Scientists attempt to measure speed of gravity

spaceflightnow.com ^ | 5 SEP 02 | staff

[RightWhale]

its gravity will cause the quasar's position in the sky to shift by a distance that depends on the speed of gravity

Is this a fair statement?

[RightWhale]

gravity bump

[E. Pluribus Unum]

"According to Einstein's theory, the speed of gravity is assumed to be equal to the speed of light..."

Gravity and light must be the same thing. The unified field has been solved. I will accept my Nobel now.

[Joe Brower]

" While some principles - such as the speed of light is a constant - have been proven"

Even this statement is currently being reconsidered.

Einstein's relativity theory hits a speed bump.

[Alamo-Girl]

Thanks for the heads up!

[john in missouri]

Sound like "its gravity will cause the quasar's apparent position in the sky to shift by a distance that depends on the speed of gravity" would be a more fair statement.

[RightWhale]

Isn't FR great? We can discuss the speed of gravity and the attempted assassination in Afghanistan at the same time.

[RightWhale]

Just wondering if this is the same idea as the measurement of the speed of light done a long time ago by observing and timing the orbits of Jupiter's moons.

[Free the USA]

fyi

[Joe Brower]

Isn't FR great? We can discuss the speed of gravity and the attempted assassination in Afghanistan at the same time.

Har-har! Yes, it is great. As long as we don't overdo making "light" of the situation over there in that sad, sad place.

[Trickyguy]

The speed of light is not a constant. Every physicist knows
this.

[governsleastgovernsbest]

I had no idea gravity had "speed." I knew that on earth it produces acceleration of 32 ft. sec/sec. By speed, do they mean the rate at which the gravitational pull of an object reaches a given point?

[RandyRep]

I wonder if they mean that the perceived location of the quasar in the sky will change, or if the position will physically change? The gravitational law says the force exerted on one body by another is proportional to the product of their masses and inversely proportional to the square of the distance between them. Jupiter has a relatively small mass compared to stars, and probably to quasars. I would expect Jupiter to move more than the quasars will. Of course, Jupiter may move more due to the influence of its moons, the other planets, and the sun than to quasars that are light years away. Do you think these students are smart enough to figure all of this out?

None of these bodies are stationary - everything is in motion. Jupiter about the sun, the solar system about the center of the galaxy, the quasars in motion about some unseen point. The perceived location of the quasars today is not the actual physical position of them right now - we are seeing light from them where they were however many light years ago.

Since the quasars are so many light years away from Jupiter, it will take at least that many years (if speed of gravity equals the speed of light) for any perceptible change in the motion of Jupiter or the quasars to be affected by each other. If the speed of gravity is less than the speed of light, it will take longer for them (however many light years plus the difference in the speeds) to find out. I think they will be a lot older when they figure this out!

Methinks this is either a hoax or a simplicity of thought by the university professors and/or students.

[semaj]

I personally don't believe that gravity has a speed at all, it just is. At the Big Bang, (if you believe that theory) gravity was created instantaneously along with all matter. If that is the case the effects of gravity would be present in all locations at the same time. Therefore, gravity has no speed, it is a universal constant. IMHO

[Triple]

I think really poorly written

Jupiter getting really close to a Quasar, close enough for its gravity to move the quasar even a bit, I think not.

Perhaps, Jupiter will be really close to the line between the earth and the Quasar, and bend the light coming from the quasar on its way to earth.

[john in missouri]

Just wondering if this is the same idea as the measurement of the speed of light done a long time ago by observing and timing the orbits of Jupiter's moons.

Offhand, it sounds like a rather complex calculation to me, involving the expected displacement of light coming from the quasar at various moments in time during which the gravitational effect should be observable, and given the known information about Jupiter's gravitational force, the speed of light, etc.

[longshadow]

gravitational speed limit ping

[john in missouri]

By speed, do they mean the rate at which the gravitational pull of an object reaches a given point?

That's how I take it.

In other words, if you could suddenly materialize the planet Jupiter out of nonexistence, how long would it take us here on earth fo feel a gravitational tug? If the theory is correct, we should feel the first tug of gravity at the same moment as the first light waves from the planet also reach us -- the very moment it becomes visible.

[Joe Brower]

Well there, Trickyguy, I guess I'm glad I'm not a physicist, then.

[RightWhale]

The speed of light is not a constant

Thank you for the clarification.