Number of ET Civilizations In Our Galaxy Is 37,964

KentuckyFC writes "The famous Drake equation calculates the number of advanced civilizations in our galaxy right now. But the result is hugely sensitive to the assumptions you make about factors such as the number of habitable planets that orbit a host star, how many of these actually develop life and what fraction of these go on to become intelligent etc. Disagreements about these figures leads to estimates for the number of advanced civilizations ranging from 10^-5 to 10^6. Now an astronomer in Scotland has worked out how to make the calculations more precise so that different theories about the origin of planets, life and civilizations can be compared. His calculations say that the rare-life hypothesis predicts only 361 advanced civilizations in the Milky Way now. However, the so-called tortoise and hare hypothesis predicts 31,573 and the theory of panspermia says that there ought to be 37,964 extraterrestrial civilizations more advanced than our own in the Milky Way."

Comments

Only 37,964?

[AltGrendel]

Should give us plenty of room to screw up without affecting anyone.

Where to find them?

[CRCulver]

I'd be interested to know where the best place to look for ET civilizations is. A common science fiction theme, found in plausible for in Niven's Known Space universe and Vinge's rather implausible A Fire Upon the Deep has civilizations getting out of the core as fast as possible, settling the fringes of the galaxy. The increased speed of stellar activity in the core would make for a risky place to build lasting civilizations. Would everyone better than us be at the outskirts?

Then where are they?

[Reality Master 101]

The "famous Drake equation" is NOT meant to calculate anything, it's meant to start a conversation on what the parameters of intelligent life probability are.

On the other hand, the famous Fermi Paradox tells us that we're alone in the galaxy. And considering that's a direct piece of data, I tend to believe this view. People like to wave their hands and say, but, but, WE'RE here! That means that there "just have" to be more! Why are we so unique? This is the Sagan argument, and it's answered by the Anthropic Principle.

And yes, in this case, absence of evidence *IS* evidence of absence.

Re:Then where are they?

[Sockatume]

Well, I'd say the main issue with that argument is that we just plain don't have the tools to detect intelligent life outside our solar system. By analogy atoms were first proposed in Greek times at the latest, but were pure fancy until experimental tools to properly confirm their existence popped up. It was an answerable-in-principle, but still open, question.

For example, we can only just see a planet that seems to be rocky and atmosphere-bearing, which therefore meets some of the criteria for "life as we know it". We've been able to see gas giants, which might harbour life as we don't know it, for a little while now. However we can't actually resolve giveaway cues for planet-spanning civilisations, never mind lower life, either kind of planet yet. And we have no reason to assume that they'll be "chatty" in any way we can detect over long distances. To a group of aliens flying through alpha centauri whose civilisation skipped radio and went straight to fibre optic and laser, 2000AD Earth and 200,000BC Earth would be indistinguishable.

Re:Then where are they?

[Reality Master 101]

Well, I'd say the main issue with that argument is that we just plain don't have the tools to detect intelligent life outside our solar system.

Radio signals are not the only way to detect intelligent life. I think the biggest ramification of the Fermi Paradox is that we're here at all. When you do the math, even at sublight speed, it takes about 10 million years to fill a galaxy (give or take an order of magnitude) using geometric progression. That's *nothing* in the billions of years of the life of the galaxy. Yes, maybe a lot of civilizations wouldn't have expansionist goals, but it only takes one. Only one civilization has to have the desire to expand in a sublight sleep ship and the whole galaxy is filled before we even arrive on the scene.

Or, at the very least, someone would have sent out Von Neumann self-reproducing intelligent probes. We should see those everywhere, if life were common.

People hate facing up to the fact that we're alone. But it just seems to be the fact of the matter.

Re:Then where are they?

[polar red]

Or, at the very least, someone would have sent out Von Neumann self-reproducing intelligent probes. We should see those everywhere, if life were common.

probes with bacteria or virusses, or even just amino-acids ?

Re:Then where are they?

[TheRaven64]

Actually, the ancient greeks could have performed Rutherford's scattering experiment which shows not only the existence of atoms, but their (rough) structure. The ability to produce monatomic sheets of gold (gold leaf) has been around for thousands of years and the only other requirement is a source of alpha particles. This would have required an understanding of a radioactivity, however, which is much easier when you have discovered electricity.

Suspiciously absent

[NoobixCube]

No mention of species less advanced than us, but there are apparently 37,964 more advanced. I wonder why that is... Other civilizations must look at this backwater hick-world and laugh.

Re:Suspiciously absent

[4D6963]

Which is why they send us all the UFOs. I know that serious people like to dismiss UFO reports because of how over the decades we turned the whole topic into ridicule, and the masses of loonies interested in the topic didn't help, but you have to remember that lots of very well documented UFO events reported by military personel and pilots are far from explained by anything we know.

You can scoff off the whole UFO thing but you can't take a precise case (provided it's a good one of course) and explain the recorded flight paths and phenomena.

That's what strikes me regarding the SETI approach vs UFOlogy, we look as hard as we can hundreds of light years away, yet we can't be bothered to take a closer look at what happens in our own atmosphere. I'm not implying that any recorded UFO event is extraterrestrial in origin, but in many cases you have to consider this possibility by an absolute lack of alternative explanations. No matter what I think it's worth a better scientific examination of the whole thing. But unfortunately the scientific community devotes more time and energy to what it considers safe research, which is why we spend so much time in the cul-de-sac that is string theory while investing very little in seemingly more risky possibilities (the Garrett Lisi example springs to mind).

Re:The real answer

[Jeff DeMaagd]

The biggest problem I see with this person's claim is that panspermia doesn't really work well when applied to reality.

There was an experiment discussed on Science Friday where an experimenter said cosmic radiation does a good number on genetic material based on tests with actual genetic material. I think they showed that in about 80,000 years, genetic material is just broken up into a bunch of tiny, useless snippets, especially if it's on a rock passing between stars, there is much less protection against radiation than there is within a star's heliopause. Panspermia might be a workable idea for passing organisms and code between planets in one solar system, but not for interstellar travel.

Here is an interesting one.

[ShieldVV0lf]

No kidding. Our current estimates of the number of stars in the galaxy only go to about one significant figure, with upper and lower estimates differing by a factor of two. That puts a pretty serious cap on the precision of his answer.

One of my peers is an astrophysicist. Nearly all of their calculations are done to ONE significant figure. It ends up that they typically just add up exponents. The numbers are usually so huge, eg. 1E27, that they can get away with this.

When you are dealing with orders of magnitude like these, it is usually acceptable in the scientific community. Whether this de-facto standard *should* be so acceptable is still up in the air in my views :)

You won't find them

[Dammital]

Civilizations that manage to survive reach technological singularity, and simply hole up.

Ephemeral civilizations have only a short time to detect each other; I doubt that happens often.

Re:You won't find them

[jvkjvk]

Considering that we are not ourselves members of an advanced civilization I don't believe we can say what they would do.

I imagine that even an advanced human civilization would be pretty incomprehensible to us.

The instinct to reproduce and grow in numbers is fundamental to all life.

Try telling that to today's first world societies. How many of them have negative net native population growth? So why couldn't an advanced species settle for zero population growth or even negative for a few hundred thousand years (e.g. if they did start out colonizing and then thought better of it).

To "hole up" is to accept death as the local star fades--contrary to the most basic life instinct.

...aproximately 5 BILLION years later...(or whatever) Assuming you haven't managed to figure out a way to stabilize it using, you know, your advanced civilization's technology. (reminds me of the new dr who series where they went to see earth being destroyed) Or that one couldn't wait until 10K years before catastrophe and just pick up then....etc.

Advanced civilizations don't "hole up," they spread.

cite needed, i think. :)

What's more likely is that an advanced tech society treats any form of uncontrolled emission as lost power. Sound, for example is an indication that you are losing energy. Broadcast EM spectrum waves may be similarly treated. They are not likely to be spewing massive amounts of powerful EM in all directions and certainly aren't likely to be shining massive laser/microwave/xray/neutrino/?? comm beams and such at random spots in the sky - that stuff'll be point to point and they'll even most likely recapture the transmission energy.

So, even if they spread out, there would be little way to notice them unless they get on a "call your friends when drunk" jag while we happen to be listening.

Re:Aliens Cause Global Warming

[Geoffrey.landis]

Michael Crichton's criticism, unfortunately, is uninformed.

His criticism of SERI is basically saying "the hypothesis that the neutrino has a rest mass of zero is scientific, but the hypothesis that a neutrino has a rest mass that is not zero is unscientific." This is silly; the same experiments would be used to test either hypothesis. Likewise, it's silly to criticise SETI by saying it's scientific to listen for radio signals if you're trying to show that there aren't any, but it's not scientific to listen for radio signals if you're trying to see if there are any. It's the same experiment either way.

His criticism of the Drake equation is even less well informed, in that he's criticising the equation itself, not the parameters that go into it. But the equation is trivially true; it's nearly a tautology. If the correct statement is "we don't know", it's not because the equations wrong, it's because we don't know what values go on the right side. But the answer "we don't know how many civilizations are in the univererse because we don't know what the probability is that a planet with life develops a lifeform with intelligence still bounds the question-- it tells us more precisely what we don't know.

In short, Crichton should stick with novels, which he's good at, and not critiquing SETI, something he seems to know little about.

Re:Fermi paradox

[SBacks]

You're missing an entire aspect to the Fermi paradox.

The universe is old. VERY old. About 14 billion years. Earth is fairly young, about 4.5 billion years.

Assuming intelligent alien life take about as long as intelligent Earth life to evolve (give or take a billion years), these other civilizations would have billions and billions of years ahead of us.

Re:My estimate

[arminw]

....but way too many of us are willing to just simply "believe" ....

There is no way you can live your daily life without belief. When you get into a car or a plane, you BELIEVE that they will take you where you want to go. You don't know that for sure. When you go to bed at night you believe and hope that you will wake up in the morning but there is no guarantee that you will. I am sure that you have at one time or another read stories of whole families who went to bed in the evening and never saw the next day due to fire or carbon monoxide. Our lives are governed much more by belief, by faith, than the sure knowledge.

There really is no proof of anything, only evidence that we can choose to believe or not believe.

(...of the reasonably ridiculous notion that life began here when some mythical magical man in the sky...)

You and everyone else that agrees with your assumption (belief) doesn't really KNOW this, but simply believes it and then tries to pass that belief off as sure knowledge. The only evidence we have, is that life, that we are here. There is no way to do deduce from that alone how it began. Even if you invented a time machine and used it to travel back as far as necessary, what evidence would you collect there at the beginning, to bring back to convince your fellow humans at the present time? In the end, whatever evidence you did collect and bring back, would still have to be believed. It would not constitute incontrovertible proof.

If an intelligent life form came to visit us here on planet Earth, what evidence would be sufficient to convince us that this entity came from a galaxy far far away or even another universe or dimension?

Re:Aliens Cause Global Warming

[hpa]

But the equation is trivially true; it's nearly a tautology.

Not quite. It implicitly presupposes a steady-state universe, which was commonly believed at the time. However, we now know that the universe is not steady-state, and in fact is quite young (13.7 Gy) compared to the age of the Earth (4.55 Gy). Especially if the conditions in the Universe have been shifting, e.g. it has taken time for stars to build up enough metallicity, it is entirely plausible that conditions may be hospitable to life, and yet it is not common, simply because we just got there first. This is particularly important if you accept the conclusions of the Fermi Paradox, which basically states that since technological advancement is so rapid compared to evolution, the first technological civilization in a galaxy will almost inevitably colonize the galaxy before any other civilization has had time to evolve.