But a machine that was powerful enough to accelerate particles to the grand unification energy would have to be as big as the Solar System - and would be unlikely to be funded in the present economic climate.

Someone told me that each equation I included in my book would halve the sales. I did put in one equation, Einstein's famous equation, E = MC squared. I hope that this will not scare off half of my potential readers.

It is impossible to imagine a four-dimensional space. I personally find it hard enough to visualize a three-dimensional space!

[On President Bush's plan to get to Mars in 10 years] Stupid. Robots would do a better job and be much cheaper because you don't have to bring them back.

Observations indicate that the universe is expanding at an ever-increasing rate. It will expand forever, getting emptier and darker. Although the universe doesn’t have an end, it had a beginning in the Big Bang. One might ask what is before that but the answer is that there is nowhere before the Big Bang just as there is nowhere south of the South Pole.

In effect, we have redefined the task of science to be the discovery of laws that will enable us to predict events up to the limits set by the uncertainty principle.

Because there is a law such as gravity, the Universe can and will create itself from nothing.