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Re: Speed Of Light Vs. Speed Of Gravity

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Posted by Thed/">Thed on December 4, 1998 19:00:51 UTC

: : Recently I have read an article saying that the speed of light is decreasing. : if this is true it has "desastrous" consequences for the Universe as we : describe it. : Can anybody tell me more about this?

It is a brand new idea put forward by two researchers as an alternative to the commonly accepted model of the Big Bang - Guth's Inflationary Model. It is purely speculative and as yet has no evidence to support it. The full details can be read at

: About Speed of Gravity and Speed of Light. : A black holes "sucks up" everything, even light. : Light near a black hole is bended toward that hole. : In order for the light parical/wave to "feel" this : force it has to be connected with a gravity partical/wave.

: Doesn´t this mean that the speed of gravity has to : be greater than the speed of light?

Nope. Gravity (as far as is known) is not propagated as a wave or particle. Theory says that Gravity Wave exist and Gravitons exist but they have never been observed. Einstein explains Gravity simply as a problem in geometry. Granted, it is a complex problem in 4 dimensional geometry but it is still only geometry.

According to General Relativity gravity is the energy stored in spacetime when it is curved or bent by a mass. Think of a rubber band. Left by itself it is flaccid and limp. If you stretch it the energy you expend in stretching it is stored in the elestic band as potential energy. Let go and the potential energy gets transfered as kinetic energy. In the same way a larger mass bends spacetime more than a smaller mass. A larger mass causes a larger potential energy to be stored in spacetime (like the rubber). As you enter the gravitational field of a mass you acclerate because the potential energy stored in spacetime is converted to kinetic energy.

What quantum mechanics says is that energy can be viewed as a mass or a particle. So the energy you feel as gravity can also be viewed as a paticle carrying force, in the same way photons are carriers of the weak nuclear force. Particles of gravity are Gravitons, they should exist in vast numbers but have never been measured.

Gravity waves are outside my speciality.

: I.e. if I have a flashlight near a black hole, and I aim : the light away from the black hole, will the light then be reverted : towards the black hole? If so, the force comming out of teh hole : has to have a greater speed than light in order to reach : my light?

: Any comments are welcome.

If you drop a stone into a well does the water come up the well faster than the stone is dropping. How else do you explain that the stone hits the water at the bottom.

Did you know that it is possible to orbit a Black Hole just above its event horizon if you are going at 99.999999999999+ % of the speed of light.

Black Holes do not simply eat everyhting as you might think.

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