Higgs boson? What the physics?

Posted: July 10, 2012

WHAT DOES IT mean that the biggest news story in the world — last week's announcement that scientists have confirmed the existence of the Higgs boson, the "God particle" — was probably understood by .?.?. pretty much no one?

The discovery is being hailed as game-changer in how we understand the universe. Of course by "we," we mean those people who devote their lives to physics or science. The rest of us either don't care or are interested but too embarrassed to admit that we never even took chemistry class, let alone physics. (But we were great in English and home ec!)

Our complete lack of understanding is depressing, and yet the story itself is thrilling: Scientists found something important that you can't even see. And they found it by smashing things together, over and over, at high speeds, for years. Although we were proud to fathom this much of the discovery, we wanted to gain a little more understanding of the Higgs boson. So we found Gino Segre, an elementary-particle physicist from the University of Pennsylvania who also speaks clear, easy-to-understand English.

Q. First, what's an elementary particle?

A. We could start out by asking, "What's the smallest particle there is? What are the building blocks for all other matter?" Physicists call them elementary particles, objects that can not be broken down into components.

People have been worrying about this for a long time. An ancient Greek, Democritus, more than 2,000 years ago, said that everything was made up out of smallest units, which he called atoms. A physicist in 1920 would have said those smallest units were electrons and protons (and hydrogen is one electron and one proton hanging around together.)

By the 1970s, physicists had formulated something they called the Standard Model, which described all the different elementary particles that had been discovered up until then using the techniques of modern science. There are two classes: fermions, out of which matter is built, and bosons, which act to provide the different kinds of forces between fermions, such as electric or gravitational.

One by one, the predictions of the Standard Model were shown to be true, but there was still one piece missing, the answer to how all those elementary particles acquire masses. The conjectured answer was the supposed existence of a [Higgs] boson named after the retiring British physicist Peter Higgs. Without it or something very much like it, the whole Standard Model would have had to be scrapped.

Q. The New York Times described the Higgs boson as "a cosmic molasses that permeates space and imbues elementary particles that would otherwise be massless with mass." Is that a good description?

A. Nice analogy but what does it really mean? When you talk about Higgs bosons, you really are talking about two different things, a particle by itself and the kind of interaction between all other particles that it provides. These are two distinct but inseparably connected entities. Without the interaction, all other elementary particles would not have any mass. We know that something has to give them that mass, but until we actually saw the Higgs particle, we really couldn't be sure that we knew what was doing that.

The trouble is that the experiments to find Higgs bosons are incredibly sophisticated. It's like the most complicated jigsaw puzzle that you're trying to piece together to see if you have the right picture. It's like smashing plates against the wall and then trying to reassemble them. Except you're smashing billions of plates at nearly the speed of light and doing it with an accelerator that cost $10 billion.

Q. You spent time at CERN, the research center near Geneva where this was announced. What is that like?

A. I have spent three years at CERN, and Penn has had a large team working there for close to two decades. It's great: You have a lot of different people from different countries — and different cultures and currencies — working together on complicated things. That's one of the optimistic features of our present world — that you can get people together from all different countries to work on something important.

Gino Segre will be conducting a live chat on philly.com Tuesday at 1 p.m.

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