Can entropy be reversed?
“Occasionally, I drop a teacup to shatter on the floor on purpose. I’m not satisfied when it doesn’t gather itself up again. Someday, perhaps, that cup will come together.”
(Hannibal, “Ko no Mono”, 2014)
Suppose I were to show you a recording of a ball rolling, but I played it to you in reverse—would you be any the wiser? If I showed you that same ball falling, could you be certain you were watching its descent and not merely its rebound played backwards?
How about a video of a shattered teacup coming back together? In that case, you’d be quite certain you were watching a video played backwards, having no doubt as to the correct sequence of events.
You are well aware that a disordered assortment of pottery shards does not miraculously come together into the form of a teacup. Nor do you have any hopes that the split tea from said teacup will spontaneously re-heat. On that note…
The second law
The physical laws relating to heat are the only ones to distinguish between past and future. It is the transfer of heat, in the form of molecular agitation and disordering, to a colder object which indicates the arrow of time.
The second law of thermodynamics states:
The entropy of the universe tends to a maximum.
The entropy of an isolated system remains stable or increases, but never decreases. In other words, disorder magnifies over time.
As entropy cannot be reversed, increased entropy proves that time has passed.
All good things must come to an end
“This is the way the world ends, not with a bang, but a whimper.” — T. S. Eliot
What happens when this maximum entropy is reached? When all available heat energy has dissipated, when everything has the same low, approaching absolute zero temperature, the universe will be too cold to support life, that’s for sure.
The Big Bang endeth in The Big Chill.
Further reading
Rovelli, C. (2019). The order of time. Riverhead Books.
Asimov, I. (2016). The Last Question (1956). The Complete Stories, 1, 290–300.
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Just because entropy tends towards a maximum, doesn't mean it implies "time". It merely implies things are always going to get messier (with less energy) unless someone/something cleans it up by using energy (from somewhere else) to reposition/move things back into an ordered state/condition where they contain the some (likely never to be all) of the energy expended.
I just realized this a couple weeks ago, and ruined my ability to ever enjoy time-travel movies any more.
"Time" is a construct our brains invented. I'm pretty sure it isn't necessary in physics except maybe as a math construct. Our existence from birth to death is a long series of causes/forces and their effects. There's no undoing of any of it, except by applying opposite causes/forces and there's (I think) not much you can fix back exactly the way it was. (Although I did read once about a guy who figured out how to uncook hard-boiled eggs.)
"Wasting time" is simply "wasting opportunities" to have an effect upon the world around you.
There's no "past" except as memories of our past forces/effects.
And there's no "future" except as what "might happen" if we force things a particular way.
Our brains can predict and plan and think through a series of causes and effects, like dedicated Chess players thinking "moves ahead", but I don't know of too many people who have had everything they planned ever actually happen. I certainly can't get past 1 revolution of the Earth without my plans being obliterated by someone else's plans already forced/caused.
I haven't thought anymore beyond this.
But it has pretty much given me the ability to tell the "woulda/shoulda/coulda" line of pondering to cease if it isn't contributing to any cause/force I intend to try the next time I wake from sleep.
I do use the construct of time still... if I don't want to be completely overrun by the effects of others... I have to make sure my causes/forces have their effects in a way that creates ORDER and not further ENTROPY... and that means aligning MY IMPACT in the world in a civilized concert with the people around me.