First speed of gravity measurement revealed

NewScientist.com ^ | 01/07/2003 | Ed Fomalont and Sergei Kopeikin

[Movemout]

This is very interesting. The subject has been debated endlessly. I just love talented researchers like these.

[Physicist]

The fact is that the earth accelerates toward the actual position of the sun, not toward the apparent position as it would if gravity propagated at the speed of light. This isn't an opinion or an interpretation but a demonstrated phenomenon. It can't be explained by a speed of gravity that doesn't exceed the speed of light.

I've explained this to you before. All of these results are in perfect agreement with the predictions of General Relativity. The gravitational field does point to the true position of the sun, and gravity does propagate at the speed of light. There is no disagreement.

The problem here is that you're confusing the field with undulations in the field. Fields don't propagate; only changes in them do.

[Treebeard]

I WISH....hell, when all my wife's relatives showed up for Thanksgiving dinner, they sat for hours and never moved toward the (exit) door.

[Oberon]

However, like photons being responsible for the transference of the electromagnetic force, where then are the Gravitons, the particles responsible for this force?

You know, I had one in a jar on my desk just the other day... Dang, where'd it go? =]

[Oberon]

Sadly, there are many in this forum who have absolutely no idea of the gravity of this discovery.

That's heavy, man.

[xm177e2]

A couple minutes delay is almost instantaneous, when you're dealing with an orbit that lasts a year per cycle, right?

[Oberon]

brain-melting-and-dripping-out-my-ears BUMP

It's very simple. Jupiter's presence makes a gravity lens that is capable of refracting radio waves just like an eyeglass lens refracts light. The physicists checked whether the prescription on the leading edge of Jupiter was the same as the prescription on the trailing edge. It was a slick bit of work, but not hard to understand.

[steve-b]

Ping for Gravity fans!

Don't blame me; I voted for Velcro.

[kjam22]

There are a lot of things about this stuff that I don't understand. Like ... why hasn't the earth's orbit of the sun decayed after all of these years. The earth would go in a straight line if the sun's gravity suddenly ceased... so that means the sun's gravity is working against the natural tendency of the earth's movement. How has the earth maintained this momentum all of these billions of years against a constant force pulling it a different direction? Has the orbit decayed?

[PatrickHenry]

Late ping for a good thread.

[This ping list for the evolution -- not creationism -- side of evolution threads, and sometimes for other science topics. To be included, or dropped, let me know via freepmail.]

[PatrickHenry]

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.

Elegant. This work is a classic. If I recall correctly, it was the Jovian system that once was used to measure the speed of light, by observing the delay in the appearance of its moons (when coming from behind Jupiter) at different times of the year, the lag time being due to the earth being at different distances from Jupiter. I may have this backwards, and it could be that lightspeed was then known, so the delay was used to measure the size of earth's orbit. Either way, ol' Jupiter has been very useful.

[MeekOneGOP]

bttt for later read...

[ward_of_the_state]

Can somebody please get Bill Nye the Science Guy to explain this so I can understand it?

[Godel]

Is this really the first time the speed of gravity has been measured? I mean we pretty much knew it had to propagate at light speed already, im just suprised no one thought of a way test this before, or is the journalist exagerrating a bit?

[ward_of_the_state]

WHAT?!

[ward_of_the_state]

I love gravity!

It keeps the salt in the shaker.

Gravity is great until you hit your mid 30's and have had 3 or 4 kids. Then it sucks!

[aruanan]

Here is the summary portion of today's press release from Tom Flandern on the Kopeikin paper:

Summary

• S. Kopeikin misquotes Van Flandern as predicting that cg (Kopeikin’s “speed of gravity”) will be infinity. Van Flandern and Vigier are in print showing that six experiments better than Kopeikin’s already show that the speed of gravity is >> c (c = speed of light). But in posted discussions with Kopeikin and in USENET newsgroups, Van Flandern clearly states that Kopeikin’s “cg” parameter cannot be the speed of gravity and will certainly come out near the value c, as it did.

n     Asada followed up Kopeikin’s Astrophysical Journal paper with his own paper in the same journal showing that Kopeikin was simply measuring a quantity that propagated at the speed of light, and was definitely not measuring the speed of gravity.

n      Kopeikin has mostly ignored these well-founded corrections, apparently because he justified funding for his experiment by the claim that it would measure the speed of gravity.

n     Kopeikin new paper at the Los Alamos archive shockingly revises his protocol, equations, and methodology. Scientific method forbids changing the protocol after the results are in, especially when it is done to avoid an unwanted or unexpected result.

n      Kopeikin’s new equations introduce a new factor, c/cg, for time in the Einstein equations. This factor drives time intervals to zero for large values of cg, thereby making large cg results *impossible* for any experimental data regardless of reality.

n      Kopeikin’s now-forced results do a great disservice to science in general and the advancement of physics in particular because they no longer represent what his own experiment showed, much less the speed of gravity. 

I'll post the entire press release when it's online and I've gotten permission to do so.

[ward_of_the_state]

Also, the time it takes the bowl of spaghetti to hit the floor is directly proportional to the time it takes for the dog to arrive at the spill and clean it up and inversely proportional to the time it takes for mom to grab a towel and clean it up!

[Gary Boldwater]

Not all motion is relative. Acceleration is absolute.

[facedown]

Gravity is great until you hit your mid 30's and have had 3 or 4 kids. Then it sucks!

Wait 'till you pass 50. Even your earlobes start to sag!