Gravity Propagation Experiment.

[GTrax]

So - if the Sun were to be suddenly altered in a unlikely collision, The Earth would continue it's curved path for about eight minutes before we all became somewhat alarmed..

There is a excellent home-brew demonstration of gravity effect using a torsion balance, done in a University basement.
It also has a very nice video clip, and can be seen at this link ..
http://www.fourmilab.ch/gravitation/foobar/"

Could similar equipment be arranged to carry some modern instrumentation? I can imagine one moving and one fixed mass to be fitted with a mirror, and some arrangement of lasers and optical detectors, and then arrange for the fixed mass to meet with an "accident" with a view to measuring the delay before the lack of force is recorded about a metre away (3.3nS)

Unrealistic it is! I can imagine instead a heavy asymmetric dumb-bell rotated at high speed about it's balance point right up near a mass in a vacuum chamber. Both would be instrumented with a view to discovering the time delay. If necessary, a timed "accident" could be arranged (beginning to sound like a gangster movie here!) I am sure there are folk very much more skilled who could dream up an effective experiment.

Surely a direct confirmation that gravity effect really does propagate at the speed of light is essential. The search for the Higg's boson is under way. So far, it seems we have to acknowledge the Quantum Standard Model as one of the most successful physics theories ever - except for gravity! Gravity is not light. It is not like light!

Of course, if we already know this speed for sure, I freely withdraw - embarrassed.

 

[exponent137]

It seem to me that Taylor's and Hulse's pulsar gives the best estimation of speed of gravity vg. (1% if the model vg = c is used) But if model with infinite vg is used, what is then given by this pulsar?

 

[GTrax]

Thanks very much for the reply.
I had thought that cosmological observations would maybe provide a better insight and evidence.

I should explain that in this context, I was rapidly taken out of my depth by innocent questions from children. Showing them the little video clip about "basement gravity in action" led to the question "So what makes it pull - how does it really work"?

What could I say? I could hardly mention "Higgs Boson" or "Graviton". So I headed for cover, and ducked the question by quoting Melville Feynman (father of Richard), who said..

quote Melville Feynman:
"That, nobody knows! Things that are moving try to keep on moving, and things that are standing still tend to stand still, unless you push them hard. This tendency is called inertia, but nobody knows why it's true".