In our Universe, the laws of physics tell us all the possibilities for what’s allowed to conceivably exist, but only by actually observing, measuring, and experimenting with our Universe itself can we determine what’s truly real. In Einstein’s general relativity, one of the very first possibilities that was ever discovered was for a black hole: a region of space with so much matter-and-energy in one place that from within that volume, nothing, not even light, could ever escape. The flip side of... Read this story
