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Re: Black Holes And Spaceships

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Posted by fred on January 29, 1998 18:44:47 UTC

: : : : : :Suppose I choose a large black hole. One large enough so that my space ship won't be torn apart by the gravitational gradient. : : : : : :Suppose my spaceship has an engine powerfull enough to provide some velocity away from the object in the centre of the black hole. Not very difficult, as long as the black hole is a big one. : : : : : :Then as long as my engine is stocked with fuel, I can escape the black hole. Can't I. : : : : : :My question is, using a fusion engine, whats the smallest black hole I could cross the event horizon and survive to tell the tale?? : : : : No, you would not be able to escape the : : : : singularity once you cross the event horizon. : : : : Inside the event horizon, light rays are curved : : : : inward towards the singularity. No matter how : : : : powerful your rockets are, you must end up spiraling : : : : into the singularity. All matter within the : : : : event horizon must follow a path that leads to the : : : : singularity. : : : :Not true. You are talking about particles that can not generate thrust and acceleration. My spaceship can.

: : Or to put it another way, as long as I can counteract the effect of gravity and maintain a forward velocity, no matter how small, I can eventually escape. I do not need to attain escape velocity if I have an engine that will keep burning long enough. : No, inside the event horizon all light rays curve : into the singularity. That is part of the proof : that there must be a singularity inside. It may : be a long, gentle curve, but eventually it must : lead into the singularity. For a truly gigantic : black hole where the gravity at the event horizon : is at or about 1g, your spaceship can cross the : event horizon without noticing anything unusual. : But once inside the event horizon, you must follow : the path that light rays take, and that will lead : your ship into the singularity. And as you approach : the singularity, tidal forces will become a problem : before actually reaching it. : I would agree , if we are talking about a singularity, but I am not. I am just talking about sufficient mass to create a large black hole. Not a small one, with a singularity in it. Also the tidal forces in such a large black hole would not be particularly bad.( Well, I would choose a black hole large enough to avoid such forces.). Anyway, even with a singularity in the centre, I am talking in terms of seriously big. Sufficiently big so that the g force at the event horizon is relatively small, and under such circumstances it is by no means inevitable that I MUST follow the path of a photon. Consider a comet, travelling at 20Kmps, it can not escape the sun. But I could, at far less velocity, as long as I avoid tidal forces and as long as I don't go too close to the sun and as long as my fuel lasts. The shuttle is boosted to near escape velocity only because it is more efficient to accelerate to escape velocity that to travel all the way at 10Kmph. Fact is, it could make it to any place in the universe at 10kmph, if only it had enough fuel - and time.

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