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The following is an email exchange between my little sister and myself (with some slight alterations):

1) Does the Higgs boson give a particle mass or is it attracted to particles with mass?

The Higgs boson does not give particles mass. PLEASE remember that. The Higgs boson itself isn’t really that important. On the one hand, finding the Higgs boson is the easiest (and perhaps only) way for physicists to learn about what’s called the Higgs field , which is what we really want. In this sense, finding the Higgs particle is the first big step toward the main goal: understanding the properties of the Higgs field.

To the second part of your question, gravity is the force between massive bodies, and it is always attractive. So since the Higgs boson has mass yes, it is attracted to other things that have mass.

2) If the Higgs boson gives an object mass, how does it do so? … (cont’d)

In the Standard Model, all particles are by default massless. So if the Higgs boson doesn’t “give” objects mass, how do particles get mass, or why do they have mass? This is where the Higgs field comes in. The Higgs field is a field that’s present everywhere in space and time, and it interacts with most particles. (I say “most” because the Higgs field doesn’t interact with photons, which, you’ll see, is why light travels at the speed of light. If that’s confusing, you can reword it like this: because photons don’t interact with the Higgs field, they are massless, and because they don’t have mass they travel at the speed of light. This is a consequence of special relativity.)

The Higgs field has a non-zero average value, which just means that it can have physical effects. This is kind of just a technical point. Because it has a non-zero average value, particles, including electrons, quarks, bosons, etc., can interact with the Higgs field, and because they interact with the Higgs field they behave like they have mass. If the Higgs field had a zero average value, particles wouldn’t interact with it and they would be massless, or at least very light. That would be a disaster, because massless particles travel at the speed of light! Nothing like human beings, or the earth we live on, could exist without the Higgs field having a non-zero average value. I realize that this doesn’t explain how or why interacting with the Higgs field gives particles mass, or makes particles behave like they have mass, but I hope it explains why particles interact with the Higgs field in the first place.

In the Higgs field, mass is just a matter of how strongly something “feels” the Higgs field. So Earth interacts more strongly with the Higgs field than you or I do, which is why the earth has more mass. It might be helpful to think of mass in terms of inertia, which is the property that resists acceleration — acceleration can be an increase in velocity, a decrease in velocity, or a change in direction. I don’t know how much you know about inertia, but it’s pretty simple. You know when you’re in a car and you turn a corner and everyone leans to the outside and screams “GRAVITY!” Yeah, that’s actually inertia. What’s happening is that your mass wants to keep moving in a straight line at the same velocity — it doesn’t want to accelerate — because of inertia. Now the more mass something has the greater its inertia, which means it takes more effort to get it moving (if it’s sitting still) or to stop it or change its direction (if it’s moving). The Higgs field interacts with Earth more strongly than it interacts with you, which means the earth has a harder time speeding up, slowing down, and changing direction than you do. It’s kind of like the Higgs field grabs onto things and slows them down, and the more it interacts with something, the more difficult it is to accelerate that thing.

2) … How does it decide which particles to make massive?
Now why some things interact more strongly with the Higgs field than others is still something of a mystery. We have some information about how the Higgs field interacts with matter, but not much. If I had the answer to this one I would probably be famous. Or at least have a Nobel.
I hope this has helped. Remember, it’s technically still early to be calling the new particle they found at LHC the Higgs boson (though they’re 99.99999% sure that it’s the Higgs boson). We have to see how it behaves to make sure that it’s the Higgs. Is it produced as often as predicted by the Standard Model? Does it decay in the expected proportions?
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