Alien Civilisations like us extremely rare?

Not necessarily, that depends on how rare they are... you can pick some big number of chances but equally, you can pick some big denominator for the chance of it occurring.
 
I think @Angilion said the best thing so far, that until we find out how life starts then our knowledge is limited.

How do we know what we're looking for on other planets?

Have we ever found a living creature on another planet?
 
Hagar said:
Define civilised. Your area Greece 2-3000 years ago was fairly civilised. The Phoenicians and Egyptians ditto. Apart from science and better engineering and materials knowhow we have not noticeably become much more civilised.
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On the scale of cosmic existence, 300 or 3000 years makes no difference to the likely hood of coinciding in space and time with another local intelligence we would recognise, or could visit us.
 
Life exists elsewhere, the numbers and chemistry are not special. But the conditions for it to multiply is. But then again the distances (which means time) are unmanageable for most brains and we have only just tickled the surface.
 
EddScott said:
I've tended to believe that we are not the only inteligent life in the universe and the reason we haven't made contact is the reason neither has anyone else. Distance.
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Yes. As far as life-as-we-know-it goes, the nearest Earthlike planet is currently thought to be Kepler-186f, which is 580 light years away. That's about 6 trillion miles. That kind of distance is so immense I can't even fathom how far it is.

EDIT: actually there's this:

en.wikipedia.org

Proxima Centauri b - Wikipedia

en.wikipedia.org en.wikipedia.org

Which is four light years. Much closer.
 
The human race is about whose genes if any get off Earth to another long-term habitat before this one goes kaboom or fasizzle.

Will any human make it? Will we (humans) be intelligent enough?
 
RxR said:
The human race is about whose genes if any get off Earth to another long-term habitat before this one goes kaboom or fasizzle.

Will any human make it? Will we (humans) be intelligent enough?
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Well, the Mars One idea failed. And we may have World War III soon. So who knows.
 
something daft already!! said:
Earth could be the only place in the Universe where intelligent life has arisen says Prof Brian Cox.



I have often thought this to be so. What are you thoughts? We have never seen any evidence amongst the stars. We have been looking for a while now. While we can now identify some solar systems with planets, nothing so far has even hinted at life elsewhere yet.

metro.co.uk

Alien civilisation like us 'extremely rare' in the universe, says Brian Cox

While microbial life forms could be common, the physicist believes creatures like us are unlikely.
metro.co.uk metro.co.uk
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I think he said elsewhere that they may be as rare as one per galaxy i.e. the nearest would be andromeda which is... two million light years away or as near as impossible to contact. I suspect the exact argument varies as to context: this was to dismiss the threat of UFO's but the point is: they're rare. So rare as to be almost impossible. It relies on an an extremely improbable series of events such as a large satellite that keeps the planetary rotation stable so it doesn't flip-flip a stable star over immmense periods of time a stable carbon cycle a planetary system that doesn't become a hot jupiter like most (ours started out like that but due to unlikely orbital resonance amongst the outer planets it actually went into reverse) and a whole lot of other unlikely scenarios that its like winning the lottery multiple times over: it doesn't mean its impossible it just so astronimically unlikely that we are very rare indeed this planet took four and half billion years to come up with us thats a third of the age of the entire universe and for amost all that time life was no more advanced than a bacterium even where life exists intelligent life is by no means guaranteed. Or even likely. Life may be unlikely especially intelligent life but its not entirely a random prediction it is more likely in some scenarios than others thats where something known as the Drake equation comes in and its what the predictions of one per galaxy or even per universe comes from that even if you sift out all the unlikely scenarios theres still a few, a very few, that fall through the net.

Angilion said:
Maybe. That's something else we don't know about life. That's a long list that starts with what life actually is. It's not as clear-cut as it might seem. We operate on the "I know it when I see it" principle, but it's not really nailed down. Hence, for example, the debate about whether or not viruses are alive.
Yes. All known life is. But that's far too small a sample size to draw conclusions from. It might be as small as 1, with all known life descending from a single lifeform and thus sharing the very basics.
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Theres a reason to suppose other life will be carbon based though and its based in chemistry: carbon almost uniquely can exist in multiple forms and form long chains e.g.. hydrocarbons nothing else can do that silicon can exist in up to 4 atoms strung together before it falls apart hence science fiction stories of silicon based life but its a very poor relation to carbon. Carbon based compounds are so diverse and various that it even has its own branch of chemisty: organic.
 
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Blackjack Davy said:
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Theres a reason to suppose other life will be carbon based though and its based in chemistry: carbon almost uniquely can exist in multiple forms and form long chains e.g.. hydrocarbons nothing else can do that silicon can exist in up to 4 atoms strung together before it falls apart hence science fiction stories of silicon based life but its a very poor relation to carbon. Carbon based compounds are so diverse and various that it even has its own branch of chemisty: organic.
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Good point.

Though this thread is speculation up to and including entirely incorporeal life, so who knows? Or maybe some other species of carbon-based people somewhere created bona fide AIs long ago and then disappeared. Went extinct or did something we have no words for that took them out of the universe. Whatever the reason, they're not here any more in this scenario. But the AIs they created are and those AIs have evolved themselves over time. Maybe built themselves bodies to walk around in. Are they alive?
 
dowie said:
Not sure how you come to that conclusion, surely the argument in the OP is just that not only is some form of life rather rare but for life to develop as far as it has is so rare that we might be the only instance at this sort of level of evolution.
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because the chance we are the only living things in the universe is so low i feel like if we truly are surly god must be real lol
 
Isn't believing something in the absence of evidence the basis of religion?

Our inability to survey much of the universe doesn’t change the fact that we have yet to find any evidence that inteligent life exists anywhere other than here.

So just "feeling" like there *has to be* life elsewhere is its own leap of faith.

The univers is massive, allowing for many chance combinations, but *we don't know how many chances are required to produce intelligent life.*

Intelligent life may be so tricky to produce that it takes an entire universe to randomly produce the results we see on this planet(or anything like it)...one time.
 
Might be the same ocean, but its not the same boat.

I also do not think its a leap of faith, its a leap of current known facts and well unproven a good educated case. The universe is just to big for something else to have taken a grab and tried elsewhere.

I will agree our little blue dot is just lucky and we are doing great not looking after it.
 
SPG said:
Might be the same ocean, but its not the same boat.

I also do not think its a leap of faith, its a leap of current known facts and well unproven a good educated case. The universe is just to big for something else to have taken a grab and tried elsewhere.

I will agree our little blue dot is just lucky and we are doing great not looking after it.
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Considering something to be absolutely certain without any evidence of it is a leap of faith. A number of people have decreed that it's absolutely certain that there's life elsewhere and a number of people have decreed that it's absolutely certain that there's life at least as intelligent as humans elsewhere. Those are leaps of faith.

Saying something like "Given the size of the universe and the fact that the chance of life is non-zero, I think it's probable that there's life elsewhere" isn't a leap of faith. It's a small step of faith, maybe, but not a leap :) The faith being in assigning a probability to something when the probability of it is completely unknown.

Unless you get into the idea of the universe being infinite, of course. In that case, everything that's possible would have happened an infinite number of times.
 
It's time to refer to Douglas Adams (again).

Population of the universe: None. Simple mathematics tells us that the population of the Universe must be zero. Why? Well given that the volume of the universe is infinite there must be an infinite number of worlds. But not all of them are populated; therefore only a finite number are. Any finite number divided by infinity is zero, therefore the average population of the Universe is zero, and so the total population must be zero.

Now where's the old 0.999r=1 thread? :cry:
 
Feek said:
It's time to refer to Douglas Adams (again).

Population of the universe: None. Simple mathematics tells us that the population of the Universe must be zero. Why? Well given that the volume of the universe is infinite there must be an infinite number of worlds. But not all of them are populated; therefore only a finite number are. Any finite number divided by infinity is zero, therefore the average population of the Universe is zero, and so the total population must be zero.
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...and that any people you may meet from time to time are merely the products of a deranged imagination.

The thread seems to have taken a turn to the metaphysical thats usually the point at which I bow out lol.
 
Lysander said:
Yes. As far as life-as-we-know-it goes, the nearest Earthlike planet is currently thought to be Kepler-186f, which is 580 light years away. That's about 6 trillion miles. That kind of distance is so immense I can't even fathom how far it is.

EDIT: actually there's this:

en.wikipedia.org

Proxima Centauri b - Wikipedia

en.wikipedia.org en.wikipedia.org

Which is four light years. Much closer.
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I dislike the phrase "Earthlike" in this context because it has a very different meaning in astronomy than it does in daily usage and that leads some people to incorrectly conclude that Earthlike planets are like Earth. It just means that they're probably a roughly similar size to Earth and probably have a fairly similar gravity on the surface and probably have a solid surface and probably have at least some parts of the planet between 0C and 100C. That's it. An Earthlike planet isn't necessarily (and probably isn't) anything like Earth. It might be devoid of any atmosphere and be completely sterile. It might have a very dense atmosphere and rain concentrated acid. It might be highly irradiated by the star it orbits. It might have no seasons, which would be a problem for life. It might be tidally locked to its star with half the planet being extremely hot and half being extremely cold and frequently having 500mph storms. Earthlike doesn't mean like Earth. It might not even be Earthlike in the astronomy sense because measurements aren't certain at the distances involved.

dave28 said:
We are the Aliens of space lol
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I'm an alien and so is my wife!
 
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