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Flux capacitor back to future1/21/2024 There are various applications where engineers want electromagnetic signals (such as light or radio waves) in a circuit to behave a bit like cars around a roundabout. It complicates the diversion of electronic and radio signals around a circuit. Microscopic reversibility presents an important technological challenge. How does this irreversiblity emerge from microscopic laws that are reversible? This remains a mystery. This is obvious in our everyday experience: a scrambled egg is not reversible. At the macroscopic scale, the entropy of the universe - a measure of disorder or randomness - always increases, so that there is an arrow of time. Unlike Doc Brown, we can’t make the clock tick backwards. Since the microscopic laws of physics appear to be unchanged under this mathematical transformation, we say the universe possesses time reversal symmetry, even though we cannot actually reverse time in reality. This mathematical transformation reverses the flow of time in our equations. Indeed, the basic equations of physics look essentially the same if we replace time with its negative. A beam of light travelling in one direction obeys exactly the same laws of physics as a beam of light travelling in the opposite direction. The collision of two billiard balls looks pretty similar in reverse even more so for the collision of two atoms. Source: Tom Staceīut at a microscopic level, the story is not that clear. Golf doesn’t look so convincing in reverse. This might seem obvious: people don’t usually walk or talk backwards spilt milk doesn’t spontaneously jump back into its carton a golf ball doesn’t miraculously launch backwards from the fairway, landing perfectly balanced on the tee at the same moment as the club catches it. You could then ask: “If I edited the movie to run backwards, and showed it to my friends, could they tell?” Suppose you make a movie of an event occurring. Time reversal symmetry is a complex sort of symmetry that physicists like to think about, and relies on the imaginary as much as the real.
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