Know how to solve every problem that has been solved.

'Conservation' (the conservation law) means this ... that there is a number, which you can calculate, at one moment-and as nature undergoes its multitude of changes, this number doesn't change. That is, if you calculate again, this quantity, it'll be the same as it was before. An example is the conservation of energy: there's a quantity that you can calculate according to a certain rule, and it comes out the same answer after, no matter what happens, happens.

The electron is a theory we use; it is so useful in understanding the way nature works that we can almost call it real.

But there is nothing in biology yet found that indicates the inevitability of death.

The worthwhile problems are the ones you can really solve or help solve, the ones you can really contribute something to... No problem is too small or too trivial if we can really do something about it.

It is surprising that people do not believe that there is imagination in science. It is a very interesting kind of imagination, unlike that of the artist. The great difficulty is in trying to imagine something that you have never seen, that is consistent in every detail with what has already been seen, and that is different from what has been thought of; furthermore, it must be definite and not a vague proposition. That is indeed difficult.

I don't feel frightened by not knowing things, by being lost in the mysterious universe without any purpose - which is the way it really is, as far as I can tell. Possibly. It doesn't frighten me.