The discussion revolves around Mach's Principle and its implications for understanding the universe's rotation relative to observers. Participants explore the validity of different frames of reference, particularly non-inertial frames, and the relationship between mass, inertia, and the structure of the universe. The conversation touches on theoretical interpretations and challenges related to Mach's Principle.
Participants express multiple competing views regarding the interpretation and implications of Mach's Principle, with no consensus reached on its validity or applicability to the universe.
Limitations include the lack of precision in defining Mach's Principle and the unresolved nature of the relationship between mass, inertia, and the universe's structure. The discussion also highlights the complexity of applying classical physics concepts in non-inertial frames.
In the rotating frame where you are at rest and the universe is spinning, there is a centrifugal force on the rest of the universe trying to tear it apart. But there is also a Coriolis force that is twice as large. That Coriolis force is strong enough to cancel the centrifugal (that's one factor of one) and enough to provide the centripetal acceleration to keep the contents of the universe in orbit around your head (that's the other factor of one).WCOLtd said:How come when I spin around, the universe doesn't fly apart as if its rotating around me? Why is my frame of reference that I am at rest and its the universe spinning around me not valid?
As @jbriggs444 mentioned, it is a perfectly valid frame, it is just non-inertial. If you are using the right kind of mathematical objects, called "tensors", then you can write the laws of physics the exact same way in inertial and in non-inertial frames. However, most of the high-school and undergraduate physics that you will see does not use tensors. So in those math classes the laws of physics look quite a bit different in inertial and non-inertial frames.WCOLtd said:How come when I spin around, the universe doesn't fly apart as if its rotating around me? Why is my frame of reference that I am at rest and its the universe spinning around me not valid?
Roughly speaking, that accelerometers at rest measure 0 acceleration. To get more detailed would probably go beyond a B thread.WCOLtd said:What defines the inertial frame?
That is the way most people feel, but Nature doesn't care about our apriori strong affinities.WCOLtd said:It seems to me from an apriori perspective that Mach's Principle is so strong. That's why I have a strong affinity to it.