Levitation by cooling
A ball is kept on a table, and is at the same temperature as its surroundings. Suppose the ball becomes colder and begins to rise up in the air on its own.
It is converting its internal energy to potential energy. Does this violate the law of conservation of energy ?
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1 solution
The analogy to this is dropping a spring from a certain height so that it falls and hits a surface. Then momentarily, the kinetic energy it had, which has been converted from gravitational potential energy, is converted into the spring's elastic potential energy.... which is then converted back into kinetic energy and eventualy back into gravitational potential to the point of beginning. This can repeat cyclically and can happen. The spring has bounced.
It is proposed that a ball can do that, converting its internal heat energy into kinetic energy, etc., as if the internal heat energy is similar to elastic potential energy. Newtonian mechanics using the Conservation of Energy law doesn't prohibit this from happening. However, thermodynamics and statistical mechanics does prohibit this from happening, as this woud be reversing entropy.
A ball that is dropped does get hotter when it strikes the surface... but the reverse doesn't happen. In classical mechanics, everything is reversible in time, but in thermodynamics and statistical mechanics, it is not.