How can there possibly be a "speed of gravity"?

>>8802641
Your question doesn't make sense. What sort of conceptual problems are you having with it? 1- It's easy to understand and it's well specified in the math. 2- It's how the world actually is, according to the evidence.

>>8802654
http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html
>To begin with, the speed of gravity has not been measured directly in the laboratory—the gravitational interaction is too weak, and such an experiment is beyond present technological capabilities. The "speed of gravity" must therefore be deduced from astronomical observations, and the answer depends on what model of gravity one uses to describe those observations.
If gravity has a finite "speed" and therefore acts locally it would lead to bizarre phenomena like celestial objects continuing to orbit non-existent centers of gravity. So then where has this ever been observed? The author even admits that giving gravity a finite "speed" violates all known observations in the Solar System, so then why do it at all?

If gravity was instantaneous, you could transmit information faster than light just by wiggling a heavy object and measuring the change in attraction to that object some distance away.

>>8802705
>If gravity has a finite "speed" and therefore acts locally it would lead to bizarre phenomena like celestial objects continuing to orbit non-existent centers of gravity.

Correct.

>The author even admits that giving gravity a finite "speed" violates all known observations in the Solar System

What? No. The author almost certainly does not say that, and I don't even need to read it to know that.

>>8802714
>>8802705
Welp, the author did say that:
>Putting a "light travel delay" (technically called "retardation") into newtonian gravity would make orbits unstable, leading to predictions that clearly contradict Solar System observations.

Conclusion: Author doesn't know what they're talking about, and so stop reading that page.

>>8802715
Or we both just need to read to the next paragraph, where he corrects his misleading sentence, and says that GR is indeed consistent with solar system observations.

Because of you not understanding what gravity is, or actually, what anything is.

>>8802713
By that standard entanglement violates the speed of light as well.

>>8802725
Leddit tier posts like this should be ban worthy.

>>8802731
Yes and no.

Yes according to standard interpretations.

No because you cannot use it to communicate faster-than-light.

>>8802731
>>8802735
That was unclear. Let me try again. If gravity acted instantaneously, you could trivially built a machine that allowed faster-than-light communication: One side wiggles a large mass, and the other side detects movement in this mass.

You cannot do that with entanglement. Quantum entanglement does not allow communication. You cannot communicate with entanglement. The poor starting analogy is that imagine a machine that creates two boxes, and at random it puts red balls or blue balls in the box. It will always be 2 red balls or 2 blue balls, but you don't know which until you open one of the boxes. As soon as you open one of the boxes, then you know what the other box contains, even if the box is now very far away. However, that doesn't allow you to communicate faster-than-light.

In actuality, entanglement is weirder than that: It cannot be that the boxes contents are fixed when the two paired boxes are made. Instead, it's something more like: when one of the boxes is opened, it randomly rolls right then to determine the contents of both boxes. Thus, it fixes the contents of the other box instantaneously, faster-than-light, but you still cannot use it to communicate. You cannot control the color of the ball in the box - which is what would be required for communication.

>>8802731
You can't transmit a message with entanglement though

>>8802741
This is correct.

If the moon instantly vanished, and gravity propagated faster than c, then we could infer from tidal forces, among other effects that it was gone before we saw it disappear.

>>8802734
What? Is it not a fact that no one understands gravity?

>>8802713
>If gravity was instantaneous, you could transmit information faster than light just by wiggling a heavy object and measuring the change in attraction to that object some distance away.
Has anyone actually tested this and proven it false?

>>8802776
Not exactly. We've tested other predictions. GPS is practically the sole practical engineering project that relies on general relativity to work. Without it, GPS locations would be wildly off. Every time you use GPS, that's a testament to the correctness of GR.

>>8802762
>speaking for every human on earth

>>8802762

We don't really 'understand' anything. We only describe observed behavior. We don't understand why electrons and protons are attracted to each other, but we can use our observations of it to accurately describe the behavior. Saying we don't understand gravity is a bit like saying we don't understand why pushing a ball makes it roll forward. Why not perpindicular? Why not parallel? Why roll at all? If an object existed that exhibited such a behavior we'd describe it in the same way.

>>8802641
Causality cannot be violated. Fucking pleb.

>>8802641
An infinite "speed of gravity" would break causality. If the sun were to disappear suddenly, the Earth would immediately fling off into space, so we would know instantly. The shortest time of "knowledge of an event occurring" is the distance between us and the event, divided by the speed of light.

>>8803530
Information cannot travel faster than light. There is nothing wrong with non-particles being faster than light.

>>8802715
>Author doesn't know what they're talking about, and so stop reading that page.

Actually it's you that doesn't know what they're talking about. The fact the Newtonian gravity can't be made relativistic in a "simple" way was the reason the GR had to be developed.

>>8803541
There is if they can be used to communicate information

>>8803541
Gravitational waves exist, and they have been measured to move at the speed of light.

You seem to be making blanket statements here. Gravity is thought to be a particle (we're just not sure how yet).

I'd urge you to read up a bit more on special and general relativity. You're acting like a timecube guy.

>>8802705
so, we shouldn't have went along with theoretical predictions about quarks until we observed them? what about the higgs, bozo?

>>8803541
this is a fundamental misunderstanding of waves, gravity, and physics in general. gravity is a concept, but gravity has a physical affect. a gravity wave is the same as a wave in water; they both have a physical medium, whether it be H2O molecules, aether, space time, or whatever you want to call it. look at the special and general theories of relativity, for example, the speed of light in a vaccum is constant and nothing can travel faster, but in reality, where vacuums don't exist, the speed of light changes depending on the medium, while things can in fact travel faster than light, ie. Cherenkov radiation. this medium that light travels through is the same medium that gravity affects and it has a finite speed because the pull of gravity links all matter affecting it and can not skip from one place to another without traveling through the medium; even if wormholes do exist, this fact remains.

>>8804155substitute "anything with mass or energy" for "matter" in the last sentence, and this

>>8803585
>Gravitational waves exist, and they have been measured to move at the speed of light.
Indirectly, sure, but certainly not directly. The LIGO events could not be linked to any other observation, thus the source is not identified, thus you can't really say anything about propagation speed. There is a upper limit of course, but that's all there is.

>>8804195
They were detected in coincidence.

>>8802731
bollocks.
isn't the result of entanglement just because of conservation laws? if one particle as x spin then the other must have -x. We only "know" this because of preconceived notions of how the universe works. If we didn't, then there's no way we could make the error of saying that information has been transferred to the other particle when we make a measurement.
And measurement is a wholly problematic notion to start with.

>>8802758
>If the moon instantly vanished, and gravity propagated faster than c, then we could infer from tidal forces, among other effects that it was gone before we saw it disappear.
Nobody has ever observed such an effect, if so, please provide an example.

>>8803155
>Causality cannot be violated.
>>8803530
>An infinite "speed of gravity" would break causality
Causality isn't necessarily violated by faster than light travel. We would just need to assume that cause and effect are also relative.

>>8804227
Doesn't help you at all you dolt

>>8802776
>faster than light
>by wiggling a heavy object
>just by wiggling an object heavy enough to make a measurable change in attraction to that object "some distance" away

--earlier on /sci/--
>lel senpai applied science majors r 4 brainlets ;)

>>8805250
It would if you knew what coincidence was, you fucking brainlet:
>Since Station A detected it
>Then Station B detected it
>You can estimate it's speed based on the time difference

Isn't gravity completely relative though? Like how in earth its 9.8 m / s^2

Is OP talking about acceleration due to gravity?

>>8802714

What a fucking brainlet. How is someone like this even allowed to publish?

>>8803574

I have a question for someone like you. I've been wondering for a while.

If you shake your head REALLY hard does you peanut brain get damaged and cause even further mental retardation? Or is your brain simply incased in some kind of fluid that is necrotizing it and gradually making you a vegetable?

>>8805733
Thats mean senpai.

>>8802731

Fucking kill yourself.

>>8804349

Yes this is the thinking. The entirety of the system's information needed to determine it's spin state already exists within the particle. Collapsing the wave function of a particle by measuring it and determining the other's spin does not trasmit information.

Why is everyone on this board a high schooler or a /pol/tard brainlet?

>>8804195

They were detected by numerous installations confirming it was a gravitatiom effect. If you seriously thonk that gravity isn't propagated at c then please fuck off of this board.

>>8805733
But that's completely right you filthy brainlet. Why is it always the most retarded ones that run their mouths the most?

>>8803033
I know that I know nothing, or in other words, we don't know nuffin

Speed of gravity sounds like the rate at which spacetime corrects itself as objects with mass pass through it.

>>8802641
If there wasn't speed of gravity, we could send information using gravity faster than light.

It is impossible to send information FTL, therefore there must be a limit to gravity, which probably is speed of light.

>>8802641
Gravity in the form of gravitational waves travels at the speed of light

>>8802654
I hope the mods ban you and give you a year for every single post in this thread for being a useless fucking tripfag piece of shit.