Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: CPT ArkAngel on 08/09/2010 06:27:03
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What if black holes have a stronger gravitic field than G (G is not a constant for a black hole) at a scale of galactic proportion and they have a repulsive anti gravitic field at a larger scale (G is negative)? As black holes become larger, they would cause an acceleration of the expansion of the Universe...
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This clearly does not happen because if it did the galaxies they help hold together would fall apart and we would see that happening.
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It's interesting but slightly wrong I'm afraid. It may be something I'm missing here but the gravity for a black hole outside the event horizon acts, as far as I know exactly the same way as all other gravitational objects.
"According to Birkhoff's theorem, it is the only vacuum solution that is spherically symmetric. This means that there is no observable difference between the gravitational field of such a black hole and that of any other spherical object of the same mass. The popular notion of a black hole "sucking in everything" in its surroundings is therefore only correct near the black hole horizon; far away, the external gravitational field is identical to that of any other body of the same mass."
And "If a one solar mass black hole were to suddenly replace the Sun at the center of our solar system, the orbits of the planets would not change. This is because the physical laws that determine the orbital motion of the Earth depend only on the actual mass of the Sun, and not on whether it is distributed within a sphere (like the Sun) or at a point (like a black hole)."
That has to do with the way gravity is 'distributed' through the universe, so it's only when passing the so called 'event horizon', and possibly also when becoming 'frame dragged' outside the event horizon of a rotating black hole, that you will find gravity to become any real danger for you. Also, a anti gravitational field is an interesting idea but I don't really know of any experiments proving it, and I seriously doubt that you can find it inside a black hole. What some have suggested is though that it might be possible to survive a black hole as there seems to be some areas inside that space, if I remember right, where the gravity would be as for any other space.. I read about it last year, and I'm afraid i don't have the source for it, but I could probably find it if I searched.
There is also a possibility, even without that phenomena, that the space inside the event horizon could be expanded, as seen from that frame of observation, but I think that this solution was for Schwarzschild black holes. Not that a rotating black hole couldn't have it too but there you will also have the frame dragging to account for, which should add some strangeness to that space, as a guess :)
Rotating black holes seems to be in majority in our universe, I'm not sure that we have found any non-rotating at all. And the math and properties becomes different when you look at those. "Roy Kerr found the exact solution for a rotating black hole. Two years later Ezra T. Newman found the axisymmetric solution for a black hole which is both rotating and electrically charged."
look here (http://en.wikipedia.org/wiki/Black_hole#Physical_properties)
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I'm not aware of anything that suggests or implies that G would be different in the vicinity of a BH: there just doesn't seem to be any terms left over from BH solutions to account for such a difference (and the solutions seem to make sense without the need for any such additional terms).
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I know all that but still, no one is absolutely sure how spacetime can be define beyond the event horizon. Is there a singularity at the middle of the black hole or not? Maybe the event horizon is the singularity... Spacetime is so curved at the event horizon that light has to go faster than C. Spacetime is infinitely stretched. Maybe black holes are linked to other parts of our Universe and they may have a gravitic field at these other places... Some serious scientists say that that the acceleration of the expansion of the Universe will cause everything in the Universe to go faster than light in a few billion years. Seems like a black hole to me. What if black holes have images at the edge of the Universe? I know it is farfetched but i really feel there is something wrong with standard models of dark matter and dark energy. People have created those theories according to very few data and until now, no experiment confirm them. In fact some experiments deny them.
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People have created those theories according to very few data and until now, no experiment confirm them. In fact some experiments deny them.
What experiments are those?
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Very precise torque measurements and all astronomical measurements made always show discrepancies between the models and the data. I did not find all for sure... There is simply not enough data to conclude that the standard models are false i must admit. I just feel that there should be more elegant theories, maybe a larger scale effect theory rather than a particle theory... I just hope people will keep an open mind regarding future strange and unexplained data. If i can generate new ideas.......
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I do know there are theories that propose modifications of mainstream gravitational theories to account for these things. For example, see: http://en.wikipedia.org/wiki/Modified_Newtonian_dynamics#Consistency_with_the_observations
But this still requires that all objects obey the same laws--just that the laws are slightly different from the current models, so black holes wouldn't be special in these cases.
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I just found an interesting article about measurements of gravitational lenses effect that goes with the dark matter theory... Maybe Dark Energy and Dark Matter are not related after all...
http://home.slac.stanford.edu/pressreleases/2006/20060821.htm
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http://home.slac.stanford.edu/pressreleases/2006/20060821.htm
In this article, What i find strange in the simulation of the colliding clusters, is that Dark matter seems not to interact at all with anything. Is it not supposed to be interacting with gravity of the matter and Dark matter? When to clusters collide is it not supposed to be gravity by far the main interaction of matter (baryonic) because clusters are mainly composed of empty space? Does the difference in the behaviour of matter and dark matter should not be so great???
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Now i understand. The observation of x-rays are from gas in the clusters, not stars, so the stars are mostly with the dark matter...
http://en.wikipedia.org/wiki/Bullet_Cluster