We have observed visible objects (stars) that are close enough to be orbiting a supermassive black hole and they follow the expected orbits. If supermassive bl

We have observed visible objects (stars) that are close enough to be orbiting a supermassive black hole and they follow the expected orbits. If supermassive black holes do something new and strange with gravity--something big enough to affect an entire surrounding galaxy--it seems likely it should somewhat affect the trajectories of the nearest objects too. That's not to rule out something strange about black hole gravitation, but the observations do constrain some versions of how strange things can be.