Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Evaporating black holes, a kind of flux of space?

  1. Sep 11, 2010 #1
    If a black hole can "evaporate" via Hawking radiation then there is a radial flux of energy from the black hole? Put a box around on such evaporating black hole. When the black hole is gone there is less space in the box? If so is that space carried away by the Hawking particles?

    Thanks for any help!
     
  2. jcsd
  3. Sep 12, 2010 #2

    Chalnoth

    User Avatar
    Science Advisor

    I assume you're talking about a perfectly transparent box, just a hypothetical region around the black hole? I don't really know how you would go about making any sort of statement about how much space there is within the box in the first place.
     
  4. Sep 12, 2010 #3
    I thought General Relativity allowed us to measure volumes of regions with and without mass inside? The ratio the the radius to the circumference of some region gives a measure of the mass inside that region? A region with more mass has a greater volume then the same region with no mass?

    Thanks for your time!
     
    Last edited: Sep 12, 2010
  5. Sep 12, 2010 #4

    Chalnoth

    User Avatar
    Science Advisor

    No, General Relativity really doesn't talk about volumes directly.

    Perhaps you were thinking about an entire universe? If we take a universe with a black hole and a positive cosmological constant, that universe has a future horizon. Anything that happens beyond this horizon "now" will never reach us (a global now is a bit arbitrary, but if we say that "now" is the time at which different places see the same CMB temperature we currently see, we can talk sensibly about it). Similarly, anything we release now (whether light rays or something else) will never reach anything that lies beyond that horizon.

    After the black hole evaporates and the radiation all redshifts away, the horizon is larger than it was with the black hole there.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook