Question: Do you believe that there is another life somewhere in the universe?

Keith Brain answered on 17 Jun 2010:

That is a tricky one. My feeling is that if life has evolved here, then the Universe is big enough and old enough for it to have started elsewhere too. However, the conditions for life are likely to be very special (eg. on planets of the right size, not too close and not too far away from their sun or suns, made of the right stuff), and so the nearest like forms are likely to be a very long way away.

This isn’t a great argument, because conditions around the earth are “special” – we know that they are “special” because we’re here to think about such questions! So, we have to be very careful about inferring things about the rest of the universe just by looking at our very special earth.

Of course, I’m quite open to being wrong about this. There are a series of Philosophical argument, based around something called the “Anthropic principle”, that try to get to grip with this – you might want to search the net for more on this, but its pretty tricky stuff.