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Q & A: particles and heat

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Most recent answer: 06/19/2011
Q:
Why in particle physics is the dissipation of energy through heat and sound not taken into account?
- Bob (age 19)
Seattle, WA
A:
Sound is a collective mode of behavior of large numbers of particles. In systems with only a very small number, it wouldn't mean anything to talk about sound. "Heat" is a word loosely used for energy distributed statistically in thermal modes. Again, for very small numbers of particles, one can keep track of all the modes. Nothing is left to statistically distribute.

On the other hand, in some types of particle physics, those involving collisions of large nuclei, there are enough unobserved modes for the ideas of heat and temperature to be more or less useful. In other types of fundamental physics, closely related to fundamental particle physics, ideas of temperature, heat, and sound are used a great deal. For example, the types of particles and interactions present are believed to have undergone temperature-driven phase transitions as the early universe expanded and cooled. Sound waves from that universe are still visible as ripples in the cosmic microwave background.

Mike W.

(published on 06/19/2011)

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