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Comment by adammarples | Hacker News Reader

This sounds wrong, lots of electricity does useful work that doesn't turn into heat (moving an electric vehicle, making plastic items) or escapes as other waste (light, sound, etc)

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In the case of the car: when you accelerate, it turns most of that electric energy into kinetic energy (and turns some of it into heat). As you cruise along at a constant velocity, it's turning most of that electricity into heat: It's overcoming air and road friction, aka, rubbing against things and producing heat. Etc.

Waste light and sound get absorbed by surfaces, thus, turned into heat (unless the waste light is in the right IR band to pass out through the atmosphere).

What about flipping bits in a processor? Current processors do produce waste heat, but I don't think all of the energy in a processor gets converted to heat and it's not a requirement for computation that heat be generated, e.g. if we had superconducting processors.

Actually, it is a physical requirement that erasing information generates waste heat. https://en.wikipedia.org/wiki/Landauer%27s_principle

We're still pretty far from that limit, but unless your plan is to never erase bits, you're going to waste energy.

> On the other hand, recent advances in non-equilibrium statistical physics have established that there is no a priori relationship between logical and thermodynamic reversibility.[19] It is possible that a physical process is logically reversible but thermodynamically irreversible. It is also possible that a physical process is logically irreversible but thermodynamically reversible. At best, the benefits of implementing a computation with a logically reversible system are nuanced.[20]

It's not necessarily a requirement (see reversible computing), but we're very far from knowing how to do it if indeed it's possible at all. current processors do convert all of the energy they use into heat. To set a transistor one way, you put a bunch of charge onto its gate. To set it the other way, you take those electrons and dump them to ground. All of that current flowing is converted to heat.

Those are actually all converted to heat eventually, just with more steps.

Moving an electric vehicle causes motion, but that motion is absorbed by the air and ground via friction with both, aka heat.

Light is just energy in a photon — when it hits a surface that absorbs it, it becomes heat. And it can be quite a lot actually! If you put your hand in front of a really bright flashlight, you’ll notice a warm feeling. If you turn off the flashlight, it goes away immediately, proving that is the light itself causing the heat.

Approximately all of the energy we use as electricity is just changing something into heat with some useful work in between

Think of heat as like nature's income tax, every energy transaction you do is subject to a heat tax. Eventually almost all energy is converted into heat. Even the sun converts every chemical into its lowest energy state and releases all that energy in the atoms as heat. The primary thing the universe currently does is turn matter into heat, and tries to distribute that heat evenly.

Eventually most of the energy for earth either becomes heat in the earth, gets radiated into space, or slows the earths rotation around the sun, or spin. Of all of these things the dominant two are heat radiating into space (this is by far the largest), and heating the earth, with a few things like the tides slowing the rotation of the earth.

A little bit of it gets stored as chemical energy through plants and animals, but eventually those get burned either through fire, or chemical decomposition.

To give you an idea of how much heat escapes, if the sun stopped, and we used our nuclear arsenal to replace it, we'd have about 30 minutes of sunlight.

The idea that AC causes heat in cities to any real extent is laughable, if AC was capable of changing the temperature of the earth to any meaningful degree we'd just water cool the heat exchanger and solve global warming by dumping the heat into the ocean.

Sound and light are heat. Heat is movement of atmos. When the sound or light physically hit a surface, they cause the surface to heat up a bit.

It's all heat in the end.

Moving an electric vehicle turns into heat. Because routes are cyclical all of the potential energy turns into heat in the end. You buy a book case and haul it to the top of a hill, eventually that book case is going to the dump, which will be downhill.

Manufacturing products via endothermic processes does not turn all of the energy into heat, but then again exothermic processes can exceed the energy used.

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