theory is here to stay. [Click here for more Space.com videos...](https://videos.space.com/m/OXcbz76g/string-theory-examined-with-nasas-chandra-x-ray-observatory-observations?list=9wzCTV4g) ## String theory FAQs answered by an expert We asked Nick Geiser, a theoretical physicist at UCLA, a few frequently asked questions about string theory. ![Nick Geiser in front of a blackboard.](https://cdn.mos.cms.futurecdn.net/ijuYubKj7AU3iL3mPmm5Rk.jpeg) Nick Geiser Theoretical physicist Nick Geiser is a PhD candidate in theoretical physics at UCLA and will join the University of Michigan as a Leinweber and Van Loo Postdoctoral Fellow, working with Professor Henriette Elvang in the Leinweber Center for Theoretical Physics in June 2023. Geiser's research spans several areas of theoretical high-energy physics centered around scattering amplitudes. Scattering amplitudes are fundamental objects in theoretical physics that can be measured in experiments and reveal deep connections between physics and pure mathematics. Outside of research, Geiser works with a variety of organizations to support under-represented minority groups in STEM fields. ### What is string theory? String theory is a collection of ideas in theoretical physics in which the fundamental building-blocks of nature are not particles (such as the point-like electron) but instead strings. Imagine microscopic wiggling rubber bands. String theory is primarily a theory of [quantum gravity](https://www.space.com/quantum-gravity.html) which elegantly combines the theories of gravity and quantum mechanics. Physicists have been searching for a theory of quantum gravity for nearly one hundred years. Moreover, ideas from string theory have been used to solve problems in mathematics and other fields of theoretical physics. In many ways, string theory is a language that can be used by theoretical physicists to solve problems and to investigate the mathematics of the universe. ### Who invented string theory? String theory was discovered by accident! In 1969, Italian physicist Gabriele Veneziano wrote down a formula describing the scattering of four strings, the now-famous Veneziano amplitude. Veneziano was trying to describe the physics of particles like the [proton](https://www.space.com/protons-facts-discovery-charge-mass) and neutron, not strings. In the following years, physicists around the world began to unravel string theory from that first formula. The full picture of string theory has become clearer over the following fifty years. There were several bursts of new ideas and deep insights in the 1970s, 1980s, and 1990s, and string theory is still an active field with thousands of researchers around the world. ### Has string theory been proven? No experiment has definitively proven string theory to be the fundamental theory of nature. However, the ideas of string theory have passed countless theoretical and mathematical tests over the last fifty years. Fundamental physics is a long-game. Einstein first predicted [gravitational waves](https://www.space.com/25088-gravitational-waves.html) in 1915, and they were first detected by the [LIGO](https://www.space.com/LIGO-Laser-Interferometer-Gravitational-Wave-Observatory.html) experiment in 2015, one hundred years later! Future particle physics experiments, gravitational wave observatories, or cosmological measurements may offer definitive tests of string theory. ### How many dimensions are there in string theory? String theory predicts ten total spacetime dimensions, but we clearly live in a world with four dimensions (three space and one time)! Thankfully, it is not a problem to get from ten to four. Six of the dimensions predicted by string theory could be wrapped into a small compact shape. These compactified dimensions could then only be seen by a large, precise experiment like CERN's [Large Hadron Collider](https://www.space.com/large-hadron-collider-particle-accelerator). ## What is string theory? String theory is a framework that physicists use to describe how forces usually conceptualized on a gigantic level, like gravity, could affect tiny objects like electrons and protons. In [Albert Einstein](https://www.space.com/15524-albert-einstein.html)'s theory of general relativity, gravity is a force that warps space-time around massive objects. It's one of the [four forces](https://www.livescience.com/the-fundamental-forces-of-nature.html) that physicists use to describe nature. But unlike the other forces (electromagnetism, the strong force and the weak force), gravity is so weak that it can't be detected or observed on the scale of a particle. Instead, its effects are only noticeable and important on the scale of moons, planets, stars and galaxies. Get the Space.com Newsletter Breaking space news, the latest updates on rocket launches, skywatching events and more\! By signing up, you agree to our [Terms of services](https:\/\/futureplc.com\/terms-conditions\/) and acknowledge that you have read our [Privacy Notice](https:\/\/futureplc.com\/privacy-policy\/). You also agree to receive marketing emails from us that may include promotions from our trusted partners and sponsors, which you can unsubscribe from at any time. Gravity seems not to exist as a particle of its own, either. Theorists can predict what a gravity particle should look like, but when they try to calculate what happens when two such "gravitons" smash together, they get an infinite amount of energy packed into a small space — a sure sign, according to astrophysicist Paul Sutter in a [previous article for Space.com](https://www.space.com/32147-why-is-gravity-so-hard-to-understand.html), that the math is missing something. One possible solution, which theorists borrowed from nuclear physicists in the 1970s, is to get rid of the idea of problematic, point-like graviton particles. Strings, and only strings, can collide and rebound cleanly without implying physically impossible infinities. [![Tangled yarn to represent the complexity of string theory.](https://cdn.mos.cms.futurecdn.net/mCY6r3XpvQYrGyb28ENwcM.jpg)]() String theory math required six additional dimensions (for a total of 10) [visible only to the little strings](https://www.space.com/41947-gravitational-waves-reveal-no-extra-dimensions.html), much as a powerline looks like a 1D line to birds flying far overhead but a 3D cylinder to an ant crawling on the wire. (Image credit: Shutterstock) "A one-dimensional object — that's the thing that really tames the infinities that come up in the calculations," string theory expert Marika Taylor, a theoretical physicist at the University of Southampton in England, told Space.com. What to read next - [![A cylinder-like shape with stars within. There\&\#039;s a glow toward the left and a grid pattern all around it.](https://cdn.mos.cms.futurecdn.net/SmcBfLjCAEkg9NziAM9CuH.png) How fast is the universe actually expanding? Ripples in spacetime could finally solve 'Hubble tension'](https://www.space.com/astronomy/how-fast-is-the-universe-actually-expanding-ripples-in-spacetime-could-finally-solve-hubble-tension) - [![Screenshot from a new NASA animation highlighting some of the universe\&\#039;s biggest black holes, including the record-holding TON 618, which is about as massive as 60 billion suns.](https://cdn.mos.cms.futurecdn.net/LonKAe8kapjmivFoVTBLRX.jpeg) James Webb Space Telescope reveals new origin story for the universe's 1st supermassive black holes](https://www.space.com/astronomy/james-webb-space-telescope/james-webb-space-telescope-data-backs-new-origin-story-for-the-universes-1st-supermassive-black-holes) - [![An illustration shows dark matter powering the heart of a spiral galaxy](https://cdn.mos.cms.futurecdn.net/69kRCSZKQ5H5nddwqCTGR3.png) Could the Milky Way galaxy's supermassive black hole actually be a clump of dark matter?](https://www.space.com/astronomy/dark-universe/could-the-milky-way-galaxys-supermassive-black-hole-actually-be-a-clump-of-dark-matter) String theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles. A string of a particular length striking a particular note might gain the properties of a photon, another string folded and vibrating with a different frequency could play the role of a quark, and so on. In addition to taming gravity, string theory was attractive for its potential to explain so-called fundamental constants like the mass of an electron. The next step, theorists hoped, would be to find the right way to describe the folding and movement of strings, and everything else should have followed. But that initial simplicity turned out to come at the cost of unexpected complexity — string math didn't work in our familiar four dimensions (three of space and one of time). It needed a total of [10 dimensions](https://www.space.com/41947-gravitational-waves-reveal-no-extra-dimensions.html), with six visible only to the perspective of the little strings, much as a powerline looks like a 1D line to birds flying far overhead but becomes a 3D cylinder to an ant crawling on the wire. [Click here for more Space.com videos...](https://videos.space.com/m/jMcp2B0n/all-quantum-gravity-theories-suck-heres-why?list=9wzCTV4g) ## How did string theory evolve? String theory today doesn't exactly match the string theory of the 1960s and '70s. Researchers disagree over whether, with modifications, it's still the best candidate for a "theory of everything" or whether theorists should abandon it in favor of other topics. "By 1973–'74 there were many good reasons to stop working on string theory," Schwarz wrote. Physicists' attention had turned from what felt like an unfruitful exploration of tiny undetectable "soft" strings and instead taken up more compelling evidence of hadrons, subatomic particles made up of quarks whose actions couldn't be explained by strings. "What had been a booming enterprise involving several hundred theorists rapidly came to a grinding halt," Schwarz wrote. "Only a few diehards continued to pursue it." Over the next decade, a few scientists continued to pursue five different versions of string theory. Over time, the researchers began to find unexpected connections between the five ideas, which Edward Witten, a theorist at the Institute for Advanced Study in Princeton, New Jersey, gathered up and presented at a [1995 string theory conference](https://arxiv.org/abs/hep-th/9503124) at the University of Southern California. Witten argued that the five string theories each represented an approximation of a more fundamental, 11-dimensional theory as it behaved in a particular situation, much as how Einstein's space- and time-bending theories of relativity match Newton's description of objects moving at normal speeds. That was the beginning of one string theory spin-off: M-theory. The "M" is likely inspired by higher-dimensional objects called membranes, Taylor said, but since the theory has no concrete mathematical equations, the "M" remains a placeholder with no official meaning. "It was really a parametrization of our ignorance," she said. Attempts to find those general equations that would work in every possible situation made little progress, but the alleged existence of the fundamental theory gave theorists the understanding and confidence needed to develop mathematical techniques for the five versions of string theory and apply them in the context where each theory worked. [![string theory illustration shows numerous strings in an abstract shape configuration.](https://cdn.mos.cms.futurecdn.net/3JBXDjWtgHGtY4UjFCzszS.jpg)]() An artist's interpretation of string theory. (Image credit: Science Photo Library via Getty Images) Strings are far too small to detect with any conceivable technology, but one early theoretical success was physicists' ability to describe black hole entropy in a 1996 paper published in the journal [Physics Letters](https://arxiv.org/abs/hep-th/9601029). Entropy refers to the number of ways that you can arrange the parts of a system, but without being able to see into the impenetrable depths of a black hole, no one knows what type of particles might lie inside or what arrangements they can take. And yet, in the early 1970s, [Stephen Hawking](https://www.space.com/15923-stephen-hawking.html) and others used the laws of thermodynamics and, according to an article published in 2020 in the journal [Physics](https://physics.aps.org/articles/v13/80), quantum mechanics to calculate entropy inside a black hole, suggesting that black holes must have some sort of internal structure. What that structure might be, remained a mystery. Most attempts to describe the black hole's makeup fall short, but the configurations of hypothetical strings does the trick. "String theory has been able to give a spot-on counting," Taylor said — an actual possible explanation of black hole interiors, not just a rough idea. The string theory framework still faces many challenges, however: It produces an impossible number of ways to fold up the extra six dimensions. Every option seems to fit the broad features of the Standard Model that governs particle physics, with little hope of distinguishing which is the right one. Moreover, wrote astrophysicist Ethan Siegel in his blog [Starts With a Bang](https://www.forbes.com/sites/startswithabang/2019/02/12/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history/), all of those models for managing the extra dimensions rely on an equivalence between force particles and matter particles called supersymmetry. But, just like the extra dimensions that string theory requires, we don't observe supersymmetry in our world. On top of those objections, it's not clear that string theory — M-theory or not — can ever be compatible with our modern understanding of an expanding universe, replete with dark energy, reported [Quanta Magazine](https://www.quantamagazine.org/dark-energy-may-be-incompatible-with-string-theory-20180809/) in 2018. A number of physicists, such as Peter Woit of Columbia University, view these divergences from reality as fatal flaws. "The basic problem with string theory unification research is not that progress has been slow over the past 30 years," he wrote on his [blog](http://www.math.columbia.edu/~woit/wordpress/?page_id=4338), "but that it has been negative, with everything learned showing more clearly why the idea doesn't work." Taylor, however, maintains that today's models are overly simplistic, and that features like [cosmological expansion](https://www.space.com/16042-cosmology.html) and a lack of supersymmetry may someday be built into future versions. Taylor expects that, while the new era of [gravitational-wave astronomy](https://www.space.com/LIGO-Laser-Interferometer-Gravitational-Wave-Observatory.html) may bring new tidbits of information about quantum gravity, more progress will be made by continuing to follow the math deeper into string theory. "I have a theoretical bias," she said, "but I think the kind of breakthrough I'm describing would come from a chalkboard; from thought." [Click here for more Space.com videos...](https://videos.space.com/m/0rBxIHZF/theory-of-everything-tested-with-perseus-galaxy-cluster-observations?list=9wzCTV4g) ## Why is string theory still important? Regardless of whether string theory can ever be massaged into a "theory of everything," its legacy as a productive research program may be assured on mathematical merit alone. "It can't be a dead end in the sense of what we've learned just from mathematics itself," Taylor said. "If you told me tomorrow that the universe absolutely isn't supersymmetric and doesn't have 10 \[spatial\] dimensions, we've still connected whole branches of mathematics" using the string theory framework. In particular, when Witten and other researchers showed that the five-string theories were shadows of a single-parent theory, they highlighted connections called dualities, which have proven to be a major contribution to mathematics and physics. Dualities let mathematicians translate from one branch of math to another, attacking problems untenable in one framework by using calculations done in the other, for example in geometry and number theory. Other dualities have helped overcome challenges in quantum computing, according to Taylor. "It's not going to make your next-generation iPhone," she said, "But it may make your iPhone for the 22nd century." Whether string theory's ability to illuminate the dark web connecting different areas of math turns out to be a sign of its potential or just a lucky coincidence remains a subject of debate. Witten, speaking at the [Institute for Advanced Study](https://video.ias.edu/universe/2019/0529-DijkgraafWitten) in 2019, acknowledged that while he no longer feels as confident as he once did that string theory will evolve into a complete physical theory, his gut tells him that the theory remains a productive field of research. "To me, it's implausible that humans stumbled by accident on\[to\] such an incredible structure that sheds so much light on established physical theories, and also on so many different branches of mathematics," he told the audience. "I have confidence that the general enterprise is on the right track, but I don't claim that the argument I've given is scientifically convincing." ## Additional resources Find more in-depth history and explanations of current string theory science at [WhyStringTheory.com](http://whystringtheory.com/), a website created by graduate students at the University of Oxford and the University of Cambridge for the "interested layperson." Or, if you'd rather go right to the source, check out this [CERN Courier](https://cerncourier.com/a/the-roots-and-fruits-of-string-theory/) interview with string theory originator Gabriele Veneziano. If you're looking for a video explainer, watch these two videos entitled "[Why string theory is right](https://www.youtube.com/watch?v=iTTa9YcTe1k)" and "[Why string theory is wrong](https://www.youtube.com/watch?v=IhpGdumLRqs)," both from PBS Digital Studios. ### Bibliography - "Robbert Dijkgraaf and Edward Witten in Conversation - Videos \\| Institute for Advanced Study," May 30, 2019. [https://www.ias.edu/video/universe/2019/0529-DijkgraafWitten](https://www.ias.edu/video/universe/2019/0529-DijkgraafWitten) . - Schwarz, John H. "The Early History of String Theory and Supersymmetry," January 4, 2012. [https://arxiv.org/abs/1201.0981v1](https://arxiv.org/abs/1201.0981v1) . - Siegel, Ethan. "Why Supersymmetry May Be The Greatest Failed Prediction In Particle Physics History." Forbes, February 12, 2019. [https://www.forbes.com/sites/startswithabang/2019/02/12/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history/](https://www.forbes.com/sites/startswithabang/2019/02/12/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history/) . - Strominger, A., and C. Vafa. "Microscopic Origin of the Bekenstein-Hawking Entropy." Physics Letters B 379, no. 1–4 (June 1996): 99–104. [https://doi.org/10.1016/0370-2693(96)00345-0](https://doi.org/10.1016/0370-2693\(96\)00345-0) . - Witten, Edward. "String Theory Dynamics In Various Dimensions." Nuclear Physics B 443, no. 1–2 (June 1995): 85–126. [https://doi.org/10.1016/0550-3213(95)00158-O](https://doi.org/10.1016/0550-3213\(95\)00158-O) . - Woit, Peter. "Frequently Asked Questions \\| Not Even Wrong." Not Even Wrong (blog). Accessed January 17, 2022. [https://www.math.columbia.edu/~woit/wordpress/?page\_id=4338](https://www.math.columbia.edu/~woit/wordpress/?page_id=4338) . - Wolchover, Natalie. "Dark Energy May Be Incompatible With String Theory." Quanta Magazine, August 9, 2018. [https://www.quantamagazine.org/dark-energy-may-be-incompatible-with-string-theory-20180809/](https://www.quantamagazine.org/dark-energy-may-be-incompatible-with-string-theory-20180809/) . - Zayas, Leopoldo A. Pando. “A Microscopic Account of Black Hole Entropy.” Physics 13 (May 18, 2020): 80. <https://doi.org/10.1103/PhysRevX.10.021037>. Share your thoughts 0 0 0 0 Random QuizPlay a Random Quiz Filter by Category Join the community Join the Space.com Family! The best way to keep in touch and to be informed of our latest quizzes and competitions, as well as news and offers. I'm in\! Not right now Already have an account? Log in This page will close automatically once you have completed the authorisation process My Details Update your details below... Keep in the Know Would you like to be kept informed about new quizzes and offers from Future and its partners? 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Leaderboard \| Rank \| Player \| Score \| Time \| \|---\|---\|---\|---\| Log In or Register More Quizzes Log Out ![Charlie Wood](https://cdn.mos.cms.futurecdn.net/zUzE8S2ta7yMZa3HBYB6gW.jpg) [Charlie Wood](https://www.space.com/author/charlie-wood) Social Links Navigation Space.com contributor Charlie Wood is a freelance journalist covering physical sciences both on and off this pale blue dot. He contributes to Space.com and LiveScience, as well as Popular Science, Scientific American, Quanta Magazine, and others. These days he writes from New York but in previous lives he taught physics in Mozambique and science English in Japan. Find him on Twitter @walkingthedot. Read more [![A series of blue and red and green and orange analog clocks all superimposed on each other](https://cdn.mos.cms.futurecdn.net/wECuuHE7jxzT73orWxpY5.jpg) Particle Physics Is time a fundamental part of reality? 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New theory says it could be gravity behaving strangely") [![An illustration of matter pouring into a black hole, crossing an Einstein-Rosen bridge and emerging in another region of the universe](https://cdn.mos.cms.futurecdn.net/QiqgvSVLR8GjPCQ4fEyjHa.png) Astronomy Wormholes may not exist – we've found they reveal something deeper about time and the universe](https://www.space.com/astronomy/wormholes-may-not-exist-weve-found-they-reveal-something-deeper-about-time-and-the-universe "Wormholes may not exist – we've found they reveal something deeper about time and the universe") [![A cylinder-like shape with stars within. There\&\#039;s a glow toward the left and a grid pattern all around it.](https://cdn.mos.cms.futurecdn.net/SmcBfLjCAEkg9NziAM9CuH.png) Astronomy How fast is the universe actually expanding? 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Ripples in spacetime could finally solve 'Hubble tension'") [![Screenshot from a new NASA animation highlighting some of the universe\&\#039;s biggest black holes, including the record-holding TON 618, which is about as massive as 60 billion suns.](https://cdn.mos.cms.futurecdn.net/LonKAe8kapjmivFoVTBLRX.jpeg) James Webb Space Telescope James Webb Space Telescope reveals new origin story for the universe's 1st supermassive black holes](https://www.space.com/astronomy/james-webb-space-telescope/james-webb-space-telescope-data-backs-new-origin-story-for-the-universes-1st-supermassive-black-holes "James Webb Space Telescope reveals new origin story for the universe's 1st supermassive black holes") [![An illustration shows dark matter powering the heart of a spiral galaxy](https://cdn.mos.cms.futurecdn.net/69kRCSZKQ5H5nddwqCTGR3.png) Dark Universe Could the Milky Way galaxy's supermassive black hole actually be a clump of dark matter?](https://www.space.com/astronomy/dark-universe/could-the-milky-way-galaxys-supermassive-black-hole-actually-be-a-clump-of-dark-matter "Could the Milky Way galaxy's supermassive black hole actually be a clump of dark matter?") 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") [![Three sci-fi couples kissing: Peter Quill \& Gamora, Han Solo \& Leia, and Nurse Chapel \& Spock](https://cdn.mos.cms.futurecdn.net/H7cVHj3rhDjqbYimbms8PP.jpg) Space Movies & Shows The 8 best sci-fi couples to emulate this Valentine's Day](https://www.space.com/entertainment/space-movies-shows/best-sci-fi-couples "The 8 best sci-fi couples to emulate this Valentine's Day") [![Hero art for Halo: Campaign Evolved, the remake of Halo: Combat Evolved.](https://cdn.mos.cms.futurecdn.net/35Das3N4fRZYLKCqwiyaud.jpg) Space Games Halo: Campaign Evolved: Release date rumors, platforms, and everything else we know about the Halo remake](https://www.space.com/entertainment/space-games/halo-campaign-evolved-release-date-rumors-platforms-and-everything-else-we-know-about-the-halo-remake "Halo: Campaign Evolved: Release date rumors, platforms, and everything else we know about the Halo remake") MORE FROM SPACE... 1. 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Readable Markdown	![Artist\&\#039;s illustration of string theory shows numerous colored strings in an abstract configuration.](https://cdn.mos.cms.futurecdn.net/ZUxv3mD76WxYbBwUUYJnV4.jpg) String theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: Tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles. (Image credit: PASIEKA via Getty Images) String theory is the idea in theoretical physics that reality is made up of infinitesimal vibrating strings, smaller than atoms, electrons or quarks. According to this theory, as the strings vibrate, twist and fold, they produce effects in many, tiny dimensions that humans interpret as everything from particle physics to large-scale phenomena like [gravity](https://www.space.com/classical-gravity.html). String theory has been held up as a possible "theory of everything," a single framework that could unite [general relativity](https://www.space.com/17661-theory-general-relativity.html) and [quantum mechanics](https://www.livescience.com/33816-quantum-mechanics-explanation.html), two theories that underlie almost all of modern physics. While quantum mechanics does very well in describing the behavior of very small things and general relativity works well to explain how very large things happen in [the universe](https://www.space.com/52-the-expanding-universe-from-the-big-bang-to-today.html), they don't play nicely together. Some scientists think (or thought) that string theory could resolve the conundrums between the two, conquering one of the major remaining unsolved problems of physics. But after string theory gained prominence in the late 1960s and '70s, its popularity among theoretical physicists fluctuated, according to a lecture by California Institute of Technology physicist [John Schwarz](https://arxiv.org/abs/1201.0981), widely considered one of the founders of string theory. After countless papers, conferences and dry-erase markers, the breathtaking breakthrough many once hoped for seems further away than ever. Nevertheless, the flurry of thought around the very idea of string theory has left a deep imprint on both physics and math. Like it or not (and some physicists certainly don't), string theory is here to stay. ## String theory FAQs answered by an expert We asked Nick Geiser, a theoretical physicist at UCLA, a few frequently asked questions about string theory. ![Nick Geiser in front of a blackboard.](https://cdn.mos.cms.futurecdn.net/ijuYubKj7AU3iL3mPmm5Rk.jpeg) Nick Geiser is a PhD candidate in theoretical physics at UCLA and will join the University of Michigan as a Leinweber and Van Loo Postdoctoral Fellow, working with Professor Henriette Elvang in the Leinweber Center for Theoretical Physics in June 2023. Geiser's research spans several areas of theoretical high-energy physics centered around scattering amplitudes. Scattering amplitudes are fundamental objects in theoretical physics that can be measured in experiments and reveal deep connections between physics and pure mathematics. Outside of research, Geiser works with a variety of organizations to support under-represented minority groups in STEM fields. ### What is string theory? String theory is a collection of ideas in theoretical physics in which the fundamental building-blocks of nature are not particles (such as the point-like electron) but instead strings. Imagine microscopic wiggling rubber bands. String theory is primarily a theory of [quantum gravity](https://www.space.com/quantum-gravity.html) which elegantly combines the theories of gravity and quantum mechanics. Physicists have been searching for a theory of quantum gravity for nearly one hundred years. Moreover, ideas from string theory have been used to solve problems in mathematics and other fields of theoretical physics. In many ways, string theory is a language that can be used by theoretical physicists to solve problems and to investigate the mathematics of the universe. ### Who invented string theory? String theory was discovered by accident! In 1969, Italian physicist Gabriele Veneziano wrote down a formula describing the scattering of four strings, the now-famous Veneziano amplitude. Veneziano was trying to describe the physics of particles like the [proton](https://www.space.com/protons-facts-discovery-charge-mass) and neutron, not strings. In the following years, physicists around the world began to unravel string theory from that first formula. The full picture of string theory has become clearer over the following fifty years. There were several bursts of new ideas and deep insights in the 1970s, 1980s, and 1990s, and string theory is still an active field with thousands of researchers around the world. ### Has string theory been proven? No experiment has definitively proven string theory to be the fundamental theory of nature. However, the ideas of string theory have passed countless theoretical and mathematical tests over the last fifty years. Fundamental physics is a long-game. Einstein first predicted [gravitational waves](https://www.space.com/25088-gravitational-waves.html) in 1915, and they were first detected by the [LIGO](https://www.space.com/LIGO-Laser-Interferometer-Gravitational-Wave-Observatory.html) experiment in 2015, one hundred years later! Future particle physics experiments, gravitational wave observatories, or cosmological measurements may offer definitive tests of string theory. ### How many dimensions are there in string theory? String theory predicts ten total spacetime dimensions, but we clearly live in a world with four dimensions (three space and one time)! Thankfully, it is not a problem to get from ten to four. Six of the dimensions predicted by string theory could be wrapped into a small compact shape. These compactified dimensions could then only be seen by a large, precise experiment like CERN's [Large Hadron Collider](https://www.space.com/large-hadron-collider-particle-accelerator). ## What is string theory? String theory is a framework that physicists use to describe how forces usually conceptualized on a gigantic level, like gravity, could affect tiny objects like electrons and protons. In [Albert Einstein](https://www.space.com/15524-albert-einstein.html)'s theory of general relativity, gravity is a force that warps space-time around massive objects. It's one of the [four forces](https://www.livescience.com/the-fundamental-forces-of-nature.html) that physicists use to describe nature. But unlike the other forces (electromagnetism, the strong force and the weak force), gravity is so weak that it can't be detected or observed on the scale of a particle. Instead, its effects are only noticeable and important on the scale of moons, planets, stars and galaxies. Breaking space news, the latest updates on rocket launches, skywatching events and more\! Gravity seems not to exist as a particle of its own, either. Theorists can predict what a gravity particle should look like, but when they try to calculate what happens when two such "gravitons" smash together, they get an infinite amount of energy packed into a small space — a sure sign, according to astrophysicist Paul Sutter in a [previous article for Space.com](https://www.space.com/32147-why-is-gravity-so-hard-to-understand.html), that the math is missing something. One possible solution, which theorists borrowed from nuclear physicists in the 1970s, is to get rid of the idea of problematic, point-like graviton particles. Strings, and only strings, can collide and rebound cleanly without implying physically impossible infinities. [![Tangled yarn to represent the complexity of string theory.](https://cdn.mos.cms.futurecdn.net/mCY6r3XpvQYrGyb28ENwcM.jpg)]() String theory math required six additional dimensions (for a total of 10) [visible only to the little strings](https://www.space.com/41947-gravitational-waves-reveal-no-extra-dimensions.html), much as a powerline looks like a 1D line to birds flying far overhead but a 3D cylinder to an ant crawling on the wire. (Image credit: Shutterstock) "A one-dimensional object — that's the thing that really tames the infinities that come up in the calculations," string theory expert Marika Taylor, a theoretical physicist at the University of Southampton in England, told Space.com. String theory turns the page on the standard description of the universe by replacing all matter and force particles with just one element: tiny vibrating strings that twist and turn in complicated ways that, from our perspective, look like particles. A string of a particular length striking a particular note might gain the properties of a photon, another string folded and vibrating with a different frequency could play the role of a quark, and so on. In addition to taming gravity, string theory was attractive for its potential to explain so-called fundamental constants like the mass of an electron. The next step, theorists hoped, would be to find the right way to describe the folding and movement of strings, and everything else should have followed. But that initial simplicity turned out to come at the cost of unexpected complexity — string math didn't work in our familiar four dimensions (three of space and one of time). It needed a total of [10 dimensions](https://www.space.com/41947-gravitational-waves-reveal-no-extra-dimensions.html), with six visible only to the perspective of the little strings, much as a powerline looks like a 1D line to birds flying far overhead but becomes a 3D cylinder to an ant crawling on the wire. ## How did string theory evolve? String theory today doesn't exactly match the string theory of the 1960s and '70s. Researchers disagree over whether, with modifications, it's still the best candidate for a "theory of everything" or whether theorists should abandon it in favor of other topics. "By 1973–'74 there were many good reasons to stop working on string theory," Schwarz wrote. Physicists' attention had turned from what felt like an unfruitful exploration of tiny undetectable "soft" strings and instead taken up more compelling evidence of hadrons, subatomic particles made up of quarks whose actions couldn't be explained by strings. "What had been a booming enterprise involving several hundred theorists rapidly came to a grinding halt," Schwarz wrote. "Only a few diehards continued to pursue it." Over the next decade, a few scientists continued to pursue five different versions of string theory. Over time, the researchers began to find unexpected connections between the five ideas, which Edward Witten, a theorist at the Institute for Advanced Study in Princeton, New Jersey, gathered up and presented at a [1995 string theory conference](https://arxiv.org/abs/hep-th/9503124) at the University of Southern California. Witten argued that the five string theories each represented an approximation of a more fundamental, 11-dimensional theory as it behaved in a particular situation, much as how Einstein's space- and time-bending theories of relativity match Newton's description of objects moving at normal speeds. That was the beginning of one string theory spin-off: M-theory. The "M" is likely inspired by higher-dimensional objects called membranes, Taylor said, but since the theory has no concrete mathematical equations, the "M" remains a placeholder with no official meaning. "It was really a parametrization of our ignorance," she said. Attempts to find those general equations that would work in every possible situation made little progress, but the alleged existence of the fundamental theory gave theorists the understanding and confidence needed to develop mathematical techniques for the five versions of string theory and apply them in the context where each theory worked. [![string theory illustration shows numerous strings in an abstract shape configuration.](https://cdn.mos.cms.futurecdn.net/3JBXDjWtgHGtY4UjFCzszS.jpg)]() An artist's interpretation of string theory. (Image credit: Science Photo Library via Getty Images) Strings are far too small to detect with any conceivable technology, but one early theoretical success was physicists' ability to describe black hole entropy in a 1996 paper published in the journal [Physics Letters](https://arxiv.org/abs/hep-th/9601029). Entropy refers to the number of ways that you can arrange the parts of a system, but without being able to see into the impenetrable depths of a black hole, no one knows what type of particles might lie inside or what arrangements they can take. And yet, in the early 1970s, [Stephen Hawking](https://www.space.com/15923-stephen-hawking.html) and others used the laws of thermodynamics and, according to an article published in 2020 in the journal [Physics](https://physics.aps.org/articles/v13/80), quantum mechanics to calculate entropy inside a black hole, suggesting that black holes must have some sort of internal structure. What that structure might be, remained a mystery. Most attempts to describe the black hole's makeup fall short, but the configurations of hypothetical strings does the trick. "String theory has been able to give a spot-on counting," Taylor said — an actual possible explanation of black hole interiors, not just a rough idea. The string theory framework still faces many challenges, however: It produces an impossible number of ways to fold up the extra six dimensions. Every option seems to fit the broad features of the Standard Model that governs particle physics, with little hope of distinguishing which is the right one. Moreover, wrote astrophysicist Ethan Siegel in his blog [Starts With a Bang](https://www.forbes.com/sites/startswithabang/2019/02/12/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history/), all of those models for managing the extra dimensions rely on an equivalence between force particles and matter particles called supersymmetry. But, just like the extra dimensions that string theory requires, we don't observe supersymmetry in our world. On top of those objections, it's not clear that string theory — M-theory or not — can ever be compatible with our modern understanding of an expanding universe, replete with dark energy, reported [Quanta Magazine](https://www.quantamagazine.org/dark-energy-may-be-incompatible-with-string-theory-20180809/) in 2018. A number of physicists, such as Peter Woit of Columbia University, view these divergences from reality as fatal flaws. "The basic problem with string theory unification research is not that progress has been slow over the past 30 years," he wrote on his [blog](http://www.math.columbia.edu/~woit/wordpress/?page_id=4338), "but that it has been negative, with everything learned showing more clearly why the idea doesn't work." Taylor, however, maintains that today's models are overly simplistic, and that features like [cosmological expansion](https://www.space.com/16042-cosmology.html) and a lack of supersymmetry may someday be built into future versions. Taylor expects that, while the new era of [gravitational-wave astronomy](https://www.space.com/LIGO-Laser-Interferometer-Gravitational-Wave-Observatory.html) may bring new tidbits of information about quantum gravity, more progress will be made by continuing to follow the math deeper into string theory. "I have a theoretical bias," she said, "but I think the kind of breakthrough I'm describing would come from a chalkboard; from thought." ## Why is string theory still important? Regardless of whether string theory can ever be massaged into a "theory of everything," its legacy as a productive research program may be assured on mathematical merit alone. "It can't be a dead end in the sense of what we've learned just from mathematics itself," Taylor said. "If you told me tomorrow that the universe absolutely isn't supersymmetric and doesn't have 10 \[spatial\] dimensions, we've still connected whole branches of mathematics" using the string theory framework. In particular, when Witten and other researchers showed that the five-string theories were shadows of a single-parent theory, they highlighted connections called dualities, which have proven to be a major contribution to mathematics and physics. Dualities let mathematicians translate from one branch of math to another, attacking problems untenable in one framework by using calculations done in the other, for example in geometry and number theory. Other dualities have helped overcome challenges in quantum computing, according to Taylor. "It's not going to make your next-generation iPhone," she said, "But it may make your iPhone for the 22nd century." Whether string theory's ability to illuminate the dark web connecting different areas of math turns out to be a sign of its potential or just a lucky coincidence remains a subject of debate. Witten, speaking at the [Institute for Advanced Study](https://video.ias.edu/universe/2019/0529-DijkgraafWitten) in 2019, acknowledged that while he no longer feels as confident as he once did that string theory will evolve into a complete physical theory, his gut tells him that the theory remains a productive field of research. "To me, it's implausible that humans stumbled by accident on\[to\] such an incredible structure that sheds so much light on established physical theories, and also on so many different branches of mathematics," he told the audience. "I have confidence that the general enterprise is on the right track, but I don't claim that the argument I've given is scientifically convincing." ## Additional resources Find more in-depth history and explanations of current string theory science at [WhyStringTheory.com](http://whystringtheory.com/), a website created by graduate students at the University of Oxford and the University of Cambridge for the "interested layperson." Or, if you'd rather go right to the source, check out this [CERN Courier](https://cerncourier.com/a/the-roots-and-fruits-of-string-theory/) interview with string theory originator Gabriele Veneziano. If you're looking for a video explainer, watch these two videos entitled "[Why string theory is right](https://www.youtube.com/watch?v=iTTa9YcTe1k)" and "[Why string theory is wrong](https://www.youtube.com/watch?v=IhpGdumLRqs)," both from PBS Digital Studios. ### Bibliography - "Robbert Dijkgraaf and Edward Witten in Conversation - Videos \\| Institute for Advanced Study," May 30, 2019. [https://www.ias.edu/video/universe/2019/0529-DijkgraafWitten](https://www.ias.edu/video/universe/2019/0529-DijkgraafWitten) . - Schwarz, John H. "The Early History of String Theory and Supersymmetry," January 4, 2012. [https://arxiv.org/abs/1201.0981v1](https://arxiv.org/abs/1201.0981v1) . - Siegel, Ethan. "Why Supersymmetry May Be The Greatest Failed Prediction In Particle Physics History." Forbes, February 12, 2019. [https://www.forbes.com/sites/startswithabang/2019/02/12/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history/](https://www.forbes.com/sites/startswithabang/2019/02/12/why-supersymmetry-may-be-the-greatest-failed-prediction-in-particle-physics-history/) . - Strominger, A., and C. Vafa. "Microscopic Origin of the Bekenstein-Hawking Entropy." Physics Letters B 379, no. 1–4 (June 1996): 99–104. [https://doi.org/10.1016/0370-2693(96)00345-0](https://doi.org/10.1016/0370-2693\(96\)00345-0) . - Witten, Edward. "String Theory Dynamics In Various Dimensions." Nuclear Physics B 443, no. 1–2 (June 1995): 85–126. [https://doi.org/10.1016/0550-3213(95)00158-O](https://doi.org/10.1016/0550-3213\(95\)00158-O) . - Woit, Peter. "Frequently Asked Questions \\| Not Even Wrong." Not Even Wrong (blog). Accessed January 17, 2022. [https://www.math.columbia.edu/~woit/wordpress/?page\_id=4338](https://www.math.columbia.edu/~woit/wordpress/?page_id=4338) . - Wolchover, Natalie. "Dark Energy May Be Incompatible With String Theory." Quanta Magazine, August 9, 2018. [https://www.quantamagazine.org/dark-energy-may-be-incompatible-with-string-theory-20180809/](https://www.quantamagazine.org/dark-energy-may-be-incompatible-with-string-theory-20180809/) . - Zayas, Leopoldo A. Pando. “A Microscopic Account of Black Hole Entropy.” Physics 13 (May 18, 2020): 80. <https://doi.org/10.1103/PhysRevX.10.021037>. Share your thoughts 0 0 0 0 Join the community Join the Space.com Family! The best way to keep in touch and to be informed of our latest quizzes and competitions, as well as news and offers. Already have an account? Log in My Details Update your details below... Keep in the Know Would you like to be kept informed about new quizzes and offers from Future and its partners? Validate Your Mobile No. We have sent a code to . Please enter it below to verify your account. Update Your Mobile No. You may enter a new mobile number below. 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Leaderboard \| Rank \| Player \| Score \| Time \| \|---\|---\|---\|---\| Charlie Wood is a freelance journalist covering physical sciences both on and off this pale blue dot. He contributes to Space.com and LiveScience, as well as Popular Science, Scientific American, Quanta Magazine, and others. These days he writes from New York but in previous lives he taught physics in Mozambique and science English in Japan. Find him on Twitter @walkingthedot.
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