There are proofs that date back to the Greeks that are still valid today.

The greatest problem for mathematicians now is probably the Riemann Hypothesis.

We've lost something that's been with us for so long, and something that drew a lot of us into mathematics. But perhaps that's always the way with math problems, and we just have to find new ones to capture our attention.

Then when I reached college, I realized that many people had thought about the problem during the 18th and 19th centuries and so I studied those methods.

It's fine to work on any problem, so long as it generates interesting mathematics along the way - even if you don't solve it at the end of the day.

There are proofs that date back to the Greeks that are still valid today.

The definition of a good mathematical problem is the mathematics it generates rather than the problem itself.