2 upvotes, 1 direct replies (showing 1)
View submission: Ask Anything Wednesday - Engineering, Mathematics, Computer Science
I understand that part, but how could we say that its the truck accelerating, and not say, the entire universe around it?
Is the distinction just arbitrary? (This object is rotating because it is experiencing angular acceleration, and it is experiencing angular acceleration because it is rotating.) or is there some larger frame of reference? Perhaps a universal axis that everything exists in relativity to? Maybe that frame of reference is just an average of all the mass in the universe? Beats me.
Comment by jarebear at 25/07/2024 at 13:11 UTC
1 upvotes, 0 direct replies
Visually you can't differentiate the truck or the universe rotating if everything is perfectly rigidly in place (which is impossible, see my next paragraph). However, the truck and anything rigidly attached to it will experience an acceleration (resulting from some force) and the universe will not. So the truck is clearly rotating and the universe is not. We can't say the same thing with linear motion that's constant and requires no acceleration, however.
If you want to stick with the visual, no object is absolutely rigid and so everything will undergo some amount of bending or flexing when rotating. For the truck example you'll see things shift or lean slightly but not uniformly since they'll have different stiffnesses so there's no way to "tilt the camera" to make the truck look stationary. It's even more obvious when you drop something onto the truck and from its rotating frame the object goes magically flying away but from the non-rotating frame it just slides off as expected.