So, does gravity abide by the speed of light?
I mean, hypothetically, if the sun were to blink out of existence would we fell the gravitational effect immediately or 8 minutes after?
8 minutes after
>>7699554
No.
Speed of light.
>>7699551
immediately after 8 minutes
We would feel the gravitational effect 'almost' immediately. The earth would follow a tangential straight path very quickly.
Reasoning: The sun's gravity well would start to flatten from the outer edges where it is shallower, faster than close to sol, where it is very deep.
We would experience the earth suddenly moving away from the sun before it actually disappeared.
Gravitational field changes at the speed of light. So yes, 8 minutes later.
>>7699551
8 minutes bro
>>7699763
It'd take time for the energy through Minkowski space to reach us.
>We would experience the earth suddenly moving away from the sun before it actually disappeared.
No. And here's for why: If the earth moved away prior to the sun's visual disappearance, then gravity's moving faster than c. That'd cause light to behave extremely strangely.
As I understand it, relativity predict that gravity travels at the speed of light rather than instantaneously, but the primary indicator of this, gravitational waves, have never been observed.
Which on the one-hand it isn't too surprising considering how extreme a phenomenon would need to be to have an effect we could measure, but on the other hand is rather unsettling because if they don't exist a lot of laws need to be re-written.
>>7699551
Speed of light.
>>7699792
I understand this. But the 'effect' does not radiate outward from the sun, it moves inwards. It takes 8 minutes 20 seconds for the gravity well to flatten completely.
Are you really telling me that if you magically materialised a body 'x' in the solar system on earths orbit it would take 8m 20s for sun gravity to affect it?
In the case of a solar explosion, I accept gravity "waves" would radiate outward. In this scenario, the attractor is extinguished and the effect starts with us as a unique well interacting with another unique well. Justification: entanglement?
>>7699551
'abide by'?
you seem to think that the speed of light is some sort of actual inherent physical limit of the universe
>>7699551
Just a guess but I'd say instantly. It would take 8 minutes for the visual effect of the sun disappearing. Gravity isn't "faster" than light. It's an unbroken chain. The gravity of the sun effects every particle in the universe. The effect on the universe would be instantaneous. It would happen like any other physical force. Light is radiation from a source. It takes time to reach us and to "travel". But gravity doesn't travel. It's already here. May sound dumb. Feel free to criticise.
Adding to above post. The effect of gravity would disappear instantly with the disappearance of the sun. We know gravity effects light so maybe the visual aspect of the sun disappearing would be faster than 8min because it no longer has the gravity of the sun holding it back slightly.
Off topic but I like the thought that I have never really ever seen anything in the present. Everything I look at is in the past
>>7700774
>would take 8m 20s for sun gravity to affect it?
No, because the gravitational field is already there. (It would, however, take 8m 20s for the Sun to start moving.)
Changes in the gravitational field, just like changes in the electromagnetic field, propagate at c. Static fields don't need to propagate, they're just there.
>>7700802
>May sound dumb. Feel free to criticise.
I have an electromagnet. Like the gravitational field, the electromagnetic field has infinite range; every single object in the universe may be affected by my electromagnet, although to a very small degree.
I switch off my electromagnet and the field vanishes. Does it vanish instantly everywhere in the universe?
Then why would you expect the gravitational field to?
>>7700824
Like I said a guess. Coming from a pleb layman with little knowledge and no formal training. But as with light, an electromagnet comes from a power source and radiates. Again just a guess. That's how I imagine it
I think it's less than, gravity effecting an particle. Every particle effects every other from the start. I'm not sure but I think all matter in the universe was here at the Big Bang. With an electromagnet you transform matter into energy which produces the effect. So it can be switched on and off. Again probably sounds stupid to an educated person. I'll stop now
Eight minutes later from our viewpoint. Distance in space and distance in time are the same.
If you were in a rocket travelling near the speed of light, and you shot past the sun on the way to Earth just as it blinked out of existence, you would see the Earth veer off an instant later, but only because from your point of view the sun and the Earth would be thin discs right next to each other.
Could be just talking out of my ass though.
>>7700824
Sorry transforming matter sounds stupid. Generating energy to produce the effect sounds better. Ok now I'm stopping
>>7699551
Yes.
>...both papers say that light interacts with virtual particle-antiparticle pairs. In Leuchs' and Sanchez-Soto's model, the impedance of the vacuum (which would speed up or slow down the speed of light) depends on the density of the particles. The impedance relates to the ratio of electric fields to magnetic fields in light; every light wave is made up of both kinds of field, and its measured value, along with the permittivity of space to magnetic fields, governs the speed of light.
>Abstract. Standard experimental techniques exist to determine the propagation speed of forces. When we apply these techniques to gravity, they all yield propagation speeds too great to measure, substantially faster than lightspeed. This is because gravity, in contrast to light, has no detectable aberration or propagation delay for its action, even for cases (such as binary pulsars) where sources of gravity accelerate significantly during the light time from source to target. By contrast, the finite propagation speed of light causes radiation pressure forces to have a non-radial component causing orbits to decay (the “Poynting-Robertson effect”); but gravity has no counterpart force proportional to to first order. General relativity (GR) explains these features by suggesting that gravitation (unlike electromagnetic forces) is a pure geometric effect of curved space-time, not a force of nature that propagates. Gravitational radiation, which surely does propagate at lightspeed but is a fifth order effect in , is too small to play a role in explaining this difference in behavior between gravity and ordinary forces of nature.
So you see from the above, light propagates, gravity doesnt.
>>7700941
So you are saying instantly? I think you are. That's what I imagined. It can accelerate in strength but there is nowhere without it. And the acceleration would be "faster than light". But not really. Because it is its "own thing". So the effect would be instant yes? Again probably sounds stupid. Instant effect?
This is because gravity, in contrast to light, has no detectable aberration or propagation delay for its action,
I guess the answer is right there. Ignore my last post above
>>7700939
Do you think that spacetime and gravity are the same thing? It's the old marble rolling around a central mass demonstration. Gravity is the curving of spacetime. Isn't it that which made Einstein abandon any attempt to locate the "graviton?"
>>7700958
I will dodge the question until such time as eLisa confirms we cant detect gravity waves ;)
>>7701033
Can we?
