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Archive for July, 2010

Kelvin-Helmholz Fog

It frequently happens that clouds in a high upper wind develop, not just ragged edges, but edges with the most finely sculpted curls of cloud. These are called Kelvin-Helmholz waves after the men who first studied them in detail, and they appear wherever two fluids slip alongside each other at different speeds. And by fluids, I mean anything that flows, so air is a fluid by this definition.

With that in mind, I got up one morning and looked across the valley towards the mountain 12 miles away. The valley fills with fog many evenings, and in the morning the fog lifts. This morning the first spires of lifting fog were caught in an upper wind and drawn into beautiful waves.

K-H fog waves near Mt. Monadnock

This is an eastern view of the valley near Mount Monadnock, New Hampshire.

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Perhaps the most troubling thing to emerge from the “new physics” of the 20th century was Heisenberg’s principle of indeterminacy. It’s an odd principle, however you approach it, but I never doubted it until I saw that Jaki did. I don’t have a degree in physics, but he did, and his doubts were not based on ignorance, or a failure to think subtly; he flatly rejected it as an error of thought, and a serious one. His rejection is found in chapter 3 of Is There a Universe?

Since it is so fundamental to modern physics, let’s see what this is all about.

Indeterminacy

The fundamental background of Heisenberg’s formulation was that we are not able to determine both the position and the momentum of such tiny particles as electrons or any of the elementary particles. At the moment when we are able to see their position, their momentum is impossible to discern; any time we know their momentum, their position is uncertain. Thus, we can only describe their possible positions & momentums, in mathematical terms, as if the tiny things were probability fields rather than discrete objects. So the electron is now represented as a cloud of probability, and, depending on its orbit, that cloud may assume one of several particular shapes.

But for Heisenberg, it was not enough to say: “We don’t know the position and momentum of one of these particles” so we just describe their probabilities; he had to go further and say, “Since their position and momentum cannot both be known, since we can only speak of these factors as a probability function, we must agree that that’s all there is! It’s just a probability; it has no other reality. There’s no electron running around the proton in a hydrogen atom; there’s just a field of probability associated with that nucleus.

Now, the world is made of fundamental particles. If none of them are “real,” if all of them are just probability fields, then the whole universe is just a probability field.

That was fine with Heisenberg and Bohr. They said that the universe, at bottom, was quite different from the universe as we see it. What we see is basically a mirage — the creation of our own minds during the act of seeing.

And hasn’t it been the message of science all along: that the universe is stranger than we imagined?

Not so fast!

Yes, the universe is full of surprises, but these surprises have ways of being integrated into the universe as we experience it. Probability fields are different. I’m really here, not probably here. At what point does the probability become reality, Mr. Heisenberg?

And it’s not just me. My potato seems real too.

In fact, I’m not even content to say “seems” about the potato. If I walked out into the wide world doubting that this is a potato, I’d be locked up. How come Heisenberg gets away with it?

Physicists do. That’s all I can say. They have been since the 1930’s. But Jaki says bluntly that the principle of indeterminacy – called the Heisenberg Principle of Indeterminacy – should rather be called the principle of imprecision. Eeks! His words are worth quoting in full:

What is fundamentally bad in this interpretation is that it endorses a non-sequitur whereby the ontological turns into a mere function of the operational. [That is, what a thing really “is” only flows from how we can work with it. My note.] For it is a non-sequitur to claim that if an interaction cannot be expressed exactly, it cannot take place exactly. This non-sequitur, or the jump from the operational to the ontological domain, is the gist of the philosophy which Heisenberg and Bohr grafted onto what is usually called the principle of indeterminacy, but should be called the principle of imprecision.

Jaki also has an interesting footnote referencing an article the 1930’s in which the then editor of the prestigious weekly science journal, Nature, made a similar critique, saying:

“Every argument that, since some change cannot be ‘determined’ in the sense of ‘ascertained,’ it is therefore not ‘determined’ in the absolutely different sense of ‘caused,’ is a fallacy of equivocation.

Strong words.

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