Time Reversal Breaking in Classical Systems

[hokhani]

TL;DR

Classical systems without time reversal

I am looking for an example of a classical system without time reversal symmetry. I would appreciate any help.

 

[jbriggs444]

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.

 

[Filip Larsen]

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.

 

[wrobel]

the banal pendulum with friction
$$\ddot x+x=-\dot x$$
is not invariant under the change $t\mapsto -t$

 

[Andy Resnick]

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.

 

[hokhani]

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?