If the entire universe were to suddenly stop rotating, it would have significant consequences for the motion of planets and stars within it. However, it's important to note that the concept of the entire universe rotating as a whole is not well-defined, as the rotation of celestial objects and structures is typically relative to other objects or reference frames.
Nevertheless, let's consider a hypothetical scenario where all rotation in the universe, relative to some reference frame, abruptly ceases. In such a case, the specific effects would depend on the scale at which we examine the universe:
Solar System: Planets, including Earth, would no longer experience the centrifugal force caused by the rotation of the Sun. This force helps maintain the planets in their orbits. Without it, the planets would continue moving in straight lines due to their inertia. This would lead to the planets moving away from their original orbits, potentially resulting in chaotic and unpredictable paths.
Galaxies: Similar to the Solar System, the stars within galaxies would no longer experience the rotational forces that keep them in their orbits around the galactic center. Stars would continue moving in straight lines, potentially leading to disruptions in the structure of galaxies as stars drift apart or collide with each other.
Large-scale structures: On even larger scales, such as galaxy clusters and superclusters, the cessation of rotation could have complex effects. These structures are influenced by gravitational interactions among their constituent galaxies. The loss of rotation could disrupt the delicate gravitational equilibrium, potentially altering their overall structure and leading to changes in their distribution.
It's important to emphasize that this hypothetical scenario of the entire universe abruptly ceasing rotation is highly unlikely to occur in reality. The rotation of celestial objects is a result of complex interactions, including gravitational forces, angular momentum, and conservation laws. Any change in the rotation of the universe would require the influence of external forces acting on an enormous scale, which is not currently understood or supported by our scientific understanding.