It will not be humans who watch the sun's demise, six billion years from now. Any creatures that then exist will be as different from us as we are from bacteria or amoebae.

Some claim that computers will, by 2050, achieve human capabilities. Of course, in some respects they already have.

In the beginning there were only probabilities. The universe could only come into existence if someone observed it. It does not matter that the observers turned up several billion years later. The universe exists because we are aware of it.

I'm a technological optimist in that I do believe that technology will provide solutions that will allow the world in 2050 to support 9 billion people at an acceptable standard of living. But I'm a political pessimist in that I am concerned about whether the science will be appropriately applied.

One of the computer models for a four degree temperature rise would give rise to a 10 degree temperature rise in Africa. And bear in mind also that in the depth of an ice age the mean temperature drop compared to the present was five degrees.

I think all countries need to aim to cut the CO2 emissions per person, taking account of externalities like imports and exports.

All the atoms we are made of are forged from hydrogen in stars that died and exploded before our solar system formed. So if you are romantic, you can say we are literally stardust. If you are less romantic, you can say we're the nuclear waste from fuel that makes stars shine.