The Search for Life: The Drake Equation

The Search for Life: The Drake EquationFor many years our place in the universe was the subject of theologians and philosophers, not scientists, but in 1960 one man changed all that.

Dr Frank Drake was one of the leading lights in the new science of radio astronomy when he did something that was not only revolutionary, but could have cost him his career. Working at the National Radio Astronomy Observatory in Greenback in Virginia, he pointed one of their new 25-meter radio telescopes at a star called Tau Ceti twelve light years from earth, hoping for signs of extra-terrestrial intelligence.

Although project Ozma resulted in silence, it did result in one of the most seminal equations in the history of science - the Drake Equation - which examined seven key elements necessary for ET intelligence to exist, from the formation of stars to the likely length a given intelligent civilization may survive. When Frank and his colleagues entered the figures, the equation suggested there were a staggering 50,000 civilizations capable of communicating across the galaxy.

However, in the 50 years of listening that has followed, not one single bleep has been heard from ET. So were Drake and his followers wrong and is there no life form out there capable of communicating? Drake's own calculations suggest that we would have to scan the entire radio spectrum of ten million stars to be sure of contact.

But what the equation and the search for life has done is focus science on some of the other questions about life in the universe, specifically biogenesis, the development of multi-cellular life and the development of intelligence itself.

The answers to those questions suggest that, far from being a one off, life may not only be common in the universe but once started will lead inevitably towards intelligent life.

To find out about the equation's influence, Dallas Campbell goes on a worldwide journey to meet the scientists who have dedicated their lives to focusing on its different aspects.

Watch the full documentary now (playlist - 59 minutes)

Ratings: 8.41/10 from 32 users.

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45 Comments / User Reviews

  1. Alx

    lets not kid ourselves, its a glorified guesstimate.

  2. grey area

    there is life out there . space is so huge that at least 1 planet in the trillions has some type of life. humans just probably wont find any of them in our existense. also you wonder how many alien civilizations were alredy there and gone, destroyed by supernovas and asteroids and whatnot

  3. the omega man

    People with an irrational faith in the existence of thousands of alien civilizations keep trotting out this 'Drake equation' as if it's somehow more valid than, say, Pascal's Wager. It gives science a bad name. What good is an equation if the numbers to fill in the variables are totally unknowable given our current knowledge? These ET-believers just pull the numbers out of their asses, like Drake did. Garbage in, garbage out. They plug in the numbers to get the result they want to believe. We don't even know the origin of life on our own planet. How can we then estimate the numbers of planets in a galaxy with life? And out of the millions of species of life on Earth over 4 billion years, how many species of what we consider 'intelligent' life have arisen? One, out of millions.

    Here's one hard number to plug into the Drake equation: ZERO. That's the number of positive radio signals the SETI program has detected in its existence. I'm not saying there can't be intelligent life out there; I'm saying WE DON'T KNOW.

    50,000 civilizations currently in our galaxy, my ass.

  4. Marian R.

    I think you guys don't really understand Science....
    Science is not mostly about cold hard facts but searching for the truth which we can deduce, theorise and estimate through equations and experiments. That means taking all the variables and things we know or think we know and try and deduce the truth out of it.
    Of course this equation might not be accurate but the important thing is that it uses the knowledge we have to try and gain more. The more we'll know and understand about the Universe the more accurate the result of the equation will be.
    Maybe if we'd know almost all about the universe and life and the result of this equation would be 5 civilazations in the Milky Way I would still be impressed, 5x trillions of galaxies means trillions of civilisations. The key here is PROBABILITY.

  5. doc-fan

    The number of possibilities out there in space is horrifying to me. When they say there is billion stars in out galaxy, then there is another billion of galaxies out there... Think about it... Even if chance of having intelligent life is for example 0.000000001 yet since there is such vastness that even this probability can get us hundredths of civilizations. You need to be really closed minded to think that there is no other intelligent creatures like self in the reality we are living in.

  6. Achems Razor

    Great doc. love docs on cosmology et al.

    We are all interrelated with the cosmos, this doc is parallel with evolution. Waiting for you know what, yes, they will be here commenting. (LOL)

  7. Waldo

    @ the omega man

    You completely misunderstad the reason this equation is very valuable. It, for the first time I might add, broke down the problem into manageable, reasonable, and accurate variables. Even if you plug in very conservative esitimates with the vastness of our universe you come out with the certainty that life is out there somewhere other than here. Infact the vastness of outerspace is such that to entertain the slightest chance for ET works out to a mathematical certainty of its existance.

    I agree with critics that say we can't afford to put massive dollars into things like this at the present; it simply does not give us any real economic pay off. But, to completely abandon the search is just as ridiculus, and sad. Basically what i am saying is the numbers themselves are not important at this juncture, the reality that we can manage this search in a scientific manner is what is important, along with the fact that very conservative estimates yeild many possible ET civilizations. I hope in my life time we come down to actually worrying about the numbers themselves, because that means we are getting very close to our goal. But, I must admit, I hold very little hope for that. On the other hand I do feel our children will get there.

    Plus just think of the things we have learned about life and ourselves through this program and all its branches of research. It is healthy for man to ask questions such as how long do most civilizations last and how many times did life generate. We have even discoverd a whole new type of life that uses arsenic and turns it into, I think hydrogen but don't qoute me on that one. I saw the anoucement, as I am sure many of you did as well, on CNN the other day. NASA kind of hyped it up a bit and made everyone think they were about to annouce finding proof of ET. But, in reality it is very important as it, at the least, suggests that genesis took place at least twice here on earth.

  8. NIkola

    That "interesting announcement" that the scientist is talking at the part 3...
    Thats the announcment that nasa made public a month or so ago?

  9. Mike C

    God made us blabiity blah, blah.

    See now that the religees have said their 2 bobs, the people with a clue can say stuff now

  10. Waldo

    @ NIkola

    Yes it is, I talked about that in my post above.

  11. KG

    I thought the Drake was a character in one of the Seinfeld episodes. It wasn't? It's all so confusing, so so confusing. K.

  12. Apocalyptoid

    Looking at the history of science - it has constantly had to drastically modify theoretical dogmas ... that the Earth is at the centre of the cosmos ... that the world is flat. What are the dogmas lurking in our midst that we cannot even identify. The Drake equation is a good stab in the dark - a working hypothesis that can be tested until either dis-proven or trumped by an alternative hypothesis that makes better sense of the available data. Sentient beings far more ancient than us mortals could be out there - what would they look like? What if they were here among us and we simply had no idea how to recognise them? But then, before our very eyes here on Earth, we stumble upon a creature that metabolises with arsenic rather than posherous.

  13. Jim

    omega man, I haven't even watched the vid yet, just about to. But you are right that WE DON'T KNOW. But there are many other things we don't know, and people will spend their time trying to work out the likelihood of one outcome or another. I don't think any reasonable person thinks of such things as 'proofs'. It's just an exercise in figuring out the best approach to make the best possible estimates given the current knowledge. No one will ever know until ET says 'hi'.

  14. some cell

    a good equation to be use in a spore game

  15. chickenpants

    it is estimated that 48 percent of every seven goats has some form of space corn hair doo.

  16. Farren

    extra-terrestrial life, intelligent at that, is already here. now, before responding to this comment by either personally attacking me (saying i must be d u m b or ignorant or naive or some other such thing), any good scientist must review all the data.

    too many people in the scientific community now have ingrained BELIEFS and no amount of evidence will rid them of these reality-blocking beliefs. it's ingrained into the very culture of funding-based science now. you follow the accepted paradigm, or you get publicly embarrassed and receive little or no more funding.

    there are many hyped and bogus claims of UFOs out there, but then there is the smaller percentage of credible sightings/reports/recordings/claims. this site has a few good documentaries on the subject:

    ... / black-box-ufo-secrets
    ... / ufo-the-greatest-story-ever-denied
    ... / ufos-the-secret-evidence
    ... / phoenix-lights
    ... / the-secret-nasa-transmissions
    ... / the-british-ufo-files
    ... / the-disclosure-project
    ... / day-before-disclosure

    and others. those especially hardened "skeptics" might want to start with the first one (Black Box UFO Secrets), which features FAA and USAF flight audio recordings of encounters. this is straight out of reality, no teenager with a tin foil hat making fuzzy images in photoshop.

    The Disclosure Project is also very good, as it is a testimony to Congress by many high-ranking people in the FAA, NASA, the USAF, and others who were all told to keep their mouths shut years ago, but feel it is important to speak up now.

  17. Apocalyptoid


    I for one don't think what you are saying is worthy of dismissal. A recent book by journalist Leslie Kean featuring contributions from military, political and aviation personnel provides a very sober presentation of extraordinary sightings. Typically, the skeptics retort with the 'extraordinary claims require extraordinary evidence'. But Kean's point is that to gather the extraordinary evidence you actually need some kind of dedicated scientific body that is charged with the task. Admittedly, in the wake of the GFC, it's going to be hard to convince anyone in the US Congress to spend the necessary funds to make such a scientific body operate.

    I agree, the black box documentary presents some compelling sightings that defy any explanation, other than the kind of dogged debunking ones that attempt to shoe-horn observed and recorded phenomena into 'swamp-gas' type explanations. The phoenix lights - not the ones later in the evening which could have been flares - but the ones observed across a number of US states, but particularly in Arizona and its capital city, are also compelling, multi-witness sightings that remain baffling. Even the Governor of Arizona now claims that he saw something that night that was huge and did not behave like anything he had ever seen (he was formerly a military pilot).

    The one thing that the Drake equation seems to lack in its calculations is a variable that would take into account technological civilisations that were millions of years old. Who is to say that the artefacts of such civilisations would be easy to identify? Who is to say that their science would not have long ago relegated the light-speed barrier to the same dustbin of scientific history? This is speculation, but without speculation driving us to imagine new avenues for the pursuit of knowledge, our science grounds to a halt and stagnates.

  18. John

    Great Doc! It's up to date, and has some new info in the search for E.T, as well as some new ideas when thinking about the equation.

  19. bart

    @ Nikola
    Yes, the scientist who found 'something interesting' was researching Mono Lake, and it were her findings which resulted in the press conference in (I believe it was) november '10 about bacteria using arsenic in their DNA.

  20. Waldo

    @ Apocalyptoid

    I agree with you guys about there being credible sightings of unidentified flying objects, in fact I have witnessed some weird stuff myself. But, I will not get into that as it is not my point. The Drake equation does have a variable to represent the time these advanced civilizations would exist. They also talk about in this documentary the fact that these advaned cultures may have a type of long distance wireless communication that we have no way of detecting or discerning. So I think they do cover what you guys are referring to both in the equation and in this program. Of course they would never admit to the possibility of the extraterrestrials ocasionally dropping in as that would call into question the need of such things as SETI or the Drake equation at all. In fact I sometimes worry about certain contradictions involved in believing they are visiting us such as, why would they visit and never bother to introduce themselves? What possible reason would they have to be in places like were I saw what I saw, a recently deforested area in the middle of nowhere Alabama. Then again I have to live with the fact that I saw what I saw and it was so close and clear that there is simply no way it could have been some natural phenomenon. My mom and dad have also witnessed certain things that could not have been explained away, and we are not the dramatic hillbilly types that all southerners get assumed to be. We all have college educations and have never made any extaordinary claims about anything else. Once you see it it consumes you, it is hard to concentrate on work or any of the mondane everyday things we all have to deal with. I have had some real issues about what I saw. It really bothers me and in reality I wish I would have never seen it.

    Now that I have talked about it so much I feel I must share, maybe someone else has seen something similar and could share with me so I don't feel so weird about it. I was coming home late at night, around midnight I suppose.I was not sleepy at all and had nothing to drink nor do I do drugs. As I topped a hill and started driving past a cut over on my left, a cut over is a deforested area full of undergrowth and brush piles, I noticed that there was a pale green light about four to six feet off the ground keeping pace with my car as I drove along. At first I didn't think much of it as I assumed it might be a four wheeler or something- someone riding in the cut over. Then I realized it was too high off the ground, too large, and there is no way a four wheeler could drive at the same speed as my car, around thirty five or forty miles an hour, over all that undergrowth- plus it was smooth as silk never bumping up and down or swaying this way or that. It was simply gliding very gracefully and keeping almost perfect pace with me, I slowed down at this point to about fifteen miles an hour and rolled my window down. This light was about fifty feet from me and I could see it plainly. It was about the size of a beach ball. Then I realized there was another one in perfect line with the one I was looking at so it was mostly blocked unless I got a little ahead or behind then I could see it as well. They were both lit up this pale green color but they never seemed to light up the area around them. I stopped and it stopped as well. I wanted to get out of the car and I always thought I would check something out if I had the chance to see something, but I was scared as h311 I don't mind admitting. I sat there looking at this thing, it never made a sound, for about maybe three minutes or four. Then the one closest to me swung around so that it was in perfect line in front of the one that was previousely beside it. Now I am looking at both of them, I called out, "Hey". Just to see if someone would answer, when I did they both shot off up a hill and into the woods at break neck speeds. They never bumped around or rose any higher from the ground nor made a sound but shot away at blistering speeds and as they went they split up one going toward my left and the other toward the right. By the time they entered the woods, about three hundred yards away from me and the road, they looked to be maybe 100 to 150 feet apart. I saw them blinking in and out of sight as they danced away through the trees. And then nothing, silence and dark. I sat there dumb founded for I think about five minutes before driving home and telling my dad. He told me then that he and some guys he hunted with had seen these same two lights, or two that looked just like what I described, about a year before this in the wooded area that used to be the cut over. I wont go into that story as I wasn't there and this is already a huge post.

    I can't get over what I saw and I will never be the same. It makes me feel strangely depressed sometimes and alone, I really don't know why. It also makes me wonder just how much we don't know about this universe and how it works. Those things were definitely not swamp gas or reflected moon light and they were under intelligent control I have no doubt. Somehow I realise now that they knew I was there, they sensed me somehow and no doubt heard me as they reacted by getting gone in a hurry as soon as I made a sound. I know people think I am crazy, or worse a liar, but I don't care. I don't talk to people about it as I feel they are making fun of me. I saw those things as plain as day and have no doubt that they were real and beyond any technology we possess. But what in the world could they have wanted out in that cut over or around this small town hick place? It took me a long time to stop going back there and trying to get another look, but it has been about three years now and I have never seen anything like it before or since. If I ever do again I will get out and go to it, no matter how scared I am. I know now that it will eat your mind up if you don't at least try and gain some type of understanding while you have a chance. To be honest if I ever see them again I hope they either kill me or take me with them. Once you know, once you have seen, there is no going back to normal. Life is so much more difficult to deal with, I can't explain. Maybe I should see someone about the way I feel. It stold my ability to trust logic, it ripped my feet from the ground and I feel as if I am going to float away in to crazy land sometimes- so to speak.

  21. Dave

    How can anyone belive this documentary when the facts are wrong in the second paragraph of the written introduction.
    The telescopes are not in "Greenback, Virginia", they are located in "Greenbank, West Virginia".

  22. Achems Razor


    Thanks for sharing your poignant story, I myself have never saw anything of that nature, even though wish I did.

    Since antiquity there have been various sightings of such, even mentioned in the bible of those similar kinds of events.

    To much not quite empirical evidence, but have to go by volume of unexplained mystery's such as crop circles etc: to discount that these types of sightings do not exist.

  23. rtm

    hold on, can someone remind me why would people be lying about et intelligence or flying saucers?lol

  24. sanford

    It would be quite arrogant for us to believe we are the only intelligent life, but it is also quite ignorant for us to try and contact other intelligent life "out there". "They" would no doubt do to us what history has shown we have done to those who we considered less intelligent, less human and backward.

  25. Guess

    Although I really hope they are going to find alien life in space, my view about life is slowly starting to change.

    Lately, if started to believe that the world around me is some sort of highly advanced simulation. And yes I know how crazy that sounds, but when you think about it, it actually makes a lot of sense. For example, it would explain why there are things such as laws of nature (simular to programming code), which can be bend but not broken. Or why things are broken up into atoms/strings/whatever (sort of like advanced pixels). Or why the universe seems to expend (Moore's law of technology improvement) or even multiple/parallel universes (multiple simulations running at the same time with different scenario's)

    But it would also explain why it is really possible that we are alone in the universe. There was no need for other "life forms" in the program, since we are the subjects and so they just aren't out there.

    And that would also mean that there actually is something as a designer.

  26. Kyle

    UFO @ 9:22 of Part 1. Over Drake's head left side of screen, so much ironic potential.

  27. Marcin Damian Lipski

    why someone would like to make a contact with such a destructfull, expansionist and demanding civilisation like ours? I believe the guys out there are not so stupid and thats why they leave us so at least we destroy only our own planet and people

  28. Odd Andersson

    Umm you linked to this doc, can you give the link for the one you actually meant?

  29. Anthony Pirtle

    What I'm most dubious about is the number of life bearing planets which develop intelligent, technological civilizations. I think that his estimates are far higher than reason would dictate.


    without being snide, that is to say your own personal reason. so much is unknown and limitations are just that, limitations. check out "hubble deep field" photos on google, truly amazing. in regards to this doc i suspect Drake is on to something but my question is that wouldnt ETs be using either highly advanced or simplistic archaic technology (and all that in between), and communication thru our means (radio telescopes) would require them to be on a similar path as our own here on earth?

  31. Lord_Kral

    nobody ever talks about what i like to call the 'radio bubble'. i think the #1 barrier to detecting intelligent life is simply put: space-time.

    the first radio signal that humans ever sent was in the 1870s. taking into account the fact that radio signals travel at the speed of light, this means that our radio signals have only traveled 140 light years from earth. this is the 'radio bubble' surrounding earth. every year the size of the bubble increases by a radius of 1 LY (keep in mind that the diameter of our galaxy is 120,000 LY). the vast gulf of our galaxy simply means that if intelligent life somewhere is transmitting radio signals, they probably just haven't reached us yet. the key factor here is time. and it could take centuries, millenia or more for those signals to get to us and/or for our signals to get to them. Then, there's the practical logistical problem of actually meeting them face-to-face.

    Realistically, it could take tens of thousands of years just to hear their signal, and meeting them would be way way longer if not impossible.

  32. Robyn318

    The Drake equation assumes that there is life out there by working with percentages. Any percentage above zero is an affirmation of that assumption, not that there definitely is.

    Personally I think there are intelligent civilizations out there, maybe not 50,000, but at least a few.

  33. Merson78

    I thought the Microbiologist that was talking about the Arsenic tolerant Microorganism was talking a load of tripe. It could have quite easily evolved from other microrganisms. We have to find life forms which are clearly not related like organisms that don't use RNA/DNA as a genetic carrier.

  34. BIGDAVE54

    I thought that location was GREENBANK in WEST VIRGINIA.

  35. Alex Normandin

    what frequency to WE broadcast at. we are looking but not transmitting out own signal. you know? where is our broadcast at the resistance frequency of water?

    i heard this some where but i cant remember, it was from some other doc. the point was our EM 'glow' was very short. drake gives us the number of 10000 years. but look at us, we have radio for 150years, but the time where we 'lit up' the air waves was very short, around the time where we broadcast non digital TV signals. then it was common to glow with mega watts of signal power. however, in less then 50 years we now operate on a much smaller power scale now with digital communications. and now we are quiet again.

    so in 5 billion years of our solar system, one planet, one species out of million made EM noise for less then 50 years. and already we areseeing how advanced life as we know it might end very soon, if we keep killing eachother and. polluting our planet. which we most likely will.

    but again, why are we not saying hello. to me it sounds a lot more effective rather then looking for something in a very small space, call out, to make the first welcomming invite. HEY WE ARE HEAR, wanna party?? we have gin and tonic.

    what i find the most scary about the whole quation is, what if we are the only sons of bitches in the univers. then what? how spoiled and disrespectful and arrogant and irresponcible we have been. i think we want there to be other life in the iniverse so badly only so that we can feel justified in our misery, 'oh my life my planet doesn't really matter becuase somewhere there is a more advanced species out there and if we go extinct some one else can always carry the flag of life'. but what if we are the only ones here, what an embarrasing use of the universe. how frightening it is that it might go quiet forever in the next 100y.

    FWIW, 42hz is the ovious frequency we should be searching on.

  36. wt1776

    Too bad these scientists are ignorant of the obvious UFO extra-terrestrials visiting Earth. The government that funds much of this work should just tell us the truth and admit that they already know that aliens exist, and thus save all they money they spend on this SETI research. And Elvis should quit hiding now and come give us a free concert.

  37. wt1776

    Ya, it is obviously crap. One mistake and everything goes out the window. We demand perfection!!

  38. wt1776

    You've convinced me.

  39. William Russell

    Someone travels across the galaxy and were the expansionist....

  40. jim

    how did the milky way that is 13.2billion years old produce 200-400 billion stars at the rate of 3 per year? and why does the drake equation say that the milky way produces 10 stars a year?

  41. over the edge

    where does " the drake equation say that the milky way produces 10 stars a year"? and is that a constant?

  42. Jonas Namensen

    you can´t make a constant time frame for scientific development. it took us until the 1940´s to develop the first computers, and 7o years after we all have computers in our pockets. we might expand our "bubble" 1 LY every year but in 50 years we might have technology that allows far more rapid exceedings

  43. Lord_Kral

    I am very hopeful for technology solving the problem of detecting biology on exo-planets. i just hope we aren't dead as a species beforehand.

  44. bru th


    80,000 life forms divided and spread over 10 billion / light years of distance and time.
    How many had advanced tech? ..... At the right time = now....for us to in our evolved state?

    If there signal stopped 500,00 ago, or even 60 years ago???
    (with our tech, have we even been able to detect for 50 years ?
    Or theirs won't be ready for 8o,ooo years? We be gone.

    Furmy asks "Where is everybody" ? No, WHEN is everybody.... BIG TIME !

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