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No, The Laws Of Physics Are Not The Same Forwards And Backwards In Time

12 Jul 2019, 14:01 UTC
No, The Laws Of Physics Are Not The Same Forwards And Backwards In Time
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A ball in mid-bounce has its past and future trajectories determined by the laws of physics, but time will only flow into the future for us. While Newton’s laws of motion are the same whether you run the clock forwards or backwards in time, not all of the rules of physics behave identically if you run the clock forwards or backwards. (WIKIMEDIA COMMONS USERS MICHAELMAGGS AND (EDITED BY) RICHARD BARTZ)The laws of physics are not time-reversal invariant. Here’s how we know.No matter when, where, or what you are in the Universe, you experience time in only one direction: forwards. In our everyday experiences, clocks never run backwards; scrambled eggs never uncook and unscramble themselves; shattered glass never spontaneously reassembles itself. But if you were to look at the laws of physics that govern the way the Universe works ⁠ — from Newton’s laws of motion down to the quantum physics of subatomic particles ⁠ — you’d find something peculiar and unexpected: the rules are exactly the same whether time runs forwards or backwards.This corresponds to a certain symmetry of nature: T-symmetry, or time-reversal invariance. Our everyday experience indicates to us, quite strongly, that the laws of physics must violate this ...

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