# Why is there a small lower limit to temperaure (-273.15C) but almost limitless upperbound? (million of degree in a star for example)

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Is there even an upper limit to temperature?

In: Physics

Temperature measures how hard the molecules of a substance are shaking. The bottom value here is total standstil – 0 Kelvin. I’m not sure if an upper limit is possible.

First of all your question has a personal bias.

The lower limit for temperature seems low to you only because you are comparing it to the habitable temperature of Earth that you are used to.

Temperatures in the millions are relatively common because stars are common.

There is an upper limit to temperature though.

If you keep increasing the temperature in a particular spot eventually because of E=MC^2 you’ll reach that limit… which results in the creation of a black hole.

There is a lower limit because particles cannot move beyond those extremities, so nothing can remove the heat from the substance

Temperature is a measure of the average jiggling speed of the atoms or particles.

The important point is *it’s a speed*. You can’t go slower than stopped. “Not moving” is the slowest possible speed. That’s why there’s a minimum temperature. That’s why we call 0 Kelvin “absolute zero”, because that’s the temp corresponding to a particle speed of 0.

There’s no max* because things can always go faster.

*The speed of light is a max speed for things but that’s so fast it’s not really relevant to this question. Google planck temperature if you want info on this.

Temperature is effectively velocity. It’s how fast particles are vibrating.

Absolute zero is just everything being absolutely stationary.

Maximum temperature is more complicated. Obviously there is a maximum speed (light speed), but temperature is more a measure of energy, so it gets relativistic. Once you get to about 1,400,000,000,000,000,000,000,000,000,000,000 Celsius physics starts to break. But you’ll get a black hole long before that.

It’s not so much that the lower limit is small and the upper limit is big, it’s just that we’re a lot closer to the lower limit than we are to the upper limit.

Same reason why there is a lower limit to velocity. 0 speed.
It’s only called -273,15 because calling it 0 is less practical than using a water based reference (0 freeze, 100 boil).

The only way to make something colder is to take energy away from it. Once you take away all the energy, you’re at absolute zero. That’s why it’s called absolute zero, because it’s zero amount of energy.

Edit: there IS an upper limit called the Planck Temperature, where you can’t add any more energy… But it’s a VERY high temperature.