Thursday, September 11, 2014

Is It The Same Temperture In Every Possible World? Part 1

It's strange, but people didn't argue about the interpretation of classical mechanics. The usual explanation is that classical mechanics is intuitive, which is obviously untrue - if it was why are so many students so bad at it? Even if it wasn't obvious, psychologists have convincingly argued that our intuitive reactions to how objects move do not follow Newton's Laws. There are at least two facts about quantum mechanics that lead people to feel it needs interpretation:
  1. Not everything can be sharply defined at the same time. (what used to be called 'complementarity')
  2. Things are not, in general, continuous (what used to be called 'quanta')
Most of the unintuitive physics results come from the second fact. The idea that in order to get there, you must pass through here is a deeply held belief. One big reason we need mathematics is to force people - such as economists - to say it out loud.

However, the first reason clearly raises two questions. One is "Where does apparent sharpness come from?" and the other is "How does nature know what to make sharp?". The second question is very tough. There are a variety of answers. The original answer, enshrined in ancient texts, is that how you set up your experiment somehow decides what nature will make sharp. Explaining this led von Neumann to support the idea that the universe is guided by each human consciousness. Many leap all to quickly to reject this idea, but I will argue in a bit that it could conceivably be a theorem of quantum mechanics!

Harald and Niels Bohr

The most powerful man in early quantum mechanics was the great physicist Niels Bohr. Bohr's complete work runs 13 volumes, his scientific work covering 9 fat books. Throughout his graduate studies, Bohr worked on the problem of modeling solids (specifically, metals) with dynamical models. Einstein and Jean Perrin had convincingly shown that the atomic hypothesis was not just a convenient thought experiment, but a genuine description of the world. A couple years later, Einstein had published the first modern (that is, quantum) solid state physics model, which was a bit of a proof of concept showing that quantum mechanics could be used to new physics. Bohr's thesis included a proof that classical physics could not explain ferromagnetism. The intuition is that in classical physics, jiggling atoms are as likely to go one way or another, and since their little magnetic poles can point at any angle, there will always be enough room for them all to point different directions. This demonstrated that only quantum mechanics could explain solid state physics, which remains a very interesting and deeply quantum mechanical field!

But I digress. Bohr, when confronted by the question "How does nature know what to make sharp?" would say that there is nothing behind the experiment. All we do is observe, beyond that we can neither see nor speak. "Whereof one cannot speak, thereof one should remain silent." - Wittgenstein. Bohr was influenced in his description by positivism, but many have argued that he may have been more influenced by other philosophies, such as existentialism. Regardless of whether this vision was positivistic, pragmatic or mystical, it was accepted as gospel for some time. In this series of posts, I will explain what the possible replacements of silence could be. I'll have more on this subject in the fullness of time, including: 1) Why did people get bored with Bohr?, 2) What are the most prominent alternatives?, 3) What do the alternatives mean mathematically and philosophically? and 4) What can we believe?.

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