/sci/ - Science & Math

Gravity is expected to propogate at the speed of light. Last I heard experiments were confirming this.

Gravity isn't a force that moves around, it's a symptom of mass; in other words, it's the mass of an object that displaces spacetime (press your thumb into a wet balloon, it makes a dent, water droplets gravitate toward your thumb - the harder you press, the stronger the effect).

So gravity cannot be measured in terms of speed.

In Newtons gravity theory, the effect is instantanous over any distance - essentially in contradiction to the spacetime of special relativity (you could send information to the past with such "spooky action at distance").
This is resolved in general relativity, where gravitational waves can also "travel at the speed of light". The speed of light is a feature of how space relates to time, so the gravitational speed is more closer to the basics, actually.

>>6162866
What about the speed at which it radiates from a mass?

>>6162874
I guess that depends on the viscosity of space-time - but given that time is an inherent property of the space-time matrix, it cannot be subject to itself, and the effect must be instantaneous.

>>6162878
>and the effect must be instantaneous.
nope nope nope.
any information travels at the speed of light.
don't be a silly puddy

>>6162866
>Gravity isn't a force that moves around, it's a symptom of mass; in other words, it's the mass of an object that displaces spacetime (press your thumb into a wet balloon, it makes a dent, water droplets gravitate toward your thumb - the harder you press, the stronger the effect).

>So gravity cannot be measured in terms of speed.

>>6162878
>I guess that depends on the viscosity of space-time - but given that time is an inherent property of the space-time matrix, it cannot be subject to itself, and the effect must be instantaneous.

This is the stupidest crap ive read on sci in a while, you have no idea what you are talking about.

>>6162888
I have to agree.

If gravity has useable information in it (spoiler: it does) then it is limited by the speed of light. Don't know the exact research myself but I'd assume it traveled at c.

>>6162886
>gravity
>information

>>6162932
>gravity
>not information

>you
>not retarded

>>6162935
I'm picking
>me
>not retarded

Unless you are able to change gravity at a whim, there is no way you can use it to propagate information.

>>6162938
>take a mass, hold it still, measure the gravity from far away, call it a 0
>move the mass to another point, measure gravity far away, its now different, call it 1.
>moving the mass between the 2 points can send a binary signal

>>6162938
>confirmed for not knowing any physics whatsover.

Hahahah oh wow son.

>>6162919
Do we have any experimental data on this, or are we simply assuming it cannot move faster than c because to do so seems entirely impossible?

>>6162935
Take your meds EK

>>6162861
Gravity is expected, by the definition and formalisms associated with General Relativity, to travel as a wave at the speed of light.

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

Although we have not come up with an apparatus sensitive enough to conclusively prove their existence directly, the phenomenon of gravity waves is generally seen (among physicists) as just as factual as GR itself.

>>6163077
I thought current theories were leaning at gravity being an elementary particle of some sort.

>>6163084
It's not that gravity is a particle, but I assuming you are referring to the business about the Higgs Boson, yes?

Anyway, the long-story-very-short of it is there is all sorts of shit smaller than the constituents of atoms (protons, neutrons, electrons). These smaller things give rise to the things like protons, neutrons, and all kinds of properties. Anyway, the Higgs boson is the particle that should interact with a particular field, and the strength of that interaction is what we call gravitational mass.

I was better at GR than QM or particle physics though, so take that statement with a shaker full of salt and a wikipedia article or five.

>>6162878
>>6162866
Why reply if you have no idea what you are talking about?

>>6162861
Clearly this is an area which verges on quantum gravity, which if you have been paying attention we do not understand yet. However, there are currently large scale experiments to detect gravitational waves http://en.wikipedia.org/wiki/LIGO
http://en.wikipedia.org/wiki/VIRGO
which are predicted in general relativity. Given that they are predicted in relativity, they are predicted to travel at light speed or below. I'm sure there are some freaky quantum gravity theories in which gravity travels faster than light, but I am unaware of them

>I understand they are not directly comparable.
They are comparable.

>>6163066
EK hasn't posted for months.

>>6163093
I'm referring to theoretical Gravitons.

>>6163093
>>6163084
Higgs a priori is unrelated to gravity. It is to do with mass. We don't have an accepted theory of quantum gravity yet, hence string theory - not even wrong etc.