Take an outline map of the lower 48 U.S. states and four crayons. Can you shade in the map so that every state is a different color than each of its neighbors, without resorting to a fifth color? This ...

Imagine you're a mapmaker, ready to finish your masterpiece map of the world. The only thing left to do is add the colors. But how many colors do you need for the countries if you want to make sure no ...

In the 1970s, a remarkable thing was done; a computer was used to solve a math problem. This, in and of itself, was not remarkable. The difference engine could do it. But this problem was the first ...