I am reading Landau and Lifshitz’s Mechanics, where they explain how the conservation of momentum and angular momentum follow from the homogeneity and isotropy of space, respectively. They also show how the conservation of energy follows from the homogeneity of time. This makes me wonder if there is a similar conservation law that follows from the isotropy of time?
Asked
Active
Viewed 169 times
0
Qmechanic
- 201,751
-
1Could you elaborate on your distinction between homogeneity and isotropy of time? – Mauricio May 21 '23 at 20:01
-
1There is a single direction of time so it is necessarily isotropic. – Christophe May 21 '23 at 20:06
-
In my mind, the isotropy of time means physics law is the same in every time direction (analogous to space isotropy). Based on that logic, time has two directions, forward and backwards. – Manish Kumar Singh May 21 '23 at 20:13
-
8Then you are talking about time reversal. This is not a symmetry of the standard model. And even if you neglect this, it's a discrete symmetry. I.e. one that has no associated conservation law. – Connor Behan May 21 '23 at 20:23
-
entropy is conserved in a reversible process – hyportnex May 21 '23 at 20:31
-
Possible duplicates: https://physics.stackexchange.com/q/693073/2451 and links therein. – Qmechanic May 23 '23 at 01:33
1 Answers
2
Since time is only one dimensional, the only possible "isotropy" would be symmetry under time reversal. But that is a discrete symmetry and Noether's theorem only works for continuous symmetries. So there is no conservation law associated with isotropy of time.
Tarik
- 470