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First time to physics Stack Exchange and I'm about to show my extreme lack of physics knowledge. I've only been through Physics 121, particle physics. So, bear with me!

So an object, a sphere for simplicity, is rotating. I learned the formulae for angular momentum, kinetic energy, etc. but conceptually, it seems like those formulae are a macro-level representation of the complex dynamics and micro-interactions of the various particles that make up the sphere. There are other forces at work keeping the sphere's particles in sphere-shape (be it gravity, molecular bonds, whatever). Without these forces, each of the particles would fly off tangentially, correct?

In these particles' "micro-interactions" (there has to be a better description than that), is there potential for energy loss? Would this energy loss rob the sphere of its rotational kinetic energy?

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Most angular momentum or energy conservation theorem have steps in which they show that internal forces cannot change the energy of the system. So the only possibilities would be energy loss (kinetic energy) for quantum effects, particle emission, or transformation of kinetic energy in internal energy, heat, temperature variation, subsequent energy loss in black body radiation (which could be considered still particle emission) but nothing can be said without further detailed information.

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  • $\begingroup$ Would thermal radiation also be a particle emission? $\endgroup$
    – crunk1
    May 19, 2017 at 9:21
  • $\begingroup$ Thermal radiation and black body radiation are substantially the same thing, the second being ideal and in thermal equilibrium, Thermal radiation is electromagnetic radiation (light), so in terms of quantum physics it is the emission of photons, so yes, they are maslsess particles but still carry energy. $\endgroup$
    – Claudio P
    May 19, 2017 at 9:31
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No. Such an outcome would contradict the law of conservation of angular momentum.

If the object deforms, changing the moment of inertia, the angular velocity could change, but it would not become zero unless the moment of inertia became infinite. In order to remove angular momentum, there must be an external force on the object, or the object must emit particles which carry momentum.

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  • $\begingroup$ Is there a possibility of radiating heat energy? $\endgroup$
    – crunk1
    May 19, 2017 at 9:13
  • $\begingroup$ Yes there is, but if it is radiated equally in all directions it will have no effect on angular velocity. Even if directed forward, the effect will be very small, and will reduce as the object cools, so the object would not stop rotating. $\endgroup$
    – sammy gerbil
    May 19, 2017 at 12:17

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