The Dream Universe

How Fundamental Physics Lost Its Way

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This book by David Lindley is a criticism of one of the glamorous fields of physics: "Fundamental" physics, the effort to "explain everything" in one grand, hopefully nice-looking, equation. (No, that's simplifying slightly. But not much.) The topic is very similar to Sabine Hossenfelder's Lost in Math, which I read last year. (Lindley credits Hossenfelder at a number of places.)

Lindley's approach is historical, first looking at Galileo. The standard story is that Galileo was persecuted by Church authorities because he ran afoul of religious dogma. That's not quite accurate, Lindley claims. The problem was that the Church had bought into the worldview of the old Greek philosophers: Aristotle, Plato, Pythagoras. Who were all taken with the idea that the world's grand design could be revealed by thinking. Backed up, of course, with a modicum of observation, but certainly no careful experimental observation was required. And that's where Galileo's heresy resided.

So experiment-free conjecture sometimes leads us astray. Does it always? No. Lindley relates the speculations of Paul Dirac, who noted that his equation for the quantum behavior of electrons also held the possibility of a positive electron. Check it out, he urged the experimenters. And sure enough, my undergrad advisor Carl D. Anderson discovered the positron in his cloud chamber a few years later.

But (Lindley points out), Dirac also speculated about magnetic monopoles, carriers of "magnetic charge". Those, as near as anyone can tell, don't exist. So the theorize-first-experiment-later process can lead you to a dead end.

Today, Lindley contends, theoretical physicists have gone too far down the rabbit hole in their empty speculative theorizing. They're not really doing "science", they're doing philosophy, albeit philosophy with very advanced mathematics.

Along the way, he makes an interesting point about the multiverse. Our universe is (obviously) congenial to life, with just the right balances between electromagnetism, gravity, and the nuclear forces to allow atoms, molecules, stars, planets, and geckos to exist. You dink with those numbers much and you get a universe that's a large grey mass of nothing. In fact, absent evidence to the contrary, that's the way to bet.

So, they say: we're biased because we live here. There are an unimaginably large number of universes where the story is different, and ours is just one of them that occurred by microscopically small chance. (Amusingly, Lindley wonders about the spacetime setups: our universe settled out macroscopically wth three spacelike dimensions and one timelike. But—whoa!—that one over there has forty-three spacelike dimensions and seventeen timelike! What's their deal?)

Which gives us a dilemma when we're trying to explain the nature of this universe. How much detail are you going to push off to the multiverse? It's a damned convenient escape hatch.


Last Modified 2024-01-23 2:50 PM EDT