How is it possible to achieve anywhere close to absolute zero if the earth is moving?

124 views

I didn’t take physics past middle school so I don’t know if my understanding is correct. But my understanding is that temperature is proportional to the average kinetic energy of an object. So, since we’re zipping around the sun at 30 kilometers a second and everything on Earth must be moving at at least that speed, how is it that we can achieve within nanokelvins of absolute zero on Earth if the particle is still moving at 30 kilometers a second through space? Won’t the particle have to be completely at rest to achieve that?

In: Physics

The caveat is it’s always a measurement ‘in a system’

Nothing could possibly be measured in context to the whole universe, so the definitions are within the defined boundaries of that system.

It comes down to relativity as far as I know.

Everything on Earth is moving at the same base does, therefore, to each other they have the same speed, 0.

So while it might not be absolut zero sen from the universe, it is absolut zero relative to everything on Earth.

Relative to the Earth, it is *mostly* at rest. It’s true that earthquakes, butterfly wings, and scientists’ sneezes may cause the container to wobble a bit, though.

Heat is a specific case of kinetic energy where molecules of a substance are vibrating around in a random way *relative to each other*. That last part is important. Something cooled down to absolute zero on earth would still be moving in tandem with the earth but all the molecules would be moving perfectly together and so would be completely stationary relative to each other.

Interesting thought indeed! See, temperature is defined by a speed, yes, but it’s the speed the particles wobble, and not the speed through space. Temperature is a measure of an ensemble of particles in a given space. All these thermodynamic properties like pressure volume or entropy describe an entity of particles in equilibrium. These properties become meaningless if you want to describe single particles.

Temperature is related to the *random* component of molecular kinetic energy, which is independent of reference frame. Adding a uniform velocity to all particles does not affect the system’s temperature.

A side remark on something contained in your question: there’s no such thing as ‘at rest’ in the universe, except within an arbitrary frame of reference. If two stars are approaching one another, there is no way to decide if one is moving and the other is still, if they’re both approaching, or if they’re both moving the same way and one is catching up. All are equally valid, none is more right than the others.