# does gravity travel faster than light ?

Discussion in 'Physics & Math' started by RainbowSingularity, May 28, 2019.

1. ### RainbowSingularityValued Senior Member

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does gravity travel faster than light ?

3. ### AsexperiaValued Senior Member

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What's the speed of gravity?

5. ### exchemistValued Senior Member

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"Gravity" is not, itself, an entity that travels.

A disturbance in a gravitational field, however, does propagate at c. Not faster.

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7. ### Janus58Valued Senior Member

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It depends on what you mean by "travel". Gravity, as the attraction between masses, is a field ( or a curvature in space-time in GR), Light is a radiation.
Light has a field associated with it, the electromagnetic field, which is what is responsible for the force interaction between charges and magnetic poles.
Gravity has a radiation associated with it, gravitational radiation ( the gravitational waves detected by LIGO)

It doesn't make sense to compare the speed of a radiation with the "speed" of a field ( a field is just "there" and doesn't have a speed)

In each case, the radiation is due to "ripples" propagating through the field, and in both cases, they travel at c.

Photons and gravitons are quanta of their respective radiations.

While you will hear gravitons being referred as the mediating particle for gravity, this means virtual gravitons. In the same way, under QED, virtual photons are the mediators for the electromagnetic field. (Though to be fair, gravitions are still hypothetical as we have not of yet been able to gather gravity into the quantum fold. )

In essence, electromagnetic waves carry information about changes in the electromagnetic field, while gravitational radiation carries information about changes in the gravitational field.

8. ### VmedvilRegistered Member

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The Speed of Gravity is the speed of light, we were taught during physics class, this can be found by solving for the velocity of gravity from the Newtonian Equation, if the Sun disappeared the gravitational effect would be felt at the same time you saw the sun's light disappear.

Which can also be found in the equation for Schwarzchild Radius of a Black hole as "C" being the velocity of gravity term.

Last edited: Jun 8, 2019
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9. ### JJMRegistered Senior Member

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If you are using 'gravity' as a propulsion device, not sling-shot, then YES. MANY MANY TIMES FASTER THAN LIGHT.

10. ### James RJust this guy, you know?Staff Member

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I assume this is a reference to "warp drive". If that turns out to be possible, then it won't be so much that things are travelling faster than light in space, but rather that the space itself is being compressed and expanded to move an object rapidly from one region of space to another.

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11. ### TabbyStarRegistered Member

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I wish I understood the equations posited in the warp (aka; Alcubierre) drive. The only general attribute to the theory, I understand, is that it requires negative mass (not antimatter as you and others already know). Since negative mass itself is undiscovered, the warp drive concept cannot move forward to a "testing of concept" phase.

Does anyone have an opinion if, hypothetically, a ship within the warp bubble would be immune from external gravitation? Like if it traveled near a BH, or neutron star, would it be unaffected while in the bubble?

Thanks for all feedback on helping me advance my knowledge!

12. ### RainbowSingularityValued Senior Member

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I found myself asking myself this same question again today as i watched one of my favorite physicists talk about the speed of light.

this is Bowsers thread on the same subject started a year earlier than mine

is Gravity a speed ?

assuming
gravity creates speed
so there for, using very crude logic it would have a speed coefficient(would it?)

earth gravity has a speed dynamic as acceleration to mass(?)

increase the mass/gravity & it increases the speed(?)

neutron(pulsars) stars for example
sending out radiation bursts more powerful than their gravity ...(?)

our Sun(for example) sending out Coronal mass ejections, faster than its own gravity & with more force (?)

yet gravity is a weak force(this stuff is soo confusing)

the one force that binds us all.... gravity ? or electricity ?(that's probably a separate thread)

soo the clincher

they were saying
if they were on the surface of a large sun
& they jumped off a height(roof top or table)
by the time they reached the ground they would be traveling at some crazy speed

soo
while i cant understand the math
generically
i guess im wondering if mass is relative to the acceleration when the mass remains the same

an object appearing on the surface of a large body
would its mass remain the same and it just gain acceleration via gravity ?

for example a 100 kilogram human
suddenly being teleported to 5 feet above the surface of a super earth(10 times earth gravity/size)
would be traveling at X speed when they hit the ground & go splat

but their mass always remains the same ?

13. ### BeaconatorValued Senior Member

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When observed... double slit replay!

14. ### RainbowSingularityValued Senior Member

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awesome post thanks

i find it quite fascinating while sitting just over the horizon of my ability to formulate the maths

it makes me wonder about fields

so space-time is effectively a field ?
gravity = field
space-time = field
electricity = field & ?
light = wave & particle
time = ?
mass = particle ?

mass of planets and things people what ever inside that field are what ?(not a field but they create their own field & are subject to other fields & laws i.e light speed mass etc)

my original question is
can the speed of gravity as an accelerating model of force be defined as a set rule
like 10 times mass to the what ever etc

for an ends of being able to potentially quantify possible speeds inside a black hole(past the event horizon) to establish if the laws of physics as we know them do not apply once inside the black hole(assuming there is an inside and not just an opposite side)

15. ### BeaconatorValued Senior Member

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A cell expels things when it gets full. Black holes expel gama rays and above the same way

16. ### TonyYuanGravitational Fields and Gravitational WavesRegistered Senior Member

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The speed of gravity is infinite. The speed of gravitational wave is equal to the speed of light c.
We need to distinguish gravitational field from gravitational wave. They are different concepts. The speed of the effect of gravitational field on objects (gravity) is infinite.

17. ### Michael 345New year. PRESENT is 72 years oldlValued Senior Member

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Not really wanting to get to deep into this but just a couple of things to consider

Keep it simple. Just the Earth and Moon. Nothing else. As the are their gravitational fields interact with each other

Moon vanishes in a picosecond. Question becomes

How long does it take for the Earth's gravitational field to flood the region the Moon and it's gravitational field occupied?

Would a optical detector and gravitational detector, placed at the middle of Moon's now vanished, mass register detection at the same moment?

18. ### TonyYuanGravitational Fields and Gravitational WavesRegistered Senior Member

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The action of gravitational field on objects is instantaneous, which is action at a distance.

The speed of gravity is infinite. The speed of gravitational wave is equal to the speed of light c.
We need to distinguish gravitational field from gravitational wave. They are different concepts. The speed of the effect of gravitational field on objects (gravity) is infinite.

Newton told us that a long time ago. If not, the whole universe would not be what it is now. It's not going to be stable.

19. ### Q-reeusBannedValued Senior Member

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Sorry but that is a complete nonsequitur. Cannot have your cake and eat it too.
See above.
Newton, and for around two centuries following, was not able to incorporate the concept of finite propagation speed i.e. wave equation (Maxwell). Let alone later Lorentz invariance on top of that.

20. ### TonyYuanGravitational Fields and Gravitational WavesRegistered Senior Member

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The premise of Lorentz transformation is to assume that the speed of light is constant! Then you use Lorentz transformation to prove that the speed of light is constant. Maybe this is the beginning of SR contradiction theory.

21. ### Q-reeusBannedValued Senior Member

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And if observation contradicted a consistent application of Lorentz invariance - you would have a crushing argument in your favor. Alas and alack - tis not so.

22. ### TonyYuanGravitational Fields and Gravitational WavesRegistered Senior Member

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The constant speed of light is very easy to explain, and there is no need to make that kind of ignorant assumption.
Einstein's greatest contribution was to make a simple thing like God's prediction, and lost the attributes that science should have.

People who have a little bit of mathematical attempt should know that the speed of gravitational field acting on an object is infinite, which is far faster than the speed of light. Einstein's SR is a contradiction theory, and even contradicts his GR.
And that quantum mechanics that Einstein hated, haha, it's been half a century since, and humans are still being teased by Einstein's SR, which is really funny.

Last edited: Jun 16, 2021
23. ### QuarkHeadRemedial Math StudentValued Senior Member

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You are confused, my friend' Tue enough, Newton, who considered gravitation as a force, was forced to the conclusion that his scalar theory predicted instantaneous action at a distance.
He himself didn't like that, neither did anyone else.

Enter Einstein. He described gravitation as a field, not a force. (fields don't and cannot in principle travel at any speed whatever.)
The observed effects of gravitation are here described by the non-uniform spacetime metric, leading to spacetime curvature
Ever hear of the light quantum, aka photon? Einstein discovered it!

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