Event Horizons

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22 years 5 months ago #2445 by tvanflandern
If a "black hole" consisted of classical space and time, then any spacecraft inside the event horizon need only keep up a slow, steady thrust that exceeds the force of gravity at that point, and it will eventually pass through the event horizon and escape. Its speed need never exceed a snail's pace. But in GR, space and time get inverted inside an event horizon, and such "common sense" considerations do not apply. Mathematically, the event horizon is a special barrier between the hole and the outside universe.

But we are speaking of fictional mathematical concepts here. They can be built with whatever properties one's imagination chooses. -|Tom|-

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22 years 5 months ago #2448 by ohlman
Replied by ohlman on topic Reply from Vaughn Ohlman
<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>


But we are speaking of fictional mathematical concepts here. They can be built with whatever properties one's imagination chooses. -|Tom|-


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Kind of like fairy tales eh? Or star trek weapons?

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22 years 5 months ago #2476 by Jim
Replied by Jim on topic Reply from
People are too serious about blackholes. They are(or not) fiction and I wonder if you were to stuff enough mass into one to fill it up what would happen? The people how do very deep studies of blackholes say a hole simply stops working after a while and evaporates. I guess when
that happens it must become something else.

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22 years 5 months ago #2477 by Jim
Replied by Jim on topic Reply from
The math of an event horizon would produce an excape velocity that is more than the speed of light and still not stop light from exiting the blackhole. A blackhole the mass of the sun would have a g=10E14m/s2 and the light would simply redshift. More mass would produce more redshift but the photons would still exit the area anyway.

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22 years 2 months ago #2958 by n/a1
Replied by n/a1 on topic Reply from john duff
I recently did some calculations that might apply to this question. The problem came up as to how big (massive) a black hole would have to be to produce an Fg of 9.8 m/sec^2 at the Swartzchild radius. The answer works out to be about 0.485 lt. yr., with a mass of about 1500 Milky Way galaxies.

Such an object would produce no significant tidal stress.
If the mass were distributed uniformly throughout the volume (picture a large hydrogen cloud), it would be a pretty good vacuum.

And in Newtonian physics, there would be no reason a photon (or a rocket ship) couldn't travel from inside Rs to outside, although it could never escape the hole. Unless it refueled itself once it was outside.



John Duff

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