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If a massive body is moving at near light speed (or, hypothetically at light speed) and on course to hit Earth, will we feel its gravitational pull before it collides with us?

I think the answer is no because speed of gravity is same to speed of light.

Does it mean bodies moving at near light speed don't produce gravity?

From the comments>>>

if change of gravity propagates at the speed of light, and an object is moving at near light speed, does that change how much gravity there is ahead of that object?

Qmechanic
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user146021
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  • I suggest that you change your question to ask if a body is moving at near light speed. Nothing with mass can move at light speed, so what you ask can not happen. But at near light speed is potentially possible. Making the change will help your question to make sense. – foolishmuse May 19 '20 at 18:25
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    Does this answer your question? Are moving objects producing stronger gravity fields? (OP's question is actually a duplicate of a question marked a duplicate but there are links there that should be helpful) – Alfred Centauri May 19 '20 at 18:55
  • Even if the body isn't massive it'll be bending the spacetime. However the bending of the spacetime will be so tiny I'm certain we wouldn't be able to detect it. LIGO detects huge black holes and neutron stars colliding, and even then the distances it measures are 1000th the width of a proton. In GR the what produces gravity isn't necessarily mass, it's called the stress-energy tensor. So stresses, energy, pressures etc all bend the spacetime – baker_man May 19 '20 at 19:05
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    Unfortunately your question is badly garbled. An analogon for your question for speed of sound would run as follows: the V2-rockets that were used to attack London flew faster than the speed of sound. Those rockets made a huge noise, but that noise only reached the target after the rocket had impacted. That is: no noise ahead of the rocket. It could be that what you want to ask is: if change of gravity propagates at the speed of light, and an object is moving at near light speed, does that change how much gravity there is ahead of that object? – Cleonis May 19 '20 at 19:40
  • @cleonis Yes, you are correct. That is what i had in my mind but couldnt type it properly. I will edit the question. – user146021 May 19 '20 at 19:57
  • @Cleonis That's the first time I've seen the word "analogon" outside of actual Greek. – probably_someone May 19 '20 at 20:47

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Yes they will feel the force of gravity. The fact is that even though gravitational field travels at the speed of light, it doesn't mean that the field only starts to act when the object is near the Earth, any massive object curves space time, and that curvature doesn't disappear. Due to the curvature the geodesic of the particle curves in slightly, and hence it is attracted by gravity of the object.

It too causes a curvature in spacetime. The point is that curvature depends on the amount of energy, momentum and their density in a region. So yes as it has both energy and momentum, we will feel it's attraction. But how much attraction, depends upon the object's mass and speed.

Entropy
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SK Dash
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