Since the first detection two years ago, gravitational waves have promised to revolutionize our understanding of astrophysics. But to understand what the gravitational waves are telling us, we need to understand how these relativistic systems formed in the first place.
I will describe how binary black holes form in the cores of dense star clusters by simple, Newtonian gravitational interactions. I will demonstrate how these dynamically-formed binary black holes can easily explain most of the signals that LIGO has detected so far, and what distinguishes them from similar systems formed by the evolution of binary stars. Finally, I will discuss how we can potentially discriminate between different formation scenarios, and what this can tell us about astrophysics.