🕷️ Crawler Inspector

URL Lookup

Direct Parameter Lookup

Raw Queries and Responses

1. Shard Calculation

Query:

Response:

Calculated Shard: 8 (from laksa153)

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/25325-fermi-paradox.html\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.space.com/25325-fermi-paradox.html\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.space.com\/25325-fermi-paradox.html","crawl_time":1775808558,"first_indexed_time":1497112651,"http_code":200,"src_unparsed":"com,space!www,\/25325-fermi-paradox.html s443","src_root_hash":"7770394665477845008","history_drop_reason":null,"meta_title":"The Fermi Paradox - Where are all the aliens? | Space","meta_descriptions":["Discover the Fermi Paradox — why, in a vast universe full of stars and planets, haven't we found extraterrestrial life? Explore the theories behind this great mystery."],"attrs_boilerpipe_text":"The Fermi Paradox seeks to answer the question of where the aliens are. After all, the universe is incredibly old, big and filled with potentially habitable planets.\n(Image credit: bjdlzx via Getty Images)\nThe universe is vast, ancient, and teeming with billions of potentially habitable planets.\nWith so many chances for intelligent life to arise, we should expect to see evidence of extraterrestrials.\nFermi Paradox FAQs\nWas the Fermi Paradox solved?\nHumanity has been around for just 200,000 years, and we've been listening for possible radio signals from E.T. just since 1960. So the odds that we will overlap in time and space with a detectable alien civilization don't seem great. There is probably no single solution to the Fermi Paradox\nWhat is the great silence theory?\nThe \"great silence\" is the idea that there is no evidence of extraterrestrial civilizations and that we are truly alone in the universe; it is also known as the Fermi Paradox.\nAre we truly alone in the cosmos?\n(Image credit: Created in Canva Pro by Daisy Dobrijevic)\nIs the dark forest theory true?\nWhile some intelligent extraterrestrial civilizations might choose to remain hidden, as suggested by the dark forest theory, it’s unlikely that every single one would adopt the same fear-driven strategy.\nThe scale of the paradox\nOur home galaxy, the Milky Way, contains an estimated 100 to 400 billion stars.\n(Image credit: Getty Images)\nThe numbers are staggering. Our\nMilky Way\nalone contains an estimated 100 to 400 billion stars, many of them hosting planets in the\nhabitable zone\n. If even a tiny fraction of these planets develop life, and a fraction of those develop intelligence and technology, the galaxy should be buzzing with signals, megastructures, or even interstellar visitors. But so far, we’ve found nothing.\n\"Fermi grasped that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire galaxy,\" representatives of the Search For Extraterrestrial Intelligence (SETI) Institute in Mountain View, California, wrote in a\nFermi Paradox explainer\n. \"Within a few tens of millions of years, every star system could be brought under the wing of empire. Tens of millions of years may sound like a long project, but in fact it’s quite short compared to the age of the galaxy, which is roughly a thousand times more.\"\nPossible explanations\nThere are many possible hypotheses that attempt to solve the Fermi Paradox.\n(Image credit: Coneyl Jay)\nThere are numerous hypotheses attempting to resolve the paradox, ranging from the optimistic to the ominous:\n1. They're out there, but we haven't found them yet\nRadio Silence\n: We might not be listening at the right frequencies or in the right way. Civilizations could communicate using methods we haven’t discovered yet, like neutrino beams or\nquantum entanglement\n.\nBreaking space news, the latest updates on rocket launches, skywatching events and more!\nThe Cosmic Timescale\n: Humanity has only been scanning the skies for a few decades — an eye blink in cosmic history. Advanced civilizations could\nrise and fall in cycles\n, missing each other in time.\n2. They don't want to be found\nThe Zoo Hypothesis\n: Aliens could be\nobserving us\nlike we observe animals in a nature reserve, choosing not to interfere.\nThe Dark Forest Theory\n: Inspired by Liu Cixin’s sci-fi novel\nThe Dark Forest\n, this\nidea suggests\nthat intelligent species stay silent to avoid detection by potentially hostile civilizations.\n3. Something prevents their expansion\nThe Great Filter\n: This\ntheory suggests\nthat there is a nearly insurmountable barrier preventing civilizations from advancing. This could be at the stage of life’s emergence, intelligent life’s development, or a self-destructive phase like nuclear war or environmental collapse.\nSelf-Limiting Civilizations\n: Advanced societies may become so technologically sophisticated that they lose interest in space expansion, opting for virtual realities or inward development.\nImplications for humanity\nThe \"great silence\" of the cosmos represents one of the greatest mysteries of our time.\n(Image credit: Paolo Carnassale via Getty Images)\nUnderstanding the Fermi Paradox is more than just an intellectual exercise — it has real implications for our future. If the Great Filter lies behind us (e.g., life itself is incredibly rare), then we may be one of the first intelligent civilizations. If the filter is ahead (e.g., technological civilizations inevitably destroy themselves), then our survival is far from guaranteed.\nOur\nsearch for extraterrestrial intelligence\n(SETI) continues, with new projects like the\nJames Webb Space Telescope\nanalyzing\nexoplanet\natmospheres and advanced AI scanning for signals. Whether we find aliens or confirm our solitude, the answer to the Fermi Paradox will profoundly shape our understanding of our place in the universe.\nThe \"great silence\" of the cosmos may be unsettling, but it also presents one of the greatest mysteries of our time. Are we alone, or is something preventing us from hearing the others? Until we find an answer, the question remains open.\nFermi paradox expert Q&A\nWe asked Professor Heidi Jo Newberg from the Rensselaer Polytechnic Institute a few questions about the Fermi Paradox.\nHeidi Jo Newberg is an astrophysicist currently studying the structure of our galaxy. She has conducted diverse research in astrophysics, including on stars, supernovas, and both our galaxies and others. She recently received a grant from NASA to work on an alternative to conventional telescopes to detect exoplanets that could support life.\nDo modern researchers tend to accept the premise of the Fermi Paradox — that is, if intelligent life outside our planet exists, then it's likely that they would have contacted or reached Earth by now?\nI can't speak for everyone else, but no I do not believe in the premise. Because the Earth is the only planet where we know that life exists, we can only make guesses based on how life here has evolved.\nThe Earth formed about 4.6 billion years ago. Life on Earth began at least 3.5 billion years ago, since fossils of this age have been found, but simpler cells are expected to have formed earlier than that. Possibly, life on Earth started very quickly after conditions allowed for liquid water to be commonly available. On the other hand, life that had more than one cell took until about 1 billion years ago, and humans did not evolve in 0.2 billion years ago. As far as we know, humans are the only life form on the Earth that thinks about what is going on in the Universe, and could potentially communicate with other life. The first telescopes were invented about 400 years ago, and the first space probes were launched less than 100 years ago.\nWhat I take away from this is that simple life (like one celled organisms) might be easy to create, but complex life is harder, and life that tries to communicate with life elsewhere in the Universe could be extremely rare. While the technology to find and communicate with extraterrestrial life, once started, appears to develop extremely fast on the timeline of the Universe, we do not know how long modern humans will survive as a species.\nIs there a commonly accepted way to resolve the Fermi Paradox?\nI doubt there is a commonly accepted way to resolve the Fermi Paradox, other than to point to the fact that we have very little information about highly evolved intelligent life. We don't know how rare it is, how long a civilization lasts, how likely it would or would not want to communicate with us, how likely it would spread through the Galaxy, or how we would recognize and understand each other. In the absence of any real information to figure any of this out, it just seems like there are many possibilities to solve it.\nIn evaluating the Fermi Paradox, it is important to think about the vast distances of space in the Milky Way. The time for light to travel to the nearest star is more than four years. If a rocket ship travels 20,000 miles per hour, then it would take more than 33,000 years to get there. The light travel time from the Sun to the center of our galaxy is 30,000 years. The rocket travel time is a 170 million years. It is completely unclear whether life will want to, or be able to, travel over these sorts of distances to populate the Galaxy. If it is attempted, it is not clear whether there are suitable places for it to land and thrive. Spreading life throughout the galaxy might be much more difficult than Fermi supposed.\nDo researchers studying exoplanets, particularly potentially habitable ones, usually consider the Fermi Paradox?\nModern researchers looking for potentially habitable planets usually use the\nSeager Equation\nwhen they are thinking about the likelihood of finding life. This is an\nupdate\nof the Drake Equation which was a summary of what people were looking for in 1961. Note that one of the key differences is that the Seager Equation asks how many planets we can find with life that transformed the atmosphere (for example by photosynthesis), while the Drake Equation calculates the number of civilizations that are sending out detectable radio waves. In the 20th century, the SETI program looked for these civilizations and found no signals of such civilizations.\nSo you can see that the conversation has changed to the search for life that is not necessarily intelligent — something that the Earth's history would tell us is much more likely to find. I occasionally teach an Exoplanets and Life class, and the textbook I use does not talk about the Fermi Paradox. My expectation is that most researchers are not currently thinking about it. The current search is for exoplanets, habitable exoplanets with liquid water, and signs of life that is not necessarily intelligent.\nWhat are some ways current research might eventually resolve the Fermi Paradox?\nAs we learn more about exoplanets, it becomes more possible to make statistical statements about the likelihood of life, and the possibility for it to spread. The basis of the paradox lies in the idea that there are hundreds of billions of stars in the Milky Way, and with so many there must be other intelligent life on one of them. But we don't really have a way to assess whether that is true.\nIn six tons of sand, there are hundreds of billions of grains of sand. So, it might seems reasonable to think that there must be at least one of them that is made of uranium. But we don't look for uranium on the beach because if it was there, it would be dissolved in the water and wash away. Just having a large number of objects doesn't mean that every possibility for what those objects are must therefore exist.\nCurrent experiments are teaching us how many exoplanets there are, what the conditions are on those planets, how common it is for exoplanets to have surface temperatures that allow for liquid water, and possibly how many exoplanets exhibit atmospheric abundances that favor the existence of life. We are working towards actually finding other life of any kind that is on another planet. This information would give us some basis for then extrapolating to the probability that technological civilizations form elsewhere, and would tell us how far they might have to travel to find the nearest habitable planet where they could establish a colony.\nAdditional resources\nIf you're looking to explore the Fermi Paradox in depth, a great starting point is Stephen Webb’s book, \"\nIf the Universe Is Teeming with Aliens… Where Is Everybody?\n\" This book lays out 75 possible solutions to the paradox, covering scientific, philosophical, and speculative ideas in an accessible yet detailed way. For an engaging online read, the\nWait But Why article on the Fermi Paradox\nis a great place to start. Additionally, the\nSETI Institute’s website\nprovides up-to-date research, news, and expert insights on the search for extraterrestrial intelligence, including discussions on why we might not have found aliens yet.\nBibliography\n“The Fermi Paradox.”\nSETI Institute\n,\nhttps:\/\/www.seti.org\/fermi-paradox-0\n. Accessed 5 March 2025.\n“The Fermi Paradox - Higgs Centre for Theoretical Physics.”\nThe Higgs Centre for Theoretical Physics\n,\nhttps:\/\/higgs.ph.ed.ac.uk\/outreach\/higgshalloween-2021\/fermi-paradox\n. Accessed 5 March 2025.\n“Fermi's Paradox.”\nUniversity of Oregon\n,\nhttps:\/\/pages.uoregon.edu\/jschombe\/cosmo\/lectures\/lec28.html\n. Accessed 5 March 2025.\nShare your thoughts\n0\n1\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\nDaisy Dobrijevic joined Space.com in February 2022, having previously worked as a staff writer for All About Space magazine. She completed an editorial internship with BBC Sky at Night Magazine and worked at the National Space Centre, communicating space science to the public.\nDaisy holds a PhD in plant physiology and a Master's in Environmental Science. Based in Nottingham, U.K., she covers all things space, with a special focus on solar activity and space weather. She also has a keen interest in astrotourism and is always on the lookout for the next northern lights adventure.\nShe will be a guest speaker aboard\nHX's Solar Eclipse Expedition\nin August 2026 and will join Hurtigruten as an\nonboard astronomer\nfor a northern lights sailing in January 2027.","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\/25325-fermi-paradox.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\n**0**\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    - 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The galaxy occupies most of the image as a fuzzy blue-white oval with spiral features extending out clockwise. The light clouds are interspersed with small dark brown splotches in the same spiral pattern around the center, representing dust clouds. The galaxy’s center is a bright yellow glow. Overlaid on top of and surrounding the galaxy are several criss-crossing, faint tendrils of stars that represent satellite dwarf galaxies and star clusters that have been stretched out into long thin lines. The tendrils have various lengths and widths, though all are arcs rather than complete circles. The background is black.](https:\/\/cdn.mos.cms.futurecdn.net\/RUWT2sj9SoA9QNeJdUZ5F5.jpg) Stars Dozens of hidden star streams found in the outskirts of our Milky Way galaxy](https:\/\/www.space.com\/astronomy\/stars\/dozens-of-hidden-star-streams-found-in-the-outskirts-of-our-milky-way-galaxy \"Dozens of hidden star streams found in the outskirts of our Milky Way galaxy\")\n\n[![A blue ball is illustrated in the middle of lots of swirling dust and there are bright green loops protruding from the ball, representing the magnetic field. 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How life could thrive on moons of starless 'rogue' planets](https:\/\/www.space.com\/space-exploration\/search-for-life\/no-sun-no-problem-how-life-could-thrive-on-moons-of-starless-rogue-planets \"No sun, no problem? How life could thrive on moons of starless 'rogue' planets\")\n\n[![Split image showing a screenshot of Ryan Gosling in Project Hail Mary on the left and author Andy Weir holding up the book on the right.](https:\/\/cdn.mos.cms.futurecdn.net\/DTwgGSCpsG3SLSbYvUAt3i.jpg) Space Movies & Shows Sci-fi author Andy Weir explains the astrobiology behind 'Project Hail Mary' (interview)](https:\/\/www.space.com\/entertainment\/space-movies-shows\/i-talked-to-andy-weir-about-the-astrobiology-behind-project-hail-mary \"Sci-fi author Andy Weir explains the astrobiology behind 'Project Hail Mary' (interview)\")\n\n[![an astronaut floats above a swirling green planet](https:\/\/cdn.mos.cms.futurecdn.net\/Tt7cwV74EJuRxAM9AV683j.png) Space Movies & Shows Where should we send a real 'Hail Mary' spacecraft? 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A new study has the answers\")\n\n[![Tons of stars are seen against a dark sky.](https:\/\/cdn.mos.cms.futurecdn.net\/ByQu7tUFuSMpYdXfnazjcH.png) Stars 'At the edge of what we thought possible': Astronomers find extremely rare star from ancient universe](https:\/\/www.space.com\/astronomy\/stars\/at-the-edge-of-what-we-thought-possible-astronomers-find-extremely-rare-star-from-ancient-universe \"'At the edge of what we thought possible': Astronomers find extremely rare star from ancient universe\")\n\n[![On the left, a giant orange arc emerges, rising slightly. between that, all the way right, through the middle, seven planets of varying colors and texturs.](https:\/\/cdn.mos.cms.futurecdn.net\/JeQYsG4tEK6zMabKsPWZ8b.jpg) Exoplanets These 45 exoplanets may be the best places to search for alien life](https:\/\/www.space.com\/astronomy\/exoplanets\/these-45-exoplanets-may-be-the-best-places-to-search-for-alien-life \"These 45 exoplanets may be the best places to search for alien life\")\n\n[![An illustration shows two planets colliding around the star Gaia20ehk](https:\/\/cdn.mos.cms.futurecdn.net\/S8xCJoFb4XgrFZAAmemjPY.png) Exoplanets 'Completely bonkers': Astronomers find evidence of a cataclysmic collision between exoplanets](https:\/\/www.space.com\/astronomy\/exoplanets\/completely-bonkers-astronomers-find-evidence-of-a-cataclysmic-collision-between-planets \"'Completely bonkers': Astronomers find evidence of a cataclysmic collision between exoplanets\")\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\n[![Pink structures looks like dots all across the image. 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One small portion of that magnification represents 10 million light-years. ](https:\/\/cdn.mos.cms.futurecdn.net\/ZQyHA4S4kaqxqpH4soe5z4.jpg) Astronomy Astronomers unveil largest 3D universe map of its kind, illuminating 'hidden' cosmic structures](https:\/\/www.space.com\/astronomy\/astronomers-unveil-largest-3d-map-yet-of-hydrogen-light-in-the-early-universe-illuminating-hidden-cosmic-structures \"Astronomers unveil largest 3D universe map of its kind, illuminating 'hidden' cosmic structures\")\n\nTrending\n\n- [Artemis 2 LIVE: Moon mission updates](https:\/\/www.space.com\/news\/live\/artemis-2-nasa-moon-mission-updates-april-9-2026#mrfhud=true)\n- [Top picks of Artemis 2 merch](https:\/\/www.space.com\/technology\/nasa-artemis-2-gifts-we-love-top-picks-for-aspiring-astronauts)\n- [Night sky tonight\\!](https:\/\/www.space.com\/what-to-see-night-sky-april-2026-maps)\n- [Aurora Forecast](https:\/\/www.space.com\/live\/aurora-forecast-northern-lights-possible-tonight-april-10-12)\n- [Space Calendar](https:\/\/www.space.com\/32286-space-calendar.html)\n- [Live 4K Sen video from space\\!](https:\/\/www.space.com\/astronomy\/earth\/live-4k-video-from-space-see-earth-from-the-iss-with-sharp-eyed-sen-cameras)\n- [Best Drones](https:\/\/www.space.com\/best-drones)\n- [Lego Star Wars deals](https:\/\/www.space.com\/lego-star-wars-deals)\n- [Next Full Moon](https:\/\/www.space.com\/16830-full-moon-calendar.html)\n- [Best Telescopes](https:\/\/www.space.com\/15693-telescopes-beginners-telescope-reviews-buying-guide.html)\n- [Solar System Planets](https:\/\/www.space.com\/16080-solar-system-planets.html)\n- [Best Star Projectors](https:\/\/www.space.com\/best-star-projectors)\n- [Best Binoculars](https:\/\/www.space.com\/26021-best-binoculars.html)\n\n1. [Space Exploration](https:\/\/www.space.com\/space-exploration)\n2. [Search for Life](https:\/\/www.space.com\/space-exploration\/search-for-life)\n# The Fermi Paradox: Where are all the aliens?\n[References](https:\/\/www.space.com\/references)\n\nBy [Daisy Dobrijevic](https:\/\/www.space.com\/author\/daisy-dobrijevic)\n\nlast updated\n\nApril 4, 2025\n\nDiscover the Fermi Paradox — why, in a vast universe full of stars and planets, haven't we found extraterrestrial life? Explore the theories behind this great mystery.\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![man sits on a rock under the milky way. Are we alone in the universe?](https:\/\/cdn.mos.cms.futurecdn.net\/6SMGeKptzTqHRuipe9cC49.jpg)\n\nThe Fermi Paradox seeks to answer the question of where the aliens are. After all, the universe is incredibly old, big and filled with potentially habitable planets. (Image credit: bjdlzx via Getty Images)\n\nJump to:\n\n- [Fermi Paradox FAQs](https:\/\/www.space.com\/25325-fermi-paradox.html#section-fermi-paradox-faqs)\n- [The scale of the paradox](https:\/\/www.space.com\/25325-fermi-paradox.html#section-the-scale-of-the-paradox)\n- [Possible explanations](https:\/\/www.space.com\/25325-fermi-paradox.html#section-possible-explanations)\n- [Implications for humanity](https:\/\/www.space.com\/25325-fermi-paradox.html#section-implications-for-humanity)\n- [Fermi paradox expert Q\\&A](https:\/\/www.space.com\/25325-fermi-paradox.html#section-fermi-paradox-expert-q-a)\n- [Additional resources](https:\/\/www.space.com\/25325-fermi-paradox.html#section-additional-resources)\n\n- Copy link\n- [Facebook](https:\/\/www.facebook.com\/sharer\/sharer.php?u=https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.html)\n- [X](https:\/\/twitter.com\/intent\/tweet?text=The+Fermi+Paradox%3A+Where+are+all+the+aliens%3F&url=https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.html)\n- [Whatsapp](whatsapp:\/\/send?text=The+Fermi+Paradox%3A+Where+are+all+the+aliens%3F+https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.html?fwa)\n- [Reddit](https:\/\/www.reddit.com\/submit?url=https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.html&title=The+Fermi+Paradox%3A+Where+are+all+the+aliens%3F)\n- [Pinterest](https:\/\/pinterest.com\/pin\/create\/button\/?url=https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.html&media=https%3A%2F%2Fcdn.mos.cms.futurecdn.net%2F6SMGeKptzTqHRuipe9cC49.jpg)\n- [Flipboard](https:\/\/share.flipboard.com\/bookmarklet\/popout?title=The+Fermi+Paradox%3A+Where+are+all+the+aliens%3F&url=https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.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\/25325-fermi-paradox.html)\n\nShare this article\n\n[0](https:\/\/www.space.com\/25325-fermi-paradox.html#viafoura-comments)\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\\\/). 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\nYou are now subscribed\n\nYour newsletter sign-up was successful\n\n***\nWant to add more newsletters?\n\n![Daily Newsletter](https:\/\/cdn.mos.cms.futurecdn.net\/vfpcxVDrtfCysGSjzYjeSg.png)\n\nDelivered daily\n\nDaily Newsletter\n\nBreaking space news, the latest updates on rocket launches, skywatching events and more\\!\n\nSubscribe +\n\n![Watch This Space](https:\/\/cdn.mos.cms.futurecdn.net\/tjzmFi262iKuxrcCtSghKg.jpg)\n\nOnce a month\n\nWatch This Space\n\nSign 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.\n\nSubscribe +\n\n![Night Sky This Week](https:\/\/cdn.mos.cms.futurecdn.net\/qsHaEcQ6H695rhBoNZdK5g.jpg)\n\nOnce a week\n\nNight Sky This Week\n\nDiscover 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\\!\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\nThe universe is vast, ancient, and teeming with billions of potentially habitable planets.\n\nWith so many chances for intelligent life to arise, we should expect to see evidence of extraterrestrials.\n\nYet, despite decades of searching, the cosmos remains eerily silent. This contradiction is known as the **Fermi Paradox**, first proposed by physicist Enrico Fermi in 1950.\n\nYou may like\n\n- [![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) Where are all the aliens? Maybe they just don't want to talk to us](https:\/\/www.space.com\/space-exploration\/search-for-life\/where-are-all-the-aliens-maybe-they-just-dont-want-to-talk-to-us)\n- [![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) 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)\n- [![an astronaut floats above a swirling green planet](https:\/\/cdn.mos.cms.futurecdn.net\/Tt7cwV74EJuRxAM9AV683j.png) Where should we send a real 'Hail Mary' spacecraft? A new study has the answers](https:\/\/www.space.com\/entertainment\/space-movies-shows\/where-could-we-send-a-real-hail-mary-spacecraft-a-new-study-has-the-answers)\n\n[Click here for more Space.com videos...](https:\/\/videos.space.com\/m\/u26wmKKL\/where-is-et-seti-vs-the-fermi-paradox?list=9wzCTV4g)\n\n## Fermi Paradox FAQs\n### Was the Fermi Paradox solved?\nHumanity has been around for just 200,000 years, and we've been listening for possible radio signals from E.T. just since 1960. So the odds that we will overlap in time and space with a detectable alien civilization don't seem great. There is probably no single solution to the Fermi Paradox\n\n### What is the great silence theory?\nThe \"great silence\" is the idea that there is no evidence of extraterrestrial civilizations and that we are truly alone in the universe; it is also known as the Fermi Paradox.\n\n![graphic illustration of the fermi paradox shows two people looking up at the milky way and a graphic above their heads showing an empty fuel gauge with the image of an alien on it, indicating a distinct lack of aliens.](https:\/\/cdn.mos.cms.futurecdn.net\/RUirVJ8ZVjAsgspC3ya6z5.jpg)\n\nAre we truly alone in the cosmos? (Image credit: Created in Canva Pro by Daisy Dobrijevic)\n\n### Is the dark forest theory true?\nWhile some intelligent extraterrestrial civilizations might choose to remain hidden, as suggested by the dark forest theory, it’s unlikely that every single one would adopt the same fear-driven strategy.\n### The scale of the paradox\n![The milky way galaxy as seen over a mountain range.](https:\/\/cdn.mos.cms.futurecdn.net\/nP8zA5qg8tFCAWLwbnamph.jpg)\n\nOur home galaxy, the Milky Way, contains an estimated 100 to 400 billion stars. (Image credit: Getty Images)\n\nThe numbers are staggering. Our [Milky Way](https:\/\/www.space.com\/19915-milky-way-galaxy.html) alone contains an estimated 100 to 400 billion stars, many of them hosting planets in the [habitable zone](https:\/\/www.space.com\/goldilocks-zone-habitable-area-life). If even a tiny fraction of these planets develop life, and a fraction of those develop intelligence and technology, the galaxy should be buzzing with signals, megastructures, or even interstellar visitors. But so far, we’ve found nothing.\n\n\"Fermi grasped that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire galaxy,\" representatives of the Search For Extraterrestrial Intelligence (SETI) Institute in Mountain View, California, wrote in a [Fermi Paradox explainer](https:\/\/www.seti.org\/fermi-paradox-0). \"Within a few tens of millions of years, every star system could be brought under the wing of empire. Tens of millions of years may sound like a long project, but in fact it’s quite short compared to the age of the galaxy, which is roughly a thousand times more.\"\n\n## Possible explanations\n![An artist\\&\\#039;s image of an alien starship as viewed from a planet\\&\\#039;s surface.](https:\/\/cdn.mos.cms.futurecdn.net\/Fu7f3DbymUm8kL9RDvfA4.jpeg)\n\nThere are many possible hypotheses that attempt to solve the Fermi Paradox. (Image credit: Coneyl Jay)\n\nThere are numerous hypotheses attempting to resolve the paradox, ranging from the optimistic to the ominous:\n\n## 1\\. They're out there, but we haven't found them yet\n**Radio Silence**: We might not be listening at the right frequencies or in the right way. Civilizations could communicate using methods we haven’t discovered yet, like neutrino beams or [quantum entanglement](https:\/\/www.space.com\/31933-quantum-entanglement-action-at-a-distance.html).\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\n**The Cosmic Timescale**: Humanity has only been scanning the skies for a few decades — an eye blink in cosmic history. Advanced civilizations could [rise and fall in cycles](https:\/\/pages.uoregon.edu\/jschombe\/cosmo\/lectures\/lec28.html), missing each other in time.\n\n## 2\\. They don't want to be found\n**The Zoo Hypothesis**: Aliens could be [observing us](https:\/\/pages.uoregon.edu\/jschombe\/cosmo\/lectures\/lec28.html) like we observe animals in a nature reserve, choosing not to interfere.\n\n**The Dark Forest Theory**: Inspired by Liu Cixin’s sci-fi novel *The Dark Forest*, this [idea suggests](https:\/\/higgs.ph.ed.ac.uk\/outreach\/higgshalloween-2021\/fermi-paradox) that intelligent species stay silent to avoid detection by potentially hostile civilizations.\n\nWhat to read next\n\n- [![artist\\&\\#039;s impression of a pulsar ejecting vast pulses of radiation. ](https:\/\/cdn.mos.cms.futurecdn.net\/7kCUkCxg6mAD2CXZ9kdKRa.jpg) Astronomers searching for alien life are sharpening our cosmic clocks. Here's why](https:\/\/www.space.com\/space-exploration\/search-for-life\/astronomers-searching-for-alien-life-are-sharpening-our-cosmic-clocks-heres-why)\n- [![Images from the SETI@home project, including a screenshot of the SETI@home data and a man looking at a large computer with the same screen](https:\/\/cdn.mos.cms.futurecdn.net\/2wUmfrBEPjRk7FYcfJYAxP.jpg) This SETI program is chasing down its final 100 signals. Could one of them be from aliens?](https:\/\/www.space.com\/space-exploration\/search-for-life\/this-seti-program-is-chasing-down-its-final-100-signals-could-one-of-them-be-from-aliens)\n- [![On the left, a giant orange arc emerges, rising slightly. between that, all the way right, through the middle, seven planets of varying colors and texturs.](https:\/\/cdn.mos.cms.futurecdn.net\/JeQYsG4tEK6zMabKsPWZ8b.jpg) These 45 exoplanets may be the best places to search for alien life](https:\/\/www.space.com\/astronomy\/exoplanets\/these-45-exoplanets-may-be-the-best-places-to-search-for-alien-life)\n## 3\\. Something prevents their expansion\n**The Great Filter**: This [theory suggests](https:\/\/www.space.com\/space-exploration\/search-for-life\/how-the-great-filter-could-explain-why-we-havent-found-intelligent-aliens) that there is a nearly insurmountable barrier preventing civilizations from advancing. This could be at the stage of life’s emergence, intelligent life’s development, or a self-destructive phase like nuclear war or environmental collapse.\n\n**Self-Limiting Civilizations**: Advanced societies may become so technologically sophisticated that they lose interest in space expansion, opting for virtual realities or inward development.\n\n### Implications for humanity\n![four people stand silhouetted under a starry sky with the milky way stretching overhead.](https:\/\/cdn.mos.cms.futurecdn.net\/McWRecegXJuN5KWYE3rtBR.jpg)\n\nThe \"great silence\" of the cosmos represents one of the greatest mysteries of our time. (Image credit: Paolo Carnassale via Getty Images)\n\nUnderstanding the Fermi Paradox is more than just an intellectual exercise — it has real implications for our future. If the Great Filter lies behind us (e.g., life itself is incredibly rare), then we may be one of the first intelligent civilizations. If the filter is ahead (e.g., technological civilizations inevitably destroy themselves), then our survival is far from guaranteed.\n\nOur [search for extraterrestrial intelligence](https:\/\/www.space.com\/33626-search-for-extraterrestrial-intelligence.html) (SETI) continues, with new projects like the [James Webb Space Telescope](https:\/\/www.space.com\/21925-james-webb-space-telescope-jwst.html) analyzing [exoplanet](https:\/\/www.space.com\/17738-exoplanets.html) atmospheres and advanced AI scanning for signals. Whether we find aliens or confirm our solitude, the answer to the Fermi Paradox will profoundly shape our understanding of our place in the universe.\n\nThe \"great silence\" of the cosmos may be unsettling, but it also presents one of the greatest mysteries of our time. Are we alone, or is something preventing us from hearing the others? Until we find an answer, the question remains open.\n\n## Fermi paradox expert Q\\&A\nWe asked Professor Heidi Jo Newberg from the Rensselaer Polytechnic Institute a few questions about the Fermi Paradox.\n\n![Heidi Jo Newberg](https:\/\/cdn.mos.cms.futurecdn.net\/JNoHunAQPxQhfjHLvbB3G3.jpg)\n\nHeidi Jo Newberg\n\nSocial Links Navigation\n\nProfessor, Physics, Applied Physics, and Astronomy Rensselaer Polytechnic Institute\n\nHeidi Jo Newberg is an astrophysicist currently studying the structure of our galaxy. She has conducted diverse research in astrophysics, including on stars, supernovas, and both our galaxies and others. She recently received a grant from NASA to work on an alternative to conventional telescopes to detect exoplanets that could support life.\n\n### Do modern researchers tend to accept the premise of the Fermi Paradox — that is, if intelligent life outside our planet exists, then it's likely that they would have contacted or reached Earth by now?\nI can't speak for everyone else, but no I do not believe in the premise. Because the Earth is the only planet where we know that life exists, we can only make guesses based on how life here has evolved.\n\nThe Earth formed about 4.6 billion years ago. Life on Earth began at least 3.5 billion years ago, since fossils of this age have been found, but simpler cells are expected to have formed earlier than that. Possibly, life on Earth started very quickly after conditions allowed for liquid water to be commonly available. On the other hand, life that had more than one cell took until about 1 billion years ago, and humans did not evolve in 0.2 billion years ago. As far as we know, humans are the only life form on the Earth that thinks about what is going on in the Universe, and could potentially communicate with other life. The first telescopes were invented about 400 years ago, and the first space probes were launched less than 100 years ago.\n\nWhat I take away from this is that simple life (like one celled organisms) might be easy to create, but complex life is harder, and life that tries to communicate with life elsewhere in the Universe could be extremely rare. While the technology to find and communicate with extraterrestrial life, once started, appears to develop extremely fast on the timeline of the Universe, we do not know how long modern humans will survive as a species.\n\n### Is there a commonly accepted way to resolve the Fermi Paradox?\nI doubt there is a commonly accepted way to resolve the Fermi Paradox, other than to point to the fact that we have very little information about highly evolved intelligent life. We don't know how rare it is, how long a civilization lasts, how likely it would or would not want to communicate with us, how likely it would spread through the Galaxy, or how we would recognize and understand each other. In the absence of any real information to figure any of this out, it just seems like there are many possibilities to solve it.\n\nIn evaluating the Fermi Paradox, it is important to think about the vast distances of space in the Milky Way. The time for light to travel to the nearest star is more than four years. If a rocket ship travels 20,000 miles per hour, then it would take more than 33,000 years to get there. The light travel time from the Sun to the center of our galaxy is 30,000 years. The rocket travel time is a 170 million years. It is completely unclear whether life will want to, or be able to, travel over these sorts of distances to populate the Galaxy. If it is attempted, it is not clear whether there are suitable places for it to land and thrive. Spreading life throughout the galaxy might be much more difficult than Fermi supposed.\n\n### Do researchers studying exoplanets, particularly potentially habitable ones, usually consider the Fermi Paradox?\nModern researchers looking for potentially habitable planets usually use the [Seager Equation](https:\/\/en.wikipedia.org\/wiki\/Sara_Seager) when they are thinking about the likelihood of finding life. This is an [update](https:\/\/www.seti.org\/drake-equation-inde) of the Drake Equation which was a summary of what people were looking for in 1961. Note that one of the key differences is that the Seager Equation asks how many planets we can find with life that transformed the atmosphere (for example by photosynthesis), while the Drake Equation calculates the number of civilizations that are sending out detectable radio waves. In the 20th century, the SETI program looked for these civilizations and found no signals of such civilizations.\n\nSo you can see that the conversation has changed to the search for life that is not necessarily intelligent — something that the Earth's history would tell us is much more likely to find. I occasionally teach an Exoplanets and Life class, and the textbook I use does not talk about the Fermi Paradox. My expectation is that most researchers are not currently thinking about it. The current search is for exoplanets, habitable exoplanets with liquid water, and signs of life that is not necessarily intelligent.\n\n### What are some ways current research might eventually resolve the Fermi Paradox?\nAs we learn more about exoplanets, it becomes more possible to make statistical statements about the likelihood of life, and the possibility for it to spread. The basis of the paradox lies in the idea that there are hundreds of billions of stars in the Milky Way, and with so many there must be other intelligent life on one of them. But we don't really have a way to assess whether that is true.\n\nIn six tons of sand, there are hundreds of billions of grains of sand. So, it might seems reasonable to think that there must be at least one of them that is made of uranium. But we don't look for uranium on the beach because if it was there, it would be dissolved in the water and wash away. Just having a large number of objects doesn't mean that every possibility for what those objects are must therefore exist.\n\nCurrent experiments are teaching us how many exoplanets there are, what the conditions are on those planets, how common it is for exoplanets to have surface temperatures that allow for liquid water, and possibly how many exoplanets exhibit atmospheric abundances that favor the existence of life. We are working towards actually finding other life of any kind that is on another planet. This information would give us some basis for then extrapolating to the probability that technological civilizations form elsewhere, and would tell us how far they might have to travel to find the nearest habitable planet where they could establish a colony.\n### Additional resources\nIf you're looking to explore the Fermi Paradox in depth, a great starting point is Stephen Webb’s book, \"[If the Universe Is Teeming with Aliens… Where Is Everybody?](https:\/\/target.georiot.com\/Proxy.ashx?tsid=72128&GR_URL=https%3A%2F%2Famazon.co.uk%2FUniverse-Teeming-Aliens-Everybody-Extraterrestrial%2Fdp%2F0387955011%3Ftag%3Dhawk-future-21%26ascsubtag%3Dspace-us-2738472146419429680-21)\" This book lays out 75 possible solutions to the paradox, covering scientific, philosophical, and speculative ideas in an accessible yet detailed way. For an engaging online read, the [Wait But Why article on the Fermi Paradox](https:\/\/waitbutwhy.com\/2014\/05\/fermi-paradox.html) is a great place to start. Additionally, the [SETI Institute’s website](https:\/\/waitbutwhy.com\/2014\/05\/fermi-paradox.html) provides up-to-date research, news, and expert insights on the search for extraterrestrial intelligence, including discussions on why we might not have found aliens yet.\n\n### Bibliography\n“The Fermi Paradox.” *SETI Institute*, [https:\/\/www.seti.org\/fermi-paradox-0](https:\/\/www.seti.org\/fermi-paradox-0). Accessed 5 March 2025.\n\n“The Fermi Paradox - Higgs Centre for Theoretical Physics.” *The Higgs Centre for Theoretical Physics*, [https:\/\/higgs.ph.ed.ac.uk\/outreach\/higgshalloween-2021\/fermi-paradox](https:\/\/higgs.ph.ed.ac.uk\/outreach\/higgshalloween-2021\/fermi-paradox). Accessed 5 March 2025.\n\n“Fermi's Paradox.” *University of Oregon*, [https:\/\/pages.uoregon.edu\/jschombe\/cosmo\/lectures\/lec28.html](https:\/\/pages.uoregon.edu\/jschombe\/cosmo\/lectures\/lec28.html). 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She also has a keen interest in astrotourism and is always on the lookout for the next northern lights adventure.\n\nShe will be a guest speaker aboard [HX's Solar Eclipse Expedition](https:\/\/www.travelhx.com\/en-gb\/cruises\/solar-eclipse-expedition-2026-greenland-iceland-and-svalbard\/) in August 2026 and will join Hurtigruten as an [onboard astronomer](https:\/\/www.hurtigruten.com\/en-gb\/on-board\/on-board-team\/meet-your-astronomy-voyage-lecturers) for a northern lights sailing in January 2027.\n\n## Join the Conversation\nFollow this conversation to be notified when new comments are postedfollow\n\nLog in\n\n\\|\n\nSign up\n\nPlease follow our [community guidelines](https:\/\/www.space.com\/41418-about-us.html#section-community-guidelines).\n\n![Jump to log in or sign Up](https:\/\/cdn.viafoura.net\/assets\/defaultavatar.913f94a2fa72a280b0374131f1c9b175.png)\n\nAll Comments\n\nNEWEST\n\n**0**\n\n### All Comments\nStart the conversation\n\nPowered by\n\nView More\n\nYou must confirm your public display name before commenting\n\nPlease logout and then login again, you will then be prompted to enter your display name.\n\nLogout\n\nRead more\n\n[![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? 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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\nMORE FROM SPACE...\n\n1. [![an astronaut in an orange spacesuit with a planet](https:\/\/cdn.mos.cms.futurecdn.net\/DXR4PG5R2egauWUfnTo3Hc.png)](https:\/\/www.space.com\/entertainment\/space-movies-shows\/the-artemis-2-astronauts-got-a-private-project-hail-mary-screening-before-launch-heres-their-verdict \"The Artemis 2 astronauts got a private 'Project Hail Mary' screening before launch. Here's their verdict\")\n   \n   1\n   \n   [The Artemis 2 astronauts got a private 'Project Hail Mary' screening before launch. Here's their verdict](https:\/\/www.space.com\/entertainment\/space-movies-shows\/the-artemis-2-astronauts-got-a-private-project-hail-mary-screening-before-launch-heres-their-verdict)\n2. 2\n   \n   [Crew of tiny worms readies for April 11 launch to International Space Station](https:\/\/www.space.com\/space-exploration\/launches-spacecraft\/crew-of-tiny-worms-readies-for-april-10-launch-to-international-space-station)\n3. 3\n   \n   ['It probably will start a precedent': Why satellite company's withholding of Iran imagery has this expert worried](https:\/\/www.space.com\/space-exploration\/satellites\/it-probably-will-start-a-precedent-why-satellite-companys-withholding-of-iran-imagery-has-this-expert-worried)\n4. 4\n   \n   [A house-size asteroid is heading toward Earth tonight: Here's what you need to know](https:\/\/www.space.com\/astronomy\/asteroids\/a-house-size-asteroid-is-heading-toward-earth-tonight-heres-what-you-need-to-know)\n5. 5\n   \n   [Watch Artemis 2 race back to Earth in this telescope livestream tonight](https:\/\/www.space.com\/space-exploration\/artemis\/watch-artemis-2-race-back-to-earth-in-this-telescope-livestream-tonight)\n\nSpace is part of Future US Inc, an international media group and leading digital publisher. [Visit our corporate site](https:\/\/futureplc.com\/).\n\n[![Add as a preferred source on Google](https:\/\/cdn.mos.cms.futurecdn.net\/flexiimages\/mednnv697g1760357120.png) Add as a preferred source on Google](https:\/\/google.com\/preferences\/source?q=space.com)\n\n- [About Us](https:\/\/www.space.com\/41418-about-us.html)\n- [Contact Future's experts](https:\/\/futureplc.com\/contact\/)\n- [Terms and conditions](https:\/\/futureplc.com\/terms-conditions\/)\n- [Privacy policy](https:\/\/futureplc.com\/privacy-policy\/)\n- [Cookies policy](https:\/\/futureplc.com\/cookies-policy\/)\n- [Accessibility Statement](https:\/\/futureplc.com\/accessibility-statement\/)\n- [Advertise with us](https:\/\/go.future-advertising.com\/Spacecom-Media-Kit.html)\n- [Web notifications](https:\/\/www.space.com\/how-to-turn-off-web-notifications-for-chrome-macos.html)\n- [Careers](https:\/\/futureplc.com\/careers\/)\n- [Do not sell or share my personal information](https:\/\/www.space.com\/privacy-portal)\n\n© Future US, Inc. 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":"![man sits on a rock under the milky way. Are we alone in the universe?](https:\/\/cdn.mos.cms.futurecdn.net\/6SMGeKptzTqHRuipe9cC49.jpg)\n\nThe Fermi Paradox seeks to answer the question of where the aliens are. After all, the universe is incredibly old, big and filled with potentially habitable planets. (Image credit: bjdlzx via Getty Images)\n\nThe universe is vast, ancient, and teeming with billions of potentially habitable planets.\n\nWith so many chances for intelligent life to arise, we should expect to see evidence of extraterrestrials.\n\n## Fermi Paradox FAQs\n### Was the Fermi Paradox solved?\nHumanity has been around for just 200,000 years, and we've been listening for possible radio signals from E.T. just since 1960. So the odds that we will overlap in time and space with a detectable alien civilization don't seem great. There is probably no single solution to the Fermi Paradox\n\n### What is the great silence theory?\nThe \"great silence\" is the idea that there is no evidence of extraterrestrial civilizations and that we are truly alone in the universe; it is also known as the Fermi Paradox.\n\n![graphic illustration of the fermi paradox shows two people looking up at the milky way and a graphic above their heads showing an empty fuel gauge with the image of an alien on it, indicating a distinct lack of aliens.](https:\/\/cdn.mos.cms.futurecdn.net\/RUirVJ8ZVjAsgspC3ya6z5.jpg)\n\nAre we truly alone in the cosmos? (Image credit: Created in Canva Pro by Daisy Dobrijevic)\n\n### Is the dark forest theory true?\nWhile some intelligent extraterrestrial civilizations might choose to remain hidden, as suggested by the dark forest theory, it’s unlikely that every single one would adopt the same fear-driven strategy.\n### The scale of the paradox\n![The milky way galaxy as seen over a mountain range.](https:\/\/cdn.mos.cms.futurecdn.net\/nP8zA5qg8tFCAWLwbnamph.jpg)\n\nOur home galaxy, the Milky Way, contains an estimated 100 to 400 billion stars. (Image credit: Getty Images)\n\nThe numbers are staggering. Our [Milky Way](https:\/\/www.space.com\/19915-milky-way-galaxy.html) alone contains an estimated 100 to 400 billion stars, many of them hosting planets in the [habitable zone](https:\/\/www.space.com\/goldilocks-zone-habitable-area-life). If even a tiny fraction of these planets develop life, and a fraction of those develop intelligence and technology, the galaxy should be buzzing with signals, megastructures, or even interstellar visitors. But so far, we’ve found nothing.\n\n\"Fermi grasped that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire galaxy,\" representatives of the Search For Extraterrestrial Intelligence (SETI) Institute in Mountain View, California, wrote in a [Fermi Paradox explainer](https:\/\/www.seti.org\/fermi-paradox-0). \"Within a few tens of millions of years, every star system could be brought under the wing of empire. Tens of millions of years may sound like a long project, but in fact it’s quite short compared to the age of the galaxy, which is roughly a thousand times more.\"\n\n## Possible explanations\n![An artist\\&\\#039;s image of an alien starship as viewed from a planet\\&\\#039;s surface.](https:\/\/cdn.mos.cms.futurecdn.net\/Fu7f3DbymUm8kL9RDvfA4.jpeg)\n\nThere are many possible hypotheses that attempt to solve the Fermi Paradox. (Image credit: Coneyl Jay)\n\nThere are numerous hypotheses attempting to resolve the paradox, ranging from the optimistic to the ominous:\n\n## 1\\. They're out there, but we haven't found them yet\n**Radio Silence**: We might not be listening at the right frequencies or in the right way. Civilizations could communicate using methods we haven’t discovered yet, like neutrino beams or [quantum entanglement](https:\/\/www.space.com\/31933-quantum-entanglement-action-at-a-distance.html).\n\nBreaking space news, the latest updates on rocket launches, skywatching events and more\\!\n\n**The Cosmic Timescale**: Humanity has only been scanning the skies for a few decades — an eye blink in cosmic history. Advanced civilizations could [rise and fall in cycles](https:\/\/pages.uoregon.edu\/jschombe\/cosmo\/lectures\/lec28.html), missing each other in time.\n\n## 2\\. They don't want to be found\n**The Zoo Hypothesis**: Aliens could be [observing us](https:\/\/pages.uoregon.edu\/jschombe\/cosmo\/lectures\/lec28.html) like we observe animals in a nature reserve, choosing not to interfere.\n\n**The Dark Forest Theory**: Inspired by Liu Cixin’s sci-fi novel *The Dark Forest*, this [idea suggests](https:\/\/higgs.ph.ed.ac.uk\/outreach\/higgshalloween-2021\/fermi-paradox) that intelligent species stay silent to avoid detection by potentially hostile civilizations.\n\n## 3\\. Something prevents their expansion\n**The Great Filter**: This [theory suggests](https:\/\/www.space.com\/space-exploration\/search-for-life\/how-the-great-filter-could-explain-why-we-havent-found-intelligent-aliens) that there is a nearly insurmountable barrier preventing civilizations from advancing. This could be at the stage of life’s emergence, intelligent life’s development, or a self-destructive phase like nuclear war or environmental collapse.\n\n**Self-Limiting Civilizations**: Advanced societies may become so technologically sophisticated that they lose interest in space expansion, opting for virtual realities or inward development.\n\n### Implications for humanity\n![four people stand silhouetted under a starry sky with the milky way stretching overhead.](https:\/\/cdn.mos.cms.futurecdn.net\/McWRecegXJuN5KWYE3rtBR.jpg)\n\nThe \"great silence\" of the cosmos represents one of the greatest mysteries of our time. (Image credit: Paolo Carnassale via Getty Images)\n\nUnderstanding the Fermi Paradox is more than just an intellectual exercise — it has real implications for our future. If the Great Filter lies behind us (e.g., life itself is incredibly rare), then we may be one of the first intelligent civilizations. If the filter is ahead (e.g., technological civilizations inevitably destroy themselves), then our survival is far from guaranteed.\n\nOur [search for extraterrestrial intelligence](https:\/\/www.space.com\/33626-search-for-extraterrestrial-intelligence.html) (SETI) continues, with new projects like the [James Webb Space Telescope](https:\/\/www.space.com\/21925-james-webb-space-telescope-jwst.html) analyzing [exoplanet](https:\/\/www.space.com\/17738-exoplanets.html) atmospheres and advanced AI scanning for signals. Whether we find aliens or confirm our solitude, the answer to the Fermi Paradox will profoundly shape our understanding of our place in the universe.\n\nThe \"great silence\" of the cosmos may be unsettling, but it also presents one of the greatest mysteries of our time. Are we alone, or is something preventing us from hearing the others? Until we find an answer, the question remains open.\n\n## Fermi paradox expert Q\\&A\nWe asked Professor Heidi Jo Newberg from the Rensselaer Polytechnic Institute a few questions about the Fermi Paradox.\n\n![Heidi Jo Newberg](https:\/\/cdn.mos.cms.futurecdn.net\/JNoHunAQPxQhfjHLvbB3G3.jpg)\n\nHeidi Jo Newberg is an astrophysicist currently studying the structure of our galaxy. She has conducted diverse research in astrophysics, including on stars, supernovas, and both our galaxies and others. She recently received a grant from NASA to work on an alternative to conventional telescopes to detect exoplanets that could support life.\n\n### Do modern researchers tend to accept the premise of the Fermi Paradox — that is, if intelligent life outside our planet exists, then it's likely that they would have contacted or reached Earth by now?\nI can't speak for everyone else, but no I do not believe in the premise. Because the Earth is the only planet where we know that life exists, we can only make guesses based on how life here has evolved.\n\nThe Earth formed about 4.6 billion years ago. Life on Earth began at least 3.5 billion years ago, since fossils of this age have been found, but simpler cells are expected to have formed earlier than that. Possibly, life on Earth started very quickly after conditions allowed for liquid water to be commonly available. On the other hand, life that had more than one cell took until about 1 billion years ago, and humans did not evolve in 0.2 billion years ago. As far as we know, humans are the only life form on the Earth that thinks about what is going on in the Universe, and could potentially communicate with other life. The first telescopes were invented about 400 years ago, and the first space probes were launched less than 100 years ago.\n\nWhat I take away from this is that simple life (like one celled organisms) might be easy to create, but complex life is harder, and life that tries to communicate with life elsewhere in the Universe could be extremely rare. While the technology to find and communicate with extraterrestrial life, once started, appears to develop extremely fast on the timeline of the Universe, we do not know how long modern humans will survive as a species.\n\n### Is there a commonly accepted way to resolve the Fermi Paradox?\nI doubt there is a commonly accepted way to resolve the Fermi Paradox, other than to point to the fact that we have very little information about highly evolved intelligent life. We don't know how rare it is, how long a civilization lasts, how likely it would or would not want to communicate with us, how likely it would spread through the Galaxy, or how we would recognize and understand each other. In the absence of any real information to figure any of this out, it just seems like there are many possibilities to solve it.\n\nIn evaluating the Fermi Paradox, it is important to think about the vast distances of space in the Milky Way. The time for light to travel to the nearest star is more than four years. If a rocket ship travels 20,000 miles per hour, then it would take more than 33,000 years to get there. The light travel time from the Sun to the center of our galaxy is 30,000 years. The rocket travel time is a 170 million years. It is completely unclear whether life will want to, or be able to, travel over these sorts of distances to populate the Galaxy. If it is attempted, it is not clear whether there are suitable places for it to land and thrive. Spreading life throughout the galaxy might be much more difficult than Fermi supposed.\n\n### Do researchers studying exoplanets, particularly potentially habitable ones, usually consider the Fermi Paradox?\nModern researchers looking for potentially habitable planets usually use the [Seager Equation](https:\/\/en.wikipedia.org\/wiki\/Sara_Seager) when they are thinking about the likelihood of finding life. This is an [update](https:\/\/www.seti.org\/drake-equation-inde) of the Drake Equation which was a summary of what people were looking for in 1961. Note that one of the key differences is that the Seager Equation asks how many planets we can find with life that transformed the atmosphere (for example by photosynthesis), while the Drake Equation calculates the number of civilizations that are sending out detectable radio waves. In the 20th century, the SETI program looked for these civilizations and found no signals of such civilizations.\n\nSo you can see that the conversation has changed to the search for life that is not necessarily intelligent — something that the Earth's history would tell us is much more likely to find. I occasionally teach an Exoplanets and Life class, and the textbook I use does not talk about the Fermi Paradox. My expectation is that most researchers are not currently thinking about it. The current search is for exoplanets, habitable exoplanets with liquid water, and signs of life that is not necessarily intelligent.\n\n### What are some ways current research might eventually resolve the Fermi Paradox?\nAs we learn more about exoplanets, it becomes more possible to make statistical statements about the likelihood of life, and the possibility for it to spread. The basis of the paradox lies in the idea that there are hundreds of billions of stars in the Milky Way, and with so many there must be other intelligent life on one of them. But we don't really have a way to assess whether that is true.\n\nIn six tons of sand, there are hundreds of billions of grains of sand. So, it might seems reasonable to think that there must be at least one of them that is made of uranium. But we don't look for uranium on the beach because if it was there, it would be dissolved in the water and wash away. Just having a large number of objects doesn't mean that every possibility for what those objects are must therefore exist.\n\nCurrent experiments are teaching us how many exoplanets there are, what the conditions are on those planets, how common it is for exoplanets to have surface temperatures that allow for liquid water, and possibly how many exoplanets exhibit atmospheric abundances that favor the existence of life. We are working towards actually finding other life of any kind that is on another planet. This information would give us some basis for then extrapolating to the probability that technological civilizations form elsewhere, and would tell us how far they might have to travel to find the nearest habitable planet where they could establish a colony.\n### Additional resources\nIf you're looking to explore the Fermi Paradox in depth, a great starting point is Stephen Webb’s book, \"[If the Universe Is Teeming with Aliens… Where Is Everybody?](https:\/\/target.georiot.com\/Proxy.ashx?tsid=72128&GR_URL=https%3A%2F%2Famazon.co.uk%2FUniverse-Teeming-Aliens-Everybody-Extraterrestrial%2Fdp%2F0387955011%3Ftag%3Dhawk-future-21%26ascsubtag%3Dspace-us-2738472146419429680-21)\" This book lays out 75 possible solutions to the paradox, covering scientific, philosophical, and speculative ideas in an accessible yet detailed way. For an engaging online read, the [Wait But Why article on the Fermi Paradox](https:\/\/waitbutwhy.com\/2014\/05\/fermi-paradox.html) is a great place to start. Additionally, the [SETI Institute’s website](https:\/\/waitbutwhy.com\/2014\/05\/fermi-paradox.html) provides up-to-date research, news, and expert insights on the search for extraterrestrial intelligence, including discussions on why we might not have found aliens yet.\n\n### Bibliography\n“The Fermi Paradox.” *SETI Institute*, [https:\/\/www.seti.org\/fermi-paradox-0](https:\/\/www.seti.org\/fermi-paradox-0). Accessed 5 March 2025.\n\n“The Fermi Paradox - Higgs Centre for Theoretical Physics.” *The Higgs Centre for Theoretical Physics*, [https:\/\/higgs.ph.ed.ac.uk\/outreach\/higgshalloween-2021\/fermi-paradox](https:\/\/higgs.ph.ed.ac.uk\/outreach\/higgshalloween-2021\/fermi-paradox). Accessed 5 March 2025.\n\n“Fermi's Paradox.” *University of Oregon*, [https:\/\/pages.uoregon.edu\/jschombe\/cosmo\/lectures\/lec28.html](https:\/\/pages.uoregon.edu\/jschombe\/cosmo\/lectures\/lec28.html). Accessed 5 March 2025.\n\n**Share your thoughts**\n\n0\n\n1\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. 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Enter that code below to reset your password.\n\nSet new password\n\nPlease enter your new password below.\n\nLeaderboard\n\n| Rank | Player | Score | Time |\n|---|---|---|---|\n\nDaisy Dobrijevic joined Space.com in February 2022, having previously worked as a staff writer for All About Space magazine. She completed an editorial internship with BBC Sky at Night Magazine and worked at the National Space Centre, communicating space science to the public.\n\nDaisy holds a PhD in plant physiology and a Master's in Environmental Science. Based in Nottingham, U.K., she covers all things space, with a special focus on solar activity and space weather. She also has a keen interest in astrotourism and is always on the lookout for the next northern lights adventure.\n\nShe will be a guest speaker aboard [HX's Solar Eclipse Expedition](https:\/\/www.travelhx.com\/en-gb\/cruises\/solar-eclipse-expedition-2026-greenland-iceland-and-svalbard\/) in August 2026 and will join Hurtigruten as an [onboard astronomer](https:\/\/www.hurtigruten.com\/en-gb\/on-board\/on-board-team\/meet-your-astronomy-voyage-lecturers) for a northern lights sailing in January 2027.","meta_canonical":null}

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Boilerpipe Text	The Fermi Paradox seeks to answer the question of where the aliens are. After all, the universe is incredibly old, big and filled with potentially habitable planets. (Image credit: bjdlzx via Getty Images) The universe is vast, ancient, and teeming with billions of potentially habitable planets. With so many chances for intelligent life to arise, we should expect to see evidence of extraterrestrials. Fermi Paradox FAQs Was the Fermi Paradox solved? Humanity has been around for just 200,000 years, and we've been listening for possible radio signals from E.T. just since 1960. So the odds that we will overlap in time and space with a detectable alien civilization don't seem great. There is probably no single solution to the Fermi Paradox What is the great silence theory? The "great silence" is the idea that there is no evidence of extraterrestrial civilizations and that we are truly alone in the universe; it is also known as the Fermi Paradox. Are we truly alone in the cosmos? (Image credit: Created in Canva Pro by Daisy Dobrijevic) Is the dark forest theory true? While some intelligent extraterrestrial civilizations might choose to remain hidden, as suggested by the dark forest theory, it’s unlikely that every single one would adopt the same fear-driven strategy. The scale of the paradox Our home galaxy, the Milky Way, contains an estimated 100 to 400 billion stars. (Image credit: Getty Images) The numbers are staggering. Our Milky Way alone contains an estimated 100 to 400 billion stars, many of them hosting planets in the habitable zone . If even a tiny fraction of these planets develop life, and a fraction of those develop intelligence and technology, the galaxy should be buzzing with signals, megastructures, or even interstellar visitors. But so far, we’ve found nothing. "Fermi grasped that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire galaxy," representatives of the Search For Extraterrestrial Intelligence (SETI) Institute in Mountain View, California, wrote in a Fermi Paradox explainer . "Within a few tens of millions of years, every star system could be brought under the wing of empire. Tens of millions of years may sound like a long project, but in fact it’s quite short compared to the age of the galaxy, which is roughly a thousand times more." Possible explanations There are many possible hypotheses that attempt to solve the Fermi Paradox. (Image credit: Coneyl Jay) There are numerous hypotheses attempting to resolve the paradox, ranging from the optimistic to the ominous: 1. They're out there, but we haven't found them yet Radio Silence : We might not be listening at the right frequencies or in the right way. Civilizations could communicate using methods we haven’t discovered yet, like neutrino beams or quantum entanglement . Breaking space news, the latest updates on rocket launches, skywatching events and more! The Cosmic Timescale : Humanity has only been scanning the skies for a few decades — an eye blink in cosmic history. Advanced civilizations could rise and fall in cycles , missing each other in time. 2. They don't want to be found The Zoo Hypothesis : Aliens could be observing us like we observe animals in a nature reserve, choosing not to interfere. The Dark Forest Theory : Inspired by Liu Cixin’s sci-fi novel The Dark Forest , this idea suggests that intelligent species stay silent to avoid detection by potentially hostile civilizations. 3. Something prevents their expansion The Great Filter : This theory suggests that there is a nearly insurmountable barrier preventing civilizations from advancing. This could be at the stage of life’s emergence, intelligent life’s development, or a self-destructive phase like nuclear war or environmental collapse. Self-Limiting Civilizations : Advanced societies may become so technologically sophisticated that they lose interest in space expansion, opting for virtual realities or inward development. Implications for humanity The "great silence" of the cosmos represents one of the greatest mysteries of our time. (Image credit: Paolo Carnassale via Getty Images) Understanding the Fermi Paradox is more than just an intellectual exercise — it has real implications for our future. If the Great Filter lies behind us (e.g., life itself is incredibly rare), then we may be one of the first intelligent civilizations. If the filter is ahead (e.g., technological civilizations inevitably destroy themselves), then our survival is far from guaranteed. Our search for extraterrestrial intelligence (SETI) continues, with new projects like the James Webb Space Telescope analyzing exoplanet atmospheres and advanced AI scanning for signals. Whether we find aliens or confirm our solitude, the answer to the Fermi Paradox will profoundly shape our understanding of our place in the universe. The "great silence" of the cosmos may be unsettling, but it also presents one of the greatest mysteries of our time. Are we alone, or is something preventing us from hearing the others? Until we find an answer, the question remains open. Fermi paradox expert Q&A We asked Professor Heidi Jo Newberg from the Rensselaer Polytechnic Institute a few questions about the Fermi Paradox. Heidi Jo Newberg is an astrophysicist currently studying the structure of our galaxy. She has conducted diverse research in astrophysics, including on stars, supernovas, and both our galaxies and others. She recently received a grant from NASA to work on an alternative to conventional telescopes to detect exoplanets that could support life. Do modern researchers tend to accept the premise of the Fermi Paradox — that is, if intelligent life outside our planet exists, then it's likely that they would have contacted or reached Earth by now? I can't speak for everyone else, but no I do not believe in the premise. Because the Earth is the only planet where we know that life exists, we can only make guesses based on how life here has evolved. The Earth formed about 4.6 billion years ago. Life on Earth began at least 3.5 billion years ago, since fossils of this age have been found, but simpler cells are expected to have formed earlier than that. Possibly, life on Earth started very quickly after conditions allowed for liquid water to be commonly available. On the other hand, life that had more than one cell took until about 1 billion years ago, and humans did not evolve in 0.2 billion years ago. As far as we know, humans are the only life form on the Earth that thinks about what is going on in the Universe, and could potentially communicate with other life. The first telescopes were invented about 400 years ago, and the first space probes were launched less than 100 years ago. What I take away from this is that simple life (like one celled organisms) might be easy to create, but complex life is harder, and life that tries to communicate with life elsewhere in the Universe could be extremely rare. While the technology to find and communicate with extraterrestrial life, once started, appears to develop extremely fast on the timeline of the Universe, we do not know how long modern humans will survive as a species. Is there a commonly accepted way to resolve the Fermi Paradox? I doubt there is a commonly accepted way to resolve the Fermi Paradox, other than to point to the fact that we have very little information about highly evolved intelligent life. We don't know how rare it is, how long a civilization lasts, how likely it would or would not want to communicate with us, how likely it would spread through the Galaxy, or how we would recognize and understand each other. In the absence of any real information to figure any of this out, it just seems like there are many possibilities to solve it. In evaluating the Fermi Paradox, it is important to think about the vast distances of space in the Milky Way. The time for light to travel to the nearest star is more than four years. If a rocket ship travels 20,000 miles per hour, then it would take more than 33,000 years to get there. The light travel time from the Sun to the center of our galaxy is 30,000 years. The rocket travel time is a 170 million years. It is completely unclear whether life will want to, or be able to, travel over these sorts of distances to populate the Galaxy. If it is attempted, it is not clear whether there are suitable places for it to land and thrive. Spreading life throughout the galaxy might be much more difficult than Fermi supposed. Do researchers studying exoplanets, particularly potentially habitable ones, usually consider the Fermi Paradox? Modern researchers looking for potentially habitable planets usually use the Seager Equation when they are thinking about the likelihood of finding life. This is an update of the Drake Equation which was a summary of what people were looking for in 1961. Note that one of the key differences is that the Seager Equation asks how many planets we can find with life that transformed the atmosphere (for example by photosynthesis), while the Drake Equation calculates the number of civilizations that are sending out detectable radio waves. In the 20th century, the SETI program looked for these civilizations and found no signals of such civilizations. So you can see that the conversation has changed to the search for life that is not necessarily intelligent — something that the Earth's history would tell us is much more likely to find. I occasionally teach an Exoplanets and Life class, and the textbook I use does not talk about the Fermi Paradox. My expectation is that most researchers are not currently thinking about it. The current search is for exoplanets, habitable exoplanets with liquid water, and signs of life that is not necessarily intelligent. What are some ways current research might eventually resolve the Fermi Paradox? As we learn more about exoplanets, it becomes more possible to make statistical statements about the likelihood of life, and the possibility for it to spread. The basis of the paradox lies in the idea that there are hundreds of billions of stars in the Milky Way, and with so many there must be other intelligent life on one of them. But we don't really have a way to assess whether that is true. In six tons of sand, there are hundreds of billions of grains of sand. So, it might seems reasonable to think that there must be at least one of them that is made of uranium. But we don't look for uranium on the beach because if it was there, it would be dissolved in the water and wash away. Just having a large number of objects doesn't mean that every possibility for what those objects are must therefore exist. Current experiments are teaching us how many exoplanets there are, what the conditions are on those planets, how common it is for exoplanets to have surface temperatures that allow for liquid water, and possibly how many exoplanets exhibit atmospheric abundances that favor the existence of life. We are working towards actually finding other life of any kind that is on another planet. This information would give us some basis for then extrapolating to the probability that technological civilizations form elsewhere, and would tell us how far they might have to travel to find the nearest habitable planet where they could establish a colony. Additional resources If you're looking to explore the Fermi Paradox in depth, a great starting point is Stephen Webb’s book, " If the Universe Is Teeming with Aliens… Where Is Everybody? " This book lays out 75 possible solutions to the paradox, covering scientific, philosophical, and speculative ideas in an accessible yet detailed way. For an engaging online read, the Wait But Why article on the Fermi Paradox is a great place to start. Additionally, the SETI Institute’s website provides up-to-date research, news, and expert insights on the search for extraterrestrial intelligence, including discussions on why we might not have found aliens yet. Bibliography “The Fermi Paradox.” SETI Institute , https://www.seti.org/fermi-paradox-0 . Accessed 5 March 2025. “The Fermi Paradox - Higgs Centre for Theoretical Physics.” The Higgs Centre for Theoretical Physics , https://higgs.ph.ed.ac.uk/outreach/higgshalloween-2021/fermi-paradox . Accessed 5 March 2025. “Fermi's Paradox.” University of Oregon , https://pages.uoregon.edu/jschombe/cosmo/lectures/lec28.html . Accessed 5 March 2025. Share your thoughts 0 1 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... 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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 Daisy Dobrijevic joined Space.com in February 2022, having previously worked as a staff writer for All About Space magazine. She completed an editorial internship with BBC Sky at Night Magazine and worked at the National Space Centre, communicating space science to the public. Daisy holds a PhD in plant physiology and a Master's in Environmental Science. Based in Nottingham, U.K., she covers all things space, with a special focus on solar activity and space weather. She also has a keen interest in astrotourism and is always on the lookout for the next northern lights adventure. She will be a guest speaker aboard HX's Solar Eclipse Expedition in August 2026 and will join Hurtigruten as an onboard astronomer for a northern lights sailing in January 2027.
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How life could thrive on moons of starless 'rogue' planets") [![Split image showing a screenshot of Ryan Gosling in Project Hail Mary on the left and author Andy Weir holding up the book on the right.](https://cdn.mos.cms.futurecdn.net/DTwgGSCpsG3SLSbYvUAt3i.jpg) Space Movies & Shows Sci-fi author Andy Weir explains the astrobiology behind 'Project Hail Mary' (interview)](https://www.space.com/entertainment/space-movies-shows/i-talked-to-andy-weir-about-the-astrobiology-behind-project-hail-mary "Sci-fi author Andy Weir explains the astrobiology behind 'Project Hail Mary' (interview)") [![an astronaut floats above a swirling green planet](https://cdn.mos.cms.futurecdn.net/Tt7cwV74EJuRxAM9AV683j.png) Space Movies & Shows Where should we send a real 'Hail Mary' spacecraft? A new study has the answers](https://www.space.com/entertainment/space-movies-shows/where-could-we-send-a-real-hail-mary-spacecraft-a-new-study-has-the-answers "Where should we send a real 'Hail Mary' spacecraft? A new study has the answers") [![Tons of stars are seen against a dark sky.](https://cdn.mos.cms.futurecdn.net/ByQu7tUFuSMpYdXfnazjcH.png) Stars 'At the edge of what we thought possible': Astronomers find extremely rare star from ancient universe](https://www.space.com/astronomy/stars/at-the-edge-of-what-we-thought-possible-astronomers-find-extremely-rare-star-from-ancient-universe "'At the edge of what we thought possible': Astronomers find extremely rare star from ancient universe") [![On the left, a giant orange arc emerges, rising slightly. between that, all the way right, through the middle, seven planets of varying colors and texturs.](https://cdn.mos.cms.futurecdn.net/JeQYsG4tEK6zMabKsPWZ8b.jpg) Exoplanets These 45 exoplanets may be the best places to search for alien life](https://www.space.com/astronomy/exoplanets/these-45-exoplanets-may-be-the-best-places-to-search-for-alien-life "These 45 exoplanets may be the best places to search for alien life") [![An illustration shows two planets colliding around the star Gaia20ehk](https://cdn.mos.cms.futurecdn.net/S8xCJoFb4XgrFZAAmemjPY.png) Exoplanets 'Completely bonkers': Astronomers find evidence of a cataclysmic collision between exoplanets](https://www.space.com/astronomy/exoplanets/completely-bonkers-astronomers-find-evidence-of-a-cataclysmic-collision-between-planets "'Completely bonkers': Astronomers find evidence of a cataclysmic collision between exoplanets") [![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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[Space Exploration](https://www.space.com/space-exploration) 2. [Search for Life](https://www.space.com/space-exploration/search-for-life) # The Fermi Paradox: Where are all the aliens? [References](https://www.space.com/references) By [Daisy Dobrijevic](https://www.space.com/author/daisy-dobrijevic) last updated April 4, 2025 Discover the Fermi Paradox — why, in a vast universe full of stars and planets, haven't we found extraterrestrial life? Explore the theories behind this great mystery. 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 ![man sits on a rock under the milky way. Are we alone in the universe?](https://cdn.mos.cms.futurecdn.net/6SMGeKptzTqHRuipe9cC49.jpg) The Fermi Paradox seeks to answer the question of where the aliens are. After all, the universe is incredibly old, big and filled with potentially habitable planets. (Image credit: bjdlzx via Getty Images) Jump to: - [Fermi Paradox FAQs](https://www.space.com/25325-fermi-paradox.html#section-fermi-paradox-faqs) - [The scale of the paradox](https://www.space.com/25325-fermi-paradox.html#section-the-scale-of-the-paradox) - [Possible explanations](https://www.space.com/25325-fermi-paradox.html#section-possible-explanations) - [Implications for humanity](https://www.space.com/25325-fermi-paradox.html#section-implications-for-humanity) - [Fermi paradox expert Q\&A](https://www.space.com/25325-fermi-paradox.html#section-fermi-paradox-expert-q-a) - [Additional resources](https://www.space.com/25325-fermi-paradox.html#section-additional-resources) - Copy link - [Facebook](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.html) - [X](https://twitter.com/intent/tweet?text=The+Fermi+Paradox%3A+Where+are+all+the+aliens%3F&url=https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.html) - [Whatsapp](whatsapp://send?text=The+Fermi+Paradox%3A+Where+are+all+the+aliens%3F+https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.html?fwa) - [Reddit](https://www.reddit.com/submit?url=https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.html&title=The+Fermi+Paradox%3A+Where+are+all+the+aliens%3F) - [Pinterest](https://pinterest.com/pin/create/button/?url=https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.html&media=https%3A%2F%2Fcdn.mos.cms.futurecdn.net%2F6SMGeKptzTqHRuipe9cC49.jpg) - [Flipboard](https://share.flipboard.com/bookmarklet/popout?title=The+Fermi+Paradox%3A+Where+are+all+the+aliens%3F&url=https%3A%2F%2Fwww.space.com%2F25325-fermi-paradox.html) - [Email](mailto:?subject=I%20found%20this%20webpage&body=Hi,%20I%20found%20this%20webpage%20and%20thought%20you%20might%20like%20it%20https://www.space.com/25325-fermi-paradox.html) Share this article [0](https://www.space.com/25325-fermi-paradox.html#viafoura-comments) 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 The universe is vast, ancient, and teeming with billions of potentially habitable planets. With so many chances for intelligent life to arise, we should expect to see evidence of extraterrestrials. Yet, despite decades of searching, the cosmos remains eerily silent. This contradiction is known as the Fermi Paradox, first proposed by physicist Enrico Fermi in 1950. You may like - [![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) Where are all the aliens? Maybe they just don't want to talk to us](https://www.space.com/space-exploration/search-for-life/where-are-all-the-aliens-maybe-they-just-dont-want-to-talk-to-us) - [![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) 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) - [![an astronaut floats above a swirling green planet](https://cdn.mos.cms.futurecdn.net/Tt7cwV74EJuRxAM9AV683j.png) Where should we send a real 'Hail Mary' spacecraft? A new study has the answers](https://www.space.com/entertainment/space-movies-shows/where-could-we-send-a-real-hail-mary-spacecraft-a-new-study-has-the-answers) [Click here for more Space.com videos...](https://videos.space.com/m/u26wmKKL/where-is-et-seti-vs-the-fermi-paradox?list=9wzCTV4g) ## Fermi Paradox FAQs ### Was the Fermi Paradox solved? Humanity has been around for just 200,000 years, and we've been listening for possible radio signals from E.T. just since 1960. So the odds that we will overlap in time and space with a detectable alien civilization don't seem great. There is probably no single solution to the Fermi Paradox ### What is the great silence theory? The "great silence" is the idea that there is no evidence of extraterrestrial civilizations and that we are truly alone in the universe; it is also known as the Fermi Paradox. ![graphic illustration of the fermi paradox shows two people looking up at the milky way and a graphic above their heads showing an empty fuel gauge with the image of an alien on it, indicating a distinct lack of aliens.](https://cdn.mos.cms.futurecdn.net/RUirVJ8ZVjAsgspC3ya6z5.jpg) Are we truly alone in the cosmos? (Image credit: Created in Canva Pro by Daisy Dobrijevic) ### Is the dark forest theory true? While some intelligent extraterrestrial civilizations might choose to remain hidden, as suggested by the dark forest theory, it’s unlikely that every single one would adopt the same fear-driven strategy. ### The scale of the paradox ![The milky way galaxy as seen over a mountain range.](https://cdn.mos.cms.futurecdn.net/nP8zA5qg8tFCAWLwbnamph.jpg) Our home galaxy, the Milky Way, contains an estimated 100 to 400 billion stars. (Image credit: Getty Images) The numbers are staggering. Our [Milky Way](https://www.space.com/19915-milky-way-galaxy.html) alone contains an estimated 100 to 400 billion stars, many of them hosting planets in the [habitable zone](https://www.space.com/goldilocks-zone-habitable-area-life). If even a tiny fraction of these planets develop life, and a fraction of those develop intelligence and technology, the galaxy should be buzzing with signals, megastructures, or even interstellar visitors. But so far, we’ve found nothing. "Fermi grasped that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire galaxy," representatives of the Search For Extraterrestrial Intelligence (SETI) Institute in Mountain View, California, wrote in a [Fermi Paradox explainer](https://www.seti.org/fermi-paradox-0). "Within a few tens of millions of years, every star system could be brought under the wing of empire. Tens of millions of years may sound like a long project, but in fact it’s quite short compared to the age of the galaxy, which is roughly a thousand times more." ## Possible explanations ![An artist\&\#039;s image of an alien starship as viewed from a planet\&\#039;s surface.](https://cdn.mos.cms.futurecdn.net/Fu7f3DbymUm8kL9RDvfA4.jpeg) There are many possible hypotheses that attempt to solve the Fermi Paradox. (Image credit: Coneyl Jay) There are numerous hypotheses attempting to resolve the paradox, ranging from the optimistic to the ominous: ## 1\. They're out there, but we haven't found them yet Radio Silence: We might not be listening at the right frequencies or in the right way. Civilizations could communicate using methods we haven’t discovered yet, like neutrino beams or [quantum entanglement](https://www.space.com/31933-quantum-entanglement-action-at-a-distance.html). 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. The Cosmic Timescale: Humanity has only been scanning the skies for a few decades — an eye blink in cosmic history. Advanced civilizations could [rise and fall in cycles](https://pages.uoregon.edu/jschombe/cosmo/lectures/lec28.html), missing each other in time. ## 2\. They don't want to be found The Zoo Hypothesis: Aliens could be [observing us](https://pages.uoregon.edu/jschombe/cosmo/lectures/lec28.html) like we observe animals in a nature reserve, choosing not to interfere. The Dark Forest Theory*: Inspired by Liu Cixin’s sci-fi novel The Dark Forest, this [idea suggests](https://higgs.ph.ed.ac.uk/outreach/higgshalloween-2021/fermi-paradox) that intelligent species stay silent to avoid detection by potentially hostile civilizations. What to read next - [![artist\&\#039;s impression of a pulsar ejecting vast pulses of radiation. ](https://cdn.mos.cms.futurecdn.net/7kCUkCxg6mAD2CXZ9kdKRa.jpg) Astronomers searching for alien life are sharpening our cosmic clocks. Here's why](https://www.space.com/space-exploration/search-for-life/astronomers-searching-for-alien-life-are-sharpening-our-cosmic-clocks-heres-why) - [![Images from the SETI@home project, including a screenshot of the SETI@home data and a man looking at a large computer with the same screen](https://cdn.mos.cms.futurecdn.net/2wUmfrBEPjRk7FYcfJYAxP.jpg) This SETI program is chasing down its final 100 signals. Could one of them be from aliens?](https://www.space.com/space-exploration/search-for-life/this-seti-program-is-chasing-down-its-final-100-signals-could-one-of-them-be-from-aliens) - [![On the left, a giant orange arc emerges, rising slightly. between that, all the way right, through the middle, seven planets of varying colors and texturs.](https://cdn.mos.cms.futurecdn.net/JeQYsG4tEK6zMabKsPWZ8b.jpg) These 45 exoplanets may be the best places to search for alien life](https://www.space.com/astronomy/exoplanets/these-45-exoplanets-may-be-the-best-places-to-search-for-alien-life) ## 3\. Something prevents their expansion The Great Filter: This [theory suggests](https://www.space.com/space-exploration/search-for-life/how-the-great-filter-could-explain-why-we-havent-found-intelligent-aliens) that there is a nearly insurmountable barrier preventing civilizations from advancing. This could be at the stage of life’s emergence, intelligent life’s development, or a self-destructive phase like nuclear war or environmental collapse. Self-Limiting Civilizations: Advanced societies may become so technologically sophisticated that they lose interest in space expansion, opting for virtual realities or inward development. ### Implications for humanity ![four people stand silhouetted under a starry sky with the milky way stretching overhead.](https://cdn.mos.cms.futurecdn.net/McWRecegXJuN5KWYE3rtBR.jpg) The "great silence" of the cosmos represents one of the greatest mysteries of our time. (Image credit: Paolo Carnassale via Getty Images) Understanding the Fermi Paradox is more than just an intellectual exercise — it has real implications for our future. If the Great Filter lies behind us (e.g., life itself is incredibly rare), then we may be one of the first intelligent civilizations. If the filter is ahead (e.g., technological civilizations inevitably destroy themselves), then our survival is far from guaranteed. Our [search for extraterrestrial intelligence](https://www.space.com/33626-search-for-extraterrestrial-intelligence.html) (SETI) continues, with new projects like the [James Webb Space Telescope](https://www.space.com/21925-james-webb-space-telescope-jwst.html) analyzing [exoplanet](https://www.space.com/17738-exoplanets.html) atmospheres and advanced AI scanning for signals. Whether we find aliens or confirm our solitude, the answer to the Fermi Paradox will profoundly shape our understanding of our place in the universe. The "great silence" of the cosmos may be unsettling, but it also presents one of the greatest mysteries of our time. Are we alone, or is something preventing us from hearing the others? Until we find an answer, the question remains open. ## Fermi paradox expert Q\&A We asked Professor Heidi Jo Newberg from the Rensselaer Polytechnic Institute a few questions about the Fermi Paradox. ![Heidi Jo Newberg](https://cdn.mos.cms.futurecdn.net/JNoHunAQPxQhfjHLvbB3G3.jpg) Heidi Jo Newberg Social Links Navigation Professor, Physics, Applied Physics, and Astronomy Rensselaer Polytechnic Institute Heidi Jo Newberg is an astrophysicist currently studying the structure of our galaxy. She has conducted diverse research in astrophysics, including on stars, supernovas, and both our galaxies and others. She recently received a grant from NASA to work on an alternative to conventional telescopes to detect exoplanets that could support life. ### Do modern researchers tend to accept the premise of the Fermi Paradox — that is, if intelligent life outside our planet exists, then it's likely that they would have contacted or reached Earth by now? I can't speak for everyone else, but no I do not believe in the premise. Because the Earth is the only planet where we know that life exists, we can only make guesses based on how life here has evolved. The Earth formed about 4.6 billion years ago. Life on Earth began at least 3.5 billion years ago, since fossils of this age have been found, but simpler cells are expected to have formed earlier than that. Possibly, life on Earth started very quickly after conditions allowed for liquid water to be commonly available. On the other hand, life that had more than one cell took until about 1 billion years ago, and humans did not evolve in 0.2 billion years ago. As far as we know, humans are the only life form on the Earth that thinks about what is going on in the Universe, and could potentially communicate with other life. The first telescopes were invented about 400 years ago, and the first space probes were launched less than 100 years ago. What I take away from this is that simple life (like one celled organisms) might be easy to create, but complex life is harder, and life that tries to communicate with life elsewhere in the Universe could be extremely rare. While the technology to find and communicate with extraterrestrial life, once started, appears to develop extremely fast on the timeline of the Universe, we do not know how long modern humans will survive as a species. ### Is there a commonly accepted way to resolve the Fermi Paradox? I doubt there is a commonly accepted way to resolve the Fermi Paradox, other than to point to the fact that we have very little information about highly evolved intelligent life. We don't know how rare it is, how long a civilization lasts, how likely it would or would not want to communicate with us, how likely it would spread through the Galaxy, or how we would recognize and understand each other. In the absence of any real information to figure any of this out, it just seems like there are many possibilities to solve it. In evaluating the Fermi Paradox, it is important to think about the vast distances of space in the Milky Way. The time for light to travel to the nearest star is more than four years. If a rocket ship travels 20,000 miles per hour, then it would take more than 33,000 years to get there. The light travel time from the Sun to the center of our galaxy is 30,000 years. The rocket travel time is a 170 million years. It is completely unclear whether life will want to, or be able to, travel over these sorts of distances to populate the Galaxy. If it is attempted, it is not clear whether there are suitable places for it to land and thrive. Spreading life throughout the galaxy might be much more difficult than Fermi supposed. ### Do researchers studying exoplanets, particularly potentially habitable ones, usually consider the Fermi Paradox? Modern researchers looking for potentially habitable planets usually use the [Seager Equation](https://en.wikipedia.org/wiki/Sara_Seager) when they are thinking about the likelihood of finding life. This is an [update](https://www.seti.org/drake-equation-inde) of the Drake Equation which was a summary of what people were looking for in 1961. Note that one of the key differences is that the Seager Equation asks how many planets we can find with life that transformed the atmosphere (for example by photosynthesis), while the Drake Equation calculates the number of civilizations that are sending out detectable radio waves. In the 20th century, the SETI program looked for these civilizations and found no signals of such civilizations. So you can see that the conversation has changed to the search for life that is not necessarily intelligent — something that the Earth's history would tell us is much more likely to find. I occasionally teach an Exoplanets and Life class, and the textbook I use does not talk about the Fermi Paradox. My expectation is that most researchers are not currently thinking about it. The current search is for exoplanets, habitable exoplanets with liquid water, and signs of life that is not necessarily intelligent. ### What are some ways current research might eventually resolve the Fermi Paradox? As we learn more about exoplanets, it becomes more possible to make statistical statements about the likelihood of life, and the possibility for it to spread. The basis of the paradox lies in the idea that there are hundreds of billions of stars in the Milky Way, and with so many there must be other intelligent life on one of them. But we don't really have a way to assess whether that is true. In six tons of sand, there are hundreds of billions of grains of sand. So, it might seems reasonable to think that there must be at least one of them that is made of uranium. But we don't look for uranium on the beach because if it was there, it would be dissolved in the water and wash away. Just having a large number of objects doesn't mean that every possibility for what those objects are must therefore exist. Current experiments are teaching us how many exoplanets there are, what the conditions are on those planets, how common it is for exoplanets to have surface temperatures that allow for liquid water, and possibly how many exoplanets exhibit atmospheric abundances that favor the existence of life. We are working towards actually finding other life of any kind that is on another planet. This information would give us some basis for then extrapolating to the probability that technological civilizations form elsewhere, and would tell us how far they might have to travel to find the nearest habitable planet where they could establish a colony. ### Additional resources If you're looking to explore the Fermi Paradox in depth, a great starting point is Stephen Webb’s book, "[If the Universe Is Teeming with Aliens… Where Is Everybody?](https://target.georiot.com/Proxy.ashx?tsid=72128&GR_URL=https%3A%2F%2Famazon.co.uk%2FUniverse-Teeming-Aliens-Everybody-Extraterrestrial%2Fdp%2F0387955011%3Ftag%3Dhawk-future-21%26ascsubtag%3Dspace-us-2738472146419429680-21)" This book lays out 75 possible solutions to the paradox, covering scientific, philosophical, and speculative ideas in an accessible yet detailed way. For an engaging online read, the [Wait But Why article on the Fermi Paradox](https://waitbutwhy.com/2014/05/fermi-paradox.html) is a great place to start. Additionally, the [SETI Institute’s website](https://waitbutwhy.com/2014/05/fermi-paradox.html) provides up-to-date research, news, and expert insights on the search for extraterrestrial intelligence, including discussions on why we might not have found aliens yet. ### Bibliography “The Fermi Paradox.” SETI Institute, [https://www.seti.org/fermi-paradox-0](https://www.seti.org/fermi-paradox-0). Accessed 5 March 2025. “The Fermi Paradox - Higgs Centre for Theoretical Physics.” The Higgs Centre for Theoretical Physics, [https://higgs.ph.ed.ac.uk/outreach/higgshalloween-2021/fermi-paradox](https://higgs.ph.ed.ac.uk/outreach/higgshalloween-2021/fermi-paradox). Accessed 5 March 2025. “Fermi's Paradox.” University of Oregon, [https://pages.uoregon.edu/jschombe/cosmo/lectures/lec28.html](https://pages.uoregon.edu/jschombe/cosmo/lectures/lec28.html). Accessed 5 March 2025. 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Logout Read more [![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 they just don't want to talk to us](https://www.space.com/space-exploration/search-for-life/where-are-all-the-aliens-maybe-they-just-dont-want-to-talk-to-us "Where are all the aliens? Maybe they just don't want to talk to us") [![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? 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") MORE FROM SPACE... 1. [![an astronaut in an orange spacesuit with a planet](https://cdn.mos.cms.futurecdn.net/DXR4PG5R2egauWUfnTo3Hc.png)](https://www.space.com/entertainment/space-movies-shows/the-artemis-2-astronauts-got-a-private-project-hail-mary-screening-before-launch-heres-their-verdict "The Artemis 2 astronauts got a private 'Project Hail Mary' screening before launch. Here's their verdict") 1 [The Artemis 2 astronauts got a private 'Project Hail Mary' screening before launch. Here's their verdict](https://www.space.com/entertainment/space-movies-shows/the-artemis-2-astronauts-got-a-private-project-hail-mary-screening-before-launch-heres-their-verdict) 2. 2 [Crew of tiny worms readies for April 11 launch to International Space Station](https://www.space.com/space-exploration/launches-spacecraft/crew-of-tiny-worms-readies-for-april-10-launch-to-international-space-station) 3. 3 ['It probably will start a precedent': Why satellite company's withholding of Iran imagery has this expert worried](https://www.space.com/space-exploration/satellites/it-probably-will-start-a-precedent-why-satellite-companys-withholding-of-iran-imagery-has-this-expert-worried) 4. 4 [A house-size asteroid is heading toward Earth tonight: Here's what you need to know](https://www.space.com/astronomy/asteroids/a-house-size-asteroid-is-heading-toward-earth-tonight-heres-what-you-need-to-know) 5. 5 [Watch Artemis 2 race back to Earth in this telescope livestream tonight](https://www.space.com/space-exploration/artemis/watch-artemis-2-race-back-to-earth-in-this-telescope-livestream-tonight) Space is part of Future US Inc, an international media group and leading digital publisher. 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Readable Markdown	![man sits on a rock under the milky way. Are we alone in the universe?](https://cdn.mos.cms.futurecdn.net/6SMGeKptzTqHRuipe9cC49.jpg) The Fermi Paradox seeks to answer the question of where the aliens are. After all, the universe is incredibly old, big and filled with potentially habitable planets. (Image credit: bjdlzx via Getty Images) The universe is vast, ancient, and teeming with billions of potentially habitable planets. With so many chances for intelligent life to arise, we should expect to see evidence of extraterrestrials. ## Fermi Paradox FAQs ### Was the Fermi Paradox solved? Humanity has been around for just 200,000 years, and we've been listening for possible radio signals from E.T. just since 1960. So the odds that we will overlap in time and space with a detectable alien civilization don't seem great. There is probably no single solution to the Fermi Paradox ### What is the great silence theory? The "great silence" is the idea that there is no evidence of extraterrestrial civilizations and that we are truly alone in the universe; it is also known as the Fermi Paradox. ![graphic illustration of the fermi paradox shows two people looking up at the milky way and a graphic above their heads showing an empty fuel gauge with the image of an alien on it, indicating a distinct lack of aliens.](https://cdn.mos.cms.futurecdn.net/RUirVJ8ZVjAsgspC3ya6z5.jpg) Are we truly alone in the cosmos? (Image credit: Created in Canva Pro by Daisy Dobrijevic) ### Is the dark forest theory true? While some intelligent extraterrestrial civilizations might choose to remain hidden, as suggested by the dark forest theory, it’s unlikely that every single one would adopt the same fear-driven strategy. ### The scale of the paradox ![The milky way galaxy as seen over a mountain range.](https://cdn.mos.cms.futurecdn.net/nP8zA5qg8tFCAWLwbnamph.jpg) Our home galaxy, the Milky Way, contains an estimated 100 to 400 billion stars. (Image credit: Getty Images) The numbers are staggering. Our [Milky Way](https://www.space.com/19915-milky-way-galaxy.html) alone contains an estimated 100 to 400 billion stars, many of them hosting planets in the [habitable zone](https://www.space.com/goldilocks-zone-habitable-area-life). If even a tiny fraction of these planets develop life, and a fraction of those develop intelligence and technology, the galaxy should be buzzing with signals, megastructures, or even interstellar visitors. But so far, we’ve found nothing. "Fermi grasped that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire galaxy," representatives of the Search For Extraterrestrial Intelligence (SETI) Institute in Mountain View, California, wrote in a [Fermi Paradox explainer](https://www.seti.org/fermi-paradox-0). "Within a few tens of millions of years, every star system could be brought under the wing of empire. Tens of millions of years may sound like a long project, but in fact it’s quite short compared to the age of the galaxy, which is roughly a thousand times more." ## Possible explanations ![An artist\&\#039;s image of an alien starship as viewed from a planet\&\#039;s surface.](https://cdn.mos.cms.futurecdn.net/Fu7f3DbymUm8kL9RDvfA4.jpeg) There are many possible hypotheses that attempt to solve the Fermi Paradox. (Image credit: Coneyl Jay) There are numerous hypotheses attempting to resolve the paradox, ranging from the optimistic to the ominous: ## 1\. They're out there, but we haven't found them yet Radio Silence: We might not be listening at the right frequencies or in the right way. Civilizations could communicate using methods we haven’t discovered yet, like neutrino beams or [quantum entanglement](https://www.space.com/31933-quantum-entanglement-action-at-a-distance.html). Breaking space news, the latest updates on rocket launches, skywatching events and more\! The Cosmic Timescale: Humanity has only been scanning the skies for a few decades — an eye blink in cosmic history. Advanced civilizations could [rise and fall in cycles](https://pages.uoregon.edu/jschombe/cosmo/lectures/lec28.html), missing each other in time. ## 2\. They don't want to be found The Zoo Hypothesis: Aliens could be [observing us](https://pages.uoregon.edu/jschombe/cosmo/lectures/lec28.html) like we observe animals in a nature reserve, choosing not to interfere. The Dark Forest Theory: Inspired by Liu Cixin’s sci-fi novel The Dark Forest, this [idea suggests](https://higgs.ph.ed.ac.uk/outreach/higgshalloween-2021/fermi-paradox) that intelligent species stay silent to avoid detection by potentially hostile civilizations. ## 3\. Something prevents their expansion The Great Filter: This [theory suggests](https://www.space.com/space-exploration/search-for-life/how-the-great-filter-could-explain-why-we-havent-found-intelligent-aliens) that there is a nearly insurmountable barrier preventing civilizations from advancing. This could be at the stage of life’s emergence, intelligent life’s development, or a self-destructive phase like nuclear war or environmental collapse. Self-Limiting Civilizations: Advanced societies may become so technologically sophisticated that they lose interest in space expansion, opting for virtual realities or inward development. ### Implications for humanity ![four people stand silhouetted under a starry sky with the milky way stretching overhead.](https://cdn.mos.cms.futurecdn.net/McWRecegXJuN5KWYE3rtBR.jpg) The "great silence" of the cosmos represents one of the greatest mysteries of our time. (Image credit: Paolo Carnassale via Getty Images) Understanding the Fermi Paradox is more than just an intellectual exercise — it has real implications for our future. If the Great Filter lies behind us (e.g., life itself is incredibly rare), then we may be one of the first intelligent civilizations. If the filter is ahead (e.g., technological civilizations inevitably destroy themselves), then our survival is far from guaranteed. Our [search for extraterrestrial intelligence](https://www.space.com/33626-search-for-extraterrestrial-intelligence.html) (SETI) continues, with new projects like the [James Webb Space Telescope](https://www.space.com/21925-james-webb-space-telescope-jwst.html) analyzing [exoplanet](https://www.space.com/17738-exoplanets.html) atmospheres and advanced AI scanning for signals. Whether we find aliens or confirm our solitude, the answer to the Fermi Paradox will profoundly shape our understanding of our place in the universe. The "great silence" of the cosmos may be unsettling, but it also presents one of the greatest mysteries of our time. Are we alone, or is something preventing us from hearing the others? Until we find an answer, the question remains open. ## Fermi paradox expert Q\&A We asked Professor Heidi Jo Newberg from the Rensselaer Polytechnic Institute a few questions about the Fermi Paradox. ![Heidi Jo Newberg](https://cdn.mos.cms.futurecdn.net/JNoHunAQPxQhfjHLvbB3G3.jpg) Heidi Jo Newberg is an astrophysicist currently studying the structure of our galaxy. She has conducted diverse research in astrophysics, including on stars, supernovas, and both our galaxies and others. She recently received a grant from NASA to work on an alternative to conventional telescopes to detect exoplanets that could support life. ### Do modern researchers tend to accept the premise of the Fermi Paradox — that is, if intelligent life outside our planet exists, then it's likely that they would have contacted or reached Earth by now? I can't speak for everyone else, but no I do not believe in the premise. Because the Earth is the only planet where we know that life exists, we can only make guesses based on how life here has evolved. The Earth formed about 4.6 billion years ago. Life on Earth began at least 3.5 billion years ago, since fossils of this age have been found, but simpler cells are expected to have formed earlier than that. Possibly, life on Earth started very quickly after conditions allowed for liquid water to be commonly available. On the other hand, life that had more than one cell took until about 1 billion years ago, and humans did not evolve in 0.2 billion years ago. As far as we know, humans are the only life form on the Earth that thinks about what is going on in the Universe, and could potentially communicate with other life. The first telescopes were invented about 400 years ago, and the first space probes were launched less than 100 years ago. What I take away from this is that simple life (like one celled organisms) might be easy to create, but complex life is harder, and life that tries to communicate with life elsewhere in the Universe could be extremely rare. While the technology to find and communicate with extraterrestrial life, once started, appears to develop extremely fast on the timeline of the Universe, we do not know how long modern humans will survive as a species. ### Is there a commonly accepted way to resolve the Fermi Paradox? I doubt there is a commonly accepted way to resolve the Fermi Paradox, other than to point to the fact that we have very little information about highly evolved intelligent life. We don't know how rare it is, how long a civilization lasts, how likely it would or would not want to communicate with us, how likely it would spread through the Galaxy, or how we would recognize and understand each other. In the absence of any real information to figure any of this out, it just seems like there are many possibilities to solve it. In evaluating the Fermi Paradox, it is important to think about the vast distances of space in the Milky Way. The time for light to travel to the nearest star is more than four years. If a rocket ship travels 20,000 miles per hour, then it would take more than 33,000 years to get there. The light travel time from the Sun to the center of our galaxy is 30,000 years. The rocket travel time is a 170 million years. It is completely unclear whether life will want to, or be able to, travel over these sorts of distances to populate the Galaxy. If it is attempted, it is not clear whether there are suitable places for it to land and thrive. Spreading life throughout the galaxy might be much more difficult than Fermi supposed. ### Do researchers studying exoplanets, particularly potentially habitable ones, usually consider the Fermi Paradox? Modern researchers looking for potentially habitable planets usually use the [Seager Equation](https://en.wikipedia.org/wiki/Sara_Seager) when they are thinking about the likelihood of finding life. This is an [update](https://www.seti.org/drake-equation-inde) of the Drake Equation which was a summary of what people were looking for in 1961. Note that one of the key differences is that the Seager Equation asks how many planets we can find with life that transformed the atmosphere (for example by photosynthesis), while the Drake Equation calculates the number of civilizations that are sending out detectable radio waves. In the 20th century, the SETI program looked for these civilizations and found no signals of such civilizations. So you can see that the conversation has changed to the search for life that is not necessarily intelligent — something that the Earth's history would tell us is much more likely to find. I occasionally teach an Exoplanets and Life class, and the textbook I use does not talk about the Fermi Paradox. My expectation is that most researchers are not currently thinking about it. The current search is for exoplanets, habitable exoplanets with liquid water, and signs of life that is not necessarily intelligent. ### What are some ways current research might eventually resolve the Fermi Paradox? As we learn more about exoplanets, it becomes more possible to make statistical statements about the likelihood of life, and the possibility for it to spread. The basis of the paradox lies in the idea that there are hundreds of billions of stars in the Milky Way, and with so many there must be other intelligent life on one of them. But we don't really have a way to assess whether that is true. In six tons of sand, there are hundreds of billions of grains of sand. So, it might seems reasonable to think that there must be at least one of them that is made of uranium. But we don't look for uranium on the beach because if it was there, it would be dissolved in the water and wash away. Just having a large number of objects doesn't mean that every possibility for what those objects are must therefore exist. Current experiments are teaching us how many exoplanets there are, what the conditions are on those planets, how common it is for exoplanets to have surface temperatures that allow for liquid water, and possibly how many exoplanets exhibit atmospheric abundances that favor the existence of life. We are working towards actually finding other life of any kind that is on another planet. This information would give us some basis for then extrapolating to the probability that technological civilizations form elsewhere, and would tell us how far they might have to travel to find the nearest habitable planet where they could establish a colony. ### Additional resources If you're looking to explore the Fermi Paradox in depth, a great starting point is Stephen Webb’s book, "[If the Universe Is Teeming with Aliens… Where Is Everybody?](https://target.georiot.com/Proxy.ashx?tsid=72128&GR_URL=https%3A%2F%2Famazon.co.uk%2FUniverse-Teeming-Aliens-Everybody-Extraterrestrial%2Fdp%2F0387955011%3Ftag%3Dhawk-future-21%26ascsubtag%3Dspace-us-2738472146419429680-21)" This book lays out 75 possible solutions to the paradox, covering scientific, philosophical, and speculative ideas in an accessible yet detailed way. For an engaging online read, the [Wait But Why article on the Fermi Paradox](https://waitbutwhy.com/2014/05/fermi-paradox.html) is a great place to start. Additionally, the [SETI Institute’s website](https://waitbutwhy.com/2014/05/fermi-paradox.html) provides up-to-date research, news, and expert insights on the search for extraterrestrial intelligence, including discussions on why we might not have found aliens yet. ### Bibliography “The Fermi Paradox.” SETI Institute, [https://www.seti.org/fermi-paradox-0](https://www.seti.org/fermi-paradox-0). Accessed 5 March 2025. “The Fermi Paradox - Higgs Centre for Theoretical Physics.” The Higgs Centre for Theoretical Physics, [https://higgs.ph.ed.ac.uk/outreach/higgshalloween-2021/fermi-paradox](https://higgs.ph.ed.ac.uk/outreach/higgshalloween-2021/fermi-paradox). Accessed 5 March 2025. “Fermi's Paradox.” University of Oregon, [https://pages.uoregon.edu/jschombe/cosmo/lectures/lec28.html](https://pages.uoregon.edu/jschombe/cosmo/lectures/lec28.html). Accessed 5 March 2025. Share your thoughts 0 1 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. You will be sent a verification code to the phone number you provide. 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 Your Email Address You may enter a new email address below. You will be sent a verification code to the address you provide. Create a Username This will be publicly viewable so make it something you like\! Reset your password Enter your email address below. 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She will be a guest speaker aboard [HX's Solar Eclipse Expedition](https://www.travelhx.com/en-gb/cruises/solar-eclipse-expedition-2026-greenland-iceland-and-svalbard/) in August 2026 and will join Hurtigruten as an [onboard astronomer](https://www.hurtigruten.com/en-gb/on-board/on-board-team/meet-your-astronomy-voyage-lecturers) for a northern lights sailing in January 2027.
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