Entropy and time asymmetry

Question

I have learned in Lagrangian Mechanics that the existence of time symmetries makes energy conserved. But from thermodynamics, we know that entropy introduces the forward arrow of time, i.e., the time asymmetry. We do know that energy is also conserved in thermodynamics. Where am I missing the point? Can someone connect the dots for me?

What is time, does it flow, and if so what defines its direction? — mmesser314, Nov 25 '20 at 01:15

score 1 · Accepted Answer · answered Nov 24 '20 at 22:16

1

Time translation symmetry does not preclude an arrow of time. The former, which assumes that the laws of physics do not change over time (not that time must move forward), is assumed in both Lagrangian mechanics and thermodynamics and underlies the law of conservation of energy.

answered Nov 24 '20 at 22:16

Chemomechanics

25,546

Can you elaborate it thoroughly? – Little Physicist Nov 24 '20 at 23:12
If I can. Which part is unclear? – Chemomechanics Nov 24 '20 at 23:39

Entropy and time asymmetry

1 Answers1