Does other intelligent life exist in the universe? Until we discover aliens, or they discover us, we won't know for sure, but the famous Drake equation gives us an educated guess. Scientific American editor John Matson explains.

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9 Comments

1. 1. Benjowo 06:11 PM 11/16/12

   Well, there might be many civilizations but we haven't found them yet. It seems likely that there would be others, however some civilization had to be first one since the big bang. May be we are and therefor we are still alone for a while.

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2. 2. LarryW 06:54 PM 11/16/12

   Perhaps the factors mentioned take this into account, but I didn't hear a probability of an intelligent civilization occupying the specific and short time since the Big Bang that would overlap our specific and short time interval of 100 years.

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3. 3. StanBernsteen 07:39 PM 11/16/12

   Perhaps alien civilizations regard radio communication as primitive. They may be frantically signaling us using technology we haven't even dreamt of, wondering if there's any intelligent life here.

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4. 4. DaniEder in reply to LarryW 09:48 PM 11/16/12

   The last factor, L, takes that into account. The units are in terms of life of the Universe, so a civilization that lasts 13,600 years survives 1 millionth of the life of the Universe. Therefore the chance that it is around *right now* is one in a million.
   
   If there were a million such civilizations that rose and fell in the life of the Galaxy, then statistically there would be one around today.
   
   The problem is L is the least well known factor in the whole equation. We only have ourselves as an example, and we won't know how long our civilization will last until it ends (hopefully not soon). We would need to find the ruins of alien civilizations, or enough planets with life, to get some idea of what L is.
   
   Of course, if we find some other civilizations, then we can just ask them, but at that point we don't need the Drake Equation to make an estimate, we will know how many there are.

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5. 5. mounthell 03:01 PM 11/17/12

   If we were to be serious about this question, we might ask:
   a. Would truly intelligent life deign to communicate with basic life forms that communicate little of substance and
   b. What might be the physical basis of such "truly intelligent life"?
   
   In a., for example, why would any advanced civilization expend the effort necessary to communicate with those whose idea of substance is evident in the political arguments of those who argue that it is their tribe that shoulda been elected, darn it?
   
   B. (in view of a. above) suggests the possibility that biological intelligence, having just developed complex autonomous systems, might 'do itself in' biologically; its newly prevailing civilization then transitions to abiotic intelligent forms. If that occurred, we might ask what such intelligence could expect to learn from earthlings, and why would they bother to 'take the call.'

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6. 6. MostlyRight 04:50 PM 11/17/12

   Why limit the search to the very large? It could very well be that intelligent life exists amongst the very small.
   Imagine Planck scale objects trying to send messages to us.

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7. 7. Quinn the Eskimo 10:02 PM 11/17/12

   Perhaps, we're the Ancients that, centuries from now; civilizations undreamt of will ruminate.
   
   Especially when they find our hoard of Twinkies.

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8. 8. Raoul 11:16 AM 11/18/12

   But this ecuation yields from "none to "200.000" or perhaps more.
   And how plays the time in it?
   Are all those civilizations existing at the same time, or along of millions or billions of years?
   So, when w'll find just one?

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9. 9. Adam_Smith 10:44 AM 11/20/12

   As data accumulates, the Drake Equation gains credibility. About three decades ago I confidently dismissed it as being too full of conjectured values to be useful. It is still speculative but no longer ridiculously so.
   
   Cosmic distances being what they are we may never enjoy physical commerce with an extra-terrestrial civilization but verifying the existence of one, should that ever occur, will go far towards discrediting unscientific anthropocentric prejudices.
   

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