Why is the speed of gravity (curvature of space-time) equal to electromagnetic disturbances

[Romeo22]

The speed of electromagnetic disturbances such as light is c and according to GR, the speed of gravity is also exactly equal to c.

 

Is it a serendipitous coincidence that they both have exactly the same speed? Assuming they are unrelated phenomena. One governed by wave/photon behaviour whilst the other is due to "the speed of space itself"

Edited December 2, 2018 by Romeo22

[Janus]

Both electromagnetic waves and gravitational waves (the aspect of gravity that travels at c) are massless entities, and as such are required to travel at c, the invariant speed of the universe.  When neutrinos were first proposed and and later discovered, they also were assumed to be massless and thus were expected to travel at c.  This is a consequence of Relativity.

[StringJunky]

1 minute ago, Janus said:

Both electromagnetic waves and gravitational waves (the aspect of gravity that travels at c) are massless entities, and as such are required to travel at c, the invariant speed of the universe.  When neutrinos were first proposed and and later discovered, they also were assumed to be massless and thus were expected to travel at c.  This is a consequence of Relativity.

Do you think we'll ever be able say why  c is that speed/what limits it, or will it always be axiomatic?

[swansont]

There is a maximum speed in the universe, which places a speed limit on any transfer of information or interaction. It's not that light limits gravity or vice-versa, it's that both are limited by the same thing.

[michel123456]

23 minutes ago, Janus said:

Both electromagnetic waves and gravitational waves (the aspect of gravity that travels at c) are massless entities, and as such are required to travel at c, the invariant speed of the universe.  When neutrinos were first proposed and and later discovered, they also were assumed to be massless and thus were expected to travel at c.  This is a consequence of Relativity.

It cannot be a consequence of Relativity. Relativity is an explanation, it is not a cause.

[StringJunky]

1 minute ago, michel123456 said:

It cannot be a consequence of Relativity. Relativity is an explanation, it is not a cause.

Relativity says c is the limit. It is the reference.

[michel123456]

from graviton's wiki:

Quote

If it exists, the graviton is expected to be massless because the gravitational force is very long range and appears to propagate at the speed of light

Wich means it is the other way round.

 

It is not because they are massless they propagate at c. It is because they propagate at c that they must be massless.

 

2 minutes ago, StringJunky said:

Relativity says c is the limit. It is the reference.

I ment that Relativity is not a force of nature. Relativity cannot cause anything. It is a Theory, an explanation.

 

[StringJunky]

4 minutes ago, michel123456 said:

I ment that Relativity is not a force of nature. Relativity cannot cause anything. It is a Theory, an explanation.

 

I know. It appears to be fundamental, which means 'it is what it is'.  

[Romeo22]

2 hours ago, Janus said:

Both electromagnetic waves and gravitational waves (the aspect of gravity that travels at c) are massless entities, and as such are required to travel at c, the invariant speed of the universe.  When neutrinos were first proposed and and later discovered, they also were assumed to be massless and thus were expected to travel at c.  This is a consequence of Relativity.

This was also my initial anaysis... 

Special Relativity was already indirectly incorporated into electromagnetism by Maxwell -- the first invaraiance of c. We have come to appreciate this in SR and QFT -- the spin 2 graviton. 

But my analysis is from a purely General Relativistic viewpoint. To speak of the speed of gravity is to speak of the speed of space-time itself. 

How then does one quantify the speed of space-time? Or to overly simplify the imagination of this... How does one quantify mathematically the speed of flat Euclidean space?

Edited December 2, 2018 by Romeo22

[J.C.MacSwell]

15 minutes ago, Romeo22 said:

This was also my initial anaysis... 

Special Relativity was already indirectly incorporated into electromagnetism by Maxwell -- the first invaraiance of c. We have come to appreciate this in SR and QFT -- the spin 2 graviton. 

But my analysis is from a purely General Relativistic viewpoint. To speak of the speed of gravity is to speak of the speed of space-time itself. 

How then does one quantify the speed of space-time? Or to overly simplify the imagination of this... How does one quantify mathematically the speed of flat Euclidean space?

0 m/s?

[Rajiv Naik]

nobody is talking about Quantum entanglement.

its not true that information Travels with speed of light only- its only in our spacetimes.

otherwise all information is singularly  present in quantum state, outside the spacetime and hence in valcume which is radiation free state.

no  time is required - as time is property of speed of light in space. 

entanglement  clearly indicate that time  doesnt exist beyond space.

 

 

 

[Strange]

19 minutes ago, Rajiv Naik said:

nobody is talking about Quantum entanglement.

its not true that information Travels with speed of light only- its only in our spacetimes.

otherwise all information is singularly  present in quantum state, outside the spacetime and hence in valcume which is radiation free state.

no  time is required - as time is property of speed of light in space. 

entanglement  clearly indicate that time  doesnt exist beyond space.

!

Moderator Note

Don't hijack threads with off-topic and speculative ideas.

 

[StringJunky]

2 hours ago, Romeo22 said:

To speak of the speed of gravity is to speak of the speed of space-time itself.

I think really you should say the speed  is set by spacetime... but it's still wrong AFAIK.

[Romeo22]

54 minutes ago, StringJunky said:

I think really you should say the speed  is set by spacetime... but it's still wrong AFAIK.

AFAIK?

 

Yes the speed of space-time itself as per GR has no direct link to the speed of electromagnetic disturbances 

55 minutes ago, StringJunky said:

I think really you should say the speed  is set by spacetime... but it's still wrong AFAIK.

What are the quantitative intricacies that lead to the speed to be "set by space-time"?

Edited December 2, 2018 by Romeo22

[swansont]

6 hours ago, michel123456 said:

It cannot be a consequence of Relativity. Relativity is an explanation, it is not a cause.

Consequence does not mean cause. The theory that identified c as the speed limit is relativity. Saying it’s a consequence of relativity is perfectly fine.

 

6 hours ago, michel123456 said:

It is not because they are massless they propagate at c. It is because they propagate at c that they must be massless.

They imply each other. There’s no one way it must be presented.

 

[studiot]

Here are some conclusions that ere drawn a long time ago (1923).

Looking at a 2018 cosmology/relativity text they are still recognisable and current.

As far as I can tell we still have not resolved the questions of alternatives, though I would welcome more information.

 

 

[quiet]

Let's go slowly.

Is the propagation of waves essential? Let's put the question in another form. Could the universe exist without waves?

To give content to this post I need to propose a provisional and hypothetical answer.

H1 - If the definition of existence includes enduring a finite time, then I suppose that without waves the existence of the universe would be impossible.

In our universe, waves propagated in material media are slower than waves propagated in a vacuum. (I confess that this is the first time that this detail seems very significant to me). In our universe, the wave velocity in the vacuum is the maximum speed that a wave propagation can have.

Is there any reason that makes an infinite wave speed impossible in a vacuum?

I will try the most obvious reasoning that comes to mind. The answer depends on how we conceive the universe. In case of conceiving it as a finite system, an infinite wave velocity is impossible. Why ? Because space could never develop a spatial cycle, nor a finite portion of the cycle. Without the development of a spatial cycle or a finite portion, the existence of a wave is impossible.

H2 - In a finite universe, the maximum propagation velocity is necessarily finite.

To reach the conclusion, I did not need to squeeze my brain too much. Okay, finite universe, finite maximum propagation speed. In our universe, that finite velocity has a precise value, symbolized C.

Is it an acceptable idea to assume that C is determined by properties and conditions of the universe?

Could it happen that, after investigating those properties and those conditions, the answer to the question of this thread appeared clearly? That is to say, why the speed of electromagnetic propagation in the vacuum and the speed of the gravitational waves are equal?

Maybe is happening the same thing that tells the story of the elephant and the blinds. In case we are condemned to permanent blindness, the minimum we need is a scale model of the elephant, to be able to go through that with the hands completely, thus enabling the understanding of the form.

Edited December 8, 2018 by quiet