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

What a great example!

[Frequency Domain]

...of spurious precision.

Re:What a great example!

[deniable]

The original estimate was 32768 and an overflow flag.

Re:What a great example!

[Sockatume]

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.

Re:What a great example!

[iangoldby]

It must be right, because the answer came from a computer.

Re:What a great example!

[$RANDOMLUSER]

That's 32767 and an overflow flag.

And get off my lawn.

Re:What a great example!

[ciderVisor]

Base 13 ?

Re:yuck.

[Mastadex]

Like I said before, it adds flavor to a rather dull blend.

My estimate

[MyLongNickName]

1.

And it is as valid as this astronomer's estimation.

Re:My estimate

[Rob T Firefly]

1.

Is that the mice, or the dolphins?

Re:My estimate

[elrous0]

I wish I had mod points. There is simply no way to arrive at any meaningful number based on what we know right now (which is very little). Until we can accurately understand how life even began HERE, there is no way to know how common or uncommon this occurrence is across the galaxy.

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.

The real answer

[SmallFurryCreature]

We just don't have a clue.

The number of things we don't have a clue about is staggering.

• The number of planets that can support life. We just don't know, we presume we have observed some planets but they might be failed stars and have no direct observations for far.
• We don't know exactly where life can and cannot occur. For that matter, we only have our own planet to judge what is alive and what isn't. There is no prove one way or another that oxygen is needed for instance to create life.
• We don't know if space travel between stars is possible. Faster then light travel would change the rules as any species with such tech could settle countless planets and perhaps wipe out other civilizations OR seed them (Star Trek).
• We don't know how life starts. Was life started on earth or did it arrive from somewhere else? Huge difference between life starting on its own on every planet OR there being some galaxy wide single seed.

Counting the number of earth like planets is just plain silly. If life can only start in space and then find a planet, earth might be totally unsuitable for the first start. It also presumes life can only exist under earth like conditions yet we KNOW that even life on earth varies widely. If some species can survive on the bottom of the ocean outside the influence of the sun, is it impossible to imagine a lifeform that exist in space itself?

No, I am sorry but until we can actually go and look our estimates of the number of civilizations is between 1 and 1+.

Advanced?

[i_ate_god]

But we have no definition of advanced.

Look, just because an alien civilization has been around longer than we have, doesn't necessarily mean they will be more advanced than we are.

Maybe they could have been around one million years before us, but are stuck somewhere between Mesopotamia and Rome.

Re:Advanced?

[AdmiralXyz]

I think there's also the possibility that there HAVE BEEN more advanced civilizations in the past, but they're gone now. Think about it: the Milky Way is what, nine billion years old? Humans have only existed for a minuscule fraction of that time, and humans capable of detecting advanced civilizations for a smaller fraction still. Perhaps many such civilizations have existed throughout the history of our galaxy, but we keep "missing each other on the timeline."

Re:Then where are they?

[bailout911]

Or there is of course, another possibility: That humans are the only "intelligent" species using radio transmission as a communications medium and that any other "intelligent" species is such a great distance away and/or in a region of space where we haven't been listening that we are unable to detect them.

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.

As always, no.

[khasim]

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

Because a species of intelligent dolphins would surely be detectable from their radio transmissions.

No. That entire line of thought is based upon the incorrect assumption that WE are the model for all other species.

We're almost unique on Earth. Where we share DNA with every other animal. Why expect that from creatures who evolved on a different world?

Not to mention the incredibly SHORT time we've been looking over an incredibly SMALL portion of the galaxy.

Your entire argument is based upon another species developing the exact same technology that we have ... and using it in a fashion we can detect ... far enough in the past ... but not too far in the past ... so that we can detect it ... using the technology we have ... during the time we have been trying to detect it.

Yeah, like that "proves" anything.

My assessment

[MyLongNickName]

I am a polar bear. Don't bother to ask me how I managed to get on Slashdot and post this, you would never believe it.

However, I have been doing some estimations of my own. I have always wanted to figure out how many polar bears there are in the world. In my neighborhood here in the arctic, there aren't too many polar bears. About 350. I estimate that we roam over 20 square kilometers. Now, based on some observations I made from the bottom of a well, I figure the earth is around 500 million square kilometers. I haven't actually been outside of my corner of this world, but I imagine everything must be like it is here, and life must be exactly like it is here. I have no evidence to the contrary.

So, I figure there must be 25 million times 350 polar bears or 8.75 Billion of them.

Re:My assessment

[MyLongNickName]

And since you miss the big point, I will spell it out.

A polar bear is using the limits of his logic to speculate on the world as a whole. Had an intelligent bear been allowed to travel the world, he would see where his equation breaks down.

An intelligent human attempts to speculate about the universe as a whole. He is smart enough to realize that he has no clue about how often intelligent life occurs on "habitable" worlds, so he plugs in a variable, then proceeds to put in numbers for something he has no clue about. Since it is unknown, his number is bullshit. Drake realized this, but countless amateurs have treated these numbers as the gospel and wildly speculated about the unknown. this in and of itself isn't bad. However when folks put weight on these numbers, it is bad.

Just as the polar bear has no real clue about the planet it lives on, we have no clue about the universe we live in. I hope that as a civilization that we go out and really begin to explore this place. But as long as we are sitting here on earth, killing each other, and wasting resources on there here and now, we cannot jope to fathom the way the universe truly is.

Close neighbors?

[JoeMerchant]

But, the diameter of the milky way is about 100,000 light years - so, if we assume that pre-Galileo civilization was oblivious to ET, we as a species are only aware of civilization signs within 400 light years or so.

So, if there are 40,000 civilizations within a 100,000ly diameter, then there are approximately 2.56 civilizations within a 800ly diameter.

Personally, I feel like Earth represents the .56 of a civilization in that scenario...

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 ?

Aliens Cause Global Warming

[ciderVisor]

Michael Crichton criticised the Drake equation years ago:

http://www.crichton-official.com/speech-alienscauseglobalwarming.html

My personal guess is that there are OVER 9000 civilisations out there.

Re:Aliens Cause Global Warming

[ciderVisor]

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.

From Crichton's piece:

"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."

He IS talking about the parameters (on the right side). Your criticism is meaningless.

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

Hehehe. Marvelous. Keep it up.

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:Then where are they?

[bhiestand]

Sorry, but the logical fallacy police have to intervene in this one. Absence of evidence is indeed evidence of absence; however, it is not proof of absence. In this case, as has already been demonstrated, we would need significantly more evidence of absence before we could come to any sort of meaningful conclusion. The current evidence of absence is about the equivalent of saying we know there's not a large ET base on the surface of the bright side of the moon.

Further, there's nothing logically wrong with the pot calling the kettle black. The kettle is indeed black regardless of the color of the pot. It just makes the pot look dumb for trying to make fun of the kettle. It reminds me of this quote attributed to Jack Nicholson:

"My mother never saw the irony in calling me a son-of-a-bitch."

Re:Then where are they?

[evanbd]

A terawatt signal radiating uniformly would produce 1e12 / (4*pi*(4e16)^2) w/m^2 = 5.0e-23 w/m^2. With a dish the size of Arecibo (7.3e4 m^2) that's -144 dBm (decibels referred to milliwatts). For comparison, the received GPS signal strength is ~ -133 dBm. With a slightly narrower bandwidth, or signal processing techniques that can work at lower SNR (eg looking for a carrier wave over extended periods -- exactly the sort of stuff SETI@home does) that extra order of magnitude isn't hard to come by.

Note that there are efforts ongoing to build larger area arrays (eg the square kilometer array), improve reciever electronics (chilling the front-end amplifier lowers the inherent amplifier thermal noise, for example), and improve signal processing techniques. Also, for certain types of transmission, the 1TW estimate isn't unreasonable -- Arecibo has radar transmitters with as much as 20TW effective isotropic power (lower total power, aimed at a small fraction of the sky). Given the right sort of source signal and extended observation, something like Arecibo could see some of our leakage signals, not just intentional transmissions.

Re:Fermi paradox

[scribblej]

Correct me if I'm wrong here, but an Earth-like planet couldn't have come about much sooner, since we need so many elements that we can only get from old burned-out stars. There's gotta be a lot of cycles before there's enough material further up the atomic chart to make an interesting planet.