Black Holes

  • Thread starter madphysics
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  • #26
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I thought this issue about "gravity rainbow" was clarified here:
https://www.physicsforums.com/showthread.php?t=162490
wasn't it?
Who is mentioning "gravity rainbow" here?

Everything that has either mass or energy creates Weyl curvature. More mass or more energy means more curvature. So two photons with a different energy must create a different Weyl curvature, right?

Are you saying I am wrong about that? Then please explain what is wrong.
 
  • #27
hellfire
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Who is mentioning "gravity rainbow" here?

Everything that has either mass or energy creates Weyl curvature. More mass or more energy means more curvature. So two photons with a different energy must create a different Weyl curvature, right?

Are you saying I am wrong about that? Then please explain what is wrong.
I am not saying your statement about curvature is wrong. What I am saying is that there will not be observable consequences, because all photons travel on same geodesics in the same space-time. This is what I argued in the other thread.

So what is wrong IMO is your comment "That statement seems a bit too strong" related to Chris Hillman's statement about the Hubble images. My interpretation of this comment of you was that you are referring again to some "gravity rainbow". If you did not then I apologize for bringing this into discussion again.
 
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  • #28
SF
http://news.softpedia.com/news/Black-Holes-May-Not-Exist-57614.shtml

A new theory based on controversial new calculations says that black holes may not exist, or least not as scientists imagine. It eliminates the existence of the "event horizon" and claims to have solved a paradox in astrophysics.

Current models say that black holes are space objects which have an immense gravitational field that cuts off a region of space from the rest of the universe, trapping all matter and radiation that enters that region. Black holes are thought to form in two ways, as a direct result of the gravitational collapse of a star, or by collisions between neutron stars.

The event horizon, questioned by this theory, is a general term for a boundary in spacetime, defined with respect to an observer, beyond which events cannot affect the observer. Light emitted from inside the horizon can never reach the observer, and anything that passes through the horizon from the observer's side is never seen again.

But the existence of this event horizon contradicts the equations of quantum mechanics, which always preserve information. So, Tanmay Vachaspati and his colleagues at Case Western Reserve University in Cleveland, Ohio, US, performed new calculations to see what happens as a black hole is forming.

They used the functional Schrodinger equation, that describes the space- and time-dependence of quantum mechanical systems, to follow a sphere of matter as it collapses inwards, and predict what a distant observer would see.

The results were surprising, showing that the gravity of the collapsing mass starts to disrupt the quantum vacuum, generating what they call "pre-Hawking" radiation. This Hawking radiation is the current explanation for the preservation of information, a hypothetical flow of particles, which is thought to result from the black holes' event horizons messing with the quantum froth that is ever-present in space.

Vachaspati says that the lost radiation reduces the total mass-energy of the object, making it impossible to get dense enough to form an event horizon and a true black hole. "There are no such things", he says "There are only stars going toward being a black hole but not getting there."

His conclusion is that what really forms in there is a "black star", looking much like a black hole, but never reaching this stage. This idea seems to solve the information paradox, but faces firm opposition from other theoretical physicists.
 
  • #29
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  • #30
SF
I think you should create a new topic since it's an interesting issue.
Paste the link here when you do.
 
  • #31
George Jones
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