An illustration of heavily curved spacetime for a point mass, which corresponds to the physical scenario of being located outside the event horizon of a black hole. As you get closer and closer to the mass’s location in spacetime, space becomes more severely curved, eventually leading to a location from within which even light cannot escape: the event horizon. The radius of that location is set by the mass, charge, and angular momentum of the black hole, the speed of light, and the laws of General Relativity alone. (Credit: JohnsonMartin/Pixabay)

How low-mass black holes bend space the most

The strongest tests of curved space are only possible around the lowest-mass black holes of all. Their small event horizons are the key.

One of the most mind-bending concepts about the Universe itself is that gravity isn’t due to some unseen, invisible force, but comes about because the matter and…