# How fast is gravity?

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I thought coins at 1st, but the Zinc part made me rethink, as most are Nickel alloy.

unless its the new Copper coinage that is only plated on Zinc and Nickel(cheapskates!).

(thats why some "Copper coins" will stick to a Magnet!)

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thankyou Aeschylus for your first paragraph reply."why didnt someone just say that in the first place".

your not here to discuss breakthroughs or new conceptions in science just to accept the orthadox opinion at the time.from now on i will just ask questions for information' date='however i dont sit comfortably with presumptions,probability,virtual as solid science it seems to be "our best guess is its this"and everyone just goes along with it kind of like sheep.Well thank goodness for scientists who question and say this is silly theirs got to be a better explanation,otherwise you lot would indeed believe the earth was flat." blackholes"...[/quote']

NO I did not say that, science is certainly open to new ideas, however it is firmly shut to metaphysical crackpottery.

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I thought coins at 1st' date=' but the Zinc part made me rethink, as most are Nickel alloy.

unless its the new Copper coinage that is only plated on Zinc and Nickel(cheapskates!).

(thats why some "Copper coins" will stick to a Magnet!)[/quote']

US pennies are 97.5% zinc with a copper cladding. I was indeed referring to the fact that some pennies on a table aren't falling, and are held up by electrostatic repulsion. Conceptually no different than a magnet being held up by a frictional force.

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got ya )

heres something that HAS bugged me though, and Im sure youre the one to ask as Phsics isnt my area.

the coins on the table have Potential energy, it required energy to lift them there, but if one were to fall off that potential would become kinetic and then there would be a transfer, in way of heat on impact with the floor and sound "Chink" as it hit the floor.

now ignoring the "speed" of gravity, if the earth were to vanish, what would happen to that potential energy?

I have my answer and did provide that to my mate, but Im sure it wasnt detailed enough for his likeing

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the coin would be caught by the suns gravity and orbit it for ever....until an alien happened on your coin and said "oh look £2 coin ive got enough for a happy meal now"

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got ya )

heres something that HAS bugged me though' date=' and Im sure youre the one to ask as Phsics isnt my area.

the coins on the table have Potential energy, it required energy to lift them there, but if one were to fall off that potential would become kinetic and then there would be a transfer, in way of heat on impact with the floor and sound "Chink" as it hit the floor.

now ignoring the "speed" of gravity, if the earth were to vanish, what would happen to that potential energy?

I have my answer and did provide that to my mate, but Im sure it wasnt detailed enough for his likeing [/quote']

It would vanish with the earth.

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omg yes your right....the earth could like totally vanish...it could be absorbed by dark matter and dissapear but its ok like a photon it could reappear right...

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Since we dont know what dark matter is, how can you say it can "absorb" the earth?

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It was a "what-if" question.

Nobody was actually proposing that it could happen.

Sheesh.

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Oh I know, I think its a valid question as well, just a question that I have no idea how to answer. I was just responding to philbo1965uk's comment.

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got ya )

heres something that HAS bugged me though' date=' and Im sure youre the one to ask as Phsics isnt my area.

the coins on the table have Potential energy, it required energy to lift them there, but if one were to fall off that potential would become kinetic and then there would be a transfer, in way of heat on impact with the floor and sound "Chink" as it hit the floor.

now ignoring the "speed" of gravity, if the earth were to vanish, what would happen to that potential energy?

I have my answer and did provide that to my mate, but Im sure it wasnt detailed enough for his likeing [/quote']

It would vanish with the earth.

$U=mgh$

if the earth were to vanish, g and h would both be zero, so the potential energy would in turn become zero.

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$U=mgh$

if the earth were to vanish' date=' g and h would both be zero, so the potential energy would in turn become zero.[/quote']

Actually, if you are talking about potential energy of a body within a gravity field such as the Earth's, then the proper expression is:

U= -GMm/r

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thats similar to how I figured it, the energy to make the Earth "Vanish" would have to be strong enough to compensate for the potential energy as well or at least "Undo" it.

and yes it was hypothetical and not at all possible

Thanks for the conformation(s) and the Formula, Ill show him that when I get chance

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Another confirmation of GR, consistent (of course) with gravity acting at the speed of light.

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There is a way to prove that the speed of gravity is c, depending on your frame of reference, starting with electrodynamic field theory, and turning it into gravitational field theory by relating electric charge to inertial mass. So that a graviton is nothing more than a different name for a photon.

Regards

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I started reading this thread' date=' and I read I don't know maybe the first 30 posts.

There is a way to prove that the speed of gravity is c, depending on your frame of reference, starting with electrodynamic field theory, and turning it into gravitational field theory by relating electric charge to inertial mass. So that a graviton is nothing more than a different name for a photon.

Regards[/quote']

You still need data to confirm that the theory is correct. Gravitons have never been detected, and are also not part of GR.

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You still need data to confirm that the theory is correct. Gravitons have never been detected, and are also not part of GR.

If photons have been detected, and gravitons are photons, then gravitons have already been detected.

The photoelectric effect establishes that light behaves like a particle. Isn't that what Einstein won his nobel prize for?

Regards

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you saying gravitons are photons doesn't make it true. btw, gravtons have a different spin than photons.

Regards

edit:

Actually' date=' if you are talking about potential energy of a body within a gravity field such as the Earth's, then the proper expression is:

[b']U= -GMm/r[/b]

it is the same thing as mgh. f=ma=mg r=h $f=\frac{-GMm}{r^2}$

$mg=\frac{-GMm}{r^2)$ now multiply both sides by r $mgh=\frac{-GMm}{r}$

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If photons have been detected' date=' and gravitons are photons, then gravitons have already been detected.

The photoelectric effect establishes that light behaves like a particle. Isn't that what Einstein won his nobel prize for?

Regards[/quote']

It's a huge leap from proposing to develop a model that is analogous to photons to saying that gravitons are photons. They aren't the same thing.

Yes, Albert won "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect"

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edit:

it is the same thing as mgh. f=ma=mg r=h $f=\frac{-GMm}{r^2}$

$mg=\frac{-GMm}{r^2)$ now multiply both sides by r $mgh=\frac{-GMm}{r}$

mgh is an approximation valid when g can be considered constant. IOW for small changes in r' date=' near the surface of the earth, if you are using 9.8 m/s[sup']2[/sup]

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It's a huge leap from proposing to develop a model that is analogous to photons to saying that gravitons are photons. They aren't the same thing.

Yes' date=' Albert won "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect"[/quote']

What I am proposing, is that they are the same thing. What is so terrible with thinking this? By all means show me.

Regards

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What I am proposing' date=' is that they are the same thing. What is so terrible with thinking this? By all means show me.

Regards[/quote']

I propose that light is made up of elephants.

Why would they be the same thing? Photons are made up of light. Gravitons are supposedly made up of gravitational waves. There is currently no basis on which you can say they are the same thing.

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'']There is currently no basis on which you can say they (gravitons and photons) are the same thing.

Well yes there is, they have the same special fundamental speed, with respect to the source.

Regards

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Well yes there is' date=' they have the same special fundamental speed, with respect to the source.

Regards[/quote']

Which means that they have one property in common (zero rest mass). One shared property is no evidence of being the same thing.

The proton and positron share the same property of charge, that doesn't make them the same thing. The electron and muon share three common properties, even that does not make them the same thing.

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Which means that they have one property in common (zero rest mass). One shared property is no evidence of being the same thing.

The proton and positron share the same property of charge' date=' that doesn't make them the same thing. The electron and muon share three common properties, even that does not make them the same thing.[/quote']

Agreed, but something is still telling me that grand unification lies in some kind of simplification. Just wondering if its here. I would think that particles should be classified according to their mass.

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