Bluedun wrote:Well, this is or has been the view of some, notably Carl Sagan, the SETI man. However, no one really has much if any idea of the probabilities of life emerging on a suitable planet, even if we can estimate how many suitable planets there actually are. We don't even know exactly how life came to be on our own.
It only makes sense to talk about existence of other life in our own galaxy, other galaxies being too remote to ever communicate with, leaving out the SF nonsense. Estimates for numbers of other civilisations in our galaxy have varied from millions down to a handful.
At present we are confronted by the Fermi Paradox: if there are so many others out there, why is there no evidence for them? SETI has been listening out for some years now without success. There may be some somewhere, but my hunch is there are very few, and possibly none.
No, we are not actually confonted by any Paradox - there are quite likely to be other intelligent civilisations out there, probably many.
The problem is the failure of most of the human race to get their head round the reason why we can't find any evidence - its the distance -it is just so far away from one star (and therefore one planetary sytem) to another.
Even radio waves are going to decades, or hundreds or thousands of years to reach other planets. We are going to have to wait an awful long time for the the chance of another civilsation receiving it and sending back a message which we then receive.
The speed of light is very roughly 10 million miles a minute. If you send out a signal that you wanted to reach just a few thousand stars (and therefore potentially habitated planets to receive) it would need to encompass at least a few hundred light years.
Just do the maths and you can see how far away planets are : eg those that are 100 light years away:
100 years x 365 days x 24 hours x 60 minutes x 10million = I believe that comes to somewhere around 500 trillion miles.
And then we actually talk about aliens coming to visit us in spaceships - its a long way to come just to be nosey