I have sold more books on physics than Madonna has on sex.

One does not have to appeal to God to set the initial conditions for the creation of the universe, but if one does He would have to act through the laws of physics.

There could be whole antiworlds and antipeople made out of antiparticles. However, if you ever meet your antiself, don't shake hands! You would both vanish in a great flash of light.

One might think this means that imaginary numbers are just a mathematical game having nothing to do with the real world. From the viewpoint of positivist philosophy, however, one cannot determine what is real. All one can do is find which mathematical models describe the universe we live in. It turns out that a mathematical model involving imaginary time predicts not only effects we have already observed but also effects we have not been able to measure yet nevertheless believe in for other reasons. So what is real and what is imaginary? Is the distinction just in our minds?

I don't think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I'm an optimist. We will reach out to the stars.

I’m the archetype of a disabled genius, or should I say a physically challenged genius, to be politically correct. At least I’m obviously physically challenged. Whether I’m a genius is more open to doubt.

When I hear of Schrödinger's cat, I reach for my pistol.