[forsnax5]

Ping for Gravity fans!

[Excuse_My_Bellicosity]

Pretty wild. I always assumed that gravity was an instantaneous thing.

[Southack]

"But how can you measure the speed of gravity? One way would be to detect gravitational waves, little ripples in space-time that propagate out from accelerating masses. But no one has yet managed to do this.

Measuring the speed of gravity Kopeikin found another way. He reworked the equations of general relativity to express the gravitational field of a moving body in terms of its mass, velocity and the speed of gravity. If you could measure the gravitational field of Jupiter, while knowing its mass and velocity, you could work out the speed of gravity. The opportunity to do this arose in September 2002, when Jupiter passed in front of a quasar that emits bright radio waves. Fomalont and Kopeikin combined observations from a series of radio telescopes across the Earth to measure the apparent change in the quasar's position as the gravitational field of Jupiter bent the passing radio waves."

Then again, perhaps all that they really measured was the speed of the radio waves bending around Jupiter...

[Excuse_My_Bellicosity]

It's amazing that Einstein's theories, unprovable when he was alive, are still being shown to be right.

I remember in 1995 when they discovered that Einstein-Bose Condensate was just like Einstein (and Bose) predicted it would be in 1925.

[conservativemusician]

Fascinating stuff.

[MonroeDNA]

Geeze, we all knew that. It HAS to.

*burp*

[NEWwoman]

What Gravitas!

[Libertarianize the GOP]

http://www.freerepublic.com/perl/bump-list

[supercat]

[thoughts]: (1) Do photons interact gravitationally with each other? (2) Do gravity waves have mass?

[Nick Danger]

Perhaps there is a minimum distance -- a quantum of space -- and a minimum amount of time -- a quantum of time. There is a speed limit on light because it cannot take less than one quantum of time to travel across one quantum of space. Do I know what I'm talking about here? Absolutely not. But I don't think anyboody else does, either.

[rface]

I love gravity!

Columbia, Missouri (actually Ashland, Missouri)

[Gary Boldwater]

If gravity travels at the same speed as light is it an electromagnetic wave or is it the medium that it travels through that limits the speed of propagation of all forces?

[Semper911]

Only one tiny thing they forgot to mention in the article: No one knows what gravity is.

[DoctorMichael]

........they worked out that gravity does move at the same speed as light.......

Okay, I'm confused.

We are always shown the picture of the Einstein space/time continuum: a marble (representing a planet) rolling around on a cross-hatched sheet, circling a steep central drop-off (representing a black hole). The momentum of the marble keeps it from falling inward.

Gravity, in this model, is the curvature of the sheet (the space/time continuum).

Isn't the curvature "felt" instantaneously by the marble because gravity is embedded in the very "fabric" of the space/time continuum?

Damnit Jim, I'm a biologist, not a physicist!

[longshadow]

gravity speed bump!

[Sawdring]

But the assumption of light-speed gravity has come under pressure from brane world theories, which suggest there are extra spatial dimensions rolled up very small. Gravity could take a short cut through these extra dimensions and so appear to travel faster than the speed of light - without violating the equations of general relativity.

Their actual figure was 0.95 times light speed, but with a large error margin of plus or minus 0.25.

How fast do the "Brane World" theorists think light might travel? Could gravity travel at 1.20 times the speed of light for them to be correct? Or would it be 10,000 or 100 times the speed of light for them to be correct?

[null and void]

[vannrox]

Very interesting, especially if all the current proposals that the speed of light is variable is true. The implications are stunning!

[commish]

OK someone has to say it :

Gravity Sux! ;-)

[Godfollow]

Yes but we won't ever get our anti-gravity boots unless we can find out "why" gravity pulls us down. Maybe if we could creat something upon which the mass of a foreign body like the moon would zero in on, therefor countering the the pull of earth, and give us a lift... kind of like a magnifying glass pulling in the reys of the sun, a device could be created that would magnify the gravity pull of the moon.