if you accept that the universe is infinite, then it would be impossible for us to be alone, even if the universe isn't infinite - the hundreds of billions of galaxies, each with millions of star systems and hence planets means you can be 100% certain of life on other planets (or as close to 100% as is statistically significant)
there is a famous equation - its great because you can just plug your own numbers in....whatever you think!
The Drake equation states that:
N=R x f
p x n
e x f
l x f
i x f
c x L
where:
N = the number of civilizations in our galaxy with which communication might be possible;
and
R* = the average rate of star formation per year in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
f[ch8467] = the fraction of the above that actually go on to develop life at some point
fi = the fraction of the above that actually go on to develop intelligent life
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time such civilizations release detectable signals into space
using best guess figures for example gives you:
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 developing 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).
so using these figures, multiplying them all together gives you N=10 (ie currently 10 civilisations in our galaxy that could communicate with us).
so 10 civilistaions in each galaxy times 100 billion galaxies gives you some idea of how not alone we are
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Topic: are we alone?....... (Read 1494 times)