John Preskill

But towards the end, he looked up at the clock and he said, look, we've only got...

eight minutes left.

And this particular problem we're talking about, he said, there's two ways of tackling it.

One's very elegant and clear and easy.

And the other one is just incredibly messy.

He said, but we've only got a little time left.

So I'll just deal with the incredibly messy one.

And I thought, well, this was great.

Although that was the only official undergraduate class that Feynman taught at Caltech, there was an informal class of which he taught for many years.

It was not in the catalog.

It was not documented anywhere.

The freshmen called it Physics X. It was intended especially for freshmen.

And by word of mouth,

it would become known that Feynman was going to be in a certain classroom at a certain time and that you could come and interact with him.

Not in the catalog.

No grades.

What was it?

It was Feynman standing in front of the blackboard saying, ask me anything.

And there were rules.

The rules were, don't ask me about coursework.