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I don't understand how Hawking radiation is significant. It's far less than the cosmic background radiation everywhere in the universe. (This is why we can't "s

by grinich 18y ago

I don't understand how Hawking radiation is significant. It's far less than the cosmic background radiation everywhere in the universe. (This is why we can't "see" black holes.)

jerf 18y ago
This is something like standing on Pluto and saying you don't see what's so bright about the sun. Why not come stand on the surface of the sun and then make up your own mind? Hawking radiation is not intrinsically weak. Hawking radiation as generated by a large blackhole is weak. Flashlights are not weak; flashlights as powered by my nearly dead batteries are weak. With a different spacetime configuration you can get arbitrarily strong Hawking radiation, just like you can get arbitrarily strong light using more power. Hawking radiation around a very small black hole tears it apart relatively quickly. The Universe does not seem to like playing games like this and it tends to wipe out any structure that permits causality violation (as any FTL drive would) in an unsurvivable blaze of either Hawking-radiation or in an explosion of the vacuum energy (see Hawking's work on what would happen if you towed a wormhole around enough at relativistic speeds to cause a causality violation). And by "unsurvivable", I don't mean "probably fatal to life but we might be able to engineer around it". I mean, "unsurvivable to the space-time structure in question"; whatever mass or energy happens to get in the way is orders of magnitude away from even affecting the outcome, let alone standing a chance of survival.
- grinich 18y ago
  Thanks for the great reply! I guess I'd only read about Hawking radiation with respect to black holes, and never considered its implications on a larger scale. Sounds like it has larger implications than I thought. Were you citing a specific paper by Hawking (towing a wormhole)? I'd like to read more.
  - thwarted 18y ago
    I haven't read the Hawking paper in question specifically, but the idea of towing a worm hole around is that you move one end of a worm hole for some period of time at relativistic speeds. Since as you approach c, time slows down, so the stationary end of the worm hole is further in the future than the one that was moved around. It's a pretty stock layman's example of how time travel could be possible and I'm sure Hawking has torn a, er, hole in it some how.

by grinich 18y ago

I don't understand how Hawking radiation is significant. It's far less than the cosmic background radiation everywhere in the universe. (This is why we can't "see" black holes.)

jerf 18y ago

This is something like standing on Pluto and saying you don't see what's so bright about the sun. Why not come stand on the surface of the sun and then make up your own mind? Hawking radiation is not intrinsically weak. Hawking radiation as generated by a large blackhole is weak. Flashlights are not weak; flashlights as powered by my nearly dead batteries are weak. With a different spacetime configuration you can get arbitrarily strong Hawking radiation, just like you can get arbitrarily strong light using more power. Hawking radiation around a very small black hole tears it apart relatively quickly. The Universe does not seem to like playing games like this and it tends to wipe out any structure that permits causality violation (as any FTL drive would) in an unsurvivable blaze of either Hawking-radiation or in an explosion of the vacuum energy (see Hawking's work on what would happen if you towed a wormhole around enough at relativistic speeds to cause a causality violation). And by "unsurvivable", I don't mean "probably fatal to life but we might be able to engineer around it". I mean, "unsurvivable to the space-time structure in question"; whatever mass or energy happens to get in the way is orders of magnitude away from even affecting the outcome, let alone standing a chance of survival.

grinich 18y ago
Thanks for the great reply! I guess I'd only read about Hawking radiation with respect to black holes, and never considered its implications on a larger scale. Sounds like it has larger implications than I thought. Were you citing a specific paper by Hawking (towing a wormhole)? I'd like to read more.
- thwarted 18y ago
  I haven't read the Hawking paper in question specifically, but the idea of towing a worm hole around is that you move one end of a worm hole for some period of time at relativistic speeds. Since as you approach c, time slows down, so the stationary end of the worm hole is further in the future than the one that was moved around. It's a pretty stock layman's example of how time travel could be possible and I'm sure Hawking has torn a, er, hole in it some how.