What is the speed of gravity? Does it have mass like photons do?

Question

Specifically how fast does it take for gravity to effect something? For example if the sun suddenly disappeared how fast would the effects be known on earth? It takes approximately 9 minutes for the light that left the sun to be detected on earth. Is gravity the same way?

To clarify my question, I am referring to the speed at which gravity effects something not the acceleration of 2 bodies due to gravity. I am talking about gravity itself. In the example of the sun suddenly disappearing, at the exact moment the sun disappeared would the earth no longer be in a curved orbit instantaneously or would it take some time for the orbit to be changed?

Answer 1

Theoretically, gravity acts instantaneously. So if the Sun suddenly disappeared, there would instantaneously be no force on the Earth - not 8 minutes later, but now. However, since there's no way for that to happen, it's kinda hard to test that one. But that's what the LISA probe should be able to do - pick up gravity waves. We're not sure how gravity is propogated yet beyond the bending of spacetime - it's theorized that it's caused by particles called 'gravitons', but these are caused by mass and thus shouldn't have any. Classically, photons don't have mass either.

Answer 2

Gravity doesn't have a "speed" in the way it interacts with us here on Earth....it's a force dependent on the mass of an object and the square of the distance between it and the attracted object.

The force of gravity on Earth just happens to equate to an acceleration of 32ft per second per second to a limit caused by air resistance called terminal velocity which is around 180mph under normal circumstances....though the actual "record" for this is a great deal higher.

On a body of different mass there would be a different gravitational effect...therefore altering the above figures.

Gravity has no mass but then neither do photons so your second question is meaningless in that respect.

There is a scientific opinion that gravity has a speed somewhere between 0.8 and 1.2 times the speed of light, and a further opinion that it has a speed many billions of times the speed of light.
But so far General Relativity states that it has a speed equal to that of light so in terms of journey time from the sun it would also be around 81/2 minutes.

Answer 3

I see you're getting a lot of speculation for 'answers.' The fact is science doesn't yet know what the speed of gravity is for certain, nor whether the graviton is its messenger particle.

Gravity is one of the four fundamental forces in nature and the only one that hasn't yet been 'combined' with the other three. So-called string theory (..aka 'M Theory'...) shows some promise for doing this, but so far no cigar.

Bottom line is we don't know an awful lot about the specific workings of gravity. Another problem that muddies up the water is that we do know mass is responsible for gravitational fields, but we don't even know precisely what gives mass its characteristics like inertia.

Answer 4

Gravity propagates at the speed of light. This is pretty much impossible to disprove though as it would require a sudden change in gravity of something to occur which is pretty much impossible without the ability to make mass disappear or reappear (which cannot be done).

A photon has no rest mass. The theoretical graviton, which is what quantum physicists believe mediate the force of gravity, but haven't been able to observe it, would also have no rest mass.

Gravity is information, and if gravity propogated faster than the speed of light it would allow something to gain information about something else sooner than causality allows. If a rogue star were approaching our solar system and gravity propogated faster than light, the star would affect us before we would see it coming.

Answer 5

gravity is 9.8 meters per second squared. Gravity does not have a mass, rather gravity is a force that results from every body in the universe exerting an attractive force on every other mass in the universe. Now this force that results is proportional to to both masses of the objects and inversly proportional to the square of distance between their centers of mass. The formaula for the gravitational force is

F=G[(m1)(m2)/r2] that r2 is r squared.
Also it is not accurate to state that a photon has mass. Photons are particlelike entities that from electromagnetic waves. Becasue a photon has energy, a photon can eject an electron from a metal surface when it reacts with an electron. However, a photon is different from a normal particle. A normal particle has mass, and can travel at speed up to, but not equal to the speed of light. A photon, however, travels at the speed of light in a vacuum and does not exist as an object at rest. A photon has kinetic energy only, and has no rest energy and no mass.

Answer 6

There is some debate about this. All concerned agree that the speed of the propagation of gravity is significantly faster than the speed of light. However there is disagreement as to whether this propagation could be instantaneous.

Answer 7

I'm not a scientist but I think your question is poorly formed in that it assumes the existence of simultaneity. As I understand it, the idea of Enstein's theory of relativity is that there is no such thing as simultaneity in the universe. Time/space are relative to the observers so the 'instant' something happens say on the sun is not synonymous with a specific time somewhere else as your question assumes. Observers in different parts of the universe would 'clock' the event at different times according to their tragectories and speed relative to the event. It's a hard concept to grasp we're so used to short time and space relations that our minds can't grasp the difference of what happens at vast times and space and speeds.

Answer 8

Gravity moves at the speed of light same with all other waves. The quanta of gravity is the graviton although this hasn't been verified yet. BTW photons are massless, but you might have been confused because they do have momentum. Confusing I know :-)

Answer 9

Well, the acceleration of gravity is 9.8 metres per second squared. Gravity is a force that is affected by mass. Gravity itself cannot be weighed alone, only measured versus what it is pulling on.