Some Problems with Black Holes

This microquasar must be quite famous.... I've heard about it before in my astronomy class....

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Raw think tank I think you need to read more science articles. Dark matter is only one theory explaining the gravity that holds together galaxies. There are other theories that explain that what we observe. One of those reworks Newton’s laws of motion it is called modified Newtonian dynamics.

 

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Fascinating article, 2inquisitive. So what they are proposing is that the supposed event horizon / Schwarschild radius of a black hole is, in fact, a solid surface? Though it does solve the infinite entropy issue, I wonder what mechanism could create a hollow shell out of a solid, collapsing stellar core. I mean, the gravitational force powering the collapse pulls everything toward the centre - at what point does the centre beome a bubble?

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Yes, or MOND for short. I did a university assignment on that. The idea is that, in very low-density environments such as the fringes of galaxies, the gravitational constant increases slightly. An increase completely insignificant in everyday life, but enough to modify the behaviour of widely scattered stars or MACHOs and account for the apparent missing mass of galactic halos.

[Sorry: I think I've already said that, in a previous thread.]

 

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If galaxies needed a black hole at its center to exist then we should have had galaxies with dark holes or regions at centers of many galaxies. And argument that black hole is going to keep a galaxy in its shape is baseless as gravity reach of a star after it becomes a BH remains same, so there is no question of many BH combining or something.

Its biggest misunderstanding of science, a wake up call for science and a great lesson for future of science.

 

Do ants make U feel insulting, U r thinkni from human point of view.

Ants is an over statement, Infact I like humans, They r like pet cats for me, but how long can U live with just cats, thats boring.

 

What I really don't understand, is that time slows down to zero at the event horizon, so that from our pt of view nothing could be inside a black hole, although there has to be, right?
Also, time would go backwards outside, from the pt of view of an astronout moving into a black hole, which doesn't make sense to me either.

 

Oops, sorry just noticed my error, while checking for replies:
time wouldn't go backwards...at the event horizon it would go infinitely fast, but what then?

 

I don't see why time would slow down infinitely at the event horizon - unless the observer at that point was moving inward (or sideways, or outward) at the speed of light. The hole's gravity would certainly accelerate you enormously - but an event horizon is simply a radius at which the escape velocity is equal to light speed. I mean, Earth's surface gravity doesn't accelerate falling objects to its own escape velocity!

Not to mention that objects with mass, such as spaceships, people or protons, can never reach the speed of light, under any gravitational or other force. That's precisely why they can't escape from a black hole's event horizon.

If you were moving at high relativistic speeds, and assuming you were immune to tidal effects, radiation, debris bombardment etc, your time would indeed slow down: and you might call out briefly for Mummy while, back home, she lived another 30 years. As you crossed the boundary, you might see the stars behind you rearrange themselves over millennia of galactic drift. But then you'd hit the central singularity and cease to exist.

 

well, under high gravitation your time slows down, and the event horizon is not only the point of no return for light, but also the point where time slows down to zero relative to an observer infinitely far away.

correct me if I'm wrong...

 

Free-falling observers, as they fall past observers hovering above the horizon at various altitudes, measure those observers’ respective clocks as increasingly running slower. Free-falling observers, by their own reckoning, do not slow down on their approach to the horizon. They speed up on the approach and always cross the horizon at the speed of light relative to an observer hovering infinitesimally above the horizon (so it’s a measurement in the limit). So says general relativity.

 

Well... you would probably die when reaching the event horizon... so why bother?

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A pseudo-factual article, in one of the Doctor Who annuals I read as a kid , summed it up perfectly:

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It also suggested that all the black holes in the Universe may be somehow connected due to their effects in "bending time," and that

:m:

 

Thanks for the article. The .pdf mentioned on the page couldn't be found , though. I found a copy here, anyway:

http://www.mcs.vuw.ac.nz/~visser/cqg-gravastar.pdf

looks very interesting.

 

ok, zanket, I thought about this some more; you seem to be right.