I Time Reversal Breaking in Classical Systems

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Examples of classical systems lacking time reversal symmetry include chaotic systems and those with friction, such as a damped pendulum. Non-reciprocal optics and electromagnetic nonreciprocity are also cited as relevant examples. Systems that experience loss inherently exhibit time-reversal asymmetry. The discussion raises questions about the effects of time reversal on closed systems under external magnetic fields. Overall, the exploration highlights the complexities of time reversal in classical physics.
hokhani
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Classical systems without time reversal
I am looking for an example of a classical system without time reversal symmetry. I would appreciate any help.
 
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hokhani said:
Summary:: Classical systems without time reversal

I am looking for an example of a classical system without time reversal symmetry. I would appreciate any help.
Classical physics is symmetric under time reversal. Entropy is the only arrow that I know of classically.
 
As example of classical systems that exhibit behavior that (in some practical sense at least) is not quite symmetric regarding time reversal I guess you could look at chaotic systems.
 
the banal pendulum with friction
$$\ddot x+x=-\dot x$$
is not invariant under the change ##t\mapsto -t##
 
hokhani said:
Summary:: Classical systems without time reversal

I am looking for an example of a classical system without time reversal symmetry. I would appreciate any help.
Check out "non-reciprocal optics" or " electromagnetic nonreciprocity".

Any system with loss is also time-reversal asymmetric.
 
Thank you all for the responses. How about a closed system which is under an external magnetic field? Does time reversal change also the external magnetic field or it only reverses the time in the closed system?
 
Thread 'Why higher speeds need more power if backward force is the same?'

Thread 'Why higher speeds need more power if backward force is the same?'

Power = Force v Speed Power of my horse = 104kgx9.81m/s^2 x 0.732m/s = 1HP =746W Force/tension in rope stay the same if horse run at 0.73m/s or at 15m/s, so why then horse need to be more powerfull to pull at higher speed even if backward force at him(rope tension) stay the same? I understand that if I increase weight, it is hrader for horse to pull at higher speed because now is backward force increased, but don't understand why is harder to pull at higher speed if weight(backward force)...
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