The humor of Stephen Hawking

I'm just finishing reading A Brief History of Time. At best, I think I've understood about one-third of it, much of the rest has just been a mind-numbing mechanical exercise involving simply moving my eyes across the words on a page. But it's been absolutely fascinating, nonetheless. Here are a couple of fun excerpts:

We know that every particle has an antiparticle, with which it can annihilate. (In the case of the force-carrying particles, the antiparticles are the same as the particles themselves.) There could be whole antiworlds and antipeople made out of antiparticles. However, if you meet your antiself, don't shake hands! You would both vanish in a great flash of light.

The movement of the earth in it's orbit around the sun produces gravitational waves. The effect of the energy loss will be to change the orbit of the earth so that gradually it gets nearer and nearer to the sun, eventually collides with it, and settles down to a stationary state. The rate of energy loss in the case of the earth and the sun is very low - about enough to run a small electric heater. This means that it will take about a thousand million million million million years for the earth to run into the sun, so there's no immediate cause for worry!