Newton's Law of Universal Gravitation is used to approximately model gravitational forces close to Earth. I'm curious as to if there is a weaker-gravity limit to the law's applicability, such as in a void in the Universe. Assuming voids have less of a gravitational wave background, cosmic microwave background, or a lower matter density, does NLUG still do well in weaker gravitation, or is there another model or equation for gravitational forces for the smallest distances in our Universe's weakest gravities?
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1$\begingroup$ Newton's Law of Universal Gravitation is used to approximately model gravitational forces close to Earth. It works great for the Earth-Sun attraction, and the Sun isn’t close to Earth. $\endgroup$– GhosterCommented Mar 22 at 21:27
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2$\begingroup$ Given what we know about General Relativity, it makes sense to say that Newton's universal law of gravitation is the expression for low level gravity. $\endgroup$– Albertus MagnusCommented Mar 22 at 22:14
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1$\begingroup$ Newtonian gravity fails to be accurate when gravity is too strong, not when it is too weak. $\endgroup$– GhosterCommented Mar 23 at 0:14
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1$\begingroup$ Its an interesting question... I'm wondering how one would go about proving it. One would have to observe the effects of a very weak gravity for a very long period of time. And we'd have to do it on something many many lightyears away (millions?) $\endgroup$– Cort AmmonCommented Mar 23 at 1:20
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$\begingroup$ Newton's Law of Universal Gravitation works pretty well to approximately model gravitational forces in the Milky Way galaxy too (if you stay away from that pesky black hole in the middle). $\endgroup$– Lee MosherCommented Mar 27 at 20:56
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Modified Newtonian Dynamics (MOND) has been proposed as a mechanism to explain the velocity curves of galaxies, which is usually explained by dark matter. This idea posits exactly this kind of divergence from standard Newtonian mechanics in the limit where the gravitational interactions are weak (low acceleration). So this has been explored as a conjectural idea in physics/astronomy.
