Baby Astronaut Posted January 1, 2009 Share Posted January 1, 2009 When I first learned about black holes in a documentary, they said you could not realistically approach it because the gravity strength increased exponentially by the millimeter, or something to the effect that parts of your ship would crumble away forward one layer at a time by the sheer difference of gravity between the ship's nose and its tail. But nowadays I read about objects never reaching the black hole, and instead of a "tug" on the ship, the gravity is really just space being warped thus forcing a traveler along a slow circular descent towards the black hole. Which doesn't sound as if what I learned previously is valid anymore. Will someone illuminate me on this? Will a ship or asteroid nearing a black hole be torn apart due to the colossal gravity difference acting between the various parts of either object? Link to comment Share on other sites More sharing options...
big314mp Posted January 1, 2009 Share Posted January 1, 2009 The different gravity analogies that you list are all compatible. The object will circle in slowly when it is at a distance. Once it gets close enough, however, the gravitational field (or spacetime curvature if you prefer) changes so quickly that the object becomes shredded. It all depends on how fast the gravitational field strengthens, which is a function of distance to the black hole (among other things, like mass). Link to comment Share on other sites More sharing options...
Mr Skeptic Posted January 3, 2009 Share Posted January 3, 2009 Consider how the tides on earth are caused by the gravity of the sun and the moon. Near a black hole, the gravitational fields are far stronger, and similar effects would shred steel. For example, consider if you were a line approaching a point of gravity. When you are close to the point, it pulls the middle of the line in a different direction than it would pull a farther point on the line. Link to comment Share on other sites More sharing options...
Baby Astronaut Posted January 3, 2009 Author Share Posted January 3, 2009 Consider how the tides on earth are caused by the gravity of the sun and the moon. Near a black hole, the gravitational fields are far stronger, and similar effects would shred steel. For example, consider if you were a line approaching a point of gravity. When you are close to the point, it pulls the middle of the line in a different direction than it would pull a farther point on the line. Your analogy makes sense, except I think the line is being forced along an ever-tightening circular path, and this non-straightness would cause the line to break from the pressure of bending. For if space is warped by gravity, I would imagine that matter is forcibly warped along its path as well. Link to comment Share on other sites More sharing options...
Mr Skeptic Posted January 4, 2009 Share Posted January 4, 2009 Right. Now consider a line segment pointing toward the black hole. The part of the line nearer the black hole would be accelerated faster than the part farther from the black hole. Just like pulling on a string... if the difference in acceleration is too great, it would cause a tear. Link to comment Share on other sites More sharing options...
npts2020 Posted January 4, 2009 Share Posted January 4, 2009 Right. Now consider a line segment pointing toward the black hole. The part of the line nearer the black hole would be accelerated faster than the part farther from the black hole. Just like pulling on a string... if the difference in acceleration is too great, it would cause a tear. If the string didn't tear, could you theoretically tow the black hole to another location? Link to comment Share on other sites More sharing options...
Mr Skeptic Posted January 4, 2009 Share Posted January 4, 2009 Yes, but remember that the smallest black hole they found is still 3 solar masses. What would likely happen is that you would run out of fuel, and since you wouldn't have any tangential velocity, you would fall right in. Though I'd imagine you'd be smarter than to run out of fuel especially if you could get to a black hole. Also, you could tow anything in space with that method, although for lighter objects you couldn't pull very hard. Link to comment Share on other sites More sharing options...
Baby Astronaut Posted January 4, 2009 Author Share Posted January 4, 2009 Yes, but remember that the smallest black hole they found is still 3 solar masses. I thought the smallest black holes would be the type to appear in the Large Hadron Collider? Though I'd imagine you'd be smarter than to run out of fuel especially if you could get to a black hole. Also, you could tow anything in space with that method, although for lighter objects you couldn't pull very hard. How did you arrive at the conclusion that it's possible to tow a black hole? Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted January 5, 2009 Share Posted January 5, 2009 I thought the smallest black holes would be the type to appear in the Large Hadron Collider? How did you arrive at the conclusion that it's possible to tow a black hole? If I dropped you in space and you extended (threw) a rope toward a black hole you would be "towing" it until the rope broke. Unfortunately it would be towing you as well, in the opposite direction, only faster (assuming you are not more massive than the black hole). Rope or no rope, by the time you enter the black hole and become part of it you will have displaced it from it's original path. Link to comment Share on other sites More sharing options...
Sisyphus Posted January 6, 2009 Share Posted January 6, 2009 forcing a traveler along a slow circular descent towards the black hole. The object will circle in slowly when it is at a distance. an ever-tightening circular path, This is incorrect, although it seems to be a common misconception. You can orbit a black hole in the same way you orbit any other massive body. (If the sun collapsed into a black hole, the orbits of the planets wouldn't change.) Your path is a conic section, not a spiral. Link to comment Share on other sites More sharing options...
Baby Astronaut Posted January 6, 2009 Author Share Posted January 6, 2009 This is incorrect, although it seems to be a common misconception. You can orbit a black hole in the same way you orbit any other massive body. (If the sun collapsed into a black hole, the orbits of the planets wouldn't change.) Your path is a conic section, not a spiral. Really? That is crazy. Where might I learn further about this? Link to comment Share on other sites More sharing options...
swansont Posted January 6, 2009 Share Posted January 6, 2009 Sisyphus is right. Newtonian gravity depends on the mass, so the density doesn't matter— the basic function is like it's at a point anyway (this ignores tidal interactions). Gravitationally speaking, we wouldn't notice the difference. Link to comment Share on other sites More sharing options...
Klaynos Posted January 6, 2009 Share Posted January 6, 2009 /me bloged about this very thing not that long ago It is a VERY common misconception! Link to comment Share on other sites More sharing options...
Pete Posted January 6, 2009 Share Posted January 6, 2009 Really? That is crazy. Where might I learn further about this? You can learn about it in Black Holes and Time Warps: Einstein's Outrageous Legacy, by Kip S. Thorne and Exploring Black Holes by Taylor and Wheeler - See http://www.eftaylor.com/pub/chapter2.pdf Link to comment Share on other sites More sharing options...
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