Skydancer

The planetologists are weighing in on that one, too. A factor that Drake didn't address specifically is the chance that a planet with intelligent life would have the necessary resources to build radios. (IOW, even if the species is pre-disposed to technology, how are they supposed to do it if there are no ores or metals to play with?) Ore bodies require some sort of concentrating mechanism, and they're not sure how tricky that might be.

At the same time, we might be an unusually _dry_ planet with life. Europa could have life in its water, but even if it was intelligent, how could it develop any technology at all if they can't make fire?

elwoodblues

Maybe they can discover slood instead. It's much less difficult to discover than fire; only slightly more difficult to discover than water.

[ June 18, 2002: Message edited by: elwoodblues ]</p>

Godless Dave

Even if there is other intelligent life in the universe, and even if it is communicating with radio or some part of the electromagentic spectrum, we might never find out, or not for a long time.

We've been broadcasting radio waves for, what, 100 years? That means evidence of our existence has only traveled 100 light years from earth. There could be intelligent life on a star 150 light years from here, and they wouldn't have any evidence we exist for another 50 years. And 150 light years is close. Our galaxy is 100,000 light years across, and there are billions of galaxies. There could be hundreds of civilizations on planets in our galaxy, and we wouldn't find out for millenia. And if the nearest intelligent life is in the Andromeda galaxy - well don't hold your breath. The same thing that convinces me that extraterrestrial life is likely - the size of the universe - is the same thing that makes it unlikely we'll find it anytime soon.

LeftCoast

Maybe not. Look at our own modes of communication, as they become more advanced they generally become more focused. Tight-beam Microwave relays, fiber optic cables - cell phones which radiate omni-directionally are very low power, most of the transmission between them
is by way of much more tightly focused mediums. These methods produce much much less stray signal that could potentially be detected by an extraterrestrial - I'm sure the same goes for other (possible) civilizations.

Jayhawker Soule

Precisely. <img src="graemlins/notworthy.gif" border="0" alt="[Not Worthy]" /> Note, for example, <a href="http://www.planetary.org/html/UPDATES/seti/Contact/debate/Mayr.htm" target="_blank">Ernst Mayr on SETI</a>. The presumption of intelligent life seems to me more teleology than science. As Gould was fond of saying, we still live in the Age of Bacteria.

fando

That's a good point. As technology improves, so does the ability to produce less noise by being more efficient. However, a stronger argument against what I just said is that noise like we generate with RF communications is just too weak to be detected beyond a certain radius. We need to send intentional messages with intense beams in order to have a hope of being "heard" 10k ly away.

It would suck if the universe, and our galaxy in particular, were full of advanced civilizations who mostly keep to themselves. Maybe there really is some kind of galactic community and the only reason why we aren't in on the party is because we haven't been pinged by their infrequent surveys. Space is vast, after all.

Cretinist

If strong nano-technology is possible, and if even one technologically advanced species in our galaxy had ever decided to build von Neumann probes, the galaxy would already be fully colonized. Since that doesn't appear to be the case, the only likely explanation is that all intelligent species end up killing themselves before they ever build von Neumann probes.

<a href="http://www.ndirect.co.uk/~transhumanism/Fermi.htm" target="_blank">http://www.ndirect.co.uk/~transhumanism/Fermi.htm</a>

ishalon

nobody said "intelligent life"

Even if we were the most intelligent life forms in existence, it's still going to take us millenia before colonizing galaxies becomes normal, so advanced space travel should not be a main requirement of life...

If no life was found on other earth-like planets, and absolutely no fossils found anywhere in them, I'd find a new theory.
As long as you remember there are most likely billions of earth-like planets or other places for life to form, but discovering no alien life where all conditions of abiogenesis are would definitely mean we have the origin of life wrong.

But who says we will?

Jayhawker Soule

Nor is it.

LeftCoast

Unless there is some monumental breakthrough in propulsion, we will never colonize "galaxies", we may be able to colonize habitable planets in the nearby stellar neighborhood, but not beyond. Even at that, these colonies would immediately become the human equivalent of the geographically isolated communities that have driven evolution on earth for the past 3.5GY.

Human evolution will really start again once (if we ever) spread out to the stars. Given the distances and timeframes required to travel between the "colonies", genetic isolation would for all intents and purposes be total.

Edited to add: Presuming that we are the only intelligent race in this galaxy, by the time our descendants colonize the far side of the galaxy they will most likely bear only a passing resemblance to us, if they are recognizable at all as our descendants.

[ June 18, 2002: Message edited by: LeftCoast ]</p>