Intelegent life in the Universe, how common is it?

[Boris Godunov]

Originally posted by Darkstar
Stars are more distant between neighbors out at the fringes where we are versus the interior of the galaxy.

The fringes, such as our arm, are where you're going to have to look, because the interior is to irradiated to support life-bearing planets.

[Dauphin]

And there was me thinking you wouldn't look at the centre of the galaxy because it was too far away at 26,000 light years.

[Boris Godunov]

Why would I look in a place that is going to take a minimum of 280,000 years to tell me anything?

[Dauphin]

It would give you a chance to read War and Peace?

[Cruddy]

It depends on how you define rare and common...

...seeing as the universe mostly consists of nothing, I'd say it was very rare, compared to the amount of bugger all.

[Odin]

Originally posted by Last Conformist

Well, only if the chances of life arising on a planet are high enough. From our present knowledge it seems unlikely, but it's for all we know possible that the origin of terrestrial life was a freak occurence, with a probability of say one in 10^80 (10^80 happens to be the approximate number of electrons in the observable universe).

Thirdly, Given that human life on this planet is reletivly young, and even life on this planet is fairly recent, many probes may well have passed and missed us.

I don't know if terran life can be said to be "fairly recent"; it's been around for closer to 4 billion years, which is an appreciable amount of time even on a galactic time scale. During that time, for instance, the average metallicity has risen enough to affect planet formation.

Life is NOT a freak occurance. It can start anywhere with a source of liquid water, energy (lighting, UV light, heat from hydrothermal vents), and organics. The question is whether higher (complex multicellular) life will evolve. I think that can't happen on a Europa-like world, a biosphere needs photosynthesis if it wants to get to get anywhere.

[Odin]

Originally posted by Dauphin
It would give you a chance to read War and Peace?

[Darkstar]

Originally posted by Smiley
Darkstar, do you work in aerospace down at Huntsville?

Yeppers. I work for NASA.

[Darkstar]

Originally posted by Boris Godunov
The fringes, such as our arm, are where you're going to have to look, because the interior is to irradiated to support life-bearing planets.

See, that's just the wrong answer. We are delicate about those matters, but anything that actually evolved there wouldn't be.

Now, if we just want to find mammalian life, then we know *precisely* what to look for... earth like worlds with one or more large satellites that receive a certain amount of radiation, and has undergone several large killing incidences so as to create an environ to allow mammals to become the dominate life form.

Of course, the desire to find "mammalian" life is probably more out of some teenage Star Trek fantasy then genuine interest in finding real intelligent life, but heh, I suppose that's the only hope until "holo-decks" are invented and installed in some people's houses.

[Darkstar]

Originally posted by Odin
Life is NOT a freak occurance. It can start anywhere with a source of liquid water, energy (lighting, UV light, heat from hydrothermal vents), and organics. The question is whether higher (complex multicellular) life will evolve. I think that can't happen on a Europa-like world, a biosphere needs photosynthesis if it wants to get to get anywhere.

See now, you've made two bad assumptions.

#1) Water required. We don't know that. We just know that on EARTH, water is the medium of life. But there are so many other suitable mediums. Water, being H2O, just is very common, and if we presume all life is water based, then we are already narrowing our search to just near liquid water conditions. Follow the water, and you should eventually find life is the presumption. This works okay for us, so long as we are speaking about a very limited economics to use to search for life, but it isn't very realistic in terms of where life could be harboured, grow and evolve, and perhaps became intelligent enough for us to communicate with.

#2) You presume life requires sunlight. Very bad. Current science now presumes that all life began deep in the ocean, where no light was found. Down at the tectonic plate boundaries... living off the heat and chemicals down there. It is now thought that life spread from there to what we think of as the normal life-ecosystems here at the surface. Why is it thought that way? Because early conditions on earth was like at the smokers, not like here. Earliest evirons. Life merely requires a source of energy. There's plenty of multi-cellular beings living down there. And so long as the energy-economy allows for better utilization of the energy source (or their harverters), then you get diversity (that's evolution). So, for Europa, all it needs is a steady energy source. Why does Europa have a liquid world ocean? Because of gravitational flexes caused by Jupiter in Europa's rocky core, generating pressure and heat. So, as long as things remain the same around Jupiter for Europa (on planteray scale), it will continue to flex, and give off energy.

[Lung]

Originally posted by St Leo
Are we talking intelligent as in dolphins frolicking in the sea or intelligent as in humans building New York and selling Big Macs?

If you can convince people to fork out money for McDonalds then you must be smarter than any dolphin

[Urban Ranger]

Originally posted by Darkstar
#1) Water required. We don't know that. We just know that on EARTH, water is the medium of life. But there are so many other suitable mediums. Water, being H2O, just is very common, and if we presume all life is water based, then we are already narrowing our search to just near liquid water conditions. Follow the water, and you should eventually find life is the presumption. This works okay for us, so long as we are speaking about a very limited economics to use to search for life, but it isn't very realistic in terms of where life could be harboured, grow and evolve, and perhaps became intelligent enough for us to communicate with.

While that's true, water is the best medium there is, as far as we know.

- It stays at liquid form for a very broad temperature range
- It is very efficient in carrying heat
- It is an excellent solvent
- Ice flows on water
- Water absorbs a broad range of harmful radiation

I probably forgot a few

[Darkstar]

We are liable to find all sorts of life on Titan; If so, it won't be using water in any form.

*Liquid* water isn't very common. *Frozen* and *gaseous* states are. Liquid is only available to you in very limited circumstances.

There are better things then water for everything you listed. We are just so self-centered and self-absorded that we simply refuse to believe that anything but "odd colored humans with some schmuck on their face" could possibly be out there. And the odds of that are effectively beyond infinity. But hey, why destroy the dream of a whole world of hot, amazon alien babes are out there, desperate to talk to someone on the galactic "internet".

[Odin]

Originally posted by Darkstar

#2) You presume life requires sunlight. Very bad. Current science now presumes that all life began deep in the ocean, where no light was found. Down at the tectonic plate boundaries... living off the heat and chemicals down there. It is now thought that life spread from there to what we think of as the normal life-ecosystems here at the surface. Why is it thought that way? Because early conditions on earth was like at the smokers, not like here. Earliest evirons. Life merely requires a source of energy. There's plenty of multi-cellular beings living down there. And so long as the energy-economy allows for better utilization of the energy source (or their harverters), then you get diversity (that's evolution). So, for Europa, all it needs is a steady energy source. Why does Europa have a liquid world ocean? Because of gravitational flexes caused by Jupiter in Europa's rocky core, generating pressure and heat. So, as long as things remain the same around Jupiter for Europa (on planteray scale), it will continue to flex, and give off energy.

I said COMPLEX LIFE needed photosynthesis. Read the post before you spew stuff I already know. Chemoautothrophy is enough to sustain microbes, but animals need oxygen, and oxygen comes from photosynthesis, which cannot occur on Europa.

Life is most likely to start in water because water can desolve more things than any other natural substance and because it expands as it freezes. I'm not ruling it out, I'm just saying it's unlikely

[Urban Ranger]

Originally posted by Darkstar
We are liable to find all sorts of life on Titan; If so, it won't be using water in any form.

We have a crystal ball, don't we?

Originally posted by Darkstar
*Liquid* water isn't very common. *Frozen* and *gaseous* states are. Liquid is only available to you in very limited circumstances.

And?

Originally posted by Darkstar
There are better things then water for everything you listed.

Individually, maybe. In every aspect, highly unlikely.

Originally posted by Darkstar
We are just so self-centered and self-absorded that we simply refuse to believe that anything but "odd colored humans with some schmuck on their face" could possibly be out there.

That maybe your own view.