# The Naked Scientists Forum

### Author Topic: What is the speed of gravity?  (Read 7000 times)

#### Sumbul Arshi

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##### What is the speed of gravity?
« on: 21/02/2010 10:55:20 »
which one is faster,speed of light or speed of gravity?

« Last Edit: 21/02/2010 11:43:06 by JP »

#### Soul Surfer

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##### Re: What is the speed of gravity?
« Reply #1 on: 21/02/2010 11:00:00 »
They both travel at exactly the same speed.  The speed of light.   This has been observed and proved by experiment

#### Sumbul Arshi

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##### What is the speed of gravity?
« Reply #2 on: 21/02/2010 11:58:33 »
Then why light bents when it passes before the event horizon of a black hole.

#### flr

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##### What is the speed of gravity?
« Reply #3 on: 22/02/2010 03:25:46 »
This has been observed and proved by experiment

Can you cite an experiment (or a link) that prove what the speed of gravity is c?

#### yor_on

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##### What is the speed of gravity?
« Reply #4 on: 23/02/2010 07:44:14 »
Flr, for an alterantive view you can take a look here. speed of gravity
And here is a rebuttal to it. Aberration and the Speed of Gravity

Both papers are interesting I think :)

As for a experimental unarguable proof?
I haven't seen one yet.
==

I look at it as a field, or a spiders web.
The vibrations may well travel at light speed but the field is there all the time.
And therefore I think Tom Van Flandem might be wrong :)

And that simple fact explains inertia to me.
If the field is there at all time, then inertia will come to be at all course changes no matter where you are in 'deep space'. But that's my view. The field is what won't change there, but when it change it will need 'information' first, and that 'information' may travel at light speed. But read the papers and see for yourself. I found Tom Van Flandem's arguments quite interesting.
==

Or if I want to become a mystic :)
SpaceTimes geodesics, created from?

Ah, btw, I do see it as 'SpaceTimes Geodesics', not 'energy' even though I called it a field. At least not 'energy' of the kind we can manipulate by itself. We can manipulate it by mass or acceleration, but then we manipulate a lot of other things too. So I differ between that and 'lifting a ball' if you see what I mean.
« Last Edit: 23/02/2010 08:20:49 by yor_on »

#### Geezer

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##### What is the speed of gravity?
« Reply #5 on: 23/02/2010 08:06:02 »
I suppose the only way to prove it one way or another would be to very rapidly eliminate the mass of a rather massive body and observe the results.

Unfortunately, it seems the only way to eliminate the mass of a massive body is to convert all of its mass into energy in a fairly short time, so it's unlikely anyone, or anything, would survive the experiment and be able to report on the results.

#### syhprum

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##### What is the speed of gravity?
« Reply #6 on: 23/02/2010 20:31:06 »
I can visualise a set up whereby the the speed of gravity waves could be compared with that of Photons, let us contemplate two neutron stars orbiting about their mutual centre of gravity in such a plane that they eclipse each other, a pretty rare event no doubt.
If we could measure the variation in photon emission and the gravitational Waves emitted if the velocity of propagation was the same they would stay in phase but if it was different there would be a continuous phase drift.

#### KennyC

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##### What is the speed of gravity?
« Reply #7 on: 24/02/2010 12:40:21 »
I suppose the only way to prove it one way or another would be to very rapidly eliminate the mass of a rather massive body and observe the results.

Unfortunately, it seems the only way to eliminate the mass of a massive body is to convert all of its mass into energy in a fairly short time, so it's unlikely anyone, or anything, would survive the experiment and be able to report on the results.

Very interesting question. Gravity is really curved space, right? Due to mass. I've heard the term gravity wave and I guess there are attempts to measure them, not sure if they have been successful. I would think that the only way to measure the "speed" of gravity would be to create or destroy the mass and then measure the time required for the change to propagate from the source to the detector. Of course you have the issue of making sure the exact time is know at the detector that the mass appeared/disappeared.

#### flr

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##### What is the speed of gravity?
« Reply #8 on: 26/02/2010 17:12:46 »
Quote
the only way to measure the "speed" of gravity would be to create or destroy the mass and then measure ....

But you cannot simply create or destroy mass out of nothing.
If you make the mass out of "something"(energy I guess) then that "something" must already be there and hence already generate its gravity.
Or if you transport that "something" out of which you "make mass" in the desired location, you still move no faster than light therefore how could you see the speed of gravitational waves?

#### Robro

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##### What is the speed of gravity?
« Reply #9 on: 26/02/2010 19:14:20 »
Gravity is the observed effect of the EM waves on the trajectories of photons. As in 'photon theory', the photon reaches maximum amplitude and becomes saturated in the direction of increasing feild strength, bending its path. Since electrons, positrons, protons and neutrons and such are photons that are phase locked in to these (particles), then the speed of gravity would be 'C'. If you change the angular momentum of one object, it would be "CxT" before the other object would receive the gravitational effect of the change. This is how I think it would be.
« Last Edit: 01/03/2010 19:29:37 by Robro »

#### Vern

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##### What is the speed of gravity?
« Reply #10 on: 27/02/2010 02:07:28 »
I like to think that gravity may be an electromagnetic phenomena. It is caused by photons reaching electromagnetic saturation with the help of ambient electric and magnetic fields from other photons. In this case the ambient fields move at the speed of light, but they are already in place when a massive body moves through them.

I see that some are of the same opinion.

#### JP

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##### What is the speed of gravity?
« Reply #11 on: 27/02/2010 03:15:47 »
Robro and Vern, if you're proposing a theory outside of standard physics, could you please clearly state such?  It's important for posters to realize which models are mainstream and which aren't.

Robro, there's a forum (http://www.thenakedscientists.com/forum/index.php?board=18.0) dedicated to new theories, so if you want to describe your alternative description of gravity that's the place to do it.

Thanks,
JP (moderator)

#### Vern

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##### What is the speed of gravity?
« Reply #12 on: 27/02/2010 03:37:16 »
I'm not proposing a new theory. But I wonder if we are locked into the text book rendition of existing theories when we discuss them. Maybe sometimes that may be a little boring.

#### JP

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##### What is the speed of gravity?
« Reply #13 on: 27/02/2010 03:49:52 »
Vern, by new theory I mean anything outside of the textbook definitions.  The theory you're suggesting is outside of the textbook definitions since you seem to be suggesting that electromagnetism is the cause of gravity.  There is certainly room for alternative theories, but I think it's important that when posters ask a question, they get the standard textbook answer first.  Once they understand the textbook answer and why it's accepted, then they can better judge whether new theories offer a better explanation.  Every new theory is founded on a very solid understanding of the existing theories.

#### Vern

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##### What is the speed of gravity?
« Reply #14 on: 27/02/2010 03:53:26 »
I don't think that there is a really good text book theory of the cause of gravity. We can look at GR, and see how great it is. But it does not venture into cause.

So since the textbook rendition does not exclude it, maybe we could explore electromagnetism as a cause.
« Last Edit: 27/02/2010 03:57:32 by Vern »

#### rwjefferson

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##### What is the speed of gravity?
« Reply #15 on: 27/02/2010 18:30:57 »
which one is faster,speed of light or speed of gravity?
Which is faster, speed of sound or speed of wind?  It depends on the relative velocity of the wind and the direction of the sound energy.  Sound energy cannot escape from inside the event horizon of a hypersonic cyclone.

Which is faster, speed of light or speed of gravity?  Relatively speaking, the speed of gravity exceeds the speed of light at the event horizon of a black hole.

peace
rwj

#### Robro

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##### What is the speed of gravity?
« Reply #16 on: 01/03/2010 19:55:23 »
Vern, by new theory I mean anything outside of the textbook definitions.  The theory you're suggesting is outside of the textbook definitions since you seem to be suggesting that electromagnetism is the cause of gravity.  There is certainly room for alternative theories, but I think it's important that when posters ask a question, they get the standard textbook answer first.  Once they understand the textbook answer and why it's accepted, then they can better judge whether new theories offer a better explanation.  Every new theory is founded on a very solid understanding of the existing theories.
If mass and EM energy are the same(E=MC²), and gravitation is experienced in the vicinity of mass, then is it not EM energy that is responsible for gravitation? Is the word MASS used to describe a certain state or property of electromagnetism? And is it possible to prove the existence of anything other than electromagnetic phenomenon?
« Last Edit: 02/03/2010 08:45:41 by Robro »

#### JP

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##### What is the speed of gravity?
« Reply #17 on: 02/03/2010 00:26:14 »
Robro, you're missing a lot of important details of both general and special relativity there.  Gravity can be caused by energy, but this doesn't mean that energy is mass and especially not that EM energy is mass.  In fact, EM energy moves at the speed of light, which requires that it has zero mass.  It's also easy to see that things aside from electromagnetism exist--particles and the other forces, for example.

#### rwjefferson

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##### What is the speed of gravity?
« Reply #18 on: 03/03/2010 04:08:45 »
If mass and EM energy are the same(E=MC²),..

Relativity equivalence is not quite the same as same as.  That EM matter is a state of energy in verse mass by spacetime constant (e=mc2), does not mean mass and energy are the same.  Einstein spent the rest of his life trying to better understand spacetime aether.  Einstein did not imagine space might also be fluent.

Gravity is the flow of spacetime aether inthrough black drainhole mass.

peace
r~

#### JP

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##### What is the speed of gravity?
« Reply #19 on: 03/03/2010 08:20:16 »

#### yor_on

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##### What is the speed of gravity?
« Reply #20 on: 03/03/2010 11:09:45 »
Take a look at this Gravitational Redshift

#### Robro

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##### What is the speed of gravity?
« Reply #21 on: 03/03/2010 23:57:40 »
Interesting. More interesting is the fact that nothing, neither matter nor light can travel faster than light! At least this has never been prooven to happen! I wonder just exactly what it is that matter is made of that cannot travel FASTER than light? All things being equal...:)
« Last Edit: 04/03/2010 06:29:19 by Robro »

#### JP

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##### What is the speed of gravity?
« Reply #22 on: 04/03/2010 06:15:24 »
Mass is a property of matter.  I think you mean to say that matter can't travel faster than light (nothing can), and matter with non-zero mass requires infinite energy to even travel at the speed of light, which is physically impossible.

#### Robro

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##### What is the speed of gravity?
« Reply #23 on: 04/03/2010 06:30:28 »
Mass is a property of matter.  I think you mean to say that matter can't travel faster than light (nothing can), and matter with non-zero mass requires infinite energy to even travel at the speed of light, which is physically impossible.