4 ms·

What about the opposite? A clear explanation of what the strongest evidence for gravity NOT being fictitious but rather being a real force is?

vincent-toups 5y ago
Such a point of view is pretty much incongruous with contemporary physics. I'm not sure how one would go about even formulating the case. Despite its central presence in physics 101 the notion of force is actually not all that clearly present in fundamental physics. Newton's innovation might be said to be the representation of gravity as a force, but even in the Principia he doesn't commit to the idea because of an intuitive rejection of the non-locality implied by such a conception. So the idea that gravity is a force of the same sort as you pushing on a cart full of apples (whatever _that_ is) was never a particularly strongly held idea. I'm not an expert on the history of physics (I have read the Pricipia in translation, though) and I suspect Newton, if questioned appropriately, might have himself admitted there are issues with the conception that go beyond just non-locality. Even at the level of Lagranian physics in the contemporary style (which despite that description is hundreds of years old) the idea of forces has an ad-hoc quality to it. The description of a completely closed system doesn't really contain forces unless you explicitly include them in the form of lagrange multipliers for the constraints, and then the forces that you calculate are, in a sense, provided "externally" by processes outside of the system itself. For instance, the easiest way to represent the motion of two particles held together by a perfectly rigid rod doesn't mention the force exerted by the rod to maintain that constraint and yet simulates the motion perfectly. If we are interested in how much force the rod must exert to maintain the constraint, we can add in a largrange multiplier, but what that quantity tells us is in a sense a summary of the non-represented physics of the rod itself, which is still excluded from the system. A force then is a kind of interface between that which you are considering in detail and that which is assumed to be part of the external world. If everything in the world were simulated, then nothing would deviate from its expected motion, and thus there would be no forces at all, since all a force is is a description of how something deviates from the path it would ordinarily take if not for the intervention. On this view Newton's first law is much more important and fundamental than his second: objects always move in straight lines but we must take great care in understanding what a straight line actually is for a given physical system. Really, the seed of general relativity and the geometric formulation of field theories is right there in the first law. This explains why the second law is of so much less importance in modern physics. I'm not a professional, just an interested failed physicist, so standard equivocations apply to the above. This video by an actual professional hits on some of these ideas: https://www.youtube.com/watch?v=IBlCu1zgD4Y https://www.youtube.com/watch?v=IBlCu1zgD4Y

vincent-toups 5y ago

Such a point of view is pretty much incongruous with contemporary physics. I'm not sure how one would go about even formulating the case. Despite its central presence in physics 101 the notion of force is actually not all that clearly present in fundamental physics. Newton's innovation might be said to be the representation of gravity as a force, but even in the Principia he doesn't commit to the idea because of an intuitive rejection of the non-locality implied by such a conception. So the idea that gravity is a force of the same sort as you pushing on a cart full of apples (whatever _that_ is) was never a particularly strongly held idea. I'm not an expert on the history of physics (I have read the Pricipia in translation, though) and I suspect Newton, if questioned appropriately, might have himself admitted there are issues with the conception that go beyond just non-locality. Even at the level of Lagranian physics in the contemporary style (which despite that description is hundreds of years old) the idea of forces has an ad-hoc quality to it. The description of a completely closed system doesn't really contain forces unless you explicitly include them in the form of lagrange multipliers for the constraints, and then the forces that you calculate are, in a sense, provided "externally" by processes outside of the system itself. For instance, the easiest way to represent the motion of two particles held together by a perfectly rigid rod doesn't mention the force exerted by the rod to maintain that constraint and yet simulates the motion perfectly. If we are interested in how much force the rod must exert to maintain the constraint, we can add in a largrange multiplier, but what that quantity tells us is in a sense a summary of the non-represented physics of the rod itself, which is still excluded from the system. A force then is a kind of interface between that which you are considering in detail and that which is assumed to be part of the external world. If everything in the world were simulated, then nothing would deviate from its expected motion, and thus there would be no forces at all, since all a force is is a description of how something deviates from the path it would ordinarily take if not for the intervention. On this view Newton's first law is much more important and fundamental than his second: objects always move in straight lines but we must take great care in understanding what a straight line actually is for a given physical system. Really, the seed of general relativity and the geometric formulation of field theories is right there in the first law. This explains why the second law is of so much less importance in modern physics. I'm not a professional, just an interested failed physicist, so standard equivocations apply to the above. This video by an actual professional hits on some of these ideas: https://www.youtube.com/watch?v=IBlCu1zgD4Y https://www.youtube.com/watch?v=IBlCu1zgD4Y