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Sep 3, 2019 at 10:16 history edited Joce CC BY-SA 4.0
deleted 40 characters in body
Aug 7, 2019 at 4:47 comment added Bibek_G $\mathrm d^2\tau/\mathrm dt^2 = 0$ and not 1. and that is also not what we need here. $\mathrm d\tau^2/\mathrm dt^2 = 1$ should be edited in.
Nov 20, 2018 at 15:52 history edited Joce CC BY-SA 4.0
clarify
Jan 27, 2016 at 8:21 history edited Joce CC BY-SA 3.0
edit (thx!) changed one negation, restored meaning.
Jan 25, 2016 at 8:52 history edited user36790 CC BY-SA 3.0
added 99 characters in body
May 20, 2014 at 11:50 comment added Joce @Sachin: Really focus on the word "symmetry": if it is symmetric, then after a mirror reflection (t -> -t), you should be able to superimpose the two "images", taht is, the trajectory. Said another way, you shouldn't be able to tell that the film is being played backwards. However, when there's friction, you can: there is no mirror symmetry.
May 20, 2014 at 9:41 comment added Sachin Kumar Yes, this clarifies things. But in the reverse film, the sign of the frictional force doesn't change. My main problem was with the explanation that time reversal is equivalent to a movie played backwards, which it isn't.
May 20, 2014 at 9:39 vote accept Sachin Kumar
May 20, 2014 at 6:48 history edited Joce CC BY-SA 3.0
added 9 characters in body
May 19, 2014 at 19:47 history answered Joce CC BY-SA 3.0