Irrelevant to what? The poster claimed that there was a real thing in a physical reality. If that is true, shouldn't we have observed it before? As the statement stands it claims as absolute reality something which no one has ever seen.
Ok, so we've never seen something to be exactly 0K. We've probably also never seen anything to be exactly 3.14159K. That doesn't mean objects with temperature of exactly 3.14159K are impossible, neither that we should assume they don't exist until you point out an example.
Temperature scale is a good model that maps the territory quite well. There is nothing to suggest it will suddenly stop working at 0K, if it works very well even as we get closer and closer to absolute zero.
Contrast with most economic models which as maps correspond to territory in a similar way the map of China corresponds to the Middle Earth - there are trees and not trees, you have to turn it around to make the sea be on the proper side, and... that's about how much it matches. Be wary of zooming too much in, lest you get eaten by an Orc.
It may be a good model, but that is not what the poster claimed. The poster claimed that is was an aspect of a real, physical reality. There is no evidence of that.
In fact, there is a good argument that 0k is unachievable [0].
》 If that is true, shouldn't we have observed it before?
No. The concept of temperature is based on the bulk interactions of matter due to the motion/collisions of atoms and molecules relative to an inertial reference frame. A frame that usually has to exist outside of the system for temperature to have practical meaning so it is a concept that by definition has an absolute zero, even if we haven't observed it yet.
In this case, absolute zero really means zero motion relative to the instrument measuring the sample so it is possible for a Type 1+ civilization to build a planet sized (or bigger, don't know how the math works out but it probably has something to do with constricting atoms to a precision within a planck length) laser or other electromagnetic trap to cool some nontrivial number of atoms to absolute zero like those used for Bose-Einsten condensate experiments.
Wrong. Nonsense invocations of nomenclature and pretentious obfuscations aside, your explanation came after the fact. When temperature scales were being constructed, neither thermodynamics nor atomic theory had been at the state you presuppose. What you state are not givens, they are conclusions of theories and explanations of the observations in terms of them. To say that temperature must by definition have an absolute zero isn't saying anything. Where did this definition come from? What is heat that temperature measures (yes, heat, not temperature)? Neither Fahrenheit nor Celsius knew. Current kinetic theory explains heat as exclusively the motion of microscopic things (not just atoms, btw) and it thus follows that the absence of motion must mean the absence of heat. In the 17th century, you might be telling us that absolute zero is complete dephlogistication. But why should temperature have an absolute zero? Without your theory of heat, or at least some intuition of it that frames heat as a quantity and cold merely the absence of heat, you have no reason to claim that temperature has a lower bound.
You really need to understand the order of dependence of explanations.
Let me turn this around. What do you think the hypothesis is, and how would you know if you've succeeded? Do not use the term "absolute zero" because you think that is a hypothesis, and not a definition.
No. The definition of Absolute Zero is zero kinetic energy of the particles of a substance. You've been complaining that this definition is somehow a hypothesis, or otherwise suspect because it has never been observed, which I've said, was irrelevant, we can calculate it. It's not hard. It's junior high physics. What's the kinetic energy of something that has stopped? It's zero.
Your position is absurd. It's equivalent of saying, that distance is an unproven hypothesis, (which literally doesn't make any sense, because that's not what the word means), or perhaps more charitably a suspicious concept because we've never measured anything with zero distance between two items, because the closest two particle can get is planck length.
I'm not trying to be mean, but what you've been saying is pure gibberish.
