/sci/ - Science & Math

roughly 8 minutes

but where did it go?

Interesting thought, the only thing I can think of is because it mends time and space.. that it'd go as fast as possible... which until proven otherwise in normal physics.. that is the speed of light.

>>7571377
>Bends

>>7571373
localized macrosecond-long wormhole

>>7571349
god would appear before any effect manifests itself and would prevent any effect to manifest

In relativity, it's the speed of light.


Quantum gravity theories suggest it is slower.

We won't know for sure until we detect gravitional waves

Depends on the gravity model used.
Gravitrons would take about 8 minutes while a spacetime curvature and therefore the gravitational pull would disappear instantly.

>>7571349
The speed of light, at which information propagates, and thus the information that the sun's influence has disappeared.

>>7571528
That's not right, or else you could do FTL communication through gravity.

>>7571528
Is this really true? That would mean that the earth would just appear to veer off course of our orbit under 8 minutes before we even see the sun disappear. Makes no sense to me

>>7571539
>what is quantum entanglement
a way for infornarion to travel faster than c

>>7571540
We don't know for sure but we'll know obce we measure gravitational waves

>>7571541
>infornarion
oops

so what I've gathered so far is that is maybe is equal to speed of light, maybe slower, maybe faster, or maybe even instantaneous

>>7571549
Yes. We won't know shit until LIGO picks something up

If we ignore "gravitons" and similar models and just view gravity as the curvature of a 4-dimensional manifold, can the manifold be changed in an instant, non-smooth way or does any change in curvature happen continuously during a span of "time"?

>>7571541
can't tell if trolling, but you can't send information via quantum entanglement

>>7571568
You could theoretically.

You'd need ot find a way to manipulate spin and find 2 entangled electrons

>>7571604
No, you couldn't, not even theoretically. Quantum entanglement does not allow you to transfer any information.

Here's how quantum entanglement works, informally speaking:

Let's say you have a machine with a red ball and a blue ball and a lever. When you pull the lever, it dispenses these balls, completely randomly, into two sealed boxes.

You now have two boxes. Each box has 50% chance of having a red ball and a 50% chance of having a blue ball, and you have no way of knowing which - but they are *entangled*, in that you know that if one has the red ball, the other has the blue ball, and vice-versa. The outcomes of each individual box are random, but the boxes as a whole form a system whose outcomes are constrained.

You now take one of these boxes to, I don't know, Alpha Centauri, and I take one to Illinois, and I open my box. I have the red ball - and instantaneously, across light-years of distance, I know you have the blue one.

Faster-than-light communication! Except...not. There's no way to send a message with this, no matter how many boxes I have - painting my ball blue won't make yours red, and no matter how I shake my box before opening it, that ball's not going to change color.

Of course, it's slightly weirder than this, because speaking from a quantum-mechanical viewpoint, it's not actually determined before observation which box has the red ball and which has the blue - they're both in superposition, where either could be red or blue, but entangled together so their outcomes depend on each other.

So instead, to capture the full weirdness, imagine that we have a magic spell or something that works on two fair coins - which guarantees that, if you fairly flip one, the next flip of the other will always land on the opposite side - the state of the first coin somehow magically transmitted to the second, instantly, despite the distance.

But again, it breaks after one flip, and it only works if you fairly flip the coin.

>>7571618
>>7571604

And speaking less informally, there's an actual proof of this:

https://en.wikipedia.org/wiki/No-communication_theorem

>"the no-communication theorem [...] states that, during measurement of an entangled quantum state, it is not possible for one observer, by making a measurement of a subsystem of the total state, to communicate information to another observer."

>>7571564
Can someone answer this?

>>7571618
>painting my ball blue won't make yours red

This is where QM diverges from your example.

>>7571637
No, really, it's not.

If I have a system of two entangled spin qubits A and B, such that both A and B are 50% likely to be either spin-up or spin-down, and I observe A and it's spin-up, then I know that B is guaranteed to be spin-down.

The entanglement, like superposition, is broken upon measurement; if I flip my qubit to spin-down after observation, the other does not become spin-up.

And furthermore, doing anything to it that would allow us to determine the state before measurement *also* breaks the superposition. For quite obvious reasons - if we can guarantee that our qubit is spin-up, then there's no superposition at all.

bump

>>7571349
>speed of gravity?
wrong question
gravity does not propagate, it is structural and timeless
else orbits would be unstable and black holes ineffective
general relativity effectively reproduces newtonian gravity

>>7571676
its the exact opposite of that you dipshit.

>>7572256
"its the exact opposite of that you dipshit." he shouted from atop Mount Popsci

>>7571564
>this

>>7572256

Oh, cool. Source? Because everything I've ever read suggests he's right and you're wrong.

I'd love to be wrong, though!
And I'd love to know how you know what the world doesn't!

>>7572245
>Has never heard of quantum gravity, causality or physics.

>>7571528
according to newtonian physics the gravitational pull would disappear instantly. and since photons are going the speed of light you would still see the sun for roughly 8 minutes after the earth left its orbit and spiraled away

>>7572320
>Newtonian physics
top kek

>>7571564
>>7571634
Can someone answer?

>>7571621
But, at some fundamental level isn't simply that you know a property of other particle information that you didn't have before?

Now you know something about the physical arrangement and relations of a particle elsewhere that you did not know about before? Am I misunderstanding?

>>7572256
Do you even know what "entanglement" means and how it works?

it has been experimentally shown that gravitational waves propagate at the speed of light

>>7572439
what?

>>7573428
Link please.

>>7573339
No, you have that part right. The problem is that you only know this by deduction. You can't actually change the state of the other particle. It's like you have two boxes with the words "yes" and "no" and you ship one off to the other side of the galaxy. Then you open your box. You can easily tell what word is in the box on the other side of the galaxy, and an astute alien could tell what's in your box, but it is in no way a form of meaningful communication.

>>7572256
When two particles are entangled, they exist in a superposition. For electrons, this could be their orientation, which can be changed and measured with electromagnetic fields. These fields do work on an object. When you measure one entangled electron, you can deduce the state of the other. However, when you do work on the electron to try to flip its spin state, an equal and opposite force is produced by the electron in the form of electromagnetic radiation.
Now imagine the other electron also flipped its state, like you say it would. It would also have to emit electromagnetic radiation, which is the result of work being done on it. Now your model predicts that doing work on one object is the equivalent of doing work on two objects (or ten objects, or a million objects). Energy is being created out of nothing in your model, and no, don't even try the "what about dark energy" argument with me unless you know what you're talking about (although, if you did, you wouldn't use the argument).

Hypothetically, if some mass was entirely and essentially instantly converted into EM radiation, would the curvature of the spacetime manifold caused by that mass have to bend, as in transform in a continuous manner, back to the global curvature of that region of space, or would it just instantly snap into place? What kind of operation on a manifold with the structure of spacetime will do the former and what will do the latter? Is spacetime more elastic than rigid in how its curvature transforms according to changes in mass?

>>7572439
well, newtonian mechanincs are still useful for macroscopic objects problems, same goes for hamiltonian and lagrangian mechanics

9.8

Bumpe

>>7572320
such a poetically painfull way to die

The speed of gravity is equal to the speed of light.

If the sun suddenly vanished it would take the same time for earth to stop felling the gravitational pull from the sun as the time for sunlight to reach the earth.

>>7571349
My theory is that because Earth is constantly spinning due to the Sun's orbit, when the larger mass object loses its gravitational influence on an object of smaller mass, the lesser mass object will have a sort of free fall in space time. Somewhere the smaller mass objects end up orbiting another object of greater mass.

>>7574823
Why, how? This has been proven? By you? Tell us more.

>>7575078
By einstein.

Nothing can travel faster than light, including gravity fluctuations in space time. If they could you could easily whack together some communication device based on F=ma and have FTL communication, which breaks the laws of physics.

>>7575086
I don't think you understand the difference between "theory" and "proof" and also I don't think you've read into this subject much

>>7575093
I think that you're just spouting nonsense and aren't refuting my points. Face it, you have no idea what you're talking about. Do you seriously believe gravitational effects are instantaneous?

>>7571524
>Quantum gravity theories suggest it is slower.

Elaborate please

>>7571541

die.

Another question. What is the source of the energy for gravity ? Gravity is a strong force. For atoms to attract each other as long as they exist, they would need some sort of energy. So where is this energy coming from ?

>>7575103
>Gravity is a strong force

It really isn't.

>>7572256

please never post again

>>7575105
regardless what you think about its power level, it's a continuous attracting force and it doesn't seem to be consuming any energy input.
So where is this magical force coming from ?

>>7575097
I don't know but unlike you I don't pretend to know because none of the possible theories have enough evidence going for them and I'm going to wait until we discover the graviton or whatever it is that carries gravity

>>7575110
It arises from the fact that things in our universe has properties we call mass and energy.

Just like how the electromagnetic forces arise from the fact that things in our universe has properties we call charge.

Wouldn't the sun's gravitational hold on the planets disappear instantly with the sun? As in, the planets would continue to move from the existing inertia, but their path would no long curve in an orbit?

On a smaller scale model, doesn't gravity function like a field instead of wave; as in when an object appears, it's gravitational influence takes immediate effect? Given this, wouldn't that mean that an object disappearing would cause an immediate end to it's gravitational influence on other objects?

This is based on the law of gravity that states all mass is constantly influenced by the gravitational influence of all other mass at all times, regardless of distance. Wouldn't it make sense to infer gravity doesn't "travel", but instead it gains or loses influence based on mass and proximity?

>>7575114
It doesn't even explain the source of energy
> electromagnetic forces
Electromagnetic waevs are the outputs of energy sources, they always consume power to emit those waves.

>>7575103
Gravity is not a strong force in the actual meaning of the term. Also it doesnt have any 'implicit' energy. It simply is a property of mass.

>>7575118
no object with significant mass for gravitation changes, suddenly appears (or disappears), that's the problem.

>>7575123
force =/= energy
You only need energy to move an object against a force.

light travels .75 parsecs in 9mths
stick to it easier stood under is sum a process slowes (or accelerates)
x

>>7575147
what?

>>7575137
Gravity is a property of space-time, baka.

>>7575175
what isn't a property of space-time?

>>7575103
>>7575110
by moving against gravity you give it the energy to pull you down. No force added, only converted.
We don't know why or how though. It just kinda is that way.

>>7575141
Two rotating black holes merging to one would cause some weird space-time effects that would effect objects in their vicinity

>>7575267
They still wouldn't lose their gravitation, since they still have the same mass as before. Also, has this ever been observed? We would need to acces these effects under controlled conditions to really study them, just because it may happen somewhere out there doesn't mean it can be studied.

>>7575271
Observed, no.

But if you model a system like this on a computer the speed of gravity is crucial to what will happen.

>>7575273
Obviously, but without being able to compare your model with experimantal observations, you don't know if the speed of gravity you have choosen is correct and thus, if your results are correct.

>>7575274
Exactly, which is why people are searching for gravity waves which would be generated by these events.

I wonder if the speed can be deduced from theory alone, I doubt observations will come any time soon

>>7571539
Couldn't you do FTL communication just by moving a really long object made of something that doesn't stretch?

>>7575299
>7575110
Everything stretches.

>>7575299
Special relativity places limits on the rigidity of solid objects. So no.

>>7575305
dang, where did this number come from?

>>7575103
Gravity is tremendously weak. Many order of magnitude weaker than any other force. To prove that point, place a small magnet next to another magnet and watch it fly up and stick. One little magnet overcomes the entire pull of the Earth on the other magnet.

Reminder that the unified force implies that gravity moves at light speed.
>muh gravitons

>>7571381
>macrosecond
What?

>>7571362
Why is this thread so long? You got the correct answer with the first post...

>>7575333
>there is such a thing as objective simultaneity

>>7575338
You clearly have no clue how to greentext.

>>7575339
Bait or are you really that new? I know this is /sci/ and all but damn...

Anon is right for that matter. You cannot talk about simultaneity in a system on the length, mass, and relative velocity scales of our solar system.

>>7571564
>>7573836
Please describe how the manifold undergoes change.

and that explains why the sun is a sun at the sun
sure.

>>7575339
>implying he doesnt

>>7575572
rapid distance variation in gravity effect
makes apina go all way around
so is these very low temperatures tech
so space cold wat's the orb then glows?
simplest hydrogen escapes this function

>>7575587
wat's an apina? spins

>>7575110
> it's a continuous attracting force and it doesn't seem to be consuming any energy input.
> So where is this magical force coming from ?

Force does not require any expenditure of energy.

Force is a fundamental property of matter. It "comes" directly from the matter itself.

For example, an electron has a charge of q = -e (where e is a universal constant). This charge manifests itself as a force that automatically appears between that electron and all other charged particles in the universe. The amount of the force is F = kₑq1q2/r2, where kₑ is a universal constant and r is the distance between the electron and the other charged particle. As long as the two particles exist, that force is permanent, and requires no energy to maintain.

(Don't be confused by the fact that the force results in a "potential energy" to exists between the two particles. If the particles don't move, then the potential energy between them doesn't change, and so there is no gain or loss of potential energy. Therefore, no energy is expended to maintain that continual force between the two particles.)

>>7575595
It's a monkey orbiting the Sun.