Still Confused About the Higgs Boson? Read This

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A chance encounter at a July 4 picnic made the latest development in particle physics seem much more comprehensible. Here's what I learned.

So I was at a July 4 picnic on Wednesday where one of the other guests used to be a physics teacher at Stuyvesant High School, and he explained this whole Higgs boson thing to me in a way that made it make about as much sense as it's going to for someone who only took physics in college. And he did the whole thing without using food metaphors -- molasses, soup, etc. -- which I thought was impressive.

Basically, it's like this: Sub-atomic particles are either fermions or bosons. Fermions are the things you learned about in high school physics -- electrons, protons, neutrons and so on -- that share the quality that you can't have two of them in the same space on an atom. Think of them as the billiard balls: they can be all over the table, but not in the same space at the same time, and where they go is determined by the size of the tables. Most of the widely-known fermions are composites made up of other categories of sub-atomic particles, like quarks (which combine to form protons) and leptons, but the most important thing to know about them for the purposes of this discussion is that they are considered the matter particles.

Bosons are different. Bosons have the capacity to share space because they are more like a force than a thing in the way we normally think of "things" or "particles." And since the normal understanding of the word particle is that it's a small thing that has matter -- the mote in the sun, rather than the light itself -- perhaps a better way for lay people to think of bosons is as entities that have effects; they carry the forces (strong, weak, gravitational or electromagnetic) described by the Standard Model in physics, making them what physicists call force-carrying particles.

But if this whole particle-that-lacks-mass thing is still tripping you up, you don't need to use that word in your own head; bosons lose nothing for our purposes by being thought of as entities, even if they are still technically particles, which is to say something really small of which other things are made. Some bosons have mass and some don't. The Higgs boson has a very large mass for a sub-atomic particle, though of course it is still sub-atomic, which is to say tiny.

775px-Elementary_particle_interactions.svg.pngYes, I am aware this is image looks technical and confusing. But it lays out the fundamental building blocks of particle physics and how they interact with each other. Leptons and quarks, at top, are the two categories of matter particles. Below that, the bosons.

There are an array of different kinds of bosons, of which the Higgs boson is only the latest to be (tentatively) confirmed as existing. Here are some of the other kinds of bosons:

* Gluons. So named -- seriously -- because they help glue quarks together, mass-less gluons carry the strong force but operate only at close range, like glue, in that glue will stick two adjacent things together but not attract something from the other side of the room.

* W and Z bosons. W and Z bosons carry the weak force and operate at close range.

* Photons. Photons are mass-less wave-like particles that are the basic building blocks of light and carry the electromagnetic force.

(Gravitational force is hypothesized to be carried by the graviton boson, but that has not yet been proven. Gravity is still a bit of a mystery.)

OK, so now to the Higgs boson.

The newly discovered boson thought to be the Higgs boson was measured by the Large Hadron Collider in Europe, which is a cathedral-sized underground mechanism for creating sub-atomic collisions that break things down into component parts. Part of why it's been hard to figure out from the news stories what the Higgs boson is is there are actually three Higgs things under discussion: 1) the Higgs field, 2) the Higgs boson and 3) the Higgs mechanism.

*The Higgs field is a quantum field that the Standard Model of physics predicts pervades the universe and creates drag on particles.

*The Higgs boson is a sub-atomic particle that acts as the intermediary between the Higgs field and other particles. All fields are mediated by bosons, some of which pop into and out of existence depending on the state of the field, sort of like how rain drops emerge out of a cloud when it reaches a certain point. The electromagnetic field that pervades the universe, for example, is mediated by photons. Finding the Higgs boson would confirm that the Higgs field exists, and that field has long been postulated as a way of explaining an array of other physical phenomena.

* This interaction between the field, the boson and other particles is the Higgs mechanism. The precise nature of the mechanism is still being worked out, but it is through its complex interplay of fields and bosons (Higgs and non-Higgs) that particles acquire mass.

Because the Higgs field was hypothesized to be massless and continuous, and because of the particular properties of the Higgs boson -- both massive and rapidly decaying -- it was really hard to observe and measure any individual Higgs bosons -- if, in fact, that's what was measured recently -- until the Large Hadron Collider came online with enough force and energy to slam some bosons out of the Higgs field into a state humans can measure.

Think of it a little like this: by smashing things hard enough, a little bit of the Higgs field got chipped off into a boson that could be measured before decaying. Sort of like throwing a rock really hard at a concrete wall -- eventually part of the wall will chip off. In this case, it was like a wall that only threw off a little bit of dust in response to a major collision, and then scientists were able to tell that the wall was there because they took a picture of the dust before it blew away. Except in this case the wall is also continuous and infinite, and invisible, and we all live inside of it, and it's what gives us mass, which is to say the quality of physical existence.

Which kind of explains why some have called the Higgs boson the God particle.

Bonus explainer: A hadron is any composite subatomic particle held together by strong forces. Neutrons and protons are hadrons. So that's what's getting collided at the Large Hadron Collider. It's a term that came into use in 1962 to replace "strongly interacting particles," which was considered clumsy at the time, though in retrospect had the advantage of being moderately comprehensible to lay people.

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Garance Franke-Ruta is a former senior editor covering national politics at The Atlantic.

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