# The Naked Scientists Forum

### Author Topic: Gravitational feedback and black holes  (Read 1725 times)

#### jeffreyH

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##### Gravitational feedback and black holes
« on: 06/04/2014 22:24:59 »
Recognized wisdom suggests that when an object collapses behind its event horizon the objects in orbit will experience no change in force. I am putting together a mathematical model to show this is not the case. Initially I had thought that the gravitation would be amplified. However, initial work shows that the force of gravity will reduce. This results in a drift of objects away from the central black hole. This will result in longer more extended orbits around the central mass. Rather than the black hole clearing the centre by consuming mass the galactic masses drift outward to settle into larger and slower orbits. This explains why we have an empty region around black holes.
« Last Edit: 06/04/2014 22:26:43 by jeffreyH »

#### jeffreyH

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##### Re: Gravitational feedback and black holes
« Reply #1 on: 09/04/2014 15:05:23 »
A quick and simple description of this theory on the macroscopic scale is to take two earth sized masses. Then assume that each mass is separated by a distance 4 times the radius. That is each centre of gravity is 4 times the radius from the other. Now we can draw a straight line through both centres of gravity and continue this out to a point P away from the masses by a set distance. If we measure g from point P to each mass we can sum the contributions to give a combined g force. Now take the position directly between the two masses on the line through the centres of gravity and move each mass by a set amount so that they are closer together. This can represent and increase in density, the masses moving together and the size getting smaller. Since point P has not moved with respect to the joint centre of gravity we can now re-measure the combined g forces and will find a decrease in strength. This then shows that the field strength around a collapsing object should diminish with increasing density as suggested above. I leave this as an exercise for the reader as it is best to confirm this personally to be sure.

#### jeffreyH

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##### Re: Gravitational feedback and black holes
« Reply #2 on: 09/04/2014 15:29:00 »
Actually scrub that completely. I had an error in the calculations. In fact I have now confirmed that there is absolutely no change in the field strength. Therefore the value of 2 when used in 2GM is in fact a constant. This also verifies the fact that objects orbiting a collapsing object will be unaffected. However this will still not explain why objects nearer the collapsing object will be drawn into it. If the field strength over distance does not change then with increased density there is no reason for orbiting objects to experience an increase in force.

#### jeffreyH

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##### Re: Gravitational feedback and black holes
« Reply #3 on: 16/04/2014 20:38:50 »
An amendment. There is a variation in the factor used in gravitation. This relates to density and the speed of light. Not however c^2. I have not properly sorted out the mathematical relationships yet but may be able to use the proton as a starting point.

#### jeffreyH

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##### Re: Gravitational feedback and black holes
« Reply #4 on: 17/04/2014 00:07:32 »
Any spherical mass M with uniform density will exert a gravitational force on any point P, at a set distance from its centre of gravity, inversely proportional to the density of M.

#### jeffreyH

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##### Re: Gravitational feedback and black holes
« Reply #5 on: 17/04/2014 00:24:57 »
The smaller the scale the more insignificant the difference in field strength will be.

#### jeffreyH

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##### Re: Gravitational feedback and black holes
« Reply #6 on: 27/04/2014 22:32:42 »
Contrary to the above posts there appears to be no change in feedback and the value for g will in fact be identical for a collapsed object. This means that the orbits around black holes SHOULD be unaffected. However this is incorrect due to the strengths of the opposing fields and the difference in perturbation between masses of different densities and therefore different radial parameters. There will also be a precise definition of an accretion zone between masses. The horizon of this zone will depend upon the size of the masses and the radial distance between them. Stellar objects that orbit within the accretion zone will always be young stars and have a short life cycle. For Sag A* this can be determined by estimating the ages of the S stars in close orbit. These stars should be primary contributors to the accretion disk.
« Last Edit: 27/04/2014 22:49:02 by jeffreyH »

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##### Re: Gravitational feedback and black holes
« Reply #6 on: 27/04/2014 22:32:42 »