We are not alone...probably
According to researchers at Edinburgh University we share the galaxy with at least another 361 intelligent civilisations, and there may be as many as 38,000 planets supporting alien lifeforms.
Something about the preciseness of the first figure (how can they be so sure it's not 362?) and the vagueness of the second, gives you a clue as to the nature of this research: we're talking statistical probabilities here - mathematical extrapolations - rather than hard empirical evidence.
Even so, that doesn't mean that the data being fed into the computer model is entirely spurious. The Edinburgh team combined the latest criteria on the conditions thought to be necessary for life - the so called "Goldilocks zone" around a star where it's neither too hot nor to cold - with the latest information about planetary formation from astronomical observations.
The researchers looked at three scenarios for how life could develop. In the first they assumed that it was relatively difficult for life to get started, but easy for it to evolve once established - that scenario produced the figure of 361 intelligent civilisations.
A second scenario assumed that life was a much more common phenomenon, but that intelligence was rare. In a third, they included the possibility that life could be transferred from one planet to another by asteroid collisions. That scenario produced the figure of 38,000 planets supporting life.
Duncan Forgan, who led the team, says: "It's important to realise that the picture we've built up is still incomplete, and even if alien life forms do exist, we have no idea what form they would take."
Still, it's an encouraging thought to know that, statistically speaking, we're probably not alone.
I'm Tom Feilden and I'm the science correspondent on the Today programme. This is where we can talk about the scientific issues we're covering on the programme. 
Comment number 1.
At 15:33 6th Feb 2009, Dusty_Matter wrote:Those figures are definitely optimistic rough guesses, and there are many scientists that would disagree with those figures. The book “Rare Earth” gives an excellent example of showing just how rare life might be for our galaxy. That life will just pop up anywhere from a mixture of chemicals, is a very implausible concept. This is a topic that has a lot of debatable parameters, and so like string theory, they can make up whatever math formulas they want because there is no proof for any of it.
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Comment number 2.
At 16:16 22nd Mar 2009, eanassir wrote:I am certain we are not alone.
Will all this universe be for us alone?
The earth is a very small planet in relation to the extremely tremendent universe; is all the universe created for us only? This can't be any logical idea.
When America was not yet discovered, was it not inhabited by a completely distinct human race: Red Indians? While all the rest of people did not know there are such Red Indians.
The condition will be similar concerning Mars.
Mars has a clear atmosphere, with clouds drifted by the wind, there is water on the poles and on the tops of mountains in the form of ice; glaciers have been discovered there; in addition to the recent discovery of liquid water.
https://universeandquran.t35.com/
https://universeandquran.t35.com/new_page_2.htm
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Comment number 3.
At 16:32 22nd Mar 2009, eanassir wrote:((Life is transmissible from the broken up planets to the newly formed planets))
It cannot be that life comes from one planet to another as such.
But life is transmissible from the broken up past planets to the newly formed or present planets.
https://universeandquran.t35.com/new_page_2.htm
The indication that there were such broken up past planets is the large number of meteoritic rocks, some of which fell and is still falling everynow and then on Earth and the rest of the planets.
Some of such meteoritic rocks have some amino acids discovered on them, like the Murchison's meteorite.
https://universeandquran.t35.com/new_page_2.htm
If we imagine the earth when its Doomsday comes and it will break up into many pieces, then the seed of life will be carried by such pieces of the broken-up Earth: in the form of seeds of plants, branches of trees, corpses of dead animal and man in addition to encapsulated bacteria, fungus and other kinds of monocellular microorganisms.
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