Why We Might Be Alone in the Universe

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    Why does it appear, that humanity is the lone intelligence in the universe? The answer might be that planet Earth is more unique than we've previously assumed. The rare earth hypothesis posits exactly this - that a range of factors made Earth exceptionally unusual and uniquely able to produce intelligent life.
    In upcoming episodes we’ll be exploring the anthropic principle and its two main versions - the strong and the weak anthropic principles. The strong anthropic principle tells us that the observed universe must be able to produce observers - including the contentious idea that this predicts the existence of universes beyond our own. But in today's episode we’re going to focus on the weak anthropic principle. It says that we must find ourselves in a part of the universe capable of supporting us. For example, in a planetary biosphere rather than floating in the void between the galaxies. This may seems tautological, but accounting for this observer selection bias is important to understanding why the universe looks the way it does from our perspective. And the weak anthropic principle is much more useful than that. When combined with the apparent absence of alien civilizations, it may tell us why intelligent life is incredibly rare in our universe.
    Hosted by Matt O'Dowd
    Written by Matt O'Dowd
    Graphics by Leonardo Scholzer & Adriano Leal
    Directed by: Andrew Kornhaber
    Executive Producers: Eric Brown & Andrew Kornhaber
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    Published on 7 months ago


    1. PBS Space Time

      Hey Everyone! So this is our first episode released in 4K. Hope you enjoy the upgrade.

      1. Doozy

        Omg , enough with the space lies

      2. DetailedGaming

        Time Traveler here. I did appear in your studio but do to the fact that my matter more specifically my atoms at your current time already existed in a pre different form(s). The first law taking presidents "energy can only be transferred" I couldn't exactly transfer my current atomic structure onto the atoms how ever dispersed already existing in your time in some varying form. I'm from the future my atoms/energy exist now differently then it did in this time. So in truth to say I timed traveled would be incorrect I more or less time probed. In the future we have developed the technology to essentially what you would compare in your modern day to placing a drone within an atom of insignificance. That in your time would be made up of a molecule of air and in our time is the same of similar makeup. Then we watch learn of course we can also implement this on a large scale in a multitude of vastly varying ways I won't go into detail. In truth I found it quite humoring someone of your time would think that someone of my time would expose such blatant technological advances. However I find it equally entertaining to know that no one will take this seriously which is the joke. I did expose great technological advances.

      3. mikey forrester

        Please change the presenter PBS. The topics are interesting but I can't listen to this nasal whiny Aussie talking for more than 1 minute.

      4. Scott West

        If we're the only ones isn't it out duty to populate the vast emptiness left to just us?

      5. Zhor'i Ambassador

        Oh, you wish you were alone in the Universe. Although it would make your existence void if my people never had existed. Perhaps you should accept the real world rather than fabricate it.

    2. Keegs

      he looks like an older version of joe jonas

    3. DyingStar 117

      The fact that space is expanding more as time goes on, i believe we're less likely to find alien life now or later in the future unless we invent some kind of warp drive to cheat distance/time travel

    4. Grace M

      This theory is for snowflakes

    5. Markos70

      Are you a cosmologist or evolutionist? Because your opinions on life development certainly diminishes your other research

    6. John Dude

      Why would developing life care how long the seasons are? I think we're assuming too much about our own point of view here.

    7. Diamond Warrior

      That is total nonsense the universe is too big for only one intelligent life

    8. The Anti Reaper

      Maybe we're under a holosphere. The aliens didn't want to deal with us yet, so they just put a holographic sphere around our solar system to prevent us from noticing them yet.

    9. koho

      Yep, the emergence of intelligent life, via multi-cellular animal life forms, has for me the weak link in the Drake Equation as well. As I understand, multicellular life has evolve da few time son earth, but animal versions, only once. If you have the facts, please say so!

    10. Leandro Lapa

      Even if advanced life is not SO rare, the sheer dimension of space may be an insurmountable barrier to any possible contact.

    11. 3% Milk

      If the universe is as big as they say then without a doubt there's other life

    12. John Thibault

      Lucky? You said "one of more extremely improbable events". If you string them together what's the probability that complex life formed? Heck what's the probability the universe exists at all?

    13. Lamster66

      Ok missed the comments last week so i'll tackle 2 this week "Loop quantum gravity and Time travel EASY!" LOL

    14. Peter Parkorr

      The reason time travellers aren't posting comments in the past is because they know they're not allowed to, obviously. It goes against Buddha's teachings (the original futurist) and might kill everyone. Shame because we need plenty of survival tips these days! Go green, people.

    15. Two Triz

      There is definitely intelligent life on Jupiter using the storm to hide from aliens

    16. Unsupported Elephant

      🌍Are we alone in the universe or universes?? 🌎Some people are using science, some religion, yet others combine them two. 🌏 The most importantly we are unable to answer this without educated imagination and definitely not with the ignorance and arrogance from big institutions/organisations. If you understand this It will prove you have inner meaning and values lnkd.in/djhgww9 link to short quotations and thoughts 👍👍🙂🙂 thank you🌙🪐

    17. David Garratt

      There i a chance that we are isolated within our small small pocket of the galaxy. We may be a Barbaric unfounded Solar System. We all know life will thrive within the conditions it arrives, we as a human race don't even know what is lying beneath the deepest of Oceans. I am not saying that I believe in every possible alien life being possible but we are not alone, within the universe there would be a substantial environment to even have bacteria so without a doubt there is life out there that will some day produce thinking conscious entities such as ourselves .

    18. Thomas Allore

      Why do we assume that all possible life requires oxygen and/or water? Why cant life made of silicone or anything else that needs sulphuric acid or anything else to survive exist? Life always finds a way, right? We don't know everything and we certainly can't know that life not made of carbon doesn't exist.

    19. Angus McDonald

      So we are where we are and that's that. Maybe we are the first or maybe on the grand scale we are the 60,000 ischt but time sees all others die before us. I don't think we can ever answer this living on a rock looking at the inconceivable size that faces us. We are here for a micro second in astronomic terms and our race has been here for a small amount of time. Im here because there was no where else to be. Mind boggling !

    20. James Myers

      Honestly this episode is amazing, awesome script

    21. Nunya Damn Bidness

      rare earth hypothesis is for sheeple. 70 percent of our galaxy alone has simlar stars with habitable zones. i think life is about as common as mold appearing on bread you left out overnight.

    22. Max Held

      it would be such a bummer if we're alone out here. I have no faith that humans will pull of any universal traversing due to our seemingly inherent bias towards self destruction. So much of the universe will remain unobserved by the universes minds. That's why I like to think that there's other living beings out there who arent so prone to genocide and the like. well one can hope anyways

    23. Samuel Pope

      In the absence of a better understanding of abiogenesis it's anybodies guess.

    24. A Frustrated Gamer

      <a href="#" class="seekto" data-time="656">10:56</a> Don't say it... You just couldn't help yourself...

    25. David Andersen

      As an agnostic (Not an atheist), I am comfortable in making the following statement: Considering all the random odds we defy, it seems as if there is a God. Almost, at least. Either that, or our universe is random, beautiful, and terrifying. 😬


      Maybe we with our space travel and all are spreading earth microbes. These microbes may suffer in a new environment but may even evolve to survive accordingly. And from one small organisms intelligent life may evolve in that place millions of years later. May be that was what happened here. Some alien civilisation could have visited long before causing foreign microbes to enter earths atmosphere.

    27. Jack McPhee

      I really like these videos, but I think you should be more professional and wear some nice clothes and not some old t-shirts. I find it distracting.,

    28. Karvas X3

      He talks like there’s intelligent life in earth I don’t believe there’s any intelligent life At least not on this planet

    29. We Are Saints

      It’s almost like we were created huh

    30. Izek1el 83

      What if we made a tool to see things far away that are as they are now? Because we see things lightyears away that could have advanced way before the light of their location arrived on earth.

    31. Jhonathan Cabrera

      What if planets are just electrons in an atom and we are the make up of something much bigger.

    32. Derpy Pedro

      What a wonderful world God has made.

    33. rubiks6

      There is no such thing as "simple" life. The simplest cell in existence is extremely complex and researchers don't know how it works.

    34. MiloTheSwift


    35. Adam Graham

      I am from Asgard ! Weak Mortals ;p


      This is why we need to populate and terraform the universe

    37. Alphabet Royal

      I don't believe for one second that we are alone in the universe.

    38. Magnus Hultqvist

      I belive life in simple form thrive on several planets. But high inteligent life is extreamly uncomon.

      1. rubiks6

        There is no such thing as "simple" life. The simplest cell in existence is extremely complex and researchers don't know how it works.

    39. Caleb J

      My time machine is a budget model and I accidentally showed up during the pandemic of the 2020s sorry Matt

    40. Arthur Zettel

      Until Humans can decide to not kill automatically out of fear of what they do not understand, Extraterrestrials (Will Not) make Public Contact with World Leaders.

    41. cherry soda

      no one even knows the full extent of our universe so how can you say that intelligent life is rare

    42. ethercore

      Nice video, but you got the author's name wrong. It's not Robert Brownlee, it's Donald (Don) Brownlee. 20 years ago he was my high school job shadow. I followed him around for a day at the University of Washington and heard all about the work he and his colleagues were doing in Astrobiology. I finally didn't choose to go into the field but I'll forever be grateful for that experience. So Don, if you're reading this, thank you!

    43. Damir Bolic

      We could argue that if Earth is so rare(unique) then emergence of intelligent life is almost 100% certain on any place that has a right conditions for life( since it has emerged on Earth which by definition is rare/unique). Great video, doubt that Fermi paradox will be "solved" any time soon

    44. anonygent

      How about "functionally alone in the universe"? You could speculate that there are, were, or will be intelligent life somewhere in the universe, but the probability that it will exist in the same galaxy and time period as us, plus have characteristics that we could recognize as similar to us, are so remote that we are, for all intents and purposes, alone.

    45. Michigan USA/Singapore S.E.Asia

      But you said there are multiple universes and earths too🤔

    46. Dave Duffy

      We are the only ones like us, but who knows what’s out there or anything that our senses don’t pick up here. We are a limited species.

    47. J Scott Scott

      “Intelligent Life”. These humans are so “fool” of themselves.

    48. kendell bedenfield jr

      That's a lot of luck and coincidence your spitting.

    49. viresh dubey

      Maybe this is an AI simulation where an very advance ai was trying to create life and all the other planets are its failed attempts earth is its success.....

    50. Lonswita Chimbila

      The moon shouldn't be there, if it collided with earth it would of destroyed earth but hows it in an obit of earth at the exact distance to sustain life as we know it. A little science leads you away from God but much science leads you back. we are looking at whats observable for the answers, which is like looking at an old house and trying to work out who built it from looking at the nails holding it together. We have moved a long way past a natural process no matter how much time you want to imagine earth is, it still will not happen with out an out side source. DNA for example the code book to life is only possible if it was designed as every animal is in families, eg dogs breed dogs, cats breed cats and so on. If i made twenty cars and need them all to have basic requirements to function then they all would have a fuel tank, steering wheel, and wheels. Now thats what we observe in so many animals, eyes and two eyes, legs, tongues and so on like design principals. The information (DNA) is only being lost, not one piece of information is being added so who or what wrote to code book to life to begin with. I love it when brilliant minds try to articulate impossible ideas.

    51. Chris Stephens

      What blows my mind is the arrogance of the human scientist. Scientists believe that everything everywhere has to be carbon-based to be just to be considered “life” just because every form of life on our tiny, little, insignificant rock is.

    52. Dj Lab

      There R Aliens, And they Are Totally Hostiles. Take me 4 a Fool... But not for long though… U’ll see... Well... Feel as well... Good luck with that anyway...

    53. Christofer Jacobs

      @PBS Space Time , Is there an interpretation of the Weak Anthropic Principle which postulates the existence of a multiverse? Or is it just the Strong who does so?

    54. Chris M

      Well i see a hand in all these facts.

    55. MattWhatsGoinOn

      There's no one else out there. Prove me wrong.

    56. Mike Martin

      Billions of star systems in our galaxy, billions of galaxies in the universe. Only human hubris assumes we are the rare exception .

    57. Doozy

      Omg , enough with the space lies

    58. Jhabari Owens

      So basically we got to find other earth like planets with a moon and that has planets the size of Jupiter and Saturn and the earth like planets also have to have a tilt like ours?

    59. Philip Robertson III

      Of course we're alone in this universe. I highly doubt any intelligent alien life would show their face around this hot mess of a place.

    60. J

      If the universe is truly infinite then there must be infinite planets that support intelligent life too, now how far away this other intelligent life would be is not something you can say with any certainty. Still, based on logic and mathematics it would be much less likely that we are the only intelligent life in an unlimited universe.

    61. Jack Williams

      No mention that we may be alone because other entities could be just as likely to wipe themselves out before developing interstellar travel.

      1. Neil Hart

        That's not the point of the rare earth hypothesis whatsoever.

    62. Raz Berry925

      The Fibonacci sequence should prove this false shouldn’t it?

    63. Razak 44

      First off there are extreme limitations to what we can learn just sitting here on Earth. What we don't know vastly out weighs what we do know. The universe is immense. The idea that we are alone is naive for some and wishful thinking for others. There may be other races that actually would not be able to live on the surface of Earth without protective gear. There may be other races that think we are stupid for living on the surface of a planet because of how risky it is. We are at risk of natural cosmic disasters and of other hostile races that would kill us all for a variety of possible reasons. I think there are races that live inside planets and at the bottom of oceans and do not advertise their presence. Probably because of hard lessons learned waring with other dangerous races. We have much to learn.

    64. Rigor Mortis

      humanity is earths seed to populate the universe

    65. Roxie D.

      Thank you for this... I feel lucky and unique right now...

    66. Mike Taylor

      A near infinite set of unlikely events took place thismorning alone. Let's stop pretending we're special based on circumstance.

      1. rubiks6

        @Mike Taylor - The Drake equation is a series of factors (5th-grade math, "factors." Think multiplication.). If any one of those factors is zero, then the product is zero. It only takes one zero. 5th-grade math. (Now I'll see if you know what is the next reasonable question to ask.)

      2. Mike Taylor

        @rubiks6 Drake Equation shows high probability of life even with tiny numbers because there are an estimated 6 sextilion stars in the universe with over 13 billion years of time to brew. Improbable things become highly likely under those circumstances.

      3. rubiks6

        @Mike Taylor - There are an awful lot of parameters in the Drake equation. Many of them are unknown. Researchers don't even know _which_ parameters should be in any sort of Drake equation. If any of them are unknown then you have no basis for your claim that we are not special. It's just your opinion. You should state it as such and not denigrate those who disagree with you by accusing them of pretending. Stop pretending that you know everything.

      4. Mike Taylor

        @rubiks6 Do you have any indication that we're not-not special? Edit: The Drake Equation, if you're not trolling.

      5. rubiks6

        Do you have any indication that we're not special?

    67. roj30001

      The anthropology principle “an observed universe must be able to produce observers” a meaningless principle created by an observer and not the universe

    68. Baby Whale Crypto

      Based on our own solar system alone the chance of life in our galaxy is liberally 1 in 8 in a randomly selected solar system, excluding natural satellites of planets. So, non-intelligent life should be very common in the universe or at least in our galaxy, but let's look at intelligent life. The range of species on Earth is from 7 million to 1 trillion , not including the 99% of them that have already gone extinct according to scientists, so that puts all species that have ever existed on Earth at a very conservative number of 700,000,000 (700 million or 0.7 billion). So the odds of intelligent life (to explore space) based on our own solar system is 1/8 * 1/(.7b) or 1 in 5.6 billion - the 1/8 comes from the fact that in our solar system, Earth is the only planet hospitable enough for a very small fraction life to endure for long periods. So based on our own solar system, given that there are about 100 billion planets in our galaxy based on the sample size of 500 exoplanets that we have found locally, so very liberally about 100/8 = 12.5 billion of them have non-intelligent life. The odds of 12.5 billion planets that have non-intelligent life in our galaxy having human-like intelligence is about 50-50 (0.448). So, based on our solar system alone, we are likely the only intelligent species in our galaxy, which basically means that intelligent life is likely an extremely unusual fluke of nature. I would think of human-like intelligent life as a destructive force of nature (black holes are to nearby stars what intelligent life is to nearby non-intelligent life), basically a planetary cancer to all other living beings, eventually causing extinction of most species. Intelligence begets knowledge which begets technology which begets destruction unlike any other non-intelligent species.

      1. rubiks6

        From your first sentence - How many planetary systems have a planet like the Earth? Just in our own galaxy. All that writing and math, all based on really bad assumptions. You really weren't paying attention to the video.

    69. NeuralBrew

      There could be an enormous number of earth-like planets in our observable universe, but we would still likely be alone. The reason is the odds of proteins and self-replicating molecules necessary for life randomly forming twice in any finite universe are so astronomical. The fact that life is so unlikely seems to make it obvious that there must be an infinite number of universes and if there is life in them, they would most all be like us, alone in a vast universe.

      1. rubiks6

        "The fact that life is so unlikely seems to make it obvious that there must be an infinite number of universes ..." I'm sorry but I fail to see any connection between 'life being unlikely' and the existence of other universes. Please explain how one leads to the other.

    70. Mike

      So as usual nowadays, the scientist explains things in a very acertive manner, all based on what he knows; Very good. However, considering that it is not the first time that new information has shaken and even renderd obsolete the obsolute truth of the day. Shouldn't the scientist be more humble and take seriously into account the infinite enormousity of the yet unknown? Or is it like someone once said; which went something like this, "there is nothing else new to discover, but only to measure the known more precisely"?.

    71. Barry Ledbetter

      I admire and love the way you explain everything! Love the Upgrade!!!! Cheers!

    72. leonardo alexis

      Imagine trying to get your grandma to follow along on this video🥴 I love this so much♥️

    73. justin zacharko

      In the forever expanding universe we are not the only form of life. Just accept it. It’s pretty stupid to think we are the only planet suitable to hold life.

    74. MoneyShift 3000

      I'm sorry sir, but I think it's too early to conclude.

    75. Just some Gurl With Red hair

      Egocentric fools.

    76. temaron cansler

      heres the problem with this argument. just because its rare doesnt mean its impossible and saying that something thats rare has a 0% chance of happening is wrong. its like saying roll this 1000 sided die twice and get a one each time. its a 1/1,000,000 chance sure but eventually your gonna hit it and since the universe is infinite u have infinite chances

    77. popiposh

      I'm curious to know if our usable carbon abundance is considered a rare earth quality as well.

    78. Real One

      There is a lot of dence people in this comment section....

    79. Richard Russell

      We are not alone... To think that is reckless and arrogant.... Humans are made up of the most common elements in the universe and my guess is so is all life.... Everywhere.

    80. Ken Paulsen

      Yep. God made this whole universe for us just so we'd know how important we are to Him (and marvel about Him).

      1. Ken Paulsen

        @BatmanIsGae69 Here's an interesting tidbit... Our telescopes can see an equal distance in all directions. Beyond that distance, the galaxies are (apparently) expanding in space faster than the speed of light and so we'll never see them. So from a particular point of view, we're the center of the universe.

      2. BatmanIsGae69