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I don't think a point can rotate. What would it mean if it did? There would be no observable change. So no, I don't think the absolute center point moves. From
by librexpr 9y ago
I don't think a point can rotate. What would it mean if it did? There would be no observable change. So no, I don't think the absolute center point moves.
From a physical standpoint, though, if you wanted to talk about the absolute center point, you'd have to talk about the lowest level of particles, which gets into the weirdness of quantum mechanics (or maybe a lower level exists?). At that point, I really couldn't say what happens.
And I don't think it matters if the particles are point mass or not, except possibly for the absolute center. The point is that the rotating object is not just one thing, but made up of smaller things that have different velocities and acceleration. These differences in velocities and acceleration are what rotation is.
If there exists something that is not made up of smaller things which also rotates, then that would prove me wrong.
Of course, all the above is just speculation by someone who's hasn't had a physics class since high school, so take it with a grain of salt.
- randallsquared 9y agoThe most fundamental particle can't rotate, because that would imply that parts of it had different velocities from other parts... but it doesn't have parts at all, by initial definition. So, Democritus' atoms imply that rotation is not a fundamental motion. I think every attempt to visualize this which imagines a single object rotating is doomed. Rotation inherently implies a difference in velocities, and some attractive force keeping those velocities changing to maintain a distance. So, the existence of any attractive force, together with inertia, implies rotation and the stickiness of direction of a gyroscope. But inertia itself already implied stickiness of direction, given that a change in direction would require acceleration...
- philipov 9y agoOkay, then explain Spin. Angular momentum is defined by how a particle responds to fields, not by the relation of its parts.
- randallsquared 9y agoI'm no physicist, of course. I had thought that 'spin' was metaphorical or analogous, like quarks' color and flavor, but Wikipedia asserts that it was originally considered to be rotation about an axis. So, I've no real clue. :)
- rkagerer 9y agoWe need a new "explain it like I'm 5" guide to modern physics. Or at least, "like I'm not a mathematician".