Absolute zero

In my chemistry class, the professor mentioned that scientists have come very close to “absolute zero,” indeed within a billionth of a degree — but never actually reached it. On hearing this, I asked aloud, “What would that even mean?” And I ask the same to you, my readers: is it ontologically possible for a specific body in the universe to reach “absolute zero”? How would we describe such an object? Would we be able to measure this condition without disturbing it?

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13 Responses to “Absolute zero”

  1. gerrycanavan Says:

    Would we be able to measure this condition without disturbing it?

    I’ve Googled this for five seconds, so I’m kind of an expert. It looks like the uncertainty principle you’ve invoking is also the thing that makes it impossible to reach absolute zero in practice; bodies at absolute zero would still have quantum mechanical zero-point energy.

    It looks like if classical rather than quantum physics were true you could reach absolute zero just fine.

  2. Adam Kotsko Says:

    Did you get to the bit about how systems with negative temperatures are actually HOTTER than any positive-temperature system?!

  3. Hill Says:

    I have a further question: how does one evaluate the ontological possibility of reaching a certain temperature?

  4. Adam Kotsko Says:

    I guess I was wondering it an object “at absolute zero” could even be said to exist.

  5. Jason Hills Says:

    Adam,

    Let’s rephrase the question. Can something with no mechanical or kinetic energy exist? If we phrase it this way, then clearly something is wrong because nuclear and quantum forces cannot be fully explained in terms of this. Next, we might observe what is meant by “at absolute zero” other than in reference to heat, which implicates only certain kinds of energy. In short, definitions matter.

    Personally, I hold as axiomatic that energy is a fundamental of the universe and not reducible to material description or efficient causation when in comes to metaphysics.

  6. Adam Morton Says:

    IIRC, re: gerry’s assertion, that in QM “absolute zero” still includes the ground-state energy, so that reasoning isn’t quite right.

    As far as can be said to exist, well, “can be said” as a purely theoretical mathematical device. But since there’s no way to actually get something to absolute zero, it’s just that–a theoretical device, a limit.

  7. Adam Morton Says:

    As far as measuring it, usually what we’re measuring is the product of transition between energy states. But since at absolute zero, there’s no transition going on…

  8. Hill Says:

    I likewise understand absolute zero as a limit.

  9. Dominic Says:

    Interesting that the physical world is bounded by limits in this way. I wonder if there is any physically reachable temperature that is the lowest physically reachable temperature, or if it’s always possible to go slightly colder (i.e. for an arbitrarily small temperature e > 0, there is always another physically reachable temperature 0 < d < e) without ever actually reaching the limit.

  10. danielimburgia Says:

    I think we came closest under Pope Alexander VI (Rodrigo Borgia), though George Bush did his damnedest.

  11. Matt Frost Says:

    Think of it as an asymptotic approach, as with all theoretical limits. This is where Zeno’s paradoxes are correct, as long as you graph them on more than one axis.

  12. Adam Morton Says:

    Just to qualify a bit, the reason were talking about a limit is because temperature is a matter of statistical mechanics–that is, an average. The seeming paradoxes are not deep mysteries, but necessary consequences of the definitions.

  13. Adam Kotsko Says:

    I guess what I was thinking was that if something “was” at absolute zero in the sense of having no kinetic energy, it would be completely unaffected by anything else and would have no effect on anything else (even if it has some purely “internal” energy among its constituents) — and that would be tantamount to not existing at all. Hence a kind of “metaphysical” limit along with the physical one.


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