Astrobiology--for real!

[justTripn]

Why should we be more pessimistic about the prevelance of other civiliations?

Because it took a whole 4 billion years for our technologcial civilization to evolve (basically all the time up until the present). It was only in the past 100 years that we became capable of communicating with aliens if any exist. As for civilization of any type, it was like what? 10,000? years back to the transition from hunting gathering to agriculture? And 17,000 years back to the first aparent flouishing of culture--with painting, decorations, and long distance trade. So basically, it took the whole age of the Earth for our civilization to appear. If humans were wiped out, a new intelligent species might not even have time to rebound and reevolve before the Earth gets too hot, from the warming sun. From the little mammal mice to us was 60 million years, right? We (animals) have got only about 400 million good years left before the Earth becomes too hot for life--by too hot I mean the oceans start to boil, and boil away. (Sorry to be a bummer).

Also, if you assume your life to be taking place at some random point between the beginning and end of civilization (adjusting for population levels) well either we just happen to live WAY at the very beginning of technological civilization, or the party's not going to last very long.



Which is why I take comfort in the others have come before us idea--somewhere, sometime. I am pessimistic about faster-than-speed-of-light travel, and I suspect that civilizations, if they do tend to be long-lived, probably plataue out eventually at some (hopefully high) technological level--rather than continue growing ever more amazing forever and ever.

[justTripn]

-- if there is some property of an early, developing galaxy which prohibits or impedes the development of complex life inside the first 5 or 7 or 9 billion years, THEN there's no reason to believe that there should be other more intelligent life forms than ourselves which have been developing for the past 2 billion years or more. However, if there's no evidence to suggest that the habitibility of stars in a galaxy vary with the age of the galaxy in such a way that habitability peaks around the age we are currently at, then it is logical to assume that an arbitrary star system in our galaxy was just as likely to birth new life in the preceeding 13 billion years as it is today, i.e., that those civilizations could be still around.

There was no chance for life to evolve without the heavier elements and they had to evolve through supernovas. The sun is like a third generation star, so it contains heavy elements, like carbon, created in supernovas of previous stars that blew their gas off into space.

But that might have taken only like a billion years, so intelligent life has still had like 10 billion years to evolve elsewhere (compared to about 4 billion years for intelligent life to evolve on Earth). That's why older civilizations should be out there, IF civilization tends to survive for long periods of time and don't tend to wipe themselves out.

Moral of the story: Be careful with our little civilization! We don't know how sturdy or fragile civilizations tend to be, and this one's pretty special.

[Elessar]

-- if there is some property of an early, developing galaxy which prohibits or impedes the development of complex life inside the first 5 or 7 or 9 billion years, THEN there's no reason to believe that there should be other more intelligent life forms than ourselves which have been developing for the past 2 billion years or more. However, if there's no evidence to suggest that the habitibility of stars in a galaxy vary with the age of the galaxy in such a way that habitability peaks around the age we are currently at, then it is logical to assume that an arbitrary star system in our galaxy was just as likely to birth new life in the preceeding 13 billion years as it is today, i.e., that those civilizations could be still around.

There was no chance for life to evolve without the heavier elements and they had to evolve through supernovas. The sun is like a third generation star, so it contains heavy elements, like carbon, created in supernovas of previous stars that blew their gas off into space.

But that might have taken only like a billion years, so intelligent life has still had like 10 billion years to evolve elsewhere (compared to about 4 billion years for intelligent life to evolve on Earth). That's why older civilizations should be out there, IF civilization tends to survive for long periods of time and don't tend to wipe themselves out.

Moral of the story: Be careful with our little civilization! We don't know how sturdy or fragile civilizations tend to be, and this one's pretty special.

Right, I knew there had to be at least ONE generation of stars before you could have planets... I just meant... if there's some *other* circumstance of which we are unaware which makes it less likely for even 2nd generation stars to form planetary systems than 3rd, 4th. I mean, you might even say by pure logic there IS a good reason... With each successive stellar generation, there would have been far more supernovae, far more distribution of heavy elements, and therefore more planetary systems... The logic works. It might support Rigil's argument that, while billions of years have gone by before us, they weren't necessarily "life-bearing years" heh.

[Rigil Kent]

That's one of the reasons I have as much trouble buying the Super!Advanced!Alien!Race that so many people buy into. That doesn't mean I rule out extraterrestrial societies; I just have a problem accepting that any such societies are, by default, more advanced than humanity which seems to be the norm. I concede that it is possible, since we have no idea where the "center" of the universe really is, and the closer to that "center", the older the stars and the like.

But Vorlons and Shadows? They're fine in the realm of sci-fi, but I have boatloads of problems buying into races that advanced actually existing.

[justTripn]

There is no center of the universe. But otherwise, point taken.

[Rigil Kent]

You know what I meant, right? It's why I stated "center" and not center...

[justTripn]

Yes, the closer to the center of the visible universe, the older the stars, and some distance out from us, is a "dead zone," because it is too far in the past (for us). But we are definately at the center of our visible universe. And every other civilization would have a different visible universe of which they are the center.

[blacknblue]

Consider. Modern Humans first appeared (at least in archaic form) approximately 500,000 years ago according to paleontologists. We achieved space flight less than 100 years ago. That leaves 499,900 years of sapient life on Earth that had no way of communicating with the stars and, frankly, no interest in communicating with the stars. We only conceived of the IDEA of communicating with extra-terrestrial civilizations to any serious extent after WW2. Sixty plus years ago.

Cultural factors people. Just because an intelligent race exists doesn't necessarily mean that it will be technological. Even if we assume that a race has hands and makes tools, why would we assume that they are interested in flying? Maybe they like it on the ground. Maybe they live on a heavy gravity planet and have an instinctive fear of heights.

Or maybe they are Xenophobic. Or maybe they are like us, wamongers who continually build civilizations and then tear them back down again through slaughtering each other. Sumeria. Babylon. Egypt. Aztec Empire. Roman Empire.

How old is civilization in India? How many times has it been devastated in war? How old is civilization in China? How many times has it been shattered, and precious knowledge destroyed, in war? How many times has the tiny guttering candle of knowledge been snuffed by the sword in Europe?

It is only by the grace of God, and an extremely unusual juxtaposition of historical events, that we now have a civilization that for some reason has survived long enough to achieve the concept of space flight. How long it will endure is anyone's guess. But this is the best we have been able to achieve in 500,000 years of trying. If other races evolved nearby, and we missed them by a mere one million years (an eyeblink in geologic terms) then we are SOL.

[Elessar]

You're right that all those things describe us, but there's no reason to assume that tottering on the edge of extinction is typical among sapient lifeforms... We ourselves are all we have to go on, but it's still just one sample... In other words, we don't know squat. We could be the only ones out of the whole plethora of creatures in the Universe that have this problem... or we could be typical... there just isn't enough data to make an informed conclusion in that regard.

There's a whole bunch of arguments to the affirmative and contrary with regard to whether we are typical (and I mean in multiple facets -- biologically one could argue that we are typical of organisms that develop under a similar star on a similarly composed planet, but we don't know yet if that directly influences sociological, psychological and intellectual development) of multicellular, complex, intelligent life... Frankly, I don't think there's any way to know until we've met one.

I was watching an interesting Discovery channel show about the development of early Man and I don't recall exactly whether they were making a hypothesis or stating this as evidenced anthropological fact - but it was claimed that one of the factors which lead to our intellectual development was climate change at a critical point in proto-human history. At some point, a particular group of homo-sapiens (who would eventually "beat out" neanderthals and austrolopithicus for the dominant species) ended up in an area which, due to climate change, gradually began to lose most of its vegetation. Apparently these homosapiens were herbivores, because the climate change caused the homosapiens to migrate to a different area looking for food, and there were game herds. Soon after, their diet included meat. As I recall, they claimed that the bone structure of the jaw/skull was such that prior to that, because their diet was mostly leafy and greens, they had a strong muscular appendage which joined at the top of the skull and wrapped around the jaw bone, to help them chew harder, but as their diet changed, they didn't need that to grind up vegetation anymore, they needed incisors to cut up the meat, and then could swallow it. The claim went that once this muscular tissue disappeared (which ran from the top of the skull where the hemispheres meet) it allowed the cranial cavity to expand and the brain to actually grow larger over the next however many hundred thousand years.

Like I said, I can't recall if it was a conjecture or if they were stating for fact that this was considered to be one of the points where human intelligence and mental capacity expanded due to environmental factors, but it was interesting, convincing - and most of all, if true, a really strong piece of evidence for the arbitrariness with which perhaps evolutionary development occurs to bring a species from upright-walking animal to thinking-being.

[blacknblue]

I remember that one. It was comparing homo robustus to gracile australopithicines I think.

I do remember that it is pretty well established that eating meat is the reason our ancestors became sapient. Infusing amino acids from animal carcasses into proto-human children's diets caused their brains to overdevelop, which caused their brains to expand during the critical early years when their skulls were still soft. After a few thousand years it became normal. At least, that is what I am reading nowadays. True or not? Who knows?

[justTripn]

The geysers of Enceladus (moon of Saturn) are the new best place to look for extraterrestrial life in the solar system.

http://www.pbs.org/wgbh/nova/titan/porco.html

[Elessar]

woot! Yeah, I always liked this idea... that perhaps energy sources other than the conventional solar power of an inhabitable region of the solar system could support life, e.g., torsional and tidal force energies from Jupiter or Saturn on their moons' volcanic substrata that cause hitherto-unheard-of levels and uniformities of geothermal energy radiating to the surface, allowing for habitably high enough temperatures for single or even multi-cellular life to form and prosper, perhaps in vast undersea oceans where the heat can be felt by undersea lava vents.

Wow that was a long sentence

[justTripn]

The new consensus seems to be that life on Earth probably originated at the underwater thermal vents (rather than in tidepools--as Q was observing in All Good Things) and would most easily have been preserved there, deep underwater, during global extinction events in the age of heavy bombardment when a meter might boil off some of the ocean into space.

[Linda]

Q knew that! He was just playing with Picard.