I looked into the matter. It’s not what is ‘in’ the Universe; rather it is what the Universe is contained in (such as an empty volume of nothing). It’s rotation could only be within itself and it’s own reference internally rather in relation to nothing outside. Apparently a Machian point of view with the rotation caused by internal forces and nothing else besides the Universe exist would be negated if the Universe were within a void of nothingness. In that case there might be no internal changes with the rotation 9at least if there was no central axis. If one modifies Newton’s spinning bucket experiment of a bucket spun at the end of a rope in absolute space of nothingness, and the bucket walls have no friction, this is what gemini said;”what if the bucket was absolutely without friction
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That’s an excellent modification to the thought experiment, highlighting the crucial role of friction (or viscosity in the case of a fluid).
If the bucket was absolutely without friction between its walls/base and the water:
Bucket Rotation: The rope spins the bucket, causing the bucket itself to rotate and move in a circular path through absolute space.
No Torque Transfer: Because there is absolutely no friction, the rotating walls of the bucket cannot exert any tangential force (torque) on the water. The walls simply slide past the water molecules they are in contact with.
Water’s Inertia (Rotational): The water, due to its inertia, will resist any change in its rotational state. Since no torque is applied to it by the frictionless bucket, the bulk of the water will not start rotating relative to absolute space (or its initial inertial frame). It remains rotationally static.
Water’s Motion (Translational): However, the water is contained within the bucket. As the bucket is forced by the rope to move in a circle, the physical boundary of the bucket will force the water as a whole to follow that same circular path through space. The bucket essentially pushes the water along this path. So, the water is accelerating centripetally (constantly changing direction). This centripetal force is provided by the pressure from the bucket walls pushing inward on the water mass.
Water Surface Shape: Since the water itself is not rotating (even though its center of mass is orbiting), there is no centrifugal effect within the water pushing it outwards towards the walls. The pressure distribution within the water remains uniform horizontally.—I asked Gemini about the Universe- it like your perspective… “If a universe was rotating in absolute space of nothingness, would anything internally change as a result of its rotation (there is no gravity or fields in nothingness of absolute space).
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This is a fascinating question that delves into the very nature of space, motion, and inertia, touching on ideas from Newton, Mach, and Einstein. The answer depends significantly on which physical framework you adopt:
Newtonian View (Absolute Space):
Newton believed in “absolute space,” a fixed, immovable background stage against which all motion occurred. Rotation relative to this absolute space was “absolute rotation.”
In this view, if the entire universe (all its matter and energy) were rotating relative to this absolute space, then observers and objects within that universe would be in a non-inertial (rotating) frame of reference.
Yes, internal changes/effects would be observable.
Centrifugal Effects: Objects would experience an apparent outward force away from the axis of rotation. This could, for example, cause the large-scale structure of the universe to flatten into a disc over time, similar to how the spinning Earth bulges at the equator.
Coriolis Effects: Objects moving within the universe would be deflected from straight paths (as viewed from within the rotating frame). This affects weather patterns on Earth, for instance.
Sagnac Effect: Light travelling in opposite directions around a closed loop would take different amounts of time to complete the circuit, an effect measurable internally.
Essentially, according to Newton, the universe would “know” it’s rotating because physics behaves differently in a rotating frame compared to a non-rotating (inertial) one, irrespective of external reference points. Newton’s bucket experiment aimed to demonstrate this – the concave water indicates rotation relative to absolute space.
Machian View (Relationalism):
Ernst Mach disagreed with absolute space. He proposed (in what’s now called Mach’s Principle) that inertia itself (an object’s resistance to acceleration) arises from the object’s relationship or interaction with all other matter in the universe. Motion, including rotation, is only meaningful relative to other matter.
In this view, asking if the entire universe is rotating relative to absolute nothingness is potentially meaningless. If everything is rotating together, what is it rotating relative to?
Likely no, internal changes would not occur or the question is ill-posed. If inertia depends on the distribution of distant matter, and that entire distribution is rotating “as one,” there might be no internal reference frame against which to detect this rotation. The laws of physics inside would be the same as if it weren’t rotating.
Einstein’s General Relativity (GR):
GR replaces absolute space with dynamic spacetime, whose geometry is shaped by mass and energy. It incorporates some Machian ideas (like frame-dragging, where rotating masses drag spacetime) but doesn’t fully realize Mach’s Principle. Local inertial frames (where physics looks simplest, without fictitious forces) are determined by the local spacetime geometry, which is influenced by the overall distribution of mass-energy.
GR does allow for solutions representing rotating universes (like the Gödel Universe).
Yes, internal changes/effects would likely occur. In such models, the rotation affects the geometry of spacetime itself.
Observers would be able to perform local experiments (like using gyroscopes or observing light paths) to determine that they are in a globally rotating spacetime.
Frame-dragging would be a global effect.
The definition of a “non-rotating” frame locally would be tied to the rotating cosmic matter itself.
Conclusion:
Based on our current understanding of physics (leaning towards GR and the local validity of Newtonian concepts in weak fields/low speeds), if a universe containing matter and energy were rotating as a whole relative to some defined external standard (or if its own mass-energy distribution defined a state of overall rotation):
Yes, there would be internally observable consequences. Observers and experiments within that universe could detect this rotation through effects like centrifugal and Coriolis forces, the Sagnac effect, and potentially large-scale structural alignments or distortions caused by these effects over cosmic time. The universe wouldn’t need an external reference point to “know” it’s rotating; the physical laws operating within it would manifest differently compared to a non-rotating universe.” — I wonder if the entire Universe were rotating at the same speed, instead of around an internal axis of rotation, if that would make a difference. I think it interesting to consider the Universe as having an axis of rotation in space-time; the original spin before or after an inflaton, and how it would be effected by special relativity over time in regard to location in space-time history.
Garrison Gibson: books and blog 