What would happen if the universe rotated?

The concept of a rotating universe is an intriguing one, though it's primarily theoretical. In cosmology, the standard model of the universe, based on general relativity, does not inherently include rotation on a cosmic scale. However, if the universe were to rotate, several interesting implications could arise:

**Coriolis Effects**: In a rotating universe, objects moving through space would experience Coriolis forces, affecting their trajectories. This could impact the motion of galaxies and other cosmic structures.

**Effect on Cosmic Microwave Background**: The Cosmic Microwave Background (CMB) radiation, a remnant of the Big Bang, would be affected by rotation. There could be anisotropies (irregularities) in the CMB that reflect the rotational motion of the universe.

**Gravity and Structure Formation**: A rotating universe might affect how structures such as galaxies form and evolve. The distribution of matter could be influenced by centrifugal forces, potentially leading to non-standard cosmic evolution.

**Topology of Space-Time**: A rotating universe could have a different topology, potentially leading to unique gravitational effects and altering the behavior of light and matter in ways not seen in a non-rotating universe.

**Violation of Conservation Laws**: Depending on the model, a rotating universe might require a modification of certain conservation laws, such as those relating to angular momentum and energy.

**Influence on the Fate of the Universe**: The rotation could affect the overall dynamics of the universe, including its expansion rate and its ultimate fate. For example, a sufficiently rotating universe might have different conditions for phenomena such as cosmic collapse or expansion.

**Potential for Singularities or New Physics**: The presence of rotation could lead to scenarios involving singularities or other exotic solutions in general relativity, which may not have been explored in our current understanding of cosmology.

Overall, while a rotating universe presents many interesting theoretical questions, current cosmological models do not support this idea as a valid description of our universe. Most of the universe's large-scale structure and behavior can be effectively described without rotation, leading to a more uniform and isotropic picture as described by the cosmological principle.