There is a philosophy that says that if something is unobservable – unobservable in principle – it is not part of science. If there is no way to falsify or confirm a hypothesis, it belongs to the realm of metaphysical speculation, together with astrology and spiritualism. By that standard, most of the universe has no scientific reality – it’s just a figment of our imaginations.

Heat is the energy of random chaotic motion, and entropy is the amount of hidden microscopic information.

If necessity is the mother of invention, laziness is the father. The Einstein summation convention is the offspring of this happy marriage.

I’m afraid I am a bit of a technophobe – a nineteenth-century man caught in the twenty-first century. But there is one piece of technology that I would especially welcome: a device to automatically balance restaurant tables on all four legs so that they don’t rock back and forth.

I was from a poor Jewish family in the South Bronx. My father was a plumber, but when I was 16, he got sick and I had to take over. Being a plumber in the South Bronx wasn’t fun.

Every time a bit of information is erased, we know it doesn’t disappear. It goes out into the environment. It may be horribly scrambled and confused, but it never really gets lost. It’s just converted into a different form.

A lot of my research time is spent daydreaming – telling an imaginary admiring audience of laymen how to understand some difficult scientific idea.

I'm not an historian but I'll venture an opinion: Modern cosmology really began with Darwin and Wallace. Unlike anyone before them, they provided explanations of our existence that completely rejected supernatural agents... Darwin and Wallace set a standard not only for the life sciences but for cosmology as well.

There is so much to groak; So little to groak from.

[Richard Feynman] truly believed that if you couldn't explain something simply, you didn't understand it.