from leaning towers to particle accelerators

So I got The God Particle out of the library a week or so back. At first I loved the sense of humour that spills out irresistibly as the Nobel-prize winning Leon Lederman tells his story of particle physics. Near the beginning he has this extended - very extended - conversation with Democritus' ghost about the modern-day quest to find the ultimate indivisible building blocks of the universe. Along the way the jokes keep coming until you feel that Lederman is doing more groaning than you are.

Now Democritus coined the word "atom," and it's funny because I always knew that this meant uncuttable in Greek. But it wasn't until seeing Lederman write it as a-tom that I made the connection with "tomography," which means the imaging of slices, as in computed tomography, or CT. Duh!

I confess that the book had to go back to the library before Lederman got anywhere close to the god particle, aka the Higgs boson. This is the massive weakly-interacting critter that the Large Hadron Collider will be looking for when it starts up again after its initial technical difficulties last September. But along the way, Lederman's historical tour made a stop in Pisa where Galileo is contemplating whether to throw different weights off the conveniently leaning tower of his birthplace. Everyone since Aristotle had been hoodwinked into believing that a heavier weight has a stronger purpose to fall and so will reach the ground faster. But does it? Why didn't they just do an experiment? Well, of course, air resistance may have confused the casual observer but how hard would it be to do a half decent test?

Lederman indicates that Galileo didn't even need to do a test. He only had to perform a thought experiment to convince himself of the correct answer. I had never heard of this piece of logic and I think it's ever so clever. Assume that the lighter object does fall more slowly than a heavier one. Now tie the two objects together. The lighter object should try to hold back and slow down the heavier object, yet together they form an even heavier object that should go faster. We have a contradiction that is only resolved if indeed the two objects take the same time to fall any distance.

Anyway, I'll take a shot at talking about gauge theories and spontaneous symmetry breaking another day. If only particle physics involved such simple thought experiments or such inexpensive real experiments as the physics of Galileo's day!