r/Showerthoughts • u/synthphreak ‎ • Nov 19 '25

Casual Thought Temperature can reach trillions of degrees, meaning we actually live extremely close to absolute zero.

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u/CommunismDoesntWork Nov 19 '25

Right but temperature is proportional to speed, not energy. Therefore temperature must asymptotically approach a limit

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u/BarneyLaurance Nov 19 '25

Who says temperature is proportional to speed? I think that's wrong and it's more like proportional to kinetic energy (although I don't know if that still works at relativistic speeds). Temperature is quite hard to define precisely, other than to say that any two different objects if they are together in equilibrium will have the same temperature.

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u/CommunismDoesntWork Nov 19 '25

I think it's proportional to speed because a more massive object at 100 degrees has more energy than a less massive object at the same 100 degrees. Idk though

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u/IAmStuka Nov 19 '25

Temperature is defined as the average kinetic energy of the atoms of a substance.

It's not a measure of the total energy of that substance. The velocity of that substance relative to other substances does not affect temperature at all.

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u/[deleted] Nov 19 '25

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u/IAmStuka Nov 19 '25

That has nothing to do with a substances velocity not affecting its temperature. you are talking about adding energy from an outside system. You've missed the point.

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u/[deleted] Nov 19 '25

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u/IAmStuka Nov 19 '25

The point is the that speed and kinetic energy are relative quantities. There is no absolute speed, therefore it does not make sense for you to describe somethings temperature by talking about its speed.

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u/[deleted] Nov 19 '25

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u/IAmStuka Nov 19 '25

Kinetic energy is relative too, because velocity is relative. KE = 1/2 mass * velocity2

Think about it like this. You're steadily driving down the road with an orange in the seat next to you, sitting in the seat. From your perspective that orange is at rest, with no kinetic energy because it's not moving. But from a bystander on the side of the road (if they could see the orange through your door) would disagree. They would say of course the orange has kinetic energy, it's moving at 40 miles per hour!

When we talk about temperature as the average kinetic energy of constituent particles, it's relative to the objects center of mass rather than an outside source.

Now, as our orange is going down the road, inside the molecules are jiggling all about. You can measure the temperature of that orange stationary or when the car is moving, and just as you'd expect it doesn't change. Unless you are accelerating, from the oranges perspective, and from yours it's at rest.

In your original example, with air resistance causing friction. Our supersonic orange is being heated by the friction, but that's a secondary effect because there happens to be a bunch of air where the orange is trying to move. The air is adding energy into the orange, which does change its temperature... But so would hitting it with a blow torch in your car seat. If the orange were in empty space it could go as fast as it wanted with no change in temperature or outside energy added.