I’ll preface this by saying that I have a very good understanding of Newtonian mechanics, but only an amateur’s understanding of Einstein’s relativity.
I understand that Newton’s law of gravitation is insufficient to accurately describe and predict certain physical phenomena, and that Einstein’s relativity “fixes” this. I don’t understand, however, why we must do away with the model of gravity as a force to build a better model. Couldn’t Newton’s law of gravitation be amended to account for the discrepancies? It looks to me as if it’s a question of which mental model we prefer. Saying that gravity isn’t a force, it is a curvature, or vice-versa, sounds to me like saying that positive charges are actually negative and negative charges are actually positive, i.e., a matter of convention. Whether gravity >is< one or the other seems to me much more a matter of philosophy than physics properly.
So why is this such a central point?
In: Physics
To oversimplify it, Newtonian mechanics break the speed of light. Though the speed of light was measured in the 17th century, it wasn’t determined to be *the fastest possible* speed *anything* could move until Einstein in 1905. Newton assumed gravity as a force was instantaneous no matter how far away two objects were, because… there weren’t yet any contradictory theories to say that was impossible, and there weren’t yet any measurements taken to *prove* it was impossible.
That’s the reason Newtonian mechanics are pretty good at making predictions in broad strokes, but break down in particularly extreme situations such as near a star or black hole, or on the massive scale of galaxies (which wouldn’t be realized what exactly they were until the 1920s). At less extreme scales, the speed of light isn’t particularly *relevant,* so when it starts *becoming* relevant, Newtonian mechanics aren’t sure what to do about the discrepancies it causes.
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