Are we alone in the universe

[Bazile]

Astronomers are searching for signs of other life out there in the Milky way and other galaxies .

They appear to be looking for planets that have the same elements that supports life here on earth - eg oxygen etc .
Why do thery assume that other civilisations - if any are out there - would have developed with the same physiology as humans ?
Surely they could have developed on planets with conditions that would be otherwise lethal to humans

Dont they run the risk of missing discovering these other beings , simply by basing their search on the above assumption ?

[boink]

i imagine they're trying to bring the odds of finding one down a little, due to the fact that all they have to work with is what they know, and thats our solar system, and they know theres no living Beings on any of our planets except ours.

[trevHCS]

There seem to be 2 main approaches.

1) Look for planets with the same kind of atmospheres. Even if you find that it doesn't guarantee anything will be there and there's the problem of non-carbon based lifeforms.

2) Listen for radio signals like SETI does which at least has a chance of finding intellegent life. However considering the distances involved, it could take a while to hear them.

I guess there's also the concept of diving into the Roswell base, but I suspect even the CIA wouldn't be stupid enough to actually keep anything there. A nice distraction however.

[heathfield]

Most of the oxygen in the Earth's atmosphere originated as a waste product from early life-forms. A planet with a similar atmosphere would have to have had the same or similar lifeforms to produce the oxygen. That's asking a bit much, unless you subscribe to the theory that life here originated in outer space, and the Earth and other planets could be 'seeded'.

[jake-the-peg]

There will be a limited number of solutions to the chemistry of life.

Because we know that water and Oxygen are essential parts to the only solution we know for certain works it makes sense to base any search on that.

There are other better tests for life such as chirality ( left handed or right handed molecules) but testing for that over huge distances is pretty tough.

It's basically a case of seeing if there's any "low hanging fruit" out there

[Llamatron]

What if, we are alone.
What if we are simply the first creatures to develop this far.
So there may not be anyone else along for millions of years.

Now that's depressing.

[Bazile]

There is that possibility Llamatron .
Surely however, given the billions of stars out there - by the laws of probability , there ought to be ( or have been ) other life forms some where out there