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Speed of Gravity Experiment Challenged
An anonymous reader writes "The previous hoopla over the discovery of the speed of gravity has an opponent from the Lawrence Berkeley National Laboratory. Read about the latest calculations."
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That is not what they are trying to prove. The speed of gravity they are referring to is the speed of propigation of a change in gravity. If I am a giant mass which you are being influenced by gravitationally, and I move to a different location, does the force you feel change instantaneously? Or does it change after some set amount of time? Is that amount of time dependent on the distance you are from me? If so, then there is a speed of gravity that is not infinite. These scientists think that is is c, others do not. THAT is the controversy.
Gravity: we all know it sucks, we just don't know how fast.
What do you suppose the repurcussions would be if it could be shown that gravity was instantaneous, rather than propagating at the speed of light? Could we use that to transmit information instantaneously? Would that violate causality?
You would want gravity that moves at the speed of light. This is what most reasonable scientists expect, and probably what they assume.
All sorts of strange things can happen if it is instantaneous. According to Einstein, two people can disagree about what happens first if they are moving. A person at rest can see that event A happens at the same time as B. A person moving one direction will argue that A happens before B, while a person moving the opposite direction will argue that B happens before A. The strange thing is that everybody would be right!
Let's assume that gravity can travel at faster-than-light speed, and can be used for communication. Now, a person who is moving can see A happening, and call the operator at "B" and tell them to stop event "B from happening. The person moving in the opposite direction can see B happening and tell the operator at "A" to stop event A from happening. Who is right? Clearly, they both cannot be right!
It is possible that I am missing something here. Does anybody with more experience in this stuff have more insight?
"-1 Troll" is the apparently the same as "-1 I disagree with you."
the question could be more fundamental. Does gravity have a speed? Consider this: light is a particle (wave) traveling along a many dimensional space-time membrane. Now, we've defined (more or less) what a photon is; and, how it behaves. We expect it to travel no faster than c. The problem is, we don't really undertand the space-time thing.
We have some theories as to how space is constructed. One of the things physics is trying to do is to create a theory that ties together space, time, gravity, energy, mass, quantum mechanics (basically everything). It's proving to be very difficult and gravity is the problem. Would a gravity wave have to obey all of the "laws of physics" as we know them? maybe not. Not if our theories are wrong. A lack of understanding wrt gravity might be why we need to make claims about "dark matter" and "dark energy" in order to explain the accelerating universe.
You have to remember that our "laws" are based on observation. The rules (like no speed exceeds c) are based on mathematical models created to explain the observations. What if the models are close, but wrong?
Just something to think about.
So what you're trying to say is that the speed of gravity is 42?
Nothing to see here; Move along.