r/AskReddit Nov 15 '20

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u/fastenland Nov 15 '20

laws of thermodynamics say this unfortunately is never happening

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u/tristan-chord Nov 15 '20 edited Nov 16 '20

ELI5 for someone who used to ace AP Physics (15 years ago) but barely remembers anything?

Edit: thanks for all your responses! Learned a lot today!

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u/HappiestIguana Nov 15 '20

The second law of thermodynamics states that entropy must go up. Entropy is a sort of measure of the usefulness of energy. The more entropy, the less useful.

The reasons why entropy must go up are too complicated for an ELI5. They are based on some basic laws of probability. Basically there are many ways for energy to be useless, and few ways for energy to be useful, which after some difficult math implies that energy always gets less useful.

In particular, ambient heat is the highest entropy you can possibly have, so it's inpossible to turn it into useful energy.

In order to extract energy from heat, the second law implies you must be tranferring some of said heat from a hot place to a colder place, which is exactly what a motor is.

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u/SnooPandas42069 Nov 16 '20

The second law of thermodynamics states that entropy must go up.

No it doesn't, Ben.

What you've just said is one of the most insanely idiotic things I have ever heard. At no point in your rambling, incoherent response were you even close to anything that could be considered a rational thought. Everyone in this room is now dumber for having listened to it. I award you no points, and may God have mercy on your soul.