absolute zero

I discovered this site while trying to discover “how cold is cold ?”, and “how hot is hot ?”>
I found absolute zero and understand that, but would like to know if there is a maximum cold or hot, that extreme of temperature which cannot be exceeded ?
Any reply would be appreciated. Thank you

I seem to recall there’s a temperature at which atoms will fling their electrons off at the speed of light; supposedly one cannot get “hotter” than that.

The value escapes me I’m afraid.

Well, you can inject so much energy into an electron that it disintegrates into its constituent quarks, and in theory you could energize those quarks so much that they’d break apart… at this point it becomes conjecture.

If you found “absolute zero,” that answers the “maximum cold” part.

This column addresses the maximum high temp.

Well, finding a ceiling for temperature is a lot trickier than finding rock bottom.

Asimov once explored the question. He said that at first it would seem easy enough. The speed of light is an absolute limit, and temperature is average kinetic enery of molecules under question. At a high enough temperature, given a 0.5% increase in speed for every 1% kinetic energy boost, as the formula for kinetic energy indicates, a particular gas would have all of its molecules cramming against the speed of light.

But, wait a minute, he says, bringing in relativistic calculations. Actually, since mass increases with speed, there is no such ceiling, because each calculated boost in speed would be reduced by taking into account the greater mass.

Put another way, since energy has an assymtopic relationship with the speed of a fixed individual rest mass, you can pick any humungous amount of energy per rest mass you like, and the speed would merely correspond to something like 99.99999…% of c, rather than c times rather huge numbers, which would be rulked out. One extra 9 for about every 100 times the total energy, in case you’re interested.

So, instead he reworked the question, focusing on the practicality of discussing ultra-high temperatures. He decided that 3 billion kelvins was about the ceiling for a massive star’s core before instant supernova flash was dictated by the best known calculations.

I’m not sure about what Bob and Bryan are saying. I’ll have to check it out. Prolly what Asimov said about 2 decades ago would be dated as far as his figure is concerned.

True Blue Jack


If I read it correctly ABSOLUTE ZERO is the temperature at which all molecular movement ceases.
But, ABSOLUTE ZERO is not the coldest temperature possible.
Thanks for your reply and all the others that responded so quickly !

Your answer makes sense. I am sure there is a limit to everything. The eternal verities are certainly something other than eternal or an absolutely sure thing…it would seem logical that nothing remains static forever. The inevitable process of evolement dictates that nothing can be totally absolute. It must change aventually.
I read that Helium becomes a liqued at one degree above absolute zero. That would imply that there must be a colder temperature at which it becomes a solid.
Per haps there is no limit to how cold cold can get, or perhaps cold becomes something else after a certain point.

Nope. At standard pressure, helium can never become a solid. Quantum mechanical forces preclude it. It can only become a solid at higher pressures.

Absolute zero is an absolute for temperature measurement. How is it possible to misinterpret this, from Cecil’s original column?

It’s kind of hard to have any less movement than none at all! :smiley: How do you propose anything be colder than that? How would you define coldness under those terms?

In fact the uncertainty principle prevents there from being absolutely no motion (since otherwise it would be possible to know both the position and velocity [zero] of a particle, which is a no-no). It’s my understanding, which I’m sure others will elaborate on very quickly, that helium won’t freeze except under high pressure because the minimum possible energy is sufficient to keep it liquid.

Yes it is. How can you get less molecular movement than none?

The heat of something is (pretty much) a measure of the movement of the particles making up that thing.* If those particles are not moving at all, then the thing has no heat in it at all. If a thing has no heat in it, then it is as cold as it can possibly be.

Hence, at absolute zero, a thing is as cold as it can possibly be.


*I’m sure there are more strictly correct ways to put this, but I think this will do for our purpose.

If you stop thinking of ‘cold’ as a thing, and start thinking of it as the comparative lack of a thing (that ‘thing’ being heat), the concept of absolute zero becomes a bit easier to grasp. Things get colder because they are losing, heat, not because ‘cold’ is being added.

So, in a finite universe. There should be both extremes of heat. The total absence of heat = (zero matter)
AND the total of ALL matter…which would’ve been the point just prior to the big bang?
Both events sound very similar to the concept of singularity.

Possibly, but in the case of the big bang, you not only had all the energy in the universe in one place, you had all the matter too (except that the two were the same at that point, or at least I think so). Absolute high temperature would, I suppose, be achieved if you could impart all of the energy in the universe to a single hydrogen atom, all at the same time.
Apart from being impossible in reality, the temperature achieved by this process would still not necessarily be the absolute high, just the maximum that could be achieved with the resources on hand.

The total absence of heat doesn’t == zero matter, rather, it ==s zero movement.

I think if there is a region with zero matter, it is at absolute zero, but only because there is zero movement within that region. It doesn’t follow from this that if that region had had a lot of matter–even all the matter in the universe–that it would have had a lot of heat. If it had all the matter in the universe, but none of that matter was moving, then the region would still measure at absolute zero.


hmm, I was thinking that matter had mass and weight the atoms making up that mass therefore must have energy enough to be defined as matter. (movement=energy=heat)

If you take the matter in the universe under an “infinite” amount of pressure. More dense = more pressure = more heat = more energy.

Take a BIG something and compress it into a small something, there’s energy stored. An “infinite” amount of pressure relates to a similar amount of energy. Even if there’s no measurable amount of energy in the mass to begin with. Take a “dead” lump of carbon and compress it for eons under great pressure what do you get. (Stored energy) release that energy… big bang. More matter, bigger bang.

The definition of a singularity is a place in which our current equations no longer operate. If we could talk about the matter/energy/density/pressure there it wouldn’t be a singularity.

Absolute Zero is merely a defined place in the real universe in which known particles have no motion other than residual quantum effects.

The big bang does not in current hypotheses come from squeezing matter down to an infinite density. I’m not aware of any cosmologist who would buy that.

You’re trying to compare apples with colorless alien ten-dimensional oranges. It doesn’t work. And your physics doesn’t conform to any physics in our universe.

Funny, I basically agree with everything you just said. More or less. And yet it doesn’t really deny anything I said before.
I agree that the concept of singularity is beyond our understanding of physics. I’ve discussed this a number of times in the past.
BTW there is no absolute definition of what singularity is.
BUT we still should try to discuss the subject w/ concepts that we can at least try to grasp.
Whether you can actually define absolute zero as a “place” is disputable. The fact that motion ceases to exist is without doubt.
I never said big bang currently says anything. I only used one idea in the evolution of big bang theory to make a point. (That pressure increases heat or potential energy)
Apples to oranges? My physics? What?
You dispute that, more pressure increases heat. That’s really all in the hell I said.
That and less energy = less heat.

A perfect crystal and an imperfect crystal are both at absolute zero.
The perfect crystal is colder.

Just because all molecular motion has ceased, doesn’t mean there’s not still heat in the system. Let’s not forget atomic and nuclear motion, which is a whole 'nother bag of tricks.

Others have mentioned relativistic effects in terms of an asymptotic limit beyond which a system cannot be heated (I.E. all the particles velocities start cramming up against c has the average kinetic energy of the system increase) due to the mass increase the goes along with an increase in speed. Something I recall reading elsewhere pondered that the limit would be much less than all particles of the system moving at c, because the particles would turn into black holes. Which sounds like an interesting thing to watch.

It’s my understanding that absolute zero is the temperature at which there is no motion of any kind, not just molecular motion.