Curving space at speed of light?

[Johanpoan]

As something approaches the speed of light the objects relative mass is increasing.
When the relatvie mass is increasing it increases in gravity.

When it's close to the speed of light it's closer to curve space-time infinitely?

What happens when space-time is curved really much around an object?

Is it closer to eveything around? :)

Is everything at the same place since gravity is infinite at the speed of light? :P

 

[Mentz114]

As something approaches the speed of light ...

With respect to what ? There is no absolute motion so you can only talk about relative velocity between two frames.

the objects relative mass is increasing.
When the relatvie mass is increasing it increases in gravity.

I don't think so.

What happens when space-time is curved really much around an object?

You get a black hole and an horizon.

 

[Johanpoan]

With respect to what ? There is no absolute motion so you can only talk about relative velocity between two frames.

Where the object was for one second ago compared to where it is now for instance .

I don't think so.

But big masses as the earth, stars etc. curves spacetime abit because of their masses and volumes? Does objects that gain relative mass because of their speed when they're approaching the speed of light not create gravity?

 

[Dmitry67]

When the relatvie mass is increasing it increases in gravity.

No (common misconception)
Gravity is created by the REST mass + (in dynamic cases) by the other elements of the stress-energy tensor

As an example, say, there are 2 bodies (say, Earth and Moon) attracting to each other with the force of F
If they will be moving very fast their attraction will be lower F=F0/SQLRT(1-v^2/c^2)

 

[Johanpoan]

No (common misconception)

I read this topic https://www.physicsforums.com/showthread.php?t=68454"
And there it seems as relative mass contributes to gravity.

As an example, say, there are 2 bodies (say, Earth and Moon) attracting to each other with the force of F
If they will be moving very fast their attraction will be lower F=F0/SQLRT(1-v^2/c^2)

So it's actually the inverse? The closer an object is to the speed of light the less gravity force it has on other objects?

But a comet or some satelite traveling at close to light speed out of our solar system not in orbit of anything special. What will happen if it is passing an object? Does it have close to no affection in gravity force on the object it's passing becouse of your formula above?

 

[Dmitry67]

I guess the tread you quoted have a very good explanation:

http://lanl.arxiv.org/PS_cache/gr-qc/pdf/9909/9909014.pdf

is still the best reference I've found online.

The clearest statement that kinetic energy does indeed contribute to gravitational mass is found in the abstract of this paper.



The paper is mainly concerned with how the internal kinetic energy of a system with moving parts contributes to it's "gravitational mass" when the momentum of the system as a whole is zero. The guiding result here is that energy and pressure both cause gravity - but, for a closed system, it appears that the virial theorem requires that the appropriate intergal of energy and pressure be equal to the total energy of the system. (This is what I get from reading the paper, I've been meaning to work out some actual examples.)

If you're interested in the gravitational field of a moving object there is an unfortunate problem. As soon as the velocity gets high enough to significantly affect the gravitational field of an object, one cannot consistently view gravity as only a force - the curvature of space itself becomes important. This shows up in the curvature of light, for instance - it curves twice as much as it ought to.

A qualitiative comparison to the electric field of a moving charge can still be made if one does not want exact results. Basically one expects the field to concentrate in a transverse direction rather than to be radially uniform. To really do the problem right requires that one analyze the problem in terms of tidal forces (the Riemann tensor), rather than the "gravitational field".