Science Questions

How can energy escape a black hole?

Wed, 24th Oct 2012

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David Michaels asked:

Hi Naked Scientists]


I have listened to pretty much all your podcasts, and have built up a lot of dumb questions, and knowing the only dumb question is the one not asked, I have loaded up. (I apologize if any of these have been covered, or if I should have figured them out.)


I saw a TV show on the Universe and it showed energy being ejected from a black hole; something that light itself can't escape from. How can this happen, and if it does, should the energy have had to go into the black hole in the first place, and if it did, should it have looked to us outsiders as if it took infinite time to go into the black hole, so how could there be enough time to see it come out ?


Great show, I wouldn't change a thing (except for having really naked scientists).





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@NakedScientists In re forum Q on energy from Black Holes: likely refers to jets from accretion disk (outside BH). Cf was tweeted by @sethzenz @sethzenz, Wed, 3rd Oct 2012

The jets from the accretion disk are excess angular momentum being ejected as matter tries to get into the black hole which is quite difficult to do.

This has nothing to do with the Hawking radiation which is a very weak radiation of energy based on the fact that the event horizon has a very slight temperature above absolute zero.

The reason for this is that the strong gravitational field gradient near a black hole's event horizon causes the normal virtual particle system of the quantum mechanical vacuum to be stressed so that some of the particle antiparticle pairs are split and one falls into the hole while the other escapes.

See  the Hawking Radiation Calculator to show small this theoretical radiation is. Soul Surfer, Wed, 3rd Oct 2012

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