Given that lives need to live on planets I will work out how many planets exist.

Ok lets try and work out how many planets their are...

For arguement and simplistic sake lets state that each star has 10 planets. But we don't know yet as extrasolar planets have proved to be a rare find.

The milky way contains ~1x10¹¹ stars, lets take this as an average sized galaxy.
(source: http://curious.astro.cornell.e.....?number=31)

There are an estimated 5x10¹¹ galaxies
(source: http://imagine.gsfc.nasa.gov/d.....1127a.html)

I'm not too good with formulas so forgive me if I do this wrong.

= Planets per star
= Stars per galaxy
= Galaxies per universe

Going by the formula .

10x1x10¹¹x5x10¹¹ = 5x10²³

Out of all those planets I would suspect millions, if not, billions can support life.

And is life only exists in earth like conditions for example

Goldilocks zone,
liquid water,
abundance of elements such as Carbon, Oxygen, helium, Iron etc...
1G of gravity (G not meaning one galaxy of stars as previously stated :))
and so on...

Then it is hard to believe that life does not exist. I also strongly believe that the rare earth hypothesis is incorrect and life can thrive in harsh conditions, like an extremophobe here on Earth. Also who says that Si based lifeforms don't exist???

You could have just written Statistical probability.

Using simple probability everything points to another races living on other planets. I also don't see why other races need 1 g since they will just have adapted to whatever gravitational pull their planet has. We also don't know any of your variables, P,G, or U at the moment so your number could very well be larger or smaller.

Well the other planets must exist for a reason.

If you want to believe you evolved from a tadpole that's your choice.

I must have missed something. Did anyone here mention or even imply evolution?

that's a pretty common rational there highway.

I was expecting the slightly juicier "why aliens exist... and have been to earth!"

I think you need more Tom Cruise in your life stof.

Of course, that is assuming we were created for a reason. I believe there is extraterrestrial life somewhere in the universe. Considering the HST detected over 3,000 visible galaxies, I would have to say complex life exists somewhere in the universe besides earth. Is it possible that humans are the only complex life in the Milky Way? Yes, I believe that is a distinct possibility and is probably the case. I know some have postulated that silicon, chlorine, sulfur and a few other types of atoms may be the basis for extraterrestrial life, but I have reservations about them

Yeah, the probabilities do demonstrate that it is likely that life exists throughout the galaxy but (unfortunately) they also indicate that it is highly unlikely that there is intelligent life near by that exists in the same time period as we do ...

My personal theory is that if a species became intelligent enough to start traveling to other planets and solar systems they probably would be intelligent enough to start teraforming planets in order to colonize them (or possibly just to spread life). So it is possible that life is far more common than our simple probabilities would lead us to believe, but that it would have pockets where it was dense and it would be sparse throughout most of the galaxy.