I think the issue is not so much one of "do aliens exist" but rather do they exist in a time frame concurrent to us. The universe is very old and will continue for a long time yet. Civilizations will rise and fall, species will come into existence and vanish in the blink of the universe's eye. I'm sure that if we could go to the Restaurant at the End of the Universe and look back we would see a great deal of alien life forms, civilizations and indeed intelligent life. The chances of life occurring in the universe are high but I'm sorry Oshyan, you'd have to out live humanity in order to get a chance of even hearing from it, let alone shaking its tentacle.
There is of course the
Drake equation follow the link for a detailed explanation.
Considerable disagreement on the values of most of these parameters exists, but the values used by Drake and his colleagues in 1961 were:
* R* = 10/year (10 stars formed per year, on the average over the life of the galaxy)
* fp = 0.5 (half of all stars formed will have planets)
* ne = 2 (stars with planets will have 2 planets capable of supporting life)
* fl = 1 (100% of these planets will develop life)
* fi = 0.01 (1% of which will be intelligent life)
* fc = 0.01 (1% of which will be able to communicate)
* L = 10,000 years (which will last 10,000 years)
Drake's values give N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10,000 =
10and a more modern value:
N = 7 × 0.5 × 2 × 0.33 × 0.01 × 0.01 × 10000 =
2.31So umm the odds don't look good, sorry
Richard