Nature's Temperature Limit?

Well, in a classical sense there would be an upper limit (Planks Temperature) as well as a lower limit (Absolute Zero). However, even at Absolute Zero the atoms still have zero point energy. The next question is, how much energy can be put into an atom or molecule? Well there is a theoretical limit and that would be the sum of all the energy in the universe. That is not going to happen anytime soon, but it did happen during the Big Bang where the temperature was about 1023 Kelvins.

Only 1023 K anonymous???

That's only hot enough to make steel glow cherry red at a guess!!

John

Ha!!! Good catch!

That is supposed to be 10^32. For some reason the superscript did not take. ;-)

http://library.thinkquest.org/19957/current/kelvinbody.html

"Upon first guess, most people would think that to get below absolute zero, you would need to go from positive to zero then down to negative. However, paradoxically, negative absolute temperatures can only be obtained through infinite temperatures (as the temperature goes to infinity, the ratio gets closer to one, and by inverting the population, the ratio goes above one). Population inversions really do happen in everyday life. They are the basis for lasers, in which the numbers of excited molecules outway those in the ground state. Therefore, lasers share properties with molecules below absolute zero. The concept of negative absolute temperatures has been verified using the magnetic field example"

As to the topic of the highest possible temperature, I remembered reading several years ago that negative Kelvin was infinitely hot, so I googled it. I don't even pretend to understand this , just thought I would throw it in the discussion. Perhaps somebody else understands it. If I'm reading this right the highest possible temperature is below absolute zero. If Somebody can explain this to me feel free, I'm going to go get more aspirin.

I suspect it depends on your definition of "limit". Man made? Stellar? Does anyone have an educated guess as to the temperature in the core of a giant supernova? The core temperature has increased up to the point of creating element # 26. As the radiation pressure decreases and the sudden collapse of the star to the resulting "explosion", the temparature must be up there. If we accept "inflation" after the Big Bang, then we may accept an ultimate temperature at the core of the Big Bang, whether it is from a singularity or a rebound, etc. I would think that would be your "maximum" allowable temperature. But is it meaningful? It couldn't be measured. A more measurable temperature spike may be infalling matter falling onto the surface of a neutron star, and the resulting "explosion".

So far the replies in this thread have gone in directions deeper and more surprising than I expected. I now feel less certain about the very definition of "temperature" (the p-chem definition seems too limited -- no mention of neutron stars!). I will chew on what I've read. I also want to take a specific angle of attack and attempt to calculate the temperature that corresponds to a cloud of hydrogen atoms with an average speed of half the speed of light (assume no fusion occurs). Then we can see how this back-of-the-envelope calculation compares to the Plank temperature. In any case, it becomes increasingly clear that temperature does have an upper limit.

From Wikipedia:

The Planck temperature, named after German physicist Max Planck, is the unit of temperature, denoted by T_P, in the system of natural units known as Planck units. It is one of the Planck units that represent a fundamental limit of quantum mechanics. The Planck temperature is the fundamental upper limit of temperature; modern science considers it nonsensical to conjecture about anything hotter, as this is the upper limit at which matter can operate. Beyond this, everything turns into energy as all subatomic particles become so excited they break down. It is the temperature of the Universe during the first instant (the first unit of Planck time) of the Big Bang according to current cosmology.

http://en.wikipedia.org/wiki/Planck_temperature

Hi svangali.

I suppose it is the same with time, what is time? Time, temperature, they are both relative, some one said to me yesterday that it was warm for this time of the year, I live in the UK so he was right. But for some one who lives in Mali it would have been cold! Thus we have the relative temperatures.

In physics as in nature there is no absolute, be it up or down, + or -, we have to get away from this idea.

Spencer.

"does nature place an upper limit on temperature? I think that it does, since material particles cannot reach or exceed the speed of light"

Surely relativity means that as a particle approaches the speed of light its' energy approaches infinity? I'm no physicist, just throwing that in there! (admittedley this brings up the whole relativity Vs quatum physics argument, GUT's ...there is no end to this discussion!)

On a side issue I think I am correct in saying that the highest temperature man has acheived is around 100,000,000K in a prototype nuclear fusion reactor.

Surely relativity means that as a particle approaches the speed of light its' energy approaches infinity?

Excellent point! TheZorses very astutely caught this important omission on my part. I had overlooked the relativistic mass increase that particles experience as they approach the speed of light. This refutes my argument for a temperature limit based on the speed of light (since -- even without reaching the speed of light -- particles can keep increasing their kinetic energies without limit). The calculation I had intended to do would need to include relativistic mass increase. But no need to do that calculation anymore, since my entire premise has crumbled.