The next topic is going to be black holes, and…

The next topic is going to be black holes, and this is a similar situation. Fifteen, twenty years ago black holes were sort of poised 1 on the boundary between theoretical physics and science fiction. A boundary that is more 2 than you might believe. But again, in the past fifteen years or so this has been converted into a standard topic in observational 3.

There are dozens, probably hundreds of objects we can point to in the sky and say, "yes those things are black holes." And so now, the current topic of research is do these things that we are pretty sure are black holes actually behave in the 4 bizarre, science-fiction manner that the theoretical physicists have been talking about for the past thirty or forty years. So, to what extent are these very exotic behaviors actually 5 in real life?