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I What would happen if you moved a black hole?

  1. Feb 27, 2017 #1
    Ignoring for the moment the plausibility of this scenario, what would happen? A black hole is the ultimate gravity well, right? In some circles, they're even considered tears in the fabric of the universe. So what would happen to that fabric if you moved the black hole?

    Would it behave like, for instance, air or water currents do when an object passes through it? Or would it move as if it were "friction-less," for lack of a better term?

    Keep in mind, I'm pretty ignorant. I just had this idea and wanted an answer.

    Thanks in advance.
  2. jcsd
  3. Feb 27, 2017 #2


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    probably not in any mainstream science circles that I am aware of
    please provide a valid source for that claim
    if you cannot, then there isn't really any point discussing sci fi
  4. Feb 27, 2017 #3
    Not really relevant to the question, more of a flavor text than anything. The question still remains: what would happen if you moved a black hole? Better yet, what is happening because the black holes are moving? How is space-time reacting to that movement?

    Please keep in mind, I'm the ignorant one, as I admitted frankly and without qualification in my initial post. It would be kind of hard to cite a fact that I myself admitted I don't have. If I'm wrong, I'd value a correction over a dismissal.
  5. Feb 27, 2017 #4


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    There isn't really anything special about a black hole moving, any more than any other object moving. For example, if you could compress a planet to a tiny black hole, then it would continue to orbit the Sun in the same orbit as before.

    Likewise, any black hole moves in response to the gravity of other objects, such as stars, planets and, of course, other black holes.
  6. Feb 27, 2017 #5


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    Well, space-time is modeled as a type of field, and a field is simply a mathematical way of describing interactions between objects (or even other fields) by way of assigning values to points in space and time. The values can describe something like a vector force, as the classical E&M field does, or it can describe the very complicated geometrical properties of space-time. The motion of a black hole just means that these values change. Once the BH moves past a region the values (may) return to their previous states, or at least something close to their previous states.
  7. Feb 27, 2017 #6
    Thanks for the replies, you guys, that pretty much answers my question. Especially the part about the nature of fields.

    Thanks again for entertaining a rube like me.
  8. Mar 4, 2017 #7
    It's perhaps worth pointing out that in many ways black holes are so extraordinary simply because they are so small. They are small enough to let an observer get close to the centre of mass where peculiar things happen, but at "normal" distances from the centre of mass space-time is pretty much as we'd expect it to be. If the Sun was (magically) replaced by a black hole of the same mass (and didn't emit torrents of Hawking radiation) the only obvious effect on the rest of the solar system would be that it had got dark.
  9. Mar 4, 2017 #8


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    really ? what is your definition of small ? ....
    I doubt that that is an accurate statement considering for example, the BH at the centre of our galaxy is estimated to be in the order of hundreds of thousands to billions of solar masses

    Physical size is going to vary and for BH's that continue to accumulate mass, they will continue to grow in size
    Last edited: Mar 4, 2017
  10. Mar 4, 2017 #9
    Something movable? Okay, I wasn't thinking of supermassive black holes. But stellar-mass black holes have radii of a few km, to tens of km, which is small by most astronomical standards.
  11. Mar 5, 2017 #10


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    It wouldn't. Hawking radiation is black-body radiation, and the effective "temperature" of the surface of a black hole is inversely proportional to the mass. A sun-sized black hole has a temperature of only a few nanokelvins, so is "colder" than the space around it; it absorbs more energy from the cosmic background radiation than it emits as Hawking radiation.
  12. Mar 5, 2017 #11

    Vanadium 50

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    It would be somewhere else. That's pretty much it - nothing special happens.

    To add to Nugatory's response, the sun's luminosity would be 55 orders of magnitude less if it were a black hole. The luminosity would be one octillionth of a watt.
  13. Mar 5, 2017 #12
    All motion is relative, therefore, moving a black hole is equivalent to moving yourself, so conduct an experiment...

    1. Move.
    2. Record your observations.
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