There are many different kinds of radioactive waste and each has its own half-life so, just to be on the safe side and to simplify matters, I base my calculations on the worst one and that's plutonium.

People have alleged that I have inspired many young people over the years, but I say, it was just the opposite.

Overpopulation is perhaps the biggest problem facing us, and immigration is part of that problem. It has to be addressed.

Have fun saving the world, or you are just going to depress yourself.

There is more inside you than you dare think.

If something's going wrong with this planet we'd better fix it here and not look for some sort of escape.

I'm always impressed with what young people can do before older people tell them it's impossible