Some questions about the speed of light

[Ryanbighead]

• If the yet-to-be-discovered graviton is the messenger particle of gravity, then gravity can but propagate at the speed of light.
• If the effect of gravity were instantaneous, could this property be exploited to allow faster-than-light communication? Movements of objects far away would be known before light signals of those objects reached the observer.
• Imagine the sun were to suddenly disappear. If gravity propagates at the speed of light, earth would continue along its orbit for approximately eight minutes before flying off into space.
• If the speed of light is not invariable but medium-specific, could gas, dust, or hypothetical dark matter effect its speed in space?
• How is the distance of far-away objects in space measured, and what would be the role of the above point on this?

NO!

I see now what you are doing! Having us discuss the questions posed in your homework under the guise of a healthy debate / chat thing.

Naughty!

If you want someone to do it for you; R150/page.

 

[isie]

"................anyone with a computer and orbit computation or numerical integration software can verify the consequences of introducing a delay into gravitational interactions. The effect on computed orbits is usually disastrous because conservation of angular momentum is destroyed. Expressed less technically by Sir Arthur Eddington, this means: “If the Sun attracts Jupiter towards its present position S, and Jupiter attracts the Sun towards its present position J, the two forces are in the same line and balance. But if the Sun attracts Jupiter toward its previous position S’, and Jupiter attracts the Sun towards its previous position J’, when the force of attraction started out to cross the gulf, then the two forces give a couple. This couple will tend to increase the angular momentum of the system, and, acting cumulatively, will soon cause an appreciable change of period, disagreeing with observations if the speed is at all comparable with that of light.” (Eddington, 1920, p. 94)"

Source http://www.metaresearch.org/cosmology/speed_of_gravity.asp

would gravity not be an extenstion of a body, sort of a field around that object - so the suns gravitational field of influence extends to basically the edge of the solar system and all objects with in that field are subject to said influence, hence the reason its 'instantanious'

 

[Humberto]

So if gravity is instantaneous and nothing can travel FTL, then I would think that the "Higgs boson"(Gravity) is not a particle but an oscillation(of some sort in multiple dimensions) and that everything shares this interaction IE. the bigger the mass the more Gravity it has
...(eks afrikaans)

Perhaps gravity isn't one of the fundamental forces, but merely a distortion of spacetime.

 

[Sinbad]

would gravity not be an extenstion of a body, sort of a field around that object - so the suns gravitational field of influence extends to basically the edge of the solar system and all objects with in that field are subject to said influence, hence the reason its 'instantanious'

no, it extends to infinity. It diminishes in intensity with distance though

 

[Cius]

@Mike: No he is not. He is saying if there where any delay orbits would become faster and faster due to the delay. Hence there is no speed of gravity. Its instant. Even something faster than the speed of light would have some delay causing the effect. Hence its not measured by times. The effect is instant.

@Sinbad: Not sure what you are asking. What couple???

 

[zippy]

Some posts about the speed of gravity:
http://www.physicsforums.com/showthread.php?t=164489

 

[zippy]

Perhaps gravity isn't one of the fundamental forces, but merely a distortion of spacetime.

I believe that's what Einstein says.

It's not a force.

You could probably measure the speed at which the change in gravitational effects occur as a star loses mass. The Sun's gravitational influence must be getting less as it loses mass. I imagine we don't have the technology to measure this yet.

I think this speed can't be faster than the speed of light, but because the loss of stellar mass is gradual, it's impact on planets orbiting is do small that the time taken for the change to be felt is not a major issue.

 

[Sinbad]

@Mike: No he is not. He is saying if there where any delay orbits would become faster and faster due to the delay. Hence there is no speed of gravity. Its instant. Even something faster than the speed of light would have some delay causing the effect. Hence its not measured by times. The effect is instant.

@Sinbad: Not sure what you are asking. What couple???

This one

when the force of attraction started out to cross the gulf, then the two forces give a couple. This couple will tend to increase the angular momentum of the system,

 

[Swa]

1. Is it known why the speed of light is constant, why photons always travel at the speed c exactly?
2. Is it understood why c = 299,792,458 m/s? What is special about this number, other than the fact that it represents the speed of light?
3. Does gravity also propagate at the speed of light?

1. If you mean why they travel at the specific speed then no. It's believed that this is the ultimate speed attainable though so massless photons would travel at that speed.
2. Again same as in number one. It's believed by some to be the maximum speed at which "empty" space can interpret information so no information (particles, photons, atoms) can travel faster.
3. It's believed so.

 

[Jings]

Does electricity propogate at the speed of light?

 

[DrJohnZoidberg]

Does electricity propogate at the speed of light?

Basically yes, but the medium it travels through (e.g. A copper wire) makes it slower.

 

[RiaX]

Does electricity propogate at the speed of light?

Not so simple. In an open field then yes electricity would travel at the speed of like, inside a vaccuum like space. However electricity does not travel at the speed of light when its conducted through matter.

 

[azbob]

Does electricity propogate at the speed of light?

It can travel even faster.

 

[DrJohnZoidberg]

It can travel even faster.

:erm: Electric current propagates as a wave, which cannot travel faster than the speed of light.

http://en.wikipedia.org/wiki/Speed_of_electricity

 

[azbob]

:erm: Electric current propagates as a wave, which cannot travel faster than the speed of light.

http://en.wikipedia.org/wiki/Speed_of_electricity

Cherenkov radiation

 

[Jings]

Cherenkov radiation

Have you been researching alternates to the Big Bang Theory?

http://www.journaloftheoretics.com/articles/3-3/musha-final.pdf

 

[azbob]

Have you been researching alternates to the Big Bang Theory?

http://www.journaloftheoretics.com/articles/3-3/musha-final.pdf

Haha no, I've messed around a bit with photonics crystals so encountered it there.

 

[eitai2001]

AFAIK nothing in space time (including gravity) can travel FTL, though space itself can travel FTL - well at least expansion of space" between galaxies observed by those galaxies furthest away from us they are moving away from us at speeds greater then light

1) If gravity does not propogate faster than light, then how do black holes exists (where light cannot travel fast enough to escape the gravity of a blackhole). My theory, gravity propogates at different speeds depending on the mass of the underlying object, and in the extreme (a black hole), it is faster than light.

2) (A sideline comment) ... If space is infinite, then how is it expanding (How does something infinite expand)? Does that mean it is finite? And if so, what lies outside the boundaries of space? Don't you wish you knew

 

[RiaX]

Careful when using a black hole to explain your theory about things traveling faster than light. Firstly we dont know what happens at the singularity, secondly for something to be seen it must emit light a black hole is too dense to allow photons to leave, think of the sun. It takes an incredible amount of time for a photon to go from the core to the surface. So that may not even be possible in a black hole.

Gravity does not propgate faster than light but the same therefore light will not be able to leave once it goes over the even horizon. Since nothing can travel faster than light, light itself cannot escape.

About your second point. Again think of a black hole, its gravity is so immense that its theorised the singularity is a single point. Now what other object do we know of that was a single point ? the universe itself, so its possible that a black hole could be the cause of a universe like structure. Its called a white out i think ... all opinion though