never been there

DON'T SCROLL DOWN YET!!! TRY THE CALCULATION FIRST

I thought about it a while, and I think E&C is where this belongs.

The Drake Equation calculator - how many civilizations do you think there are in the galaxy?

It's a bit sluggish, so you can also try the google cache

I have some thoughts on this, but go ahead, try it yourself first.

never been there

Well, I figured there is 0.0000066 of a civilization somewhere in the galaxy capable of communicating with us. But not quite.

Look at it from the other sentient civilization's point of view. We've been emitting radio waves for 100 years. That means that only stars within 100 light-years of us could hear our signals. A bit of searching came up with the number of 15,000 stars, not the 100 billion I accepted for the number of stars in the whole galaxy.

We could be more optimistic and assume other civilizations stay in the radio business for 1000 years. That has a big effect because ten times more time equals 1000 times more space - so we now have 15,000,000 stars to start with.

As for the prompts from the calculator, I look at them this way:
fp - fraction of stars with planets. An awful lot of stars are binary, and even if there's a planet or two in the mix, they are going to experience some harsh seasons, so might as well leave them out. I think 20% is optimistic.
ne - number of viable planets per star. Ours has one, or maybe two planets in the "Goldilocks" range. But based on the planets found elsewhere, near-circular orbits are pretty rare. We also have little to go on as to whether the rocky matter gets to make planets, or ends up as the core of some gas giant. Not .33, but .0033.
fl - fraction of planets where life actually evolves. The lucky planet has to have not only the right temperature, but the right chemistry. I'm an optimist, so I'd say of that 1% of cases, all evolve life. But I still have a 100x beef over ne, so I factor it in here, .01%
fi - fraction of above where intelligent life (whatever that means) evolves. I put 1%, given that intelligence, when it arises, is a pretty good strategy. But if you think Steven Jay Gould was right, the odds could be a lot longer - there's a lot of luck involved.
fc - fraction that communicate. More precisely, those that communicate in a manner detectable at a distance. If we had somehow come across infra-red lasers and glass fibres first, we might not ever have bothered with radio. IR repeaters on every utility pole would take care of wireless needs within the cities or on highways. I'm putting .01% to make up for some of my earlier optimism.

fL - fraction of a planet's life in which the communicating civilization survives. Sample set of one, average = 100 years. It is 100 years so far, and Stephen Hawking points out that the universe is not such an old place compared to how long it took life on earth to get this far. So the 100 years so far is a relevant number.

So that's how I got my .0000066 value. But as I said to start with, we're looking at 15,000 stars, not 100 billion, based on that 100 years. That's 1.5E-7 times the number, or a 1.67E-12 chance of receiving a signal from another civilization, assuming we recognize it when we receive it.

But give us 1000 years in business (the universe is plenty old enough for that), and it's a 1.67E-8 chance!

Photon

I've always thought that the Drake equation was really nothing more than idle fascination, due to the huge uncertainties involved in any one of those probabilities. I think we'll have much better statistics once concerted efforts to discover whether any life exists (or has existed) on other candidate bodies within our own solar system (like Mars, Europa, Io, and Titan) are complete. If we find no evidence of life there at all, then these bodies which have coalesced out of the same (more or less) original molecular cloud that the earth did will lower any expected probabilities of life developing considerably, or at least show that environment (and maybe not chemistry) is the critical factor.

I think, however, that Europa is a great candidate for life, based both on environment and chemistry, and I can't wait for a mission dedicated solely to this prospect. Maybe Beagle III?

Photon

N = N* fp ne fl fi fc fL

The numbers I chose were similar to the above post, with a few exceptions:

N ~ 2E+11

fp ~ 0.6 ( I think a more generous estimate is needed here, given the relatively high numbers of planets that have been detected with modern techniques around candidate stars. Also, I think that conservation of angular momentum in any single star system would almost certainly produce large orbiting bodies. I mean isn't that why most of the stars that have been detected are multiple star systems?)

ne ~1 (without evidence of another object in our own solar system that can support life, this is a reasonable estimate)

fl ~ 0.1 (this one is pure conjecture on my part. Assuming that conditions are such that life
can evolve, what are the chances that it actually will? Assuming that laws of chemistry are responsible for the formation of the first replicators, this should be close to 1. Given many factors in regards to appropriate mixing of material, it could be significantly lower. This is probably the one that causes the greatest single uncertainty in the Drake equation IMO.)

fi ~ 1E-8 (Evolution on our own planet has shown that intelligence is an advantageous trait, but that it is also difficult to come by. By the sheer numbers of species on this planet that don't have "intelligence" which is a highly subjective term anyway, I'm guessing 1 in about 100 million.)

fc ~ 0.3 (I think one of the signs of an intelligent species is likely to be the desire to communicate and learn. Technology (with inventions of fire and evolutionary adaptations to manually manipulate the enviroment) and language will certainly be an asset, but since the desire to communicate with an alien species may only be a curiosity trait that humans share, I think 30 % is reasonable.)

fL ~2E-6 (Given a 10000 year estimate for the duration of a technologically active civilization, that hasn't transcended the desire to communicate, with a planet lifetime of about 5 billion years, gives an estimate of the above)

Multiplying the above factors yields:

7.2 E-5 civilizations in our galaxy that might communicate with us.

This is pretty pessimistic, but I think another factor should be added here, concerning the fact that if there is life that has evolved differently than that on earth, that we aren't likely to be able to communicate with eachother at all, unless they have a logic similar to ours and communicate via mathematics, but how many forms could that take? Only imagination really restricts us.

Consequently, I don't think the chance that we will contact extraterrestrial life is very high, though that doesn't stop me from donating my computer time to the setiathome project!

Jesus Tap-Dancin' Christ

N*: 100 billion. Why choose something other than the estimates?

fp: since current estimates are 20%-50%, why choose anything outside of that range? I chose 20%, to be a pessimist.

Ne: 1. I know this isn't going to be very convincing, but look around us--we only know how life looks on our own damned planet. Why should we assume that these conditions are th only that give rise to life? Life is, at it's very core, just self-sustaining chemical reactions. You can NOT tell me that there are NO planets in this solar system where such a loose definition will allow for 'life'. Mercury? Why not under the surface? Same with Venus? There are so many variables on our own planet as to what constitutes a valid place for life to exist that we can't make any judgements as wo where life can and cannot exist. Further add into the mix the possibilities of moons of larger planets (such as Europa orbiting Jupiter) harboring life, or contianing such conditions that will allow for life, you have a HUGE range.

One is quite conservative.

fl: 20%. Actually, this is probably higher, given the very, very loose definition of life that I have given, but I'll go with 20%.

fi: 80%. Yeah, I know. Pretty high. But why not? Given the lifespan of a star in the yellow or lower range (10+ billion years), and a few billion years of life working on a planet, why the hell not get something intelligent at some point? The odds of a sapient species is one in how many million? Big whoop. How many millions of species have populated this planet at some point or another? How many die each day? How many are born each day? Lots and lots and lots. Each one is a chance, however small, of being sapient.

Buy enough lottery tickets, one is bound to win.

fc: 90%. Why would they not look at the satars and wonder if someone else is out there? Unless they're xenophobes, they're probably going to make an attempt at comminicating.

fl: 1/1000000. Probably longer, since if they can comminicate, they can survive. IF they're good at communicating, they may be able to habitate outside of their planet as well.

N=2880.

never been there:

You make a very anthropic argument to extraterrestrial life. Why the hell should our standard be used at all? Further, your use of such a tribling number of stars has no basis--the comminication factor is put in for fl--which means you filtered twice.

contracycle

Never been there is perfectly jusitifed in changing the number of stars - that is just refining the equation to address a smaller volume of spoace. Instead of examining life in the whole galaxy - the orignial structure - NBT's modification limits it to either our EM shell or a multiplier of that shell. Thats fair enough; it just changes the answer to one that applies only to that limited volume.

I tend to discount the probability of life developing technology, as I thinnk that this may require relatively unusual circumstances. But I don't discount the probability of life being intelligent, becuase although I agree the overhwleming majority of critters are not very, I think we have a handful that are near our own intellect at least. If we do have multiple independantly evolved intellects, then this outcome must have a high probability.

Secular Pinoy

On the debate concerning the Drake equation, and of the SETI program's probability of success, I find the debate between Ernst Mayr and Carl Sagan to be helpful in seeing the difference between outlook of evolutionary biologists and physicists. In the debate, I think Mayr's objections to the evolution of intelligent life are spot-on and Sagan's critique falls short of rebutting it.

contracycle

Hi Pinoy. I've just read the debate, and I find Mayr's objections exceedingly weak and comprehensively rebutted by Sagan.

Photon

I agree that Sagan admirably defended his position here. I think that since the probabilities involved are so subjective, and difficult to estimate, that a priori rejection of the possibility of communication with ET life is folly. The whole SETI project might be a waste of time, but more evidence is needed, I think, before a judgement can be made.

Secular Pinoy

I knew most infidels would see it that way. Sagan seems to be, like Dawkins, a sort of idol. Oh well...