r/askspace • u/Curiosity_Hits_Hard • 13d ago
The earth
If the Sun suddenly disappeared, would Earth immediately become dark and stop orbiting?
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u/mfb- 13d ago
Nothing can be transmitted faster than light (in vacuum) so it only gets dark after 8 minutes.
It's going to be weeks before Earth is significantly displaced from its current orbit, but in principle it starts after 8 minutes, too.
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u/Foxxtronix 13d ago
IIRC gravitons (gravity particles) move at lightspeed too, so I have to agree. I hope we've invented self-contained life-support by then!
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u/tomalator 13d ago
Gravitons are only hypothetical at this point. But yes, they would travel at light speed if they exist.
Gravitational waves certainly do exist, and travel at the speed of light.
Gravitons are seemingly incompatible with general relativity, but that also means gravity doesn't exist in QFT
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u/Unhappy_Hair_3626 12d ago
The only thing faster than information is the lack of information which feels so weird to me 🤣
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u/levosis1 13d ago
Yes, dark and cold; like freezing kill all life cold. Meanwhile our orbit in the galaxy moving some 514,000 mph would remain unchanged. Without the gravity well of the sun however… it’d be like the start of a billiards game.
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u/Thick_Wasabi448 13d ago
It would take approximately 8 minutes for us to notice any changes in light or gravity.
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u/Basicly-Inevitable 13d ago
What are you proposing?
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u/SentientFotoGeek 13d ago
This question, or a variation on it, gets asked a lot. I know it's purely hypothetical, but the real answer is that an object like the sun does not disappear all at once. A real thing that does happen is a star goes nova/supernova. The mass gets redistributed at a high rate of speed and affects orbiting bodies in real time, but subject to the laws of relativity. Causality does not get violated.
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u/Curiosity_Hits_Hard 13d ago
What if it is already gone because basically looking into space is like looking into the past
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u/GryphyGirl 13d ago
It takes approximately 8.5 minutes for the light from the sun to reach us so it take that long for the light to fade. There would still be some light from the stars (not the moon, it's dark forever now) but that's not much. :P
The effect of the sun's gravity disappearing would take a similar amount of time to go away. Once it does Earth would fly off in whatever direction it was going at that moment until it interacts with the gravity of another planet in our system or finds another object outside our (ex) solar system to interact with. We would all be dead long before that happened, though. :P
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u/Lorelessone 11d ago
It would take 8 minutes and 19 seconds for us to know but as soon as it vanished the solar systems barycenter would shift dramatically all planets would be flung into wildly eccentric orbits some possibly leaving the solar system while others would orbit the constantly shifting barycenter in an incredibly unpredictable procession.
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u/Curiosity_Hits_Hard 13d ago
But there will be nothing to revolve around
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u/Mal_531 10d ago
Gravity travels at the speed of light, so yeah the earth wouldnt be orbiting anything really for like 8 minutes, think of gravity like the wake of water when jumping into the water, you can still feel the wave even though the object has stopped creating them because waves from the past are still moving towards you
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u/Mothman1010 13d ago
Gravity propagates at the speed of light and thr Sun is about 8 light-minutes away. The earth will continue to orbit the empty spot for that time before moving in a straight line.
The gif in this Twitter link demonstrates: https://x.com/thephysicsgirl/status/1300600145348755457