Talk:Drake equation

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[edit] Rare Earth refutation

This really begs to be contrasted with Ward and Brownlee's Rare Earth hypothesis, which many believes lays waste to the Drake Equation. Any thoughts?

[edit] Drake overly optimistic?

What about the possibility that even if an alien civilization did exist, from what they could gather of our culture they wouldn't want to communicate with us? Was Drake being overly optimistic about us?

Why do you say that the currently observed value of N = 0? What are we, chopped liver? (Or are you saying that we are not able to communicate interstellarly?) ----

Does "fairly conservative" f_l, f_i, f_c and L has any meaning ? --Taw

f_l, f_i and L are the really contentious ones, I think. We can make a fair stab at guesstimating R* and f_p now, given recent advances in astronomy. -- The Anome

Existence of human race now acknowledged. -- The Anome

Claim that f_l = 1 is weird. In "planets which can potentially support life" in Solar System they usually list Venus, Earth and Mars. So f_l here is 1/3. Unless they say that only Earth is capable of supporting life. In that case n_e is way too high.

This whole thing is rather fuzzy and ill-defined, IMO. For example, if I were listing "planets which can potentially support life" for the solar system, Venus would emphatically _not_ be included. On the other hand, Europa, Callisto, and maybe Ganymede would be on there; these three moons are thought to have liquid water oceans under their crusts (Ganymede is the iffiest, Europa is almost certain). Uranus and Neptune may also have liquid water layers, though even if they do conditions there would be somewhat extreme for life as we know it and may not be suitable. Basically, IMO, we simply don't know enough about the universe yet to be proposing actual numbers for some of these variables yet. -BD

We certainly don't know enough to produce good numbers, but even guesses within a few orders of magnitude are better than nothing. It doesn't take much accuracy to make certain theories more or less likely than others, or to present interesting problems. In particular, the estimates given as "conservative" are sufficient to generate the Fermi paradox; if our guesses are two low, it's even more remarkable; if our guesses are way too high, Fremi becomes expected but then the low numbers themselves are hard to explain. --LDC

If there are a couple of orders of magnitude of flexibility to a couple of the terms in an equation like this, then I don't see how it can be reasonably used to suggest _anything_ with enough certainty to base a serious discussion on. I see the Drake equation as more of a suggestion of what we should be trying to find out in the future than as a useful analysis of life in the galaxy at this point, and wanted to make sure the article didn't give the wrong impression (ie, that "scientists say there should be aliens everywhere" or that "scientists say we're alone in the universe").

So what exactly is the Fermi paradox? The estimates for the parameters given in the article yield N=0.01, which doesn't seem to be excessively high. --AxelBoldt

See my examples now in the article -- The Anome

Being new here, I won't take the privledge of removing this particular statement, but I want to alert you that in all of my studies of genetics and molecular biology, I have never encountered the suggestion that outside mutagens (such as UV, as stated in this article) are necessary to produce the genetic variation that alows organisms to adapt to changing environments. I have only encoutered this idea in science fiction books from the 1950s or so (Asimov and Heinlein), and I think that this was just a bunch of speculation from biolgists of the time who had no idea of the mechanism of how mutations occur.

We now know that mutations occur by changes in the DNA sequence. We know that DNA must constantly be copied, and that any copying device has some error rate. We know that there are multiple DNA polymerases (copying enzymes) each with its own characteristic error rate. The error rate is itself an evolvable trait, even as it affects evolution. If it is necessary to have mutations for long term survival of a lineage (which I believe it is), then any lineage that ceases to have mutations will die out a la natural selection, and only the ones that have mutations will persist. Thus, even this trait (mutation rate) will acquire a sort of optimum, just as other traits do, and it will be adapted based upon the lifestyle of the organism and the environment that it lives in.

adam

Too bad it probably won't be on the actuarial exam. It has a nice mnemonic to it, just think "pelican".

F_l=1 is quite optimistic, since it means every planet that can develop life does. -Padde 00:38, 15 April 2006 (UTC)

[edit] Removed paragraph

Removed this paragraph: It's a very common misconception often spread by the popular media that the evidence supports the value of N equal to 1 - there's one human civilization in the galaxy. But the galaxy is just an arbitrary probed area - we could as well probe each two galaxies, each 100 galaxies, or each one thousandth of a galaxy - and the conclusion should be the same number of such civilizations per galaxy. According to this fallacious thinking, the evidence would have supported N equal to one half, one hundredth, and one thousand as well as exactly 1.

On the contrary, the popular media gives the impression that N is equal to hundreds, if not thousands of civilizations in our galaxy (Star Trek, Babylon 5, Star Wars, many sci fi movies and shows like the X-Files, stories of UFO and government conspiracies to cover up the "truth"... etc...).
The rest doesn't make sense due to the fact that we know of at least one civilization. Anything beyond that is speculation based on the equation here (some parameters we do know better than others). And if there is only one civilization between two galaxies (a lonely thought) that would give an N = 0.5 for each of those galaxies. There is nothing fallacious about that - it is just probability. I suggest a read of anthropic principle. --mav

This probably has changes some of the numbers, but not sure how. http://news.bbc.co.uk/1/hi/sci/tech/3588721.stm

Edward 12:23, 2 Apr 2004 (UTC)

Is there any source discussing what Drake meant by an estimate of 10 years as the value of L? Does such a pessimistic view reflect the fact that he was living during the Cold War, or did he think that in general a civilization that develops interplanetary communications will wipe itself out within 10 years? I mean, it took us humans decades to go from understanding light and using radio, to detonating a nuclear weapon.

Yes, I think it's at least generally assumed that he was thinking of nuclear annihilation. BTW we actually detonated a nuclear weapon before the development of our first radio system that had any reasonable chance of communicating with an interstellar civilisation (Trinity test in 1945, Jodrell Bank opened in 1947). Securiger 12:12, 4 Nov 2004 (UTC)

[edit] Fuzziness

I do not think that our article adequately conveys the "fuzziness". As BD and someone else remarked above, the basic problem, is that for several of the parameters we really have no idea, or at least the range of plausible estimates varies by several orders of magnitude. And when you multiply variations of orders of magnitude several times, you end up with a huge range. This is occasionally hinted at in the article, but is never really made clear. Rather than listing several people's estimates and results, would it not be more useful to multiply out the ranges of estimates, to show the range of the results? (This is easier if we work in orders of magnitude - OoM being logarithmic we could then add instead of multiply - but that might lose some readers.) An example to explain what I mean:

Parameter	low estimate	high estimate	ratio	my comments
R*	10	20	2	The only parameter we have any real handle on, and it's already got a factor of 2:1
f_p	0.1	0.75	7.5
n_e	.5	5	10	Up to here, it's wild estimates with at least some observational basis. All the rest are pure guesswork.
f_l	.001	1	1000	I think most people who argue for values close to 1 are making a common statistical inferential error; see "Anthropics and stuff" below
f_i	$10 - 7$	0.5	$0.5 \times 10^7$
f_c	.01	.1	10	I can't believe our uncertainty in this is really so low. People just haven't been exercising their imaginations enough.
L	66	$109$	$1.5 \times 10^7$
N	$3.3 \times 10^{-11}$	$3.75 \times 10^9$	$1.125 \times 10^{20}$	Yes folks, that's 20 orders of magnitude.

All of these parameters were taken from either our own article, or one of the ones in our extlinks. But I make no claim they are comprehensive, just an example. Securiger 12:12, 4 Nov 2004 (UTC)

[edit] Effects of personal bias

As an aside, having discussed this with quite a few people over the years, and read a few learned monographs on it, I have come to the conclusion that most people make up their minds beforehand - perhaps either wanting to believe that human life is especially unique, or wanting to believe that alien visitation is just a few years away - and then choose parameter ranges that satisfy those desires. The Drake equation tends to add excessive dignity to this process of biased, wild guessing. Really for at least four of those parameters, the only intellectually honest estimate is "we have no idea", which means the final answer is "we have no idea". Not very satisfactory, but true nonetheless. Securiger 12:12, 4 Nov 2004 (UTC)

[edit] Anthropics and stuff

Another point whilst I'm rambling on; our statement:

What evidence is currently visible to humanity suggests that f_l is very high; life on Earth appears to have begun almost immediately after conditions arrived in which it was possible, suggesting that abiogenesis is relatively "easy" once conditions are right.

suffers from the Self-Sampling Assumption. We can in fact deduce nothing about f_l from our own presence on earth, since our own presence somewhere is a given, or else we would not be making the observation in the first place. For example, suppose that the true value of f_l is so extremely low that there probably exists only one planet in the Universe with life on it. Evidently then, we the observers are on that planet, and we know of one civilization (us) and no others, because there are no others. Now consider a parallel universe where f_l is billions of times higher, but, for some reason, no contact has been established. Any given group of observers knows of one civilisation (themselves) and no others, for reasons unknown to them. The observations are identical in both cases; by observing the existence of your own civilisation, you can deduce nothing at all about f_l. To cut a long story short, in estimating any of these parameters, you can't count yourself. (The exception is L; since it doesn't affect our ability to observe ourselves, we can use ourselves as an estimator for L. I think.)

Actually, not an exception. The L estimate will never stop increasing, because if it does, no one is left to make that observation.

The best that we can do is observe that there is another planet nearby where maybe life could have appeared, but apparently didn't, so f_l is certainly less than 1. Note incidentally, that this is already implicitly taken care of in the definition of N, which is for extraterrestrial civilisations only; N does not include our own civ. Securiger 12:12, 4 Nov 2004 (UTC)

Another way of looking at the question is to ask how many degrees of freedom we have in estimating each parameter. For many of them, we have zero degrees of freedom, since we only have the one sample (ourselves). Thus, no valid estimate can be made, just various wild-ass guesses.Dogface 20:04, 28 July 2006 (UTC)

[edit] What is N << 1 ?

What is this terminology used in the article? N << 1

How does it differ from N < 1 ?

N < 1 means N is less than 1 (possibly by an infinitesimal amount); N << 1 means N is much less than 1. Exactly how much "much less" means is a bit vague and usually determined by context. In some contexts, it means "so much less that within the limits of accuracy of our calculation, we can ignore it". In other contexts it can be taken to mean an order of magnitude less. Securiger 18:27, 15 Nov 2004 (UTC)

What you are saying is it should be

N approx zero, an infinitesimal. BernardZ 05:47, 6 March 2007 (UTC)

[edit] 2?

for N not >>1, there should be some discussion of the conditional probability of the presence of a second civilization, given the presence of one (i.e. we know we are here, but we are interested if there is anyone else). dab (ᛏ) 14:52, 13 Jan 2005 (UTC)

I imagine that if N not >> 1 then it is independent of the number of civilizations observed. Just because our star system came up "heads", it wouldn't affect the chances of the other star systems. The only way I can conceive of it not being independent is the chance for intergalactic war between civilizations, and I don't remember us engaging in any genocidal space campaigns =P Intangir 08:32, 13 November 2005 (UTC)

However it probably would be argued to being a Poissonic distribution. Low probabilities and discrete values.

If we assume that the average number we can expect = X Then the probability is PR(N) =(exp(-x) * X^N)/N!

therefore the probability of no ETI life is Pr(0)=exp(-X)

therefore the probability of one ETI life Pr(1)=exp(-X)*X = X*Pr(0)

So we can say that Pr(N>0) = 1-Pr(0) Pr(N>1) = 1-Pr(0)-X*Pr(0)

You could say using the Anthropic principal that the Pr(N>0) could be anything say an infinitesimal as there would be no discussion on this question if N=0.

So what are the odds that some else is there. The odds that there is someone else is

Pr(X>1)/Pr(X>0)= 1- X/(1/Pr(0)-1) = 1 - X /(Exp(X)-1)

Odds knowing that Pr(N>0)
×	Pr(N=1)	Pr(N>1)
0.001	1.000	0.000
0.101	0.950	0.050
0.201	0.903	0.097
0.301	0.857	0.143
0.401	0.813	0.187
0.501	0.770	0.230
0.601	0.729	0.271
0.701	0.690	0.310
0.801	0.652	0.348
0.901	0.616	0.384
1.000	0.582	0.418

Of course I am simplifying it a lot. Another issue is as the universe gets older, I would expect the X to go up over time. BernardZ 23:57, 20 February 2007 (UTC)

[edit] Michael Crichton on the Drake equation???

Removed the following from the article:

Michael Crichton denounced the Drake Equation as pseudoscience in the Caltech Michelin Lecture entitled "Aliens Cause Global Warming" (meant to be a serious lecture with a catchy title), 17 January 2003:

Cast your minds back to 1960. John F. Kennedy is president, commercial jet airplanes are just appearing, the biggest university mainframes have 12K of memory. And in Green Bank, West Virginia at the new National Radio Astronomy Observatory, a young astrophysicist named Frank Drake runs a two week project called Ozma, to search for extraterrestrial signals. A signal is received, to great excitement. It turns out to be false, but the excitement remains. In 1960, Drake organizes the first SETI conference, and came up with the now-famous Drake equation:

N=N*fp ne fl fi fc fL

Where N* is the number of stars in the Milky Way galaxy; fp is the fraction with planets; ne is the number of planets per star capable of supporting life; fl is the fraction of planets where life evolves; fi is the fraction where intelligent life evolves; and fc is the fraction that communicates; and fL is the fraction of the planet's life during which the communicating civilizations live.

This serious-looking equation gave SETI an serious footing as a legitimate intellectual inquiry. The problem, of course, is that none of the terms can be known, and most cannot even be estimated. The only way to work the equation is to fill in with guesses. And guesses-just so we're clear-are merely expressions of prejudice. Nor can there be "informed guesses." If you need to state how many planets with life choose to communicate, there is simply no way to make an informed guess. It's simply prejudice.

As a result, the Drake equation can have any value from "billions and billions" to zero. An expression that can mean anything means nothing. Speaking precisely, the Drake equation is literally meaningless, and has nothing to do with science. I take the hard view that science involves the creation of testable hypotheses. The Drake equation cannot be tested and therefore SETI is not science. SETI is unquestionably a religion. Faith is defined as the firm belief in something for which there is no proof. The belief that the Koran is the word of God is a matter of faith. The belief that God created the universe in seven days is a matter of faith. The belief that there are other life forms in the universe is a matter of faith. There is not a single shred of evidence for any other life forms, and in forty years of searching, none has been discovered. There is absolutely no evidentiary reason to maintain this belief. SETI is a religion.

One way to chart the cooling of enthusiasm is to review popular works on the subject. In 1964, at the height of SETI enthusiasm, Walter Sullivan of the NY Times wrote an exciting book about life in the universe entitled WE ARE NOT ALONE. By 1995, when Paul Davis wrote a book on the same subject, he titled it ARE WE ALONE? ( Since 1981, there have in fact been four books titled ARE WE ALONE.) More recently we have seen the rise of the so-called "Rare Earth" theory which suggests that we may, in fact, be all alone. Again, there is no evidence either way.

Back in the sixties, SETI had its critics, although not among astrophysicists and astronomers. The biologists and paleontologists were harshest. George Gaylord Simpson of Harvard sneered that SETI was a "study without a subject," and it remains so to the present day.

But scientists in general have been indulgent toward SETI, viewing it either with bemused tolerance, or with indifference. After all, what's the big deal? It's kind of fun. If people want to look, let them. Only a curmudgeon would speak harshly of SETI. It wasn't worth the bother.

And of course it is true that untestable theories may have heuristic value. Of course extraterrestrials are a good way to teach science to kids. But that does not relieve us of the obligation to see the Drake equation clearly for what it is-pure speculation in quasi-scientific trappings.

The fact that the Drake equation was not greeted with screams of outrage-similar to the screams of outrage that greet each Creationist new claim, for example-meant that now there was a crack in the door, a loosening of the definition of what constituted legitimate scientific procedure. And soon enough, pernicious garbage began to squeeze through the cracks.

Comment: Crichton is a film-maker and a thriller writer, do his comments really add to this article? In any case, he fails to understand the concept of falsifiability. The Drake equation is not the issue, the value of N is. The Drake equation is just a back-of-envelope calculation made about the Fermi paradox. Falsifiable hypotheses can be made by setting bounds on the value of N, and making observations that can falsify these hypotheses. For example, just just one otherwise-unexplainable signal (prime numbered pulses, for example) recieved by SETI@home would do the job of setting a lowerbound of N=2. Or the sighting of some Dyson spheres, or other examples of engineering capable of being seen from lightyears away. Alternatively, you could go round the galaxy, enumerating civilizations, a task which whilst lengthy (a few hundred thousand years) is entirely physically possible, given von Neumann machines and a lot of civilizational patience. -- The Anome 14:13, May 21, 2005 (UTC)

I agree, Crichton is way off the mark here: he appears to think that DE is same thing as e.g. the law of gravity. DE is used for estimation purposes, it is not a physical law. If we knew the real value of N, we wouldn't need DE, would we? Moreover, when he says that DE is not scientific, he is again off the mark, because it exactly follows the scientific approach to cracking hard problems, which is dividing them into smaller subproblems, separating well-defined ones from ill-defined ones along the way. GregorB 17:35, May 30, 2005 (UTC)

Wow - just lost a lot of respect for ol' Crichton. I'm not so concerned about the Drake equation - I agree with the substance of what Crichton says - it is a little silly, but as GregorB says, it wasn't meant as a law, just an attempt at an estimate. However, that attack on SETI is out of the ballpark ridiculous. His claim that "SETI is a religion" just doesn't make any sense. If SETI was a group of people who dogmatically believed in the existence of extraterrestrials, then they would be a religion. However last I checked, they were searching for extraterrestrial life, not assuming its existence. I see no distinction in that respect between SETI and particle physicists. No one would reasonably claim that particle physics is a religion because it involves searching for new particles that aren't known to exist! Religious groups don't spent millions on equipment to search for evidence of their beliefs - they just believe them. How did he miss that? Sorry, this doesn't have much to do with the article, but oh well. --Bmk 04:47, 7 July 2006 (UTC)

A new number for Ne could be 4 being that in our star system there are 2 planets and 2 moons which might develope life. They are Earth, Mars, and the moons Europa and Titan which may be developing life. Theoretically counting only ours as a primary source because we don't know how many planets are actually out there that are capable of creating life let alone sustaining it. Concluding the fact that the majority of the stars in the Milky Way are red dwarfs (which cannot have a planet around it because it would erode away any atmosphere on a planet). We took most of Drake's original numbers and added a few of our own and got N=8 so we think there are only 8 planets out there like ours that could communicate with us... comments please!!! need help with this one...!!!!

WP:NPOV states that various views must be represented fairly, proportionately and without bias. Crichton is not alone in his perception. I encountered this equation in a philosophy class in which it was labelled a pseudo-science. Shawnc 07:09, 17 December 2006 (UTC)

[edit] Nitpick: lower bound on L

I changed the following from the article:

A lower bound on L can be estimated from the lifetime of our current civilization....

I don't think that's estimating a lower bound, because our civilization might have a longer lifetime than the average (expected) lifetime. Maybe "pessimistic value of L" would be more accurate? Wmahan . 05:53, 2005 Jun 15 (UTC)

I think it would make a decent lower bound in that we are not dead yet and do not expect to be dead next year. Our technology is futher expected to outlive us (at least in detectble terms). But throwing the value of L away I think the deravation of the equation with respect to R* and L needs a bit more fleshing out for the less geek of readers. The stated goal of counting civlazations which we should be able to detect would seem at first anyway to call for a count of stars of the proper type at the proper distance. The rest of the equation is pretty simple as its all fractions of fractions of fractions, but I think the years aspect of the equationneeds further explination in the article. Dalf | Talk 06:43, 14 October 2005 (UTC)

[edit] Different version of the equation

It seems to me that the equation with "R* is the rate of star formation in our galaxy" gives an estimate of the number of civilizations that come on line each tear.

The astronomy book "Horizons: Exploring the Universe", by Michael Seeds gives a different version of the equation:

N = N* x f_p x n_LZ x f_L x f_i x F_S (6 terms instead of 7)

where

N = number of communicative civilizations in the galaxy

N* = # of stars in the galaxy - NOT the number of new stars/year

f_p = fraction of stars with planets

n_LZ = # planets of star in life zone

f_i = fraction that evolve intelligence

f_L = fraction of planets suitable for life

F_S = fraction of star's life that has a technoligal civilization

Needless to say, with the number of stars in the galaxy in there instead of the number of new stars/year, the result is much larger. He gives the pessimistic result 0.00002 and the optimistic 10,000,000.

Also, another point - f_i is normally limited to <= 1, i.e. at most one intelligent per planet. But there could be more than one per planet. Earth could evolve other intelligent species later. Bubba73 04:36, 22 Jun 2005 (UTC)

P.S. On second thoght, I guss the two versions are pretty much equivalent. One thing, near the end of the article for the current estimates, in the body it lists f_i as 0.01 but 1E-7 is used in the calculations.

Also, it should be noted that the number of intelligent civilizations is extimated to be considerably higher than the number that we can communicate with. Bubba73 04:54, 22 Jun 2005 (UTC)

[edit] What is N, really?

Should N be the number of communicative civilizations out there (ie right now)?

As currently phrased in the article, the equation instead gives the rate at which new stars are forming which will someday house communicative civilizations times the average length of the civilizations. Of course, these civilizations take time to blossom, that the equation does not take into account the age of the galaxy should be a clear indicator that N is not the number of communicative extraterrestrial civilizations in our galaxy right now (this follows from the observation that a relatively young galaxy with the same rate of star formation would be treated identically to our own). It seems the our version of the equation somehow misrepresents the equation. Either what we are representing N as meaning should be changed, or some of what the terms represent need to be changed, though it would seem to be the former, judging from the above post. Of course we aren't the first to make this mistake, it seems to be everywhere so...

...maybe I'm wrong. Maybe there is some analysis (which is missing from the article) which shows that the age of the galaxy is somehow already taken into account. Or maybe the Drake Equation relies on the assumption of a relatively 'steady-state'(ie all terms in the equation have been the same for billions of years) galaxy, much older than the average time it takes for civilizations to evolve (i think that only in such a case would the rate*length = current number of civilizations).

...or maybe this is a valid criticism of the equation which others somewhere have pointed out. (ie the Fermi Paradox solution which posits that we are among the earliest civilizations).

Anyone know which it is? Intangir 06:17, 13 November 2005 (UTC)

[edit] I think the Current Estimates Section Should be removed

The current estimates section should be removed or at least edited to indicate that it's mostly baloney. To the reader, it seems to indicate that current evidence suggests those values are more or less correct while in fact they just certain people's opinions of what the values ought to be. In science, there are not supposed to be experts and the opinion of one person should be given no more weight than the opinion of any other. As the links at the bottom of the document and discussion in this section show, there is wide spread disagreement over the values.

Also, I have taken several astro classes in which the Drake Equation is discussed and never heard claimed values that remotely approach for resemble those $f i$ . The claim neither gives a citation for the figure or explains why radiation dosage must be as low as Earth. Indeed, much of the experimentation regarding the formation of life seems to indicate that higher doses of certain sorts of radiation may actually encourage the formation of life.

Many astronomers, Frank Drake included, seem to believe that we really don't have any good ideas of any of the values other than R*. With future space missions such as Kepler and TPF we may get a better idea for $f p$ and $n e$ . Everything else is guesswork, not science, and it shouldn't be presented like it is.

How about ranges for values instead? Are there papers that say things like "well, the laws of physics say it can't be less than X, and if it were more than Y then the stars at night would outshine the moon"? Otherwise, I think consensus figures are a good idea, as long as they have an adequate disclaimer. --noösfractal 17:32, 24 August 2005 (UTC)

Ranges are even worse unless we are going to put what the actual ranges are given the unknowns (in which case the ranges will be so large 0-1 for example as to only confuse the matter). I think a discussion of what sort of considerations are made when thinking about each number is worthwhile. I think doing an example where the numbers used are called out as being guesses (or perhaps two examples one that generates a really high value and oen a really low). Using talking about the numbers Drake used originall is also ok since that is historically accurate and not claiming any values for the number but simply stating the ones that Drake used. Dalf | Talk 06:47, 14 October 2005 (UTC)

I agree with the original poster, this section is absolute bollocks. If anything, current estimations place N above 10,000.

[edit] Possibility of other life

Has the possibility that non-intelligent ET life-forms exist been documented? That would be M = N * (1 / L) * (1 / fc) * (1 / fi). We know that N >= 1, so M must be very high. I guess a flaw with this is observer bias, i.e. N could be less than 1. Neurodivergent 19:27, 11 January 2006 (UTC)

[edit] Value of L

Doesn't the value of L (67 years) assume we'll go extinct tomorrow? L should be based on the life expectancy of the species, assuming we'll keep using this technology. The doomsday argument might be helpful, although flawed for various reasons. Neurodivergent 19:41, 11 January 2006 (UTC)

I have many problems with this equation.

"fc is the fraction of the above which are willing and able to communicate". These should be broken into seperate parts. The ablity to communicate and the willingness to do so are not congruent.
"L is the expected lifetime of such a civilization". Since it's been pointed out that technology and knowledge go with a civilization this should be changed to "expected evolutionary lifetime of a sentient species"(eg: The Roman Empire is long gone but much of their technology, culture, and knowledge is alive and well in almost all current cultures)
It doesnt take into account many of the smaller events here on Earth that may have led to the formation of life. Such as, the Earth's magnetic core. As well as, though probably less important, the moon's affects and the rate of rotation.

"(Note, however, that in the year 2001 a value of 50 for L can be used with exactly the same degree of confidence that Drake had in using 10 in the year 1961.)"

Is this supposed to mean 10,000 or 50,000? It doesn't make any sense if not... 82.32.65.149 10:06, 10 May 2006 (UTC)

The article is about a historical equation created by one person, right? Is there a place to argue about the details of what makes up the equation? ADyuaa 23:17, 8 January 2007 (UTC)

[edit] What about zero?

Question: In mathematics, when any number of variables is multiplied together,if one of the variables equals Zero, the result is Zero. So, doesn't plugging a zero into this equation also make the answer zero? Joeylawn 05:33, 12 March 2006 (UTC)

No worries there: none of them is zero, or we wouldn't be here. -Padde 00:37, 15 April 2006 (UTC)

[edit] Please revert f_p

Someone changed the value of f_p to 10.5 from 0.5. That's impossible, f_p is the fraction of stars that have planets and so must be less than or equal to 1.

[edit] Notation

f_i = f_c = 0.01 is poor notation. It suggests that f_i and f_c are intrinsically equal for some reason. I have fixed this. Padde 00:36, 15 April 2006 (UTC)

[edit] Fermi Paradox

If anyone is interested Fermi Paradox is on peer review. I'd like to get some feedback to get it back to FA status. Marskell 10:32, 28 April 2006 (UTC)

[edit] Literature

If I remember right, the Drake Equation is mentioned in Sphere by Michael Crichton. I don't have a copy of it to hand, so I can't check it though :'( --H2g2bob 00:43, 26 May 2006 (UTC)

[edit] Gary Bates a reliable reference?

The following reference is currently in the article:

Bates, Gary (2004). Alien Intrusion. Master books. ISBN 0-89051-435-6.

Can someone verify that this is a reliable reference? A quick look at the amazon (UK) reviews [1] makes me doubt it. It was added by 68.85.27.47 (talk • contribs) back on the 25 February 2006 [2]. Mike Peel 21:05, 6 August 2006 (UTC)

[edit] Roddenberry's fudge

I think putting this fake equation in the opening section is confusing to a casual reader - in an article named for an equation, the first thing on the page that looks like a mathematical construct should be the subject of the article!

I'd suggest trimming that section out and placing it in a 'trivia' or 'culture' section, below the main content. Radagast 04:04, 4 December 2006 (UTC)

[edit] Equation vs. Variables

Why is the Drake equation considered bad science? From what I can see, it's just a multiplication of probabilities which seem quite reasonable. People who argue with it seem to be mostly quibbling over the estimates of the variables. What's the problem with the equation itself? Maybe we currently have no way of knowing most variables, but we come closer to figuring them (at least some of them) out daily, and it becomes a good guideline of other factors to estimate (scientifically) to determine N. ADyuaa 23:10, 8 January 2007 (UTC)

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