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The Drake Equation: Is there really other Life in the Universe?

  1. Nov 4, 2011 #1
    The possibility of life on other planets has been one of our oldest doubts.... and oldest hopes. Many believe that we are the only ones here in an infinite and lonely universe, but, as put so eloquently by in the film Contact, based on the novel by Carl Sagan, "If it is just us, it seems like an awful waste of space."

    So, could life really exist elsewhere? Why haven't we found other civilizations by now? I hope to be able to provide you with a bit of understanding to the possibility of extraterrestrial life.

    The way we can calculate the possibility of life is by the Drake Equation, created by Frank Drake in the early 1960s. It states:

    N= [r* x fp x ne x fl x fi x fc] L where:

    N= number of possible civilizations to communicate with

    R* = is the rate at which stars capable of sustaining like are formed

    fp = the fraction of these stars which have planets

    ne = the number of planets similar to Earth in the planetary system

    fl = the fraction of the Earth-like planets that hold life

    fi = the fraction of life that becomes an intelligent civilization

    fc = the fraction intelligent civilizations that attempt to communicate

    L= the number of years the civilization remains able to communicate.

    When these numbers are taken into consideration, we realize that there is a great possibility of life out there. There are about 400 billion stars in our galaxy, so there could be life right next door (relatively speaking, since that may be hundreds of thousands of light years away). Even if there is no life in the Milky Way, there are billions of other galaxies to turn to. We likely will not contact such civilizations in our lifetime, but it gives us a new kind of hope and dream for the future of our planet and the future of mankind.
     
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  3. Nov 4, 2011 #2
    So how is L estimated? Based on how many years the dodo bird existed or what?
     
  4. Nov 4, 2011 #3
    The problem with the equation, in my opinion, is that the variables are TOO variable, that is to say the numbers applied to each variable are way too dependent on individual interpretations.

    The more I consider this topic, which I find very interesting, the more I lean towards the rare Earth hypothesis. Also, the anthropic principle can be considered an answer to the Drake equation and why we haven't found bunk yet!

    I do not agree with you, however, that many people think we're 'alone in the universe.' In fact, I believe most people think that there is intelligent life in the universe other than humans--I know I do. I think it is more probable that we're separated by such vast distances through space (and perhaps time as well) that contact remains difficult, but I hope not improbable!
     
    Last edited: Nov 4, 2011
  5. Nov 4, 2011 #4
    I never found this to be a useful equation. It's an obvious equation (though it assumes that life can only form on planets and that the planets must be Earth-like to sustain life), trouble is we can make reasonable estimates for only a few of the terms. Once we hit "fraction of Earth-like planets that hold life", we are guessing - absolutely guessing, with no foundational numbers to start with whatsoever. And so, we can come up with any final number we want.
     
  6. Nov 4, 2011 #5

    DaveC426913

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    It is useful for what it is. It defines the variables. It is up to the future to assign numbers.

    Most great ideas are obvious with 20/20 hindsight.
     
  7. Nov 5, 2011 #6

    Chronos

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    The Drake equation suggests intelligent life is not unique to earth. I view it as an extension of the Copernican principle.
     
  8. Nov 5, 2011 #7
    But it's not a great or revolutionary idea, it's an obvious equation that must obviously be true within the constraints of life only on earth-like planets and several other implicit assumptions. It is alluring to some people, perhaps because it looks like an attempt to get at an answer, and in a sense it is - but breaking up the problem of estimating a number into a problem of estimating a half-dozen numbers does not illuminate anything unless those numbers are easier to estimate individually, and here is why the equation does not really advance anything.

    Even a single, solitary data point of finding fossilized nanobacteria in a martian floodplain would make a huge improvement in our sense of what "fl" might be, but otherwise it could be anything from near unity to infinitesimally small with as many zeros after the decimal point as you like. We have no clue and can only guess, and your guess, my guess, and the guess of a three-year-old are all equally valid. :wink:
     
  9. Nov 5, 2011 #8

    DaveC426913

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    And yet no one thought to define it until Drake came along. 20/20

    You're second-guessing the thoughts of others. You don't think it's an answer and I don't think it's an answer, so who are you claiming is more naive than us?

    But it does. Before it came along, the answer to 'how many ETs might there be out there' was plain and simply 'your guess is as good as mine'.

    The Drake equation demonstrates - in its first few terms if not the last few - that the fields that are ripe for the sewing of life are certainly myriad. Millions upon millions. And I think that actually brings a great degree of optimism to the search for ET.
     
  10. Nov 5, 2011 #9
    Neither of us can say who first wrote it down as an equation. We know that someone named Drake wrote it down and popularized it, but it's not E= mc2 - there is nothing profound about it, it's obvious.

    Defensive, aren't we.

    Ah, here is the crux of the issue - when you write it down this way, you can easily convince yourself that the number of Earth-ish planets with Earth-ish atmospheres and water must be vast, and that the number of civilizations with intelligent life out there must also be vast, and therefore that it makes sense to spend money to build equipment to search for it in a statistical way, which is appropriate for something that you have at least some statistical handle on but is not appropriate for a total unknown.

    I'd personally rather spend the money on other pursuits. Even if the cost only adds up to an additional scientific experiment or capability for the next Mars lander, that seems to me to be money better spent - at least we have good reason to believe that we are looking at a planet that at one time shared Earth's most life-nurturing characteristic, liquid water, and so a careful search can shed some light on one of the totally unknown terms in the Drake equation, "fl", particularly if the search is fruitful.
     
  11. Nov 5, 2011 #10
    Someone should find the equation for computing the number of single hot women in the neighborhood, and name it after himself. Then the equation should be cited whenever discussing related topics. It should also be spelled with capital "E" due to its importance, unlike more trivial equations such as the Callan–Symanzik equation.
     
  12. Nov 5, 2011 #11

    epenguin

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    It depends maybe how earth-like is earth-like. I suggest this is one of the parameters that we can have the best idea of. When I last heard there has been life on earth for at least 90% of its history, and we cannot exclude that it is near 100%. That suggests a reasonable estimate of this parameter is 1.
     
  13. Nov 5, 2011 #12
    Is it not naive of us to be looking almost exclusively for radio signals? Humans on planet Earth, our only point of reference on this matter, have been using radio for little more than 100 years in, what, approximately 200,000 years of 'existence?'

    Will humans even be using radio type technology to communicate among ourselves in 50 years? Is radio and its variants already being replaced on Earth by "better" technology?

    Perhaps radio is a particularly transient technology that technologically advanced civilizations abandon relatively quickly which is why we haven't heard anyone out there?
     
  14. Nov 5, 2011 #13
    The Drake equation is outdated and overly simplistic. Our knowledge of astrobiology, cosmology, and physics is far more advanced than it was 50 years ago. I'm not sure why people hang on to it so rigidly. The Rare Earth theory is far more convincing to me, and the formula far more sophisticated. It is likely that there are only a handful of civilization's in our galaxy, perhaps less.
     
  15. Nov 5, 2011 #14

    DaveC426913

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    You keep saying this. And I keep saying everything is obvious in hindsight.

    I'm not sure what you thought I meant but this is non sequitur. You should reread what I wrote.

    I'm saying who exactly do you think is being fooled by [this equation claiming to answer more than it is]? You're not fooled. Neither am I.

    So who exactly do you think you're protecting from misunderstanding?


    Who can?

    Again, you're not fooled. Why do you think you're the first person to realize that the Drake equation makes no predictions?
     
  16. Nov 5, 2011 #15
    What do you propose we look for instead? We don't have the technology to search for anything we produced prior to radio. And it doesn't seem we can search for things we may use in the future before we know what they are. In other words, searching for radio may have problems, but it's the only thing we can search for.
     
  17. Nov 6, 2011 #16
    Dale, I don't have a better proposition. I just meant to impart that perhaps we shouldn't deduce from the lack radio signals that we're necessarily alone, but rather that we (humans) aren't technologically on the same page as other more advanced civilizations, so to speak.

    The Drake equation's power, IMHO, is in the wonderment and awe it inspires in some people, not in its scientific contribution. As far as I know, the Drake equation hasn't really expanded cosmology in any meaningful way but it probably has inspired some people that will make significant contributions one day.
     
  18. Nov 6, 2011 #17
    Dale, I don't have a better proposition. I just meant to impart that perhaps we shouldn't deduce from the lack radio signals that we're necessarily alone, but rather that we (humans) aren't technologically on the same page as other more advanced civilizations, so to speak.

    The Drake equation's power, IMHO, is in the wonderment and awe it inspires in some people, not in its scientific contribution. As far as I know, the Drake equation hasn't really expanded cosmology in any meaningful way but it probably has inspired some people that will make significant contributions one day.
     
  19. Nov 6, 2011 #18

    DaveC426913

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    I think it is generally understood that our search of ET is in its infancy. No one's making any conclusions based on lack of data. (http://en.wikipedia.org/wiki/Fermi_paradox" [Broken]... :smile:)
     
    Last edited by a moderator: May 5, 2017
  20. Nov 6, 2011 #19
    In a similar way, I prefer the mediocrity principle.. to quote http://en.wikipedia.org/wiki/Mediocrity_principle" [Broken]:

    "The idea is to assume mediocrity, rather than starting with the assumption that a phenomenon is special or has somehow violated the laws of the universe."
     
    Last edited by a moderator: May 5, 2017
  21. Nov 6, 2011 #20
    They're using more methods than that. For example, they look for signs of the right gasses for any planets found - nitrogen, ozone etc.
     
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