[Physics] Does gravity have 'elasticity'? If a solid sun-sized object zooms across space at the speed of light, then abruptly stops, does it take gravity some time to 'settle' around it?
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Using your choice of words it would be "stable/static". Effects of gravity moves at the speed of light. Perhaps a better example would be Earth orbiting the Sun.
The Earth is 8 light minutes away from the Sun. Meaning, the sunlight we see on Earth at this exact second left the Sun about 8 minutes ago. If we wave a magic wand and make the Sun blink out of existence in a fraction of a second, the Earth would continue to orbit the, now non-existent, Sun for the next 8 minutes. After 8 minutes the Earth would stop its circular orbit and head straight out of the solar system at what ever direction it was traveling at the end of the 8 minutes.
That's amazing, thank you! A ghostly remnant of gravity still exerting 8-ish minutes of influence on earth (in the event of the sun's instantaneous disappearance) is something I never heard or thought about before, but it makes sense. It's hard to visualise it though. Like the earth is a marble circling a drain after plug has been pulled and the water is all but gone. Then the minute it is gone, the marble just keeps going in a straight line 👀
That’s amazing, thank you! A ghostly remnant of gravity still exerting 8-ish minutes of influence on earth (in the event of the sun’s instantaneous disappearance) is something I never heard or thought about before, but it makes sense.
Also for us standing on the sun facing side of Earth when the magic wand was waved would still see the sun shining in the sky for 8 minutes because that light had already left the sun before it blinked out of existence. We on Earth would experience the loss of the Sun's gravitational influence on the planet and the light of the sun at the same moment as both light and gravity travel at the speed of light.
I think it's easier if you imagine space/time like a flat plane that dips depending on how much mass the central object (like the sun for example) has. Earth circles around that dip much like your drain plug analogy. If the sun disappears, it still takes time for that dip to rise back up to a flat surface. That's the speed of gravity.
As soon as space/time begins to flatten beneath the earth, its momentum begins to turn into a straight line, rather than an orbit.