Archive for the ‘Physics’ Category

I was reading an article about Occam’s Razor (and how’s that for an attention-grabber, sports fans) that defined it along the lines of “Of two possible explanations for something, the simplest one is probably correct.” That’s been bothering me ever since. It rather seriously mis-states what Occam’s Razor is all about. It has nothing to do with probability and is not a predictor.

The logical principle elucidated by the Franciscan friar William of Occam (or Ockham), c. 1285-1349, is sometimes given as Numquam ponenda est pluralitas sine necessitate. “Entities are no to be feigned without necessity” is one translation. Let’s say we had theory A (simple) and theory B (complex). If we relied just on the formulation above and new evidence came to light that theory A can’t explain, then wouldn’t that prove Occam’s Razor (OR) wrong?

Not at all. In fact OR demands that the simpler explanation that accounts for all the observed phenomena is to be accepted as correct. It can’t be proved or disproved; it’s an axiom or heuristic principle. We don’t say that in Euclidean space “parellel lines probably never meet.” By definition, they can’t.

For much of the Middle Ages the Ptolemaic system was capable of explaining the motion of the stars and planets. It was based on the notion that they had to move in circles (because, as we know from Aristotle, circles are the perfect shape). To explain observed irregularities astronomers had to add circles on top of circles (epicycles) in ever more complex patterns.

Now, of course, we “know” that the movement of Earth around the sun (Copernicus) and the elliptical nature of planetary orbits (Kepler) explain the  motions we see. But how do we know that we know this? In theory epicycles could multiply and be refined endlessly to account for new observations; but eventually OR caused that monstrously complex system to collapse under its own weight.

Here’s the ironic part: probably many today would use OR to argue against the idea of a supernatural Creator. But for Occam himself, his principle was a grand demonstration of God, the one entity who exists by necessity and whose marvelous economy is to be found throughout the plenitude of created world.

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Update 12/20/10: one of my favorite sites, Astronomy Picture of the Day, notes that this eclipse solstice is the first in 456 years, and that no one has yet figured out when the next one will be.

This is a pretty neat coincidence: there will be a total eclipse of the moon early in the morning of December 21st (Eastern time); in the evening of the same day the December solstice (winter solstice) arrives.

Coincidence … or conspiracy? You be the judge.

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pictured, left to right: Messor barbarus; physicist Murray Gell-Mann

This post’s title comes from one of the great imaginative romances of the 20th century – and from quantum mechanics. As you might suspect, there’s a connection.

T.H. White’s The Once and Future King is a brilliant re-creation of King Arthur (with the Round Table, Lancelot, Guinevere and all the rest). It’s the direct basis of at least two other works: the musical Camelot and Walt Disney’s The Sword in the Stone. Re-reading it this month I was also struck by how much the relationship between Merlyn the magician and the boy Arthur (aka the Wart) resembles that between Dumbledore and Harry Potter. I later learned that J.K. Rowling has described the Wart as “Harry’s spiritual ancestor.”

The Sword in the Stone is the first of four sections of the novel, and the only one about Arthur as a boy. Merlyn’s tutorship includes changing the Wart into, among other things, a fish in the moat, a falcon in the mews, and an ant in a glass case. White’s ant world is the ultimate totalitarian society (its appearance in 1939 is hardly coincidental). The Messor barbarus ants know only two concepts: Done and Not-Done. They obey all orders sent wirelessly to their antennae. They never ask questions. Everything Not Forbidden is Compulsory is the slogan carved above each tunnel in their nest.

It’s also Gell-Mann’s Totalitarian Principle, coined by physicist Murray Gell-Mann as a basic law of quantum mechanics. Any interaction between sub-atomic particles not expressly prohibited by some natural law must be assumed to be probable (the soft version) or must be inevitable (the hard version). Astronomers now have indirect though pretty good photographic evidence that black holes are real; but long before that, their existence was considered almost certain because (a) the laws of physics said that they could exist, and (b) no known law prevents them from existing.

Gell-Mann had a flair for such things. He also coined the term quark, the never-seen subatomic building block of observable particles, from a passage in James Joyce’s Finnegans Wake (‘Three quarks for Muster Mark!’). A physicist after my own heart.

The Once and Future King is one of the great, great books of the 20th century. I’m certain that the Disney cartoon is a two-edged sword (ha!) in that most people wrongly assume the novel is aimed only at children.

They’re wrong. Read it. It will break your heart.

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