There’s more to that question than meets the eye. Black holes ain’t like nothing else in the Universe, havin’ all kinds strange quantum properties as well as some curious gravitational ones too. So when it comes to cruisin’ the cosmos, do black holes move like classical objects such as stars or like quantum objects such as photons?
Carol “Kilo” Herzeneberg, some kinda freelance scientist in Chicago, has done some calculatin’ n’ computin’ and come up with an answer. She reckons that big black holes move-to-the-groove like stars and small black holes get-down-to-the-beat like photons. And the threshold between these behaviours occurs for a black hole about the size of a nucleon.
That might sound lil but a black hole that size would have mass of about 2 trillion kilograms (2 x 10^12 kg). That’s about the mass of Wyoming, which is about as close as you can get to a black hole on Earth.
Here’s something for Kilo Herzenberg to Gedanken about: how many of these things are a-floatin’ and a-driftin’ round the cosmos and what’s the probability of one of them popping into existence anywhere near Earth in my life time?
Ref: arxiv.org/abs/0709.1741: How do Black Holes Move, as Quantum Objects or as Classical Objects?