# Is there a highest temperature? [duplicate]

Im new to physics and do not yet know of all of the terms and math.

I was wondering about temperature. I read that there is the lowest temperature which is absolute zero where nothing happens, i.e. no vibrational activity from atoms.

My question is; is there also a highest temperature, i.e. an absolute max temperature?

## marked as duplicate by John Rennie, ACuriousMind♦, David Z♦Jun 5 '15 at 12:46

• There's a peculiarity to the absolute temperature scale - the highest temperatures are lower than zero. So the lowest possible temperature is "the smallest value higher than zero", while the highest possible temperature is "the largest value smaller than zero" - see en.wikipedia.org/wiki/Negative_temperature. Not something you'd see in a lab or a particle accelerator, but useful in physics math. – Luaan Jun 5 '15 at 12:28
• @Luaan. Ok, i have to digest what you just said. I cannot fully comprehend it at the moment. But thanks for this interesting input. – Lanka Jun 5 '15 at 12:30
• @Luaan: Not everything that is written on Wikipedia is actually correct or well written and this one certainly isn't. Negative temperatures only occur in systems with inversion and those systems are NOT in thermal equilibrium, hence the negative temperature is not a real thermodynamic temperature, at all. – CuriousOne Jun 5 '15 at 15:36

In a thermodynamical settings in particle physics, the highest temperature will be the temperature at which point you reach an equilibrium with particle creation from the random particle collision.

The Hagedorn temperature is the temperature at which quarks, when heated, will produce more quarks, which will lower the temperature back.

• Thank you for the answer. How can heated quarks produce more quarks? Could you give a short answer or refer me to some litterature on this. – Lanka Jun 5 '15 at 11:17
• As a general rule, it's better to ask a new question for something this different, but in a nutshell, quarks are like teenage girls at a slumber party. They hate being alone and they hate to wear the same color outfit. – userLTK Jun 5 '15 at 11:34

I found an answer to my own question. The quote is from "Is there an absolute maximum temperature?"

We posed this question to Sam Gregson, High Energy Particle Physicist at the University of Cambridge...

Sam -
The temperature of a system is simply related to the amount of energy in that system. Because the system can't have a negative energy, there is only so much heat you can remove from it and so a limit to how cold you can get. This is called absolutely zero. We’ve got very close to it. Scientists in Finland have cooled rhodium atoms to a 10th of a billionth of a degree above absolute zero. On the other hand, an absolute maximum temperature would require there to be a limit to the amount of energy you can give to a particle. As far as we know, there is no such limit.

Although the speed of light is the universal speed limit, the reason you can't get there is that this would require an infinite amount of energy. So this speed limit does not limit the amount of energy and therefore, the temperature of an individual particle.

The most energetic particle ever observed was a cosmic ray over Utah, travelling at 99.999999999985% of the speed of light. Probably a single proton with about 50 joules of energy. This is equivalent to about 5 trillion trillion degrees Celsius and there is no evidence that this is the hottest you could get to.

As far as we know, you are just limited by the amounts of energy you can give to a particle. So you could say that the absolute maximum temperature is a temperature equivalent to all the energy in the universe, concentrated onto one particle. But that limits more accounting than basic physics.

Hannah -
Thanks, Sam Gregson from Cambridge and CERN. So temperature is related to thermal energy and Einstein’s theory of relativity means that although a particle has a universal speed limit, it doesn’t have an energy limit. If you took all of the energy in the universe and put it into one particle, you'd essentially run out of energy before you run out of capacity for energy which is why we have no absolute maximum temperature.

• Small point to add, but velocity isn't exactly temperature and velocity is also relative. So, I'm not sure that super fast moving particle should count, but that's just my opinion. Obviously Sam Gregson is much smarter than I am, but I think he's kind of cheating with the answer. There's no limit up to but not including the speed of light you can give a particle, but if you were flying along with that particle at that speed, it wouldn't feel hot to you. Now the instant that particle hit the atmosphere - that would be a valid temperature, if you could measure it. – userLTK Jun 5 '15 at 11:24