Is gravity instant or does its effect travel at the speed of light?

Question

To put it another way, if the Sun suddenly ceased to exist, would the Earth immediately move off at a tangent, or would it continue to orbit the point where the Sun was for a further 9 minutes, until we saw the Sun disappear, then move off at a tangent?

I asked this in Physics but only got 1 answer, which seems to contradict itself!

Answer 1

It would be instant as gravity is not a moving force it is a result of the bending of space, though it is rather more complicated.

Answer 2

well the question doesnt make sense.

gravity is a difficult subject. if the sun just dissapeared, meaning it is not a black hole, then there would be no pull to hold any of the planets in place. it would be instant.  

Answer 3

Gravity appears to be an instant force. As a result if you remove the sun Earth would instantly go off at a tangent.

Do not confuse gravity as an object, it is a force.

No object or particle (including a photon) can travel faster than the speed of light, however gravity is not a particle.

Gravity is a force that a particle gives off, it is not a particle in itself.

Answer 4

spin a ball on a string..... let go the string.... off it goes.... the ant on the ball sees a receding you..... till he's too far away to see you anymore or you walk away.....

is gravity instant?.... hold a bowling ball at about eye level.... let go....  

Answer 5

well I think gravitons are the particles that influence gravity, this is theory as of yet, I dont think the particle has been observed. But if this is the case then considering no particle can travel faster than the speed of light I would say that the effects of gravity are not instant.

Answer 6

Einstein predicted the existence of gravity waves that propagate at the speed of light. This fact has confused many scientists in thinking that the force of gravity propagates at the speed of light. In fact, Einstein insisted that gravity does not propagate at any speed; it is just a warping of 4D space-time. This amounts to a tacit assumption that gravity propagates at infinite speed. For a galaxy a million light years away, the formulas of general relativity yield acceleration toward where the that galaxy is now, not where it was a million years ago.

If the force of gravity did propagate at the speed of light, the sun's gravity would be pulling on the Earth in the direction where the sun was 8 minutes ago. That would pull the Earth into higher and higher orbits. Solar systems and galaxies could not exist because gravity would throw planets and stars out of orbit.

Personally, I believe the speed of gravity is many times faster than light; I tend to agree with VanFlandern on this (though most of his theories are too wacky for me). He says gravity is at least 20 billion times faster than light. That means the speed of gravity is to the speed of light as the speed of light is to the speed of a snail.

Answer 7

  The effect of gravity travels at the speed of light.

  The earth would act as though the sun was still there for about 8 minutes the fly off at a tangent.

  The force of gravity is a quantum entity so it must have a single unit,the graviton.

A photon is more familiar and travels through space at the speed of light to announce it's existence.

  A graviton announces it's existence at the speed of light,but it acts like the force of a tsunami the graviton itself doesn't travel it moves as a wave and space itself transmits it's force at the speed of light.

Answer 8

I would think it would be in an instant

Maybe you can test it out with magnetics since their pull is kind of similar  

Answer 9

I've heard both sides of this story.  

If the sun were instantaneously  removed (whatever explanation a fiction writer can come up with here, would be great), it would take 8 minutes for us to "see" the effects of it being gone.  The question if the sun is gone at say, 12:00, would our gravitational interaction with the sun be instantaneously severed at the point in time where it disappeared...  i.e. would we still see it during the 8 minutes that we floated off into the vast cosmos?

Gravity and time do have an interaction, but I don't always fully understand it.

Most of the recent studies I've looked at I haven't done so in detail, but evidence suggests that in a vacuum, the effects of  gravity also travel at the speed of light.   So, when the daytime sky went black, our revolution around a mass that no longer existed would be synchronous.

<edit>

To the question ASKER:

I'm curious as to what this contradictory response you got was.  Just me being my typical nosey self!

<edit 2>

Even though Phillip J's answer contradicts mine, it's based in fact and logic.  (Thumbs up) It appears this might be one of those questions that hasn't become "knowable" yet.  I'd be really interested in anyone that can propose a way to test this question.

Answer 10

The effect travels at the speed of light!

It is not instant

There was even an experiment done to prove it using th VLBI

Check out work by Sergei Kopeikin at the University of Missouri:

http://en.wikipedia.org/wiki/Sergei_Kope...

and his work on the speed of gravity

http://en.wikipedia.org/wiki/Speed_of_gr...

So we would not move off at a tangent until the moment that we saw that the sun was gone...