Black hole comes in all sizes ranging from microscopic black hole on a quantum scale to supermassive black hole that resides in the center of probably every galaxy. Photon have no rest mass hence they can go at roughly 300000000 m/s in vacuum, on the other hand black hole contain lots of mass concentrated in a tiny region of space. I am curious whether a black hole perhaps even micro black hole (assuming it doesn't disappear immediately) could move at speed of light in theory or do I treat them like any star? (Angular momentum do not count)

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    $\begingroup$ No, a black hole can not move at the speed of light in vacuum because (as you stated) it has mass. Nothing that has mass (no matter how slight) can move at the speed of light. $\endgroup$ – hft Sep 28 '15 at 2:14
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    $\begingroup$ A proper answer is probably a bit more involved than it at first seems. You would have to start with an actual definition of a black hole (i.e. of an event horizon, the surface separating regions of spacetime capable of communicating to future null infinity). Then you realize event horizons are themselves null surfaces so it becomes tricky to even think how they are moving at anything but the speed of light. So you'd have to work to reconcile these global and local properties, etc. $\endgroup$ – user10851 Sep 28 '15 at 2:22
  • $\begingroup$ The simple answer is what hft said, anything with rest mass can't travel at the speed of light and things as heavy as stars rarely travel close to that speed. So, yes, treat black holes as any star in terms of movement, velocity, momentum, etc. Now a micro black hole, if they exist and I think they don't, could only be created in stupendously and probably impossibly energetic circumstances, so if those actually do exist, they might travel close to the speed of light, but that's theoretical. I like Chris White's answer too. $\endgroup$ – userLTK Sep 28 '15 at 5:00

If a black hole travels from point A to point B, long distance at the speed of light you can say it's a wormhole.


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