This Halloween I had a bit of a revelation. Between all the Sarah Palin costumes and dissertations on the physics of ghosts, I realized that the W and Z bosons are brain-eating zombies; a fact which helps to understand why physicists are trying so hard to find the Higgs boson. Let me explain.
First, what are the W and the Z (aside from annoyingly uncreative choices for names)? You’ve probably heard that there are 4 forces in nature: gravity, electromagnetism, the strong force, and weak force. Each of these forces is caused by exchanges of messenger particles. So what binds an electron to a proton — thus forming a hydrogen atom — is a constant stream of photons flying back and forth; hence, the photon is the messenger of the electromagnetic force. Similarly, gravity is transmitted by gravitons, and the strong force by gluons. The weak force is a bit odd. It has 3 messengers which are all slight different from each other: the Z, the W+ and the W-.
Now, to begin with all of these messengers are massless, and move at the speed of light, c. It’s not just that massless particles can move so fast; they have to. (Here is a good explanation as to why.) This is related to the fact that they have only two ways of moving. They can vibrate left to right as they move forward, or oscillate up and down, again as they move forward — somewhat like Zombies lurching as they move, only really, really fast zombies. What they can’t do is vibrate forward and backward along the direction that they’re moving. They’re dancing zombies that can’t stand still; and if they can’t stand still, they can’t have a mass.
Then there’s the Higgs: alone in its house in the woods, happily standing still, and completely unaware of the menacing weak messengers light-speed lurching. On it’s own, pre-brain-eating, the Higgs vibrates in 4 different ways. I don’t have a good way of describing these, but for each of the three weak messengers, the Higgs has a way of moving that is exactly what that particle needs to stand still. And here we learn that, not only are they brain-eating zombies, but they’re the special kind of brain-eating zombies that learn from the brains they eat. So the Z and W+ and W- zombies invade, and each one eats a part of the Higgs’ brain. When it does, it learns how to vibrate back and forth. It learns how to run in place — and that means they acquire a mass.
What of the photon and the gluon? There’s a fourth direction remaining, but it turns out to be inedible. Poor photon, it’s left out and doesn’t learn how to stand still, so it has to always zoom along at the speed of light. On the other hand, if that wasn’t true life as we know it couldn’t exist, so it’s probably a good thing.
That fourth type of vibration is very interesting though. It corresponds to something that looks a lot like the other particles that we know and love. It takes a lot of energy to make the Higgs vibrate in that way (which turns out to largely be why it’s inedible). This is the famous “Higgs boson” that physicists are looking for at the big particle accelerators. It’s the visible sign that our picture of the origin of mass is correct.
What I find amazing about this analogy is that, while it is forced in a few places, it’s actually remarkably accurate. Physicists really do talk about the Z and W bosons “eating” parts of the Higgs, and that description fits the math quite well. The bit that they eat might as well be the brain.