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Does the uncertainty principle apply to low temperatures like this or is it strictly position and momentum?
should absolute zero be even lower than -273.15c ?
One thing I noticed about your questions is that absolute zero is a theoretical limit. There's a reason no experiment has been done at absolute zero or 0 deg K.It has to do with the so-called Planck energy of quantum particles; none of these is ever at 0 deg K, because then it would have no rest energy or ground state. It wouldn't be a particle any more.
Hi. I'm fairly sure we've had some other threads discussing temperature and the sorts of issue that @neilep has raised.This is a short summary of how I see the current situation. Note that (i) I'm only one person and don't claim any special expertise in this field of study, (ii) It is apparent that our notion of temperature is changing, so that whatever is said here will probably change again in a few years.Summary: Historically temperature was understood in many different ways. One simple approach is that temperature was the thing you measure when you stick a thermometer into something. Problems with this approach were too numerous to mention. For example, how do you build a reliable thermometer? Sticking a thermometer into some liquid is reasonably easy but sticking a thermometer into some solid is often impossible. How do you ensure you're getting good thermal contact etc? In the very old days, some things just didn't have a temperature if you couldn't stick a thermometer into it. At a later time, let's say between 1848 (when Lord Kelvin was developing his Kelvin scale) and 2019 (when the weights and measures commitee redefined temperature) it was quite popular to define and consider temperature using a thermodynamic approach. That actually worked quite well. Since May 2019, international agreement has been to define temperature based on a Kinetic Theory approach. That's not my fault, it's just what was done by the weights and measures committee and whoever establishes the SI units for Science. They wanted to improve our definition and undertstanding of temperature and it was thought that basing temperature on this theoretical framework would make it more objective and absolute. Just to be clear about this - the modern Kelvin scale is NOT the one that Lord Kelvin developed, we kept the name but ditched most of the notions that Lord Kelvin used. We have a great model and good understanding for this kinetic theory approach IF the substance is an ideal gas. The trouble is that most things are NOT ideal gases. We have a few other reasonable classical models for other things but by no means do we have a good classical model for the microscopic behaviour of everything. One very important thing to note is that the sort of microscopic mechanics that is used in these models and that the weights and measures committee have declared we MUST use, are based on classical mechanics and NOT quantum mechanics. This is a problem because some things are evidently quantum mechanical but we never-the-less have to do some translation into an equivalent classical system when we assign a temperature to that system. As mentioned already, we have some good classical microscopic models for some things but sometimes we just do not have any such model that we can use. Overall, the attempt by the weights and measures committee to make temperature more objective and absolute have caused as many problems as they may have hoped to solve. Reference: Spend the time reading Wikipedia's entry for "temperature" and you'll get some idea of how temperature has been redefined. https://en.wikipedia.org/wiki/Temperature. That Wikipedia entry has been edited and adjusted since the last time I looked at it about 1 year ago. As mentioned, it is very likely to keep changing in the near future. Anyway, one answer or reply we can offer to the OP is the following:You just aren't allowed to use a quantum mechanical model for the substance you are trying to assign a temperature to. You would HAVE to translate the behaviour of your substance into some classical microscopic model. What you'll then end up with is a temperature that says something about the average kinetic energy per particle, even if it's a total abstraction to imagine that anything like individual classical particles could be found in this substance or thing. In your case, despite your assertion that this thing has temperature 0 k, it probably won't be and can't be 0 k. You probably can't obtain an official temperature of precisely 0 Kelvin unless the zero point energy of your thing actually is 0 and the corresponding classical model would have particles with 0 kinetic energy.Best Wishes.(Last edit to fix some spelling errors).