I never really understood why people say gravity isn't a force. I understand that gravity is just the motion of objects travelling in a straight line (longest proper time) through space time, but does that really mean it isn't a force?
Justin, first you have to define waht you mean by the term "force"
If you want to say it is a force, it would seem to be something analogous to centrifugal force which most physics texts say does not actually exist
Exactly. It is just the result of not being in an inertial frame, and hence thinking there is a force acting: gravitational, centrifugal, and coriolis forces.
The real force is the earth's up-push on you, accelerating you vertically upwards. The weight of an object in your hand is the upwards force you are exerting on that object, accelerating it out of its preferred inertial frame. Gravity exerts no real force.
Einstein expanded on the concepts of time, space, mass, etc. but I don't see that as causing an incommensurability in any non-trivial sense.
I couln't diasgree more. We are talking paradigm shift of the millenium. GR reduces to Newtonian mathematics, it does not reduce to Newtonian thinking.
Newtonian mechanics is a limiting case of GR from the point of view of the mathematics and the methodology. The change to GR is a total upheaval from the perspective of its metaphysics
Precisely.
The change from Aristotlean science to modern science is profound, not so much because of the change in mathematics and metaphysics, but because of the introduction of systematic empirical methodology.
I think we have another major change this last century that marked the rise of deductive reasoning over empiricism in fundemental physics: GR is probably the precursor of this but it is even more apparent in particle physics, particularly non-Abelian gauge theory leading to electroweak and QCD. String theory is of course the epitome of this approach, but unlike those theories mentioned, it has much to prove...
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