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eldude2879 t1_ixvxcai wrote

Reply to comment by lacgibra in How would one calculate the gravity of a planet? by LoreCriticizer

using newton is not good enuff for precise calculations of planets

we have to use einstein, by that we have to stop thinking of gravety as a force and think of curved space time

Einstein's general relativity states that, in a Schwarzschild spacetime (which approximates our solar system), gravity is slightly different from the inverse square law by an extra fourth power term. It is this extra small term that causes the perihelion motion of Mercury's orbit. If we take this extra term into account and follow the same logic of classical considerations, we find that planets' orbits aren't closed, but are precessing consistently. Mercury's orbit has an apprant precession about 43 arcs per century at its perihelion position which is exactly the amount of precession observed.

https://physicsworld.com/a/correcting-einsteins-calculation-of-the-orbit-of-mercury/

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lacgibra t1_ixw0h05 wrote

Well yeah Newton's doesn't explain Mercury's precession. I were sticking the context of the questioner and I had mentioned defining it classically, you need to think what it is when required. You can't just tell all the concepts that neglected friction, air resistance are wrong, for the classical assumption gravity has to be assumed as force. Relativity got better explanation apsidal precession and all at the end of the day approximately g = 9.81 m/s². Not lower than that or higher than that.

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eldude2879 t1_ixw1mi9 wrote

light behind a galaxy that can be seen because of the mass of the galaxy infront is seen not because of gravity force

as we know photons have no mass so gravity has no effect if you think of it as a force

the space time is bend so the photons get bend with it

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lacgibra t1_ixw20m9 wrote

Okay do me a favour, workout a classical problem considering gravity as curved space time. Simple pendulum, compound pendulum, linear Harmonic oscillator two body problem anything.

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lacgibra t1_ixw2ey4 wrote

I'm simply saying, I apply gravity as space-time curve when I apply the Einstein's relativity in action. If had explained the question in the first scenario using relativity, I would've mentioned gravity as space time curve

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eldude2879 t1_ixw2f7o wrote

well, I am just a simple electrician with some knowledge of Einstein

I admit using Newton is perfectly fine if you dont need super precise

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lacgibra t1_iybna3g wrote

Yeah yeah quantum mechanics is wrong too, because it's foundation was laid by classical mechanics.

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