“If the Universe Is Teeming with Aliens… Where Is Everybody?” -Stephen Webb

If stars, planets, and biological processes are so common in the Universe, then where is everyone?

Image credit: NASA / Space Shuttle Atlantis mission 110.

Image credit: NASA / Space Shuttle Atlantis mission 110.

Here on Earth, we take for granted how easy it was for life to form. Our world has been around for some four-and-a-half billion years, and the oldest records of life go back to nearly the oldest rocks: 3.8 billion years ago.

But if we ran the “experiment” of having a Solar System similar to our own form in the Universe over and over again, how many times would we see life arise on Earth?

Image credit: © 2002, ReefNews, Inc.

Image credit: © 2002, ReefNews, Inc.

And of those times, how often would we see intelligent life arise, and how long would such a civilization last in that phase?

In other words, we’re asking about one of the biggest questions of them all: given our galaxy, with some 200-to-400 billion stars, all the planets around those stars, and a Universe with at least 200 billion Milky Way-like galaxies, how many of those worlds have life on them? How many of those have intelligent life on them? And how many of those have intelligent life on them at the same time we have intelligent life on ours?

Image credit: Alex Cherney of TWAN, via http://twanight.org/newTWAN/photos.asp?ID=3004497.

Image credit: Alex Cherney of TWAN, via http://twanight.org/newTWAN/photos.asp?ID=3004497.

For this week’s throwback Thursday, go check out the entire amazing, in-depth answer at Medium, and then leave your comments here!

Comments

  1. #1 R F
    Planet Earth
    February 20, 2014

    There’s something missing from your analysis. It may simply be that we are late to the party as Avi Loeb believes; the ambient temperature of the universe early on was such that every planet in the cosmos was capable of supporting liquid water. Life on many of those planets would likely have been extinguished as the universe cooled, but perhaps some would have survived, or propagated to other worlds via lithopanspermia.

  2. #2 PJ
    February 20, 2014

    Whichever the case may be, even if both lifeforms had developed the same form of communication, the distance between them would not allow that link to take place. If, for instance, our closest neighbour were 1k LY away, the round trip would be 2k LY. Anything we received from them is already 1k years old. Would their technology be the same a thousand years after having sent a message? Pretty doubtful.
    As much as I believe there IS life out there, the odds of detection are not favorable at the moment. We just keep listening, maybe, one day ………

  3. #3 Cleon Teunissen
    February 21, 2014

    Hi Ethan,

    I noticed the turn of phrase: “So that begs the question …”

    Here the verb ‘to beg’ looks somewhat odd. Your intention is clear, of course. Your meaning is: “This raises the question …”, and if you want emphasis you might say instead: “this cries out the question …”.

    The expression ‘begging the question’ has quite a history. It was introduced into english in the 16th century to denote a particular logical fallacy. The latin name of that logical fallacy is ‘petitio principi’. It’s when you’re arguing a particular point, but your reasoning takes the very thing you’re supposed to demonstrate as a prior assumption.

    In medieval formal debate during preliminaries one opponent would formally beg the other to acknowledge a set of prior assumptions. If a prior assumption was actually dependent on the point to be argued, the other opponent could raise the objection that the first opponent was begging the question.

    Nowadays most often the “this raises the question” meaning is intended, rather than the logical-fallacy-meaning. In that sense using the expression ‘begging the question’ in the meaning of “raising the question” is not wrong. Language is a living entity.

    Still, you’re a science blogger, and you very much want to foster critical thinking. Let’s try and keep the expression ‘begging the question’ available to refer to the logical fallacy.

    http://begthequestion.info/

  4. #4 Wow
    February 21, 2014

    Well, I would say that “begging the question” is more frequently used in the sense of “you’re assuming a different question has been answered when it hasn’t even been asked”.

    Take “Halal is cruel”. Arguing that it causes unnecessary pain and suffering to the animal begs the question: “Is it, or could it be, done in a manner that doesn’t, to any more extent than any other butchering of animals for food does?”.

    As in that question is going begging for an answer and, like beggars in the street, is pretended by most never to even exist.

  5. #5 Rick
    February 21, 2014

    Even if there is no one out there within a reasonable distance, Earthlings may still one day meet true aliens. Consider that we will eventually travel to the stars. I believe Fermi supposed that it would take 500 years between colonization and a subsequent star hop. Instead, let’s guess 10,000 years. Then we set off in both directions and circumnavigate the galaxy in 100 million years. The two groups would meet on the other side in 100 million years. with a divergence of 200 million years of evolution. Mastery of genetics will mean the difference could be much greater than 200 million years. And communication between the two group might be 300,000 years delayed. We may well one day meet Earthling aliens.

  6. #6 BillK
    London, UK
    February 21, 2014

    From the history of life on Earth, it may well be that bacteria are widespread throughout the universe.
    After a billion years of life, by a unique accident, a bacterium and an archaeon merged and started the eukaryote chain of life. This accident has never happened again in the following 2 billion years of life on earth.
    See:
    http://nautil.us/issue/10/mergers–acquisitions/the-unique-merger-that-made-you-and-ewe-and-yew

    The universe is a BIG place with room for much life creation at the bacterium level. And even the rare accident of eukaryotes creation may have happened elsewhere. But it may happen in a galaxy far, far away.

  7. #7 Rick
    February 21, 2014
  8. #8 Wow
    February 21, 2014

    Rick, #5, rather like ring species.

  9. #9 Sinisa Lazarek
    February 21, 2014

    @Ethan

    Illustration of moon base was done by Dennis Davidson.

  10. #10 Sinisa Lazarek
    February 21, 2014

    p.s. most of them were done for http://www.nss.org

  11. #11 Ethan
    February 21, 2014

    Sinisa,

    Thank you for that! I have made the edits on the original, and now I know! The “Davidson” watermark on the lower right should have enabled me to do better detective work.

    Cleon,

    You are talking about “prescriptivist” versus “descriptivist” linguistics here. Yes, the way I used the phrase begs the question would have been wildly inappropriate hundreds of years ago, but — as Wow has pointed out — this is simply common use of the phrase now in many parts of the world. Much as I myself get a bee in my bonnet about the use of the word “literally” to mean “figuratively”, the pronunciation of “nuclear” as “nuke-YOU-lurr”, or the phrase “I could care less” to mean “I couldn’t care less”, I am sympathetic to your plight.

    But you are fighting a losing battle; linguistics is not a science and it evolves according to the way people use words. I can try to be mindful of that — it certainly is no more difficult to say “raises the question” or “assumes an answer to a question we haven’t considered” — but be aware that the vast majority won’t be. This is a change in English that has already occurred.

    Also, to R F and PJ,

    These are good comments that would require a significantly longer response than one I am prepared to give right now.

    But, when the Ask Ethan series gets moved over to Medium — which will happen, most likely, at the start of March — I will start a new series here at the end of the week (Friday/Saturday-ish) exclusive to ScienceBlogs, where I answer the best (chosen by me) comments-of-the-week. These are both excellent candidates for that. :-)

  12. #12 oldebabe
    February 21, 2014

    Well, and as you must know, any connection/interface with any other/potential aliens is certainly over an incredible distance. Maybe some day we, or someone else in the universe, will find a way to overcome the mileage.

  13. #13 Ian
    Earth, mostly
    February 21, 2014

    I enjoyed your article, for the most part, except for the basic premis.
    We have pilots, astronaughts, military leaders, politicians, scientists of various disciplines, aeronautic experts, etc. etc. all claiming to have witnessed or otherwise experienced or recorded unknown phenomon that they, in thier expert opinion, can not attach to any known terrestrial, or physical phenomenon and that would seem to run contrary to the laws of classical physics. They are dismissed, ridiculed and their expertise is mocked and belittled. Your article neglects to mention this there by perpetuating the myth that we have experts of the highest order in various agencies around the world that are prone to hallucinations, or otherwise can’t tell shingles from shinola. Are we alone? Perhaps. Has contact already happened? Perhaps. We can’t continue to ignore what may already be on our door step and risk missing the forest because of the trees. The better question to me, beyond ‘Are We Alone’, is how will we know we have made contact, and will we understand it when it happens?

  14. #14 Sinisa Lazarek
    February 21, 2014

    @ R F

    you can check the discussion about that here
    http://scienceblogs.com/startswithabang/2014/01/24/ask-ethan-21-why-does-life-exist/

    from #24 onward

  15. #15 Alan L.
    Australia
    February 21, 2014

    @ Ian #13

    That would imply that there was something seriously wrong with our current understanding of gravity which supposedly is caused by the warping of space-time in the presence of matter. The success of GR has laid to rest any alternative hypothesis, so the existing scientific doctrines regarding gravity and its cause remain unassailable.

    You would also need to believe that every single government on Earth has deliberately kept every clever Earth scientist in the dark about the existence of space aliens and spacecraft and, in effect, shot Earth’s scientific progress through the foot with a howitzer.

    Such a worldwide and long standing agreement between all governments is simply inconceivable.

    Also inconceivable is the possibility that all of Earth’s clever scientists could be successfully duped by this implausible alliance of governments, bearing in mind that people like Joe Biden are a commonplace in such entities.

    If there exists a special type of particle acting as a source or conduit to enable the gravitational force to leak into our familiar universe from the Randall-Sundrum bulk this would suggest the existence of a ‘push’ gravity force. However, chuckling Richard Feynman laid that possibility to rest many years ago, so ‘pull’ gravity now has us all firmly in its grip.

    There is no reasonable option but to accept that the clever scientists of Earth are correct and that gravity is simply something geometric in nature caused by a warping of the space-time in the presence of matter, in accordance with the principles developed by Einstein.

  16. #16 Cleon Teunissen
    February 21, 2014

    Hi Ethan,

    I’m not sure you read *all* of my comment.

    I wrote:
    “Nowadays most often the ‘this raises the question’ meaning is intended, rather than the logical-fallacy-meaning. In that sense using the expression ‘begging the question’ in the meaning of ‘raising the question’ is not wrong. Language is a living entity.”

    Just sayin': I’m totally with you on the descriptivist side, man.

    It’s just that while some changes are neutral (for example: a sentence like ‘I hanged my coat in the closet’ becoming the common form) the ‘begging the question’ shift rests on a *misunderstanding*.

    Anyway, I hope I’ve persuaded you that for you as a scientist and a promotor of critical thinking it’s one to be mindful of.

    I know, I know; no such thing as stemming the tide. But you don’t have to join in.

  17. #17 Ian
    Earth
    February 21, 2014

    @ Alan #15
    Actually no, none of that applies. One, you are making assumptions that some how our or anyone’s government is involved in some sort of cover up. ? Two, my point is if we keep looking at the same things in the same way we will keep seeing, or not seeing, the same things. In other words, I didn’t mention anything about space travel, gravity or cover ups, but that is where your mind went.
    If we look at our history we see how incredibly successful as a species we have been and we also see how our knowledge base changes over time. The catch is our knowledge doesn’t expand linearly. As species we seem doomed to keep making the same mistakes (and losing stuff) over and over again. Currently there is no known mechanism, science or technology that we have in place that will successfully predict or reveal to everyone’s satisfaction whether we are alone in the universe or not. We still debate how the Incas built their cities for Pete’s sake!

  18. #18 Peter Barratt
    February 21, 2014

    @ Ethan #11 RF & PJ

    Many thanks, Ethan, look forward to that.

  19. #19 will motill
    February 22, 2014

    i think people are forgetting for a planet with millions and bilions of species of life
    even our relatives that are 98% identical genetically
    none can speak .
    complex language is required for complex thought
    i wish someone would then calculate the odds
    of that 1 in a _____?
    dinosaurs and other creatures were around for hundreds of millions of years whats the odds they spoke no pottery or nothing found next to them all that time they didn’t evolve enough to learn to speak.

    there is wishful thinking there is speculation
    then there is reflection on past examples but that is not conducive to what we what to believe so lets ignore it

  20. #20 Brett
    February 22, 2014

    Fermi’s Paradox has never really bothered me much on the issue of whether or not there’s intelligent life elsewhere, just because there are so many potential filters between “life” and “intelligent life traveling the stars”:

    Biologists like PZ Myers have pointed this out before. We’ve seen intelligence and tool-using capabilities in some species of mammals, birds, and octopi, but it’s pretty basic and only a handful even have self-awareness that we can crudely measure (the mirror test). Only two species actually make tools on Earth (humans and New Caledonian Crows), and no line except for the hominid and australopithecus apes has ever made anything more sophisticated than a creatively shaped hook/stick or used fire.

    We have no idea whether human-level intelligence was something that was going to probably develop sooner or later out of one of the more intelligent bird, mammal, or octopi lineages, or whether human-level intelligence is a “extreme edge” type of phenomena that simply would have occurred without some special conditions leading to selection and drift towards it among a particular lineage of apes.

  21. #21 Andy Brice
    UK
    March 29, 2014

    Ethan,

    There is an issue you didn’t address here. An advanced civilization could, in theory, colonize our galaxy in a few million years. For example using self-replicating robotic probes. Humans are perhaps only a few hundred years away from having that capability. Given the age of the galaxy, even if there were only a handful of other intelligent species, some of them could easily have become this technologically advanced millions of years ago and colonised the whole galaxy by now. In that case there is a paradox to be answered.

    Perhaps most intelligent species don’t leave their home worlds (I find this hard to believe)?

    Perhaps they have already been here, but we just don’t know it (plausible)? Perhaps they created us?

    Perhaps most planets with life get snuffed out by massive asteroids, gamma ray bursters etc and we are a statistical fluke (plausible)?

    It is a fascinating question! Love the blog BTW.

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