🕷️ Crawler Inspector

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Raw Queries and Responses

1. Shard Calculation

Query:

Response:

Calculated Shard: 97 (from laksa082)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa097.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, ml_categories_json AS ml_categories_json, ml_types_json AS ml_types_json, ml_intent_types_json AS ml_intent_types_json, meta_language AS meta_language, attrs_author AS attrs_author, ifNull(toUnixTimestamp(attrs_publish_time), 0) AS attrs_publish_time, ifNull(toUnixTimestamp(attrs_original_publish_time), 0) AS attrs_original_publish_time, ifNull(attrs_is_republished, 0) AS attrs_is_republished, ifNull(attrs_nr_words, 0) AS attrs_nr_words, ifNull(attrs_boilerpipe_nr_words, 0) AS attrs_boilerpipe_nr_words, ifNull(body_ext_links_number, 0) AS body_ext_links_number, ifNull(body_int_links_number, 0) AS body_int_links_number, ifNull(meta_nofollow, 0) AS meta_nofollow, ifNull(meta_noarchive, 0) AS meta_noarchive, ifNull(props_was_rendered, 0) AS props_was_rendered, ifNull(src_redirect, \'\') AS src_redirect, ifNull(download_time_msec, 0) AS download_time_msec, ifNull(download_ttfb_msec, 0) AS download_ttfb_msec, ifNull(download_size, 0) AS download_size FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://www.nyas.org/ideas-insights/blog/talking-physics-string-theorys-dangling-claims/\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.nyas.org/ideas-insights/blog/talking-physics-string-theorys-dangling-claims/\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.nyas.org\/ideas-insights\/blog\/talking-physics-string-theorys-dangling-claims\/","crawl_time":1776030128,"first_indexed_time":1759132255,"http_code":200,"src_unparsed":"org,nyas!www,\/ideas-insights\/blog\/talking-physics-string-theorys-dangling-claims\/ s443","src_root_hash":"5511971663342622697","history_drop_reason":null,"meta_title":"Talking Physics: String Theory’s Dangling Claims - NYAS","meta_descriptions":["Theoretical physicist and Columbia University professor Brain Greene delves into the intense rivalry between loop quantum gravity and string theory."],"attrs_boilerpipe_text":"Blog Article\nTalking Physics: String Theory’s Dangling Claims\nTheoretical physicist and Columbia University professor Brain Greene delves into the intense rivalry between loop quantum gravity and string theory, and how it ties to Einstein.\nPublished January 1, 2004\nBy Rich Kelley\nAs philosopher Paul Feyerabend once noted, science moves more rapidly when there are several competing approaches to a problem. Much of the excitement in theoretical physics today surrounds the intense rivalry between loop quantum gravity (LQG) and string theory.\nBoth theories aspire to achieve the Holy Grail of modern physics: the unification of general relativity and quantum mechanics. They both have their champions and detractors. Both have had difficulty finding experimental verification of their predictions, yet both claim to be on the verge of discovering results that will do just that.\nLoop quantum gravity’s best known proponent is Lee Smolin, author of Three Roads to Quantum Gravity, and a research physicist at Perimeter Institute for Theoretical Physics in Waterloo, Canada. String theory’s most high-profile current spokesperson is Brian Greene.\nProfessor of Physics and Mathematics at Columbia University, Greene came to The New York Academy of Sciences (the Academy) on Oct. 16, 2003, for an informal conversation as part of his whirlwind tour to promote the NOVA series based on The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory, his bestselling 1999 book. Four years in the making and with a budget of $3.5 million, “The Elegant Universe” premiered with a two-hour segment, “Einstein’s Dream” and “String’s the Thing” on PBS on Tuesday, Oct. 28, 2003, and concluded with a one-hour program, “Welcome to the 11th Dimension,” on November 4.\nString Theory’s Core\nMuch as he did in his first NOVA segment, Greene began his talk by briefly describing the history of the conflict: how Einstein revolutionized our worldview by conceiving of space and time as a continuum, spacetime; how scientists in the 1920s and ‘30s invented quantum mechanics to describe the microscopic properties of the universe; and how these two radical worldviews clashed.\nString theory promises to reconcile these two views of spacetime – Einstein’s vast fabric and the jittery landscape of quantum mechanics. The NOVA animations made clear just how visually captivating this story is. One showed an “elevator of the imagination” traveling to floors smaller by 10 orders of magnitude to illustrate the transition from the placid Einsteinian realm of large things down to the turbulent, frenetic world of atoms, electrons, protons and quarks.\nIt is at this lowest level of matter that we find the core contribution of string theory. At the smallest of scales, inside a quark, lies not a point but a fundamentally extended object that looks like a string. A vibrating loop of string. At the microscopic level the world is made up of music, notes, resonant vibrating frequencies. This is the heart of string theory.\nThe Mechanism for Reconciling Relativity\nWhat enables these strings to become the mechanism for reconciling relativity and the laws of the microworld is that these strings have size. In particle physics, point particles have no size at all. In principle you could measure and probe at any scale. But if particles have length, then it makes no sense to believe you can probe into areas that are smaller than the length of the particle itself.\nString theory posits that at the smallest of scales, the smallest elements do have a defined length, what is called Planck length, “a millionth of a billionth of a billionth of a billionth of a centimeter” (10-33 centimeter). For analogous reasons loop quantum gravity also posits a smallest unit of space. Its minimum volume is the cube of the Planck length.\nIn one of the most memorable animations from the show, we travel again to the lowest, most turbulent level of the microscopic world, the world of point particles. But much as when the landscape on a map zooms out when the scale changes, when we define the lowest level as one in which the smallest elements have a defined size, the spatial grid rises above the turbulence and the jitters calm down.\nWorlds of Dimensions\nOne of the most provocative components of string theory is its insistence that the world has more than three spatial dimensions. String theory calls for six or seven extra dimensions. In the television series, Greene focuses more on how there could be these extra dimensions, rather than on why they need to exist.\nGreene’s book acknowledges that the need for the extra dimensions is primarily driven by the mathematics behind string theory. In order for the negative probabilities of the quantum mechanical calculations to cancel out, the strings need to vibrate in nine independent spatial directions. Of course, these are not dimensions as we know them. Greene instructs us to “imagine that these extra dimensions come not uniformly large that we can see with our eyes, but small, tightly curled up. So small we just can’t see them.”\nIf any aspect of string theory is ripe for visual exploitation via animation, this is it. Many readers of the book will enjoy the series if only to get the chance to see what animated Calabi-Yau manifolds look like. In 1984 a number of string physicists identified the Calabi-Yau class of six-dimensional shapes as meeting the conditions the equations for the extra dimensions require.\nThe manifolds consist of overlapping and entwined doughnut shapes, each of which represents a separate dimension. If we zoom again into the microscopic world we can envision encountering curled up dimensions that look much like these Calabi-Yau manifolds – “simple rotating structures” in Greene’s description.\n“That’s the basic idea of string theory. In a nutshell it requires the world to have more dimensions than we are familiar with.”\nIn an extensive question-and-answer exchange after his talk, Brian Greene amplified his ideas.\nExperimental Verification\nElegant as it is, string theory has roused the ire of some physicists because it has thus far defied being able to be proven true or false by experiment. Familiar with this complaint, Greene described what he considered several promising developments.\nFor a long time string theorists had thought that the extra dimensions must be as small as the size of the Planck length and, therefore, beyond detectability. In the last few years work has been done suggesting that some dimensions might be as big as 10-2 cm. “That’s a size you can almost see with your eyes.” We haven’t seen them because the only force that could penetrate into these extra dimensions is gravity.\nUnfortunately, the force of gravity is many powers of 10 weaker than the smallest size that can be currently probed in physics laboratories. However, there are some experiments planned to be done at CERN in 2007 in which we may actually see the extra dimensions by observing the effect of gravity on other dimensions.\nGreene’s current research involves looking for signatures of string theory in astronomical data. Proponents of loop quantum gravity are also looking to the stars for confirmation of their calculations. The Gamma-ray Large Area Space Telescope (GLAST), due to be launched in 2006, should be sensitive enough to detect from the light from gamma-ray bursts the verification LQG researchers seek.\nM-Theory\nIn recent years string theory has undergone a transformation. Much of this dates from a milestone event, the “Strings 1995” conference at the University of California that marked the beginning of the Second Superstring Revolution.\nIt was there that Edward Witten delivered his startling finding that string theory requires 11 dimensions and that what had until then been viewed as five competing superstring theories are really all part of one superstring framework, which he called “M-Theory.”\nWhat the “M” refers to is not clear. “Mysterious” is one proposed meaning, since how the framework relates the theories to each other has not been defined. M-theory also “inflates” strings into two-dimensional “branes” (from “membranes”) that could contain entire alternate universes.\nAnd most important to its critics from LQG, M-theory is expected, as it develops, to enable string theory to be “background independent,” like LQG, so that it does not need to rely on the standard model of spacetime.\nThe Next Book\nFor all of their competitiveness, researchers in both string theory and LQG frequently speculate that they could be working on different paths toward what may be one unified theory. This may explain why Greene’s next book, The Fabric of the Cosmos: Space, Time, and the Texture of Reality, due from Knopf in February 2004, seems designed to encompass a range of theoretical possibilities.\nHe noted that his coverage of space and time in The Elegant Universe addressed only what was needed as background for his explanation of string theory. Many other aspects he left uncovered.\nIn his new book they get center stage as he probes how our fundamental ideas of space and time have changed in their nature and importance over the past century. If Greene’s knack for engaging broad audiences holds true, it will undoubtedly expand the ranks and enjoyment of those eager to follow the lively scramble to the ultimate Theory of Everything.\nAlso read:\nAdnan Waly: A Life and Career in Physics","attrs_markdown":"[Skip to main content](https:\/\/www.nyas.org\/ideas-insights\/blog\/talking-physics-string-theorys-dangling-claims\/#main)\n\nNYAS \\| [Blavatnik Awards](http:\/\/blavatnikawards.org\/) \\| [ISR](https:\/\/isr.nyas.org\/) \\| [Annals](https:\/\/nyaspubs.onlinelibrary.wiley.com\/journal\/17496632)\n\n[Blog](https:\/\/www.nyas.org\/ideas-insights\/blog\/) · [Event Calendar](https:\/\/www.nyas.org\/shaping-science\/events-calendar)  [Become a Member](https:\/\/www.nyas.org\/get-involved\/membership\/)   [Support Us](https:\/\/www.nyas.org\/get-involved\/support-us)\n\n[![NYAS](https:\/\/www.nyas.org\/images\/nyas-logo.png)](https:\/\/www.nyas.org\/ \"NYAS\")\n\n- [About Us](https:\/\/www.nyas.org\/ideas-insights\/blog\/talking-physics-string-theorys-dangling-claims\/ \"About Us\")\n  - 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Much of the excitement in theoretical physics today surrounds the intense rivalry between loop quantum gravity (LQG) and string theory.\n\nBoth theories aspire to achieve the Holy Grail of modern physics: the unification of general relativity and quantum mechanics. They both have their champions and detractors. Both have had difficulty finding experimental verification of their predictions, yet both claim to be on the verge of discovering results that will do just that.\n\nLoop quantum gravity’s best known proponent is Lee Smolin, author of Three Roads to Quantum Gravity, and a research physicist at Perimeter Institute for Theoretical Physics in Waterloo, Canada. String theory’s most high-profile current spokesperson is Brian Greene.\n\nProfessor of Physics and Mathematics at Columbia University, Greene came to The New York Academy of Sciences (the Academy) on Oct. 16, 2003, for an informal conversation as part of his whirlwind tour to promote the NOVA series based on The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory, his bestselling 1999 book. Four years in the making and with a budget of \\$3.5 million, “The Elegant Universe” premiered with a two-hour segment, “Einstein’s Dream” and “String’s the Thing” on PBS on Tuesday, Oct. 28, 2003, and concluded with a one-hour program, “Welcome to the 11th Dimension,” on November 4.\n\n### String Theory’s Core\nMuch as he did in his first NOVA segment, Greene began his talk by briefly describing the history of the conflict: how Einstein revolutionized our worldview by conceiving of space and time as a continuum, spacetime; how scientists in the 1920s and ‘30s invented quantum mechanics to describe the microscopic properties of the universe; and how these two radical worldviews clashed.\n\nString theory promises to reconcile these two views of spacetime – Einstein’s vast fabric and the jittery landscape of quantum mechanics. The NOVA animations made clear just how visually captivating this story is. One showed an “elevator of the imagination” traveling to floors smaller by 10 orders of magnitude to illustrate the transition from the placid Einsteinian realm of large things down to the turbulent, frenetic world of atoms, electrons, protons and quarks.\n\nIt is at this lowest level of matter that we find the core contribution of string theory. At the smallest of scales, inside a quark, lies not a point but a fundamentally extended object that looks like a string. A vibrating loop of string. At the microscopic level the world is made up of music, notes, resonant vibrating frequencies. This is the heart of string theory.\n\n### The Mechanism for Reconciling Relativity\nWhat enables these strings to become the mechanism for reconciling relativity and the laws of the microworld is that these strings have size. In particle physics, point particles have no size at all. In principle you could measure and probe at any scale. But if particles have length, then it makes no sense to believe you can probe into areas that are smaller than the length of the particle itself.\n\nString theory posits that at the smallest of scales, the smallest elements do have a defined length, what is called Planck length, “a millionth of a billionth of a billionth of a billionth of a centimeter” (10-33 centimeter). For analogous reasons loop quantum gravity also posits a smallest unit of space. Its minimum volume is the cube of the Planck length.\n\nIn one of the most memorable animations from the show, we travel again to the lowest, most turbulent level of the microscopic world, the world of point particles. But much as when the landscape on a map zooms out when the scale changes, when we define the lowest level as one in which the smallest elements have a defined size, the spatial grid rises above the turbulence and the jitters calm down.\n\n### Worlds of Dimensions\nOne of the most provocative components of string theory is its insistence that the world has more than three spatial dimensions. String theory calls for six or seven extra dimensions. In the television series, Greene focuses more on how there could be these extra dimensions, rather than on why they need to exist.\n\nGreene’s book acknowledges that the need for the extra dimensions is primarily driven by the mathematics behind string theory. In order for the negative probabilities of the quantum mechanical calculations to cancel out, the strings need to vibrate in nine independent spatial directions. Of course, these are not dimensions as we know them. Greene instructs us to “imagine that these extra dimensions come not uniformly large that we can see with our eyes, but small, tightly curled up. So small we just can’t see them.”\n\nIf any aspect of string theory is ripe for visual exploitation via animation, this is it. Many readers of the book will enjoy the series if only to get the chance to see what animated Calabi-Yau manifolds look like. In 1984 a number of string physicists identified the Calabi-Yau class of six-dimensional shapes as meeting the conditions the equations for the extra dimensions require.\n\nThe manifolds consist of overlapping and entwined doughnut shapes, each of which represents a separate dimension. If we zoom again into the microscopic world we can envision encountering curled up dimensions that look much like these Calabi-Yau manifolds – “simple rotating structures” in Greene’s description.\n\n“That’s the basic idea of string theory. In a nutshell it requires the world to have more dimensions than we are familiar with.”\n\nIn an extensive question-and-answer exchange after his talk, Brian Greene amplified his ideas.\n\n### Experimental Verification\nElegant as it is, string theory has roused the ire of some physicists because it has thus far defied being able to be proven true or false by experiment. Familiar with this complaint, Greene described what he considered several promising developments.\n\nFor a long time string theorists had thought that the extra dimensions must be as small as the size of the Planck length and, therefore, beyond detectability. In the last few years work has been done suggesting that some dimensions might be as big as 10-2 cm. “That’s a size you can almost see with your eyes.” We haven’t seen them because the only force that could penetrate into these extra dimensions is gravity.\n\nUnfortunately, the force of gravity is many powers of 10 weaker than the smallest size that can be currently probed in physics laboratories. However, there are some experiments planned to be done at CERN in 2007 in which we may actually see the extra dimensions by observing the effect of gravity on other dimensions.\n\nGreene’s current research involves looking for signatures of string theory in astronomical data. Proponents of loop quantum gravity are also looking to the stars for confirmation of their calculations. The Gamma-ray Large Area Space Telescope (GLAST), due to be launched in 2006, should be sensitive enough to detect from the light from gamma-ray bursts the verification LQG researchers seek.\n\n### M-Theory\nIn recent years string theory has undergone a transformation. Much of this dates from a milestone event, the “Strings 1995” conference at the University of California that marked the beginning of the Second Superstring Revolution.\n\nIt was there that Edward Witten delivered his startling finding that string theory requires 11 dimensions and that what had until then been viewed as five competing superstring theories are really all part of one superstring framework, which he called “M-Theory.”\n\nWhat the “M” refers to is not clear. “Mysterious” is one proposed meaning, since how the framework relates the theories to each other has not been defined. M-theory also “inflates” strings into two-dimensional “branes” (from “membranes”) that could contain entire alternate universes.\n\nAnd most important to its critics from LQG, M-theory is expected, as it develops, to enable string theory to be “background independent,” like LQG, so that it does not need to rely on the standard model of spacetime.\n\n### The Next Book\nFor all of their competitiveness, researchers in both string theory and LQG frequently speculate that they could be working on different paths toward what may be one unified theory. This may explain why Greene’s next book, The Fabric of the Cosmos: Space, Time, and the Texture of Reality, due from Knopf in February 2004, seems designed to encompass a range of theoretical possibilities.\n\nHe noted that his coverage of space and time in The Elegant Universe addressed only what was needed as background for his explanation of string theory. Many other aspects he left uncovered.\n\nIn his new book they get center stage as he probes how our fundamental ideas of space and time have changed in their nature and importance over the past century. If Greene’s knack for engaging broad audiences holds true, it will undoubtedly expand the ranks and enjoyment of those eager to follow the lively scramble to the ultimate Theory of Everything.\n\n***Also read:** [Adnan Waly: A Life and Career in Physics](https:\/\/www.nyas.org\/ideas-insights\/blog\/adnan-waly-a-life-and-career-in-physics\/)*\n\nAuthor\n***\n![Image](https:\/\/www.nyas.org\/wp-content\/uploads\/2024\/02\/nyasSwirl_Black.jpg)\n\nContributing Author\n\nSubscribe to our newsletter\n\nFollow us on social\n\n![](https:\/\/www.nyas.org\/images\/nyas-logo-clear.png)\n\n*The mission of The New York Academy of Sciences is to drive innovative solutions to society's challenges by advancing scientific research, education and policy.*\n\n[Membership](https:\/\/www.nyas.org\/get-involved\/membership\/ \"Organizational Membership\")\n\n[Donate](https:\/\/support.nyas.org\/give\/413115\/#!\/donation\/checkout)\n\n[Careers](https:\/\/www.nyas.org\/about-us\/careers\/ \"Careers\")\n\n[Contact Us](https:\/\/www.nyas.org\/contact\/ \"Contact\")\n\n[Rent Our Space](https:\/\/www.nyas.org\/shaping-science\/event\/rent-our-space\/ \"Contact\")\n\n[About Us](https:\/\/www.nyas.org\/about-us\/ \"Topics\")\n\n[Topics](https:\/\/www.nyas.org\/topics\/ \"Topics\")\n\n[Learning](https:\/\/www.nyas.org\/learning\/ \"Learning\")\n\n[Ideas & Insights](https:\/\/www.nyas.org\/ideas-insights\/ \"Ideas & Insights\")\n\n[Shaping Science](https:\/\/www.nyas.org\/shaping-science\/ \"Shaping Science\")\n\n[Get Involved](https:\/\/www.nyas.org\/get-involved\/ \"Get Involved\")\n\n**Affiliated Sites**\n\n**[*Annals of the New York Academy of Sciences*](https:\/\/nyaspubs.onlinelibrary.wiley.com\/journal\/17496632)** \\>  \nA monthly international science journal covering many areas of science; amongst the top multi-disciplinary journals worldwide. 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To find out more about cookies on this website, see our [Privacy Policy](https:\/\/nyas.org\/policies\/) and [Terms of Use](https:\/\/nyas.org\/terms-of-use\/).\n\nI Agree","attrs_readable_markdown":"Blog Article\n\n## Talking Physics: String Theory’s Dangling Claims\n### *Theoretical physicist and Columbia University professor Brain Greene delves into the intense rivalry between loop quantum gravity and string theory, and how it ties to Einstein.*\n*Published January 1, 2004*\n\nBy Rich Kelley\n\nAs philosopher Paul Feyerabend once noted, science moves more rapidly when there are several competing approaches to a problem. Much of the excitement in theoretical physics today surrounds the intense rivalry between loop quantum gravity (LQG) and string theory.\n\nBoth theories aspire to achieve the Holy Grail of modern physics: the unification of general relativity and quantum mechanics. They both have their champions and detractors. Both have had difficulty finding experimental verification of their predictions, yet both claim to be on the verge of discovering results that will do just that.\n\nLoop quantum gravity’s best known proponent is Lee Smolin, author of Three Roads to Quantum Gravity, and a research physicist at Perimeter Institute for Theoretical Physics in Waterloo, Canada. String theory’s most high-profile current spokesperson is Brian Greene.\n\nProfessor of Physics and Mathematics at Columbia University, Greene came to The New York Academy of Sciences (the Academy) on Oct. 16, 2003, for an informal conversation as part of his whirlwind tour to promote the NOVA series based on The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory, his bestselling 1999 book. Four years in the making and with a budget of \\$3.5 million, “The Elegant Universe” premiered with a two-hour segment, “Einstein’s Dream” and “String’s the Thing” on PBS on Tuesday, Oct. 28, 2003, and concluded with a one-hour program, “Welcome to the 11th Dimension,” on November 4.\n\n### String Theory’s Core\nMuch as he did in his first NOVA segment, Greene began his talk by briefly describing the history of the conflict: how Einstein revolutionized our worldview by conceiving of space and time as a continuum, spacetime; how scientists in the 1920s and ‘30s invented quantum mechanics to describe the microscopic properties of the universe; and how these two radical worldviews clashed.\n\nString theory promises to reconcile these two views of spacetime – Einstein’s vast fabric and the jittery landscape of quantum mechanics. The NOVA animations made clear just how visually captivating this story is. One showed an “elevator of the imagination” traveling to floors smaller by 10 orders of magnitude to illustrate the transition from the placid Einsteinian realm of large things down to the turbulent, frenetic world of atoms, electrons, protons and quarks.\n\nIt is at this lowest level of matter that we find the core contribution of string theory. At the smallest of scales, inside a quark, lies not a point but a fundamentally extended object that looks like a string. A vibrating loop of string. At the microscopic level the world is made up of music, notes, resonant vibrating frequencies. This is the heart of string theory.\n\n### The Mechanism for Reconciling Relativity\nWhat enables these strings to become the mechanism for reconciling relativity and the laws of the microworld is that these strings have size. In particle physics, point particles have no size at all. In principle you could measure and probe at any scale. But if particles have length, then it makes no sense to believe you can probe into areas that are smaller than the length of the particle itself.\n\nString theory posits that at the smallest of scales, the smallest elements do have a defined length, what is called Planck length, “a millionth of a billionth of a billionth of a billionth of a centimeter” (10-33 centimeter). For analogous reasons loop quantum gravity also posits a smallest unit of space. Its minimum volume is the cube of the Planck length.\n\nIn one of the most memorable animations from the show, we travel again to the lowest, most turbulent level of the microscopic world, the world of point particles. But much as when the landscape on a map zooms out when the scale changes, when we define the lowest level as one in which the smallest elements have a defined size, the spatial grid rises above the turbulence and the jitters calm down.\n\n### Worlds of Dimensions\nOne of the most provocative components of string theory is its insistence that the world has more than three spatial dimensions. String theory calls for six or seven extra dimensions. In the television series, Greene focuses more on how there could be these extra dimensions, rather than on why they need to exist.\n\nGreene’s book acknowledges that the need for the extra dimensions is primarily driven by the mathematics behind string theory. In order for the negative probabilities of the quantum mechanical calculations to cancel out, the strings need to vibrate in nine independent spatial directions. Of course, these are not dimensions as we know them. Greene instructs us to “imagine that these extra dimensions come not uniformly large that we can see with our eyes, but small, tightly curled up. So small we just can’t see them.”\n\nIf any aspect of string theory is ripe for visual exploitation via animation, this is it. Many readers of the book will enjoy the series if only to get the chance to see what animated Calabi-Yau manifolds look like. In 1984 a number of string physicists identified the Calabi-Yau class of six-dimensional shapes as meeting the conditions the equations for the extra dimensions require.\n\nThe manifolds consist of overlapping and entwined doughnut shapes, each of which represents a separate dimension. If we zoom again into the microscopic world we can envision encountering curled up dimensions that look much like these Calabi-Yau manifolds – “simple rotating structures” in Greene’s description.\n\n“That’s the basic idea of string theory. In a nutshell it requires the world to have more dimensions than we are familiar with.”\n\nIn an extensive question-and-answer exchange after his talk, Brian Greene amplified his ideas.\n\n### Experimental Verification\nElegant as it is, string theory has roused the ire of some physicists because it has thus far defied being able to be proven true or false by experiment. Familiar with this complaint, Greene described what he considered several promising developments.\n\nFor a long time string theorists had thought that the extra dimensions must be as small as the size of the Planck length and, therefore, beyond detectability. In the last few years work has been done suggesting that some dimensions might be as big as 10-2 cm. “That’s a size you can almost see with your eyes.” We haven’t seen them because the only force that could penetrate into these extra dimensions is gravity.\n\nUnfortunately, the force of gravity is many powers of 10 weaker than the smallest size that can be currently probed in physics laboratories. However, there are some experiments planned to be done at CERN in 2007 in which we may actually see the extra dimensions by observing the effect of gravity on other dimensions.\n\nGreene’s current research involves looking for signatures of string theory in astronomical data. Proponents of loop quantum gravity are also looking to the stars for confirmation of their calculations. The Gamma-ray Large Area Space Telescope (GLAST), due to be launched in 2006, should be sensitive enough to detect from the light from gamma-ray bursts the verification LQG researchers seek.\n\n### M-Theory\nIn recent years string theory has undergone a transformation. Much of this dates from a milestone event, the “Strings 1995” conference at the University of California that marked the beginning of the Second Superstring Revolution.\n\nIt was there that Edward Witten delivered his startling finding that string theory requires 11 dimensions and that what had until then been viewed as five competing superstring theories are really all part of one superstring framework, which he called “M-Theory.”\n\nWhat the “M” refers to is not clear. “Mysterious” is one proposed meaning, since how the framework relates the theories to each other has not been defined. M-theory also “inflates” strings into two-dimensional “branes” (from “membranes”) that could contain entire alternate universes.\n\nAnd most important to its critics from LQG, M-theory is expected, as it develops, to enable string theory to be “background independent,” like LQG, so that it does not need to rely on the standard model of spacetime.\n\n### The Next Book\nFor all of their competitiveness, researchers in both string theory and LQG frequently speculate that they could be working on different paths toward what may be one unified theory. This may explain why Greene’s next book, The Fabric of the Cosmos: Space, Time, and the Texture of Reality, due from Knopf in February 2004, seems designed to encompass a range of theoretical possibilities.\n\nHe noted that his coverage of space and time in The Elegant Universe addressed only what was needed as background for his explanation of string theory. Many other aspects he left uncovered.\n\nIn his new book they get center stage as he probes how our fundamental ideas of space and time have changed in their nature and importance over the past century. If Greene’s knack for engaging broad audiences holds true, it will undoubtedly expand the ranks and enjoyment of those eager to follow the lively scramble to the ultimate Theory of Everything.\n\n***Also read:** [Adnan Waly: A Life and Career in Physics](https:\/\/www.nyas.org\/ideas-insights\/blog\/adnan-waly-a-life-and-career-in-physics\/)*","meta_canonical":null,"ml_categories_json":"","ml_types_json":"","ml_intent_types_json":"","meta_language":"en-us","attrs_author":null,"attrs_publish_time":1072988280,"attrs_original_publish_time":1072988280,"attrs_is_republished":0,"attrs_nr_words":"1983","attrs_boilerpipe_nr_words":"1527","body_ext_links_number":8,"body_int_links_number":61,"meta_nofollow":0,"meta_noarchive":0,"props_was_rendered":0,"src_redirect":"","download_time_msec":293,"download_ttfb_msec":292,"download_size":19487}

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Boilerpipe Text	Blog Article Talking Physics: String Theory’s Dangling Claims Theoretical physicist and Columbia University professor Brain Greene delves into the intense rivalry between loop quantum gravity and string theory, and how it ties to Einstein. Published January 1, 2004 By Rich Kelley As philosopher Paul Feyerabend once noted, science moves more rapidly when there are several competing approaches to a problem. Much of the excitement in theoretical physics today surrounds the intense rivalry between loop quantum gravity (LQG) and string theory. Both theories aspire to achieve the Holy Grail of modern physics: the unification of general relativity and quantum mechanics. They both have their champions and detractors. Both have had difficulty finding experimental verification of their predictions, yet both claim to be on the verge of discovering results that will do just that. Loop quantum gravity’s best known proponent is Lee Smolin, author of Three Roads to Quantum Gravity, and a research physicist at Perimeter Institute for Theoretical Physics in Waterloo, Canada. String theory’s most high-profile current spokesperson is Brian Greene. Professor of Physics and Mathematics at Columbia University, Greene came to The New York Academy of Sciences (the Academy) on Oct. 16, 2003, for an informal conversation as part of his whirlwind tour to promote the NOVA series based on The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory, his bestselling 1999 book. Four years in the making and with a budget of $3.5 million, “The Elegant Universe” premiered with a two-hour segment, “Einstein’s Dream” and “String’s the Thing” on PBS on Tuesday, Oct. 28, 2003, and concluded with a one-hour program, “Welcome to the 11th Dimension,” on November 4. String Theory’s Core Much as he did in his first NOVA segment, Greene began his talk by briefly describing the history of the conflict: how Einstein revolutionized our worldview by conceiving of space and time as a continuum, spacetime; how scientists in the 1920s and ‘30s invented quantum mechanics to describe the microscopic properties of the universe; and how these two radical worldviews clashed. String theory promises to reconcile these two views of spacetime – Einstein’s vast fabric and the jittery landscape of quantum mechanics. The NOVA animations made clear just how visually captivating this story is. One showed an “elevator of the imagination” traveling to floors smaller by 10 orders of magnitude to illustrate the transition from the placid Einsteinian realm of large things down to the turbulent, frenetic world of atoms, electrons, protons and quarks. It is at this lowest level of matter that we find the core contribution of string theory. At the smallest of scales, inside a quark, lies not a point but a fundamentally extended object that looks like a string. A vibrating loop of string. At the microscopic level the world is made up of music, notes, resonant vibrating frequencies. This is the heart of string theory. The Mechanism for Reconciling Relativity What enables these strings to become the mechanism for reconciling relativity and the laws of the microworld is that these strings have size. In particle physics, point particles have no size at all. In principle you could measure and probe at any scale. But if particles have length, then it makes no sense to believe you can probe into areas that are smaller than the length of the particle itself. String theory posits that at the smallest of scales, the smallest elements do have a defined length, what is called Planck length, “a millionth of a billionth of a billionth of a billionth of a centimeter” (10-33 centimeter). For analogous reasons loop quantum gravity also posits a smallest unit of space. Its minimum volume is the cube of the Planck length. In one of the most memorable animations from the show, we travel again to the lowest, most turbulent level of the microscopic world, the world of point particles. But much as when the landscape on a map zooms out when the scale changes, when we define the lowest level as one in which the smallest elements have a defined size, the spatial grid rises above the turbulence and the jitters calm down. Worlds of Dimensions One of the most provocative components of string theory is its insistence that the world has more than three spatial dimensions. String theory calls for six or seven extra dimensions. In the television series, Greene focuses more on how there could be these extra dimensions, rather than on why they need to exist. Greene’s book acknowledges that the need for the extra dimensions is primarily driven by the mathematics behind string theory. In order for the negative probabilities of the quantum mechanical calculations to cancel out, the strings need to vibrate in nine independent spatial directions. Of course, these are not dimensions as we know them. Greene instructs us to “imagine that these extra dimensions come not uniformly large that we can see with our eyes, but small, tightly curled up. So small we just can’t see them.” If any aspect of string theory is ripe for visual exploitation via animation, this is it. Many readers of the book will enjoy the series if only to get the chance to see what animated Calabi-Yau manifolds look like. In 1984 a number of string physicists identified the Calabi-Yau class of six-dimensional shapes as meeting the conditions the equations for the extra dimensions require. The manifolds consist of overlapping and entwined doughnut shapes, each of which represents a separate dimension. If we zoom again into the microscopic world we can envision encountering curled up dimensions that look much like these Calabi-Yau manifolds – “simple rotating structures” in Greene’s description. “That’s the basic idea of string theory. In a nutshell it requires the world to have more dimensions than we are familiar with.” In an extensive question-and-answer exchange after his talk, Brian Greene amplified his ideas. Experimental Verification Elegant as it is, string theory has roused the ire of some physicists because it has thus far defied being able to be proven true or false by experiment. Familiar with this complaint, Greene described what he considered several promising developments. For a long time string theorists had thought that the extra dimensions must be as small as the size of the Planck length and, therefore, beyond detectability. In the last few years work has been done suggesting that some dimensions might be as big as 10-2 cm. “That’s a size you can almost see with your eyes.” We haven’t seen them because the only force that could penetrate into these extra dimensions is gravity. Unfortunately, the force of gravity is many powers of 10 weaker than the smallest size that can be currently probed in physics laboratories. However, there are some experiments planned to be done at CERN in 2007 in which we may actually see the extra dimensions by observing the effect of gravity on other dimensions. Greene’s current research involves looking for signatures of string theory in astronomical data. Proponents of loop quantum gravity are also looking to the stars for confirmation of their calculations. The Gamma-ray Large Area Space Telescope (GLAST), due to be launched in 2006, should be sensitive enough to detect from the light from gamma-ray bursts the verification LQG researchers seek. M-Theory In recent years string theory has undergone a transformation. Much of this dates from a milestone event, the “Strings 1995” conference at the University of California that marked the beginning of the Second Superstring Revolution. It was there that Edward Witten delivered his startling finding that string theory requires 11 dimensions and that what had until then been viewed as five competing superstring theories are really all part of one superstring framework, which he called “M-Theory.” What the “M” refers to is not clear. “Mysterious” is one proposed meaning, since how the framework relates the theories to each other has not been defined. M-theory also “inflates” strings into two-dimensional “branes” (from “membranes”) that could contain entire alternate universes. And most important to its critics from LQG, M-theory is expected, as it develops, to enable string theory to be “background independent,” like LQG, so that it does not need to rely on the standard model of spacetime. The Next Book For all of their competitiveness, researchers in both string theory and LQG frequently speculate that they could be working on different paths toward what may be one unified theory. This may explain why Greene’s next book, The Fabric of the Cosmos: Space, Time, and the Texture of Reality, due from Knopf in February 2004, seems designed to encompass a range of theoretical possibilities. He noted that his coverage of space and time in The Elegant Universe addressed only what was needed as background for his explanation of string theory. Many other aspects he left uncovered. In his new book they get center stage as he probes how our fundamental ideas of space and time have changed in their nature and importance over the past century. If Greene’s knack for engaging broad audiences holds true, it will undoubtedly expand the ranks and enjoyment of those eager to follow the lively scramble to the ultimate Theory of Everything. Also read: Adnan Waly: A Life and Career in Physics
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Published January 1, 2004 By Rich Kelley ![](https://www.nyas.org/wp-content/uploads/2025/01/AdobeStock_452512134-1024x767.png) Image courtesy of [WP\_7824 via stock.adobe.com](https://stock.adobe.com/images/hand-drawn-physic-formulas-science-knowledge-education-chem-formula-and-physics-math-formula-and-physics-vector-white-background-hand-drawn-line-math-formula-and-physics-formula/452512134?prev_url=detail). As philosopher Paul Feyerabend once noted, science moves more rapidly when there are several competing approaches to a problem. Much of the excitement in theoretical physics today surrounds the intense rivalry between loop quantum gravity (LQG) and string theory. Both theories aspire to achieve the Holy Grail of modern physics: the unification of general relativity and quantum mechanics. They both have their champions and detractors. Both have had difficulty finding experimental verification of their predictions, yet both claim to be on the verge of discovering results that will do just that. Loop quantum gravity’s best known proponent is Lee Smolin, author of Three Roads to Quantum Gravity, and a research physicist at Perimeter Institute for Theoretical Physics in Waterloo, Canada. String theory’s most high-profile current spokesperson is Brian Greene. Professor of Physics and Mathematics at Columbia University, Greene came to The New York Academy of Sciences (the Academy) on Oct. 16, 2003, for an informal conversation as part of his whirlwind tour to promote the NOVA series based on The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory, his bestselling 1999 book. Four years in the making and with a budget of \$3.5 million, “The Elegant Universe” premiered with a two-hour segment, “Einstein’s Dream” and “String’s the Thing” on PBS on Tuesday, Oct. 28, 2003, and concluded with a one-hour program, “Welcome to the 11th Dimension,” on November 4. ### String Theory’s Core Much as he did in his first NOVA segment, Greene began his talk by briefly describing the history of the conflict: how Einstein revolutionized our worldview by conceiving of space and time as a continuum, spacetime; how scientists in the 1920s and ‘30s invented quantum mechanics to describe the microscopic properties of the universe; and how these two radical worldviews clashed. String theory promises to reconcile these two views of spacetime – Einstein’s vast fabric and the jittery landscape of quantum mechanics. The NOVA animations made clear just how visually captivating this story is. One showed an “elevator of the imagination” traveling to floors smaller by 10 orders of magnitude to illustrate the transition from the placid Einsteinian realm of large things down to the turbulent, frenetic world of atoms, electrons, protons and quarks. It is at this lowest level of matter that we find the core contribution of string theory. At the smallest of scales, inside a quark, lies not a point but a fundamentally extended object that looks like a string. A vibrating loop of string. At the microscopic level the world is made up of music, notes, resonant vibrating frequencies. This is the heart of string theory. ### The Mechanism for Reconciling Relativity What enables these strings to become the mechanism for reconciling relativity and the laws of the microworld is that these strings have size. In particle physics, point particles have no size at all. In principle you could measure and probe at any scale. But if particles have length, then it makes no sense to believe you can probe into areas that are smaller than the length of the particle itself. String theory posits that at the smallest of scales, the smallest elements do have a defined length, what is called Planck length, “a millionth of a billionth of a billionth of a billionth of a centimeter” (10-33 centimeter). For analogous reasons loop quantum gravity also posits a smallest unit of space. Its minimum volume is the cube of the Planck length. In one of the most memorable animations from the show, we travel again to the lowest, most turbulent level of the microscopic world, the world of point particles. But much as when the landscape on a map zooms out when the scale changes, when we define the lowest level as one in which the smallest elements have a defined size, the spatial grid rises above the turbulence and the jitters calm down. ### Worlds of Dimensions One of the most provocative components of string theory is its insistence that the world has more than three spatial dimensions. String theory calls for six or seven extra dimensions. In the television series, Greene focuses more on how there could be these extra dimensions, rather than on why they need to exist. Greene’s book acknowledges that the need for the extra dimensions is primarily driven by the mathematics behind string theory. In order for the negative probabilities of the quantum mechanical calculations to cancel out, the strings need to vibrate in nine independent spatial directions. Of course, these are not dimensions as we know them. Greene instructs us to “imagine that these extra dimensions come not uniformly large that we can see with our eyes, but small, tightly curled up. So small we just can’t see them.” If any aspect of string theory is ripe for visual exploitation via animation, this is it. Many readers of the book will enjoy the series if only to get the chance to see what animated Calabi-Yau manifolds look like. In 1984 a number of string physicists identified the Calabi-Yau class of six-dimensional shapes as meeting the conditions the equations for the extra dimensions require. The manifolds consist of overlapping and entwined doughnut shapes, each of which represents a separate dimension. If we zoom again into the microscopic world we can envision encountering curled up dimensions that look much like these Calabi-Yau manifolds – “simple rotating structures” in Greene’s description. “That’s the basic idea of string theory. In a nutshell it requires the world to have more dimensions than we are familiar with.” In an extensive question-and-answer exchange after his talk, Brian Greene amplified his ideas. ### Experimental Verification Elegant as it is, string theory has roused the ire of some physicists because it has thus far defied being able to be proven true or false by experiment. Familiar with this complaint, Greene described what he considered several promising developments. For a long time string theorists had thought that the extra dimensions must be as small as the size of the Planck length and, therefore, beyond detectability. In the last few years work has been done suggesting that some dimensions might be as big as 10-2 cm. “That’s a size you can almost see with your eyes.” We haven’t seen them because the only force that could penetrate into these extra dimensions is gravity. Unfortunately, the force of gravity is many powers of 10 weaker than the smallest size that can be currently probed in physics laboratories. However, there are some experiments planned to be done at CERN in 2007 in which we may actually see the extra dimensions by observing the effect of gravity on other dimensions. Greene’s current research involves looking for signatures of string theory in astronomical data. Proponents of loop quantum gravity are also looking to the stars for confirmation of their calculations. The Gamma-ray Large Area Space Telescope (GLAST), due to be launched in 2006, should be sensitive enough to detect from the light from gamma-ray bursts the verification LQG researchers seek. ### M-Theory In recent years string theory has undergone a transformation. Much of this dates from a milestone event, the “Strings 1995” conference at the University of California that marked the beginning of the Second Superstring Revolution. It was there that Edward Witten delivered his startling finding that string theory requires 11 dimensions and that what had until then been viewed as five competing superstring theories are really all part of one superstring framework, which he called “M-Theory.” What the “M” refers to is not clear. “Mysterious” is one proposed meaning, since how the framework relates the theories to each other has not been defined. M-theory also “inflates” strings into two-dimensional “branes” (from “membranes”) that could contain entire alternate universes. And most important to its critics from LQG, M-theory is expected, as it develops, to enable string theory to be “background independent,” like LQG, so that it does not need to rely on the standard model of spacetime. ### The Next Book For all of their competitiveness, researchers in both string theory and LQG frequently speculate that they could be working on different paths toward what may be one unified theory. This may explain why Greene’s next book, The Fabric of the Cosmos: Space, Time, and the Texture of Reality, due from Knopf in February 2004, seems designed to encompass a range of theoretical possibilities. He noted that his coverage of space and time in The Elegant Universe addressed only what was needed as background for his explanation of string theory. Many other aspects he left uncovered. In his new book they get center stage as he probes how our fundamental ideas of space and time have changed in their nature and importance over the past century. If Greene’s knack for engaging broad audiences holds true, it will undoubtedly expand the ranks and enjoyment of those eager to follow the lively scramble to the ultimate Theory of Everything. *Also read: [Adnan Waly: A Life and Career in Physics](https://www.nyas.org/ideas-insights/blog/adnan-waly-a-life-and-career-in-physics/)* Author *** ![Image](https://www.nyas.org/wp-content/uploads/2024/02/nyasSwirl_Black.jpg) Contributing Author Subscribe to our newsletter Follow us on social ![](https://www.nyas.org/images/nyas-logo-clear.png) The mission of The New York Academy of Sciences is to drive innovative solutions to society's challenges by advancing scientific research, education and policy. 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Readable Markdown	Blog Article ## Talking Physics: String Theory’s Dangling Claims ### Theoretical physicist and Columbia University professor Brain Greene delves into the intense rivalry between loop quantum gravity and string theory, and how it ties to Einstein. Published January 1, 2004 By Rich Kelley As philosopher Paul Feyerabend once noted, science moves more rapidly when there are several competing approaches to a problem. Much of the excitement in theoretical physics today surrounds the intense rivalry between loop quantum gravity (LQG) and string theory. Both theories aspire to achieve the Holy Grail of modern physics: the unification of general relativity and quantum mechanics. They both have their champions and detractors. Both have had difficulty finding experimental verification of their predictions, yet both claim to be on the verge of discovering results that will do just that. Loop quantum gravity’s best known proponent is Lee Smolin, author of Three Roads to Quantum Gravity, and a research physicist at Perimeter Institute for Theoretical Physics in Waterloo, Canada. String theory’s most high-profile current spokesperson is Brian Greene. Professor of Physics and Mathematics at Columbia University, Greene came to The New York Academy of Sciences (the Academy) on Oct. 16, 2003, for an informal conversation as part of his whirlwind tour to promote the NOVA series based on The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory, his bestselling 1999 book. Four years in the making and with a budget of \$3.5 million, “The Elegant Universe” premiered with a two-hour segment, “Einstein’s Dream” and “String’s the Thing” on PBS on Tuesday, Oct. 28, 2003, and concluded with a one-hour program, “Welcome to the 11th Dimension,” on November 4. ### String Theory’s Core Much as he did in his first NOVA segment, Greene began his talk by briefly describing the history of the conflict: how Einstein revolutionized our worldview by conceiving of space and time as a continuum, spacetime; how scientists in the 1920s and ‘30s invented quantum mechanics to describe the microscopic properties of the universe; and how these two radical worldviews clashed. String theory promises to reconcile these two views of spacetime – Einstein’s vast fabric and the jittery landscape of quantum mechanics. The NOVA animations made clear just how visually captivating this story is. One showed an “elevator of the imagination” traveling to floors smaller by 10 orders of magnitude to illustrate the transition from the placid Einsteinian realm of large things down to the turbulent, frenetic world of atoms, electrons, protons and quarks. It is at this lowest level of matter that we find the core contribution of string theory. At the smallest of scales, inside a quark, lies not a point but a fundamentally extended object that looks like a string. A vibrating loop of string. At the microscopic level the world is made up of music, notes, resonant vibrating frequencies. This is the heart of string theory. ### The Mechanism for Reconciling Relativity What enables these strings to become the mechanism for reconciling relativity and the laws of the microworld is that these strings have size. In particle physics, point particles have no size at all. In principle you could measure and probe at any scale. But if particles have length, then it makes no sense to believe you can probe into areas that are smaller than the length of the particle itself. String theory posits that at the smallest of scales, the smallest elements do have a defined length, what is called Planck length, “a millionth of a billionth of a billionth of a billionth of a centimeter” (10-33 centimeter). For analogous reasons loop quantum gravity also posits a smallest unit of space. Its minimum volume is the cube of the Planck length. In one of the most memorable animations from the show, we travel again to the lowest, most turbulent level of the microscopic world, the world of point particles. But much as when the landscape on a map zooms out when the scale changes, when we define the lowest level as one in which the smallest elements have a defined size, the spatial grid rises above the turbulence and the jitters calm down. ### Worlds of Dimensions One of the most provocative components of string theory is its insistence that the world has more than three spatial dimensions. String theory calls for six or seven extra dimensions. In the television series, Greene focuses more on how there could be these extra dimensions, rather than on why they need to exist. Greene’s book acknowledges that the need for the extra dimensions is primarily driven by the mathematics behind string theory. In order for the negative probabilities of the quantum mechanical calculations to cancel out, the strings need to vibrate in nine independent spatial directions. Of course, these are not dimensions as we know them. Greene instructs us to “imagine that these extra dimensions come not uniformly large that we can see with our eyes, but small, tightly curled up. So small we just can’t see them.” If any aspect of string theory is ripe for visual exploitation via animation, this is it. Many readers of the book will enjoy the series if only to get the chance to see what animated Calabi-Yau manifolds look like. In 1984 a number of string physicists identified the Calabi-Yau class of six-dimensional shapes as meeting the conditions the equations for the extra dimensions require. The manifolds consist of overlapping and entwined doughnut shapes, each of which represents a separate dimension. If we zoom again into the microscopic world we can envision encountering curled up dimensions that look much like these Calabi-Yau manifolds – “simple rotating structures” in Greene’s description. “That’s the basic idea of string theory. In a nutshell it requires the world to have more dimensions than we are familiar with.” In an extensive question-and-answer exchange after his talk, Brian Greene amplified his ideas. ### Experimental Verification Elegant as it is, string theory has roused the ire of some physicists because it has thus far defied being able to be proven true or false by experiment. Familiar with this complaint, Greene described what he considered several promising developments. For a long time string theorists had thought that the extra dimensions must be as small as the size of the Planck length and, therefore, beyond detectability. In the last few years work has been done suggesting that some dimensions might be as big as 10-2 cm. “That’s a size you can almost see with your eyes.” We haven’t seen them because the only force that could penetrate into these extra dimensions is gravity. Unfortunately, the force of gravity is many powers of 10 weaker than the smallest size that can be currently probed in physics laboratories. However, there are some experiments planned to be done at CERN in 2007 in which we may actually see the extra dimensions by observing the effect of gravity on other dimensions. Greene’s current research involves looking for signatures of string theory in astronomical data. Proponents of loop quantum gravity are also looking to the stars for confirmation of their calculations. The Gamma-ray Large Area Space Telescope (GLAST), due to be launched in 2006, should be sensitive enough to detect from the light from gamma-ray bursts the verification LQG researchers seek. ### M-Theory In recent years string theory has undergone a transformation. Much of this dates from a milestone event, the “Strings 1995” conference at the University of California that marked the beginning of the Second Superstring Revolution. It was there that Edward Witten delivered his startling finding that string theory requires 11 dimensions and that what had until then been viewed as five competing superstring theories are really all part of one superstring framework, which he called “M-Theory.” What the “M” refers to is not clear. “Mysterious” is one proposed meaning, since how the framework relates the theories to each other has not been defined. M-theory also “inflates” strings into two-dimensional “branes” (from “membranes”) that could contain entire alternate universes. And most important to its critics from LQG, M-theory is expected, as it develops, to enable string theory to be “background independent,” like LQG, so that it does not need to rely on the standard model of spacetime. ### The Next Book For all of their competitiveness, researchers in both string theory and LQG frequently speculate that they could be working on different paths toward what may be one unified theory. This may explain why Greene’s next book, The Fabric of the Cosmos: Space, Time, and the Texture of Reality, due from Knopf in February 2004, seems designed to encompass a range of theoretical possibilities. He noted that his coverage of space and time in The Elegant Universe addressed only what was needed as background for his explanation of string theory. Many other aspects he left uncovered. In his new book they get center stage as he probes how our fundamental ideas of space and time have changed in their nature and importance over the past century. If Greene’s knack for engaging broad audiences holds true, it will undoubtedly expand the ranks and enjoyment of those eager to follow the lively scramble to the ultimate Theory of Everything. *Also read: [Adnan Waly: A Life and Career in Physics](https://www.nyas.org/ideas-insights/blog/adnan-waly-a-life-and-career-in-physics/)*
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