### The many ways of building an empty, unchanging universe

Finding the general laws of nature is only the first step towards a physical description of the world. As a second step, indispensable when it comes to comparing theory with observation, physicists need to find simple models governed by those laws. For ...

### How many different kinds of black holes are there?

The collapse of a body to form a black hole can be a very dynamic and complicated event. But once the dust has settled, the evolution has played itself out and the system has calmed down, how many different types of black holes are there? How many kinds of ...