Physicist Brian Cox had a bit of fun on Colbert a few nights back*. At Stephen Colbert’s prompting he mentions the nonsense about time travel and the Higgs boson, (which I decided not to blog since it was so frustratingly idiotic and had no business in, for example the science section of a national newspaper not the least because it just serves to confuse readers with even more nonsense about the Large Hadron Collider (LHC) than they already have been) and then has a blast (it seems) discussing the importance of Special Relativity, [tex]E=mc^2[/tex], and why you should care, which is the subject of his new book with Jeff Forshaw.
Unfortunately he seems, at one point, to fall into the usual (high-horsed physicist) pattern of dismissing another legitimate science endeavour (food science in this case) as not science, but I’ll give him the benefit of the doubt and assume it was just a joke made in the heat of the moment. He’s too smart and likeable a guy, (and a very good public spokesperson for science education by all accounts and past appearances), to be quite so dismissive. Riffing fast and furious with Colbert will no doubt sometimes produce such slips.
By the way (and Brian does not get this wrong, but does not get the chance to say it, and I’m sure he knows it) people often get left with the impression from press releases about the LHC (see related posts below for lots of LHC background) and other popular discussions of particle physics that because the Higgs particle gives mass to all the massive elementary particles we know (an amazing thing to learn more about if we can, and that is the main point of the LHC!), that somehow this is responsible for the mass that we measure of everyday things, like a coffee mug, or the mass you measure on the scales in the bathroom. This is not really the case. The Higgs business accounts for only a tiny amount of the mass of everyday things. Most of the mass of everyday objects can be traced to the fact that the elementary particles bind together to make the big everyday stuff. When things bind together, it takes energy to defeat the force (nuclear or other) that binds them together (imagine pulling apart two objects you glued together). By [tex]E=mc^2[/tex], yes that famous equation, that binding energy is detectable as a mass. That’s mostly what you see on your scales. It does not mean that the Higgs particle – and learning more about how it gives the elementary particles their specific properties – is not important, but it is important to understand what people mean when they say we are understanding “where mass comes from” and other such phrases that are bandied about in connection with the LHC. It is not as direct as all that. Remember that when Stephen makes the joke about the weight loss program. You’d lose some mass, but it would be about as effective as most weight loss programs on the market, which is to say that your money would be better spent on just ignoring the program and getting more exercise…
Ok, anyway, here’s the Brian Cox clip. Enjoy!
| The Colbert Report | Mon – Thurs 11:30pm / 10:30c | |||
| Brian Cox | ||||
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-cvj
*Thanks T and T.
At a guess, I’d say that I don’t think so, since things would still interact through QCD, and so they’d get masses from the same sorts of interactions…
-cvj
So, if you turned off the Higgs mechanism, everything (not just elementary particles) would be massless even though most of the mass of everyday objects comes from QCD and not the Higgs mechanism directly?
Well, you can call it self interaction if you like, but it is very definitely binding. I take three bare quarks and find that there is a bound state which I call a proton or a neutron that has an energy that is ten times greater than the three quarks I started with. It is what it is: a bound state.
Ultimately, the main point is that the Higgs mechanism for generating the mass of elementary particles is not on its own responsible for most of the mass of everyday objects: The forces of interaction between the particles generate about 90% of it.
Best,
-cvj
I see. So you were including self-interaction as a type of “binding”. Thanks for the clarification.
Hi,
Thanks.
Yes, I could have said it a bit more carefully (and I ought to add a clarifying parenthetical remark later), but what I said was essentially correct. You can indeed have a positive contribution to the mass if you have the right kind of properties of the force in question, and QCD has just the right properties. Here is one way to think about it. The quark masses you get due to the Higgs mechanism are small… QCD effectively surrounds those quarks with a cloud made of virtual quarks and gluons (the massless carriers of the QCD force) that gives them an *effective* mass some ten times their bare value… giving the masses of the constituent quarks that are a little over a third of the mass of the proton or neutron…
This is rather similar in spirit to the *effective* mass of the electron that you find in models of conductivity (or whatever) in various materials. It is not the mass of the electron that you find in an elementary particle physics text. Why? Interactions, again described in quantum mechanics by a cloud or dressing of virtual particles, gives you an different, composite, object with which to describe your model.
Best,
-cvj
Hi Clifford,
I’m not sure what you’re getting at in claiming, if I understand you, that elementary particle masses negligibly contribute — relative to the binding energy — to the mass of macroscopic objects.
The binding energy contributes negatively to he mass of such objects, e.g. the four nucleons bound together in an He nucleus are less massive than when they are free.
If all you’re saying is that bare quark masses are substantially reduced by QCD interaction (binding) energies, then I agree. But your post seems to imply a the the binding energy is a positive source of mass (rather than a negative correction).
Apologies if I’m being dense.
To the second paragraph, the answer is essentially yes. The familiar elementary particles start out as massless (like, say the photon), and electromagnetism and the weak force (at least) unified. Then as the universe cools the physics gets rearranged so that the forces appear distinct from each other, and several of the particles get masses in a particular pattern given by the Higgs mechanism.
As to the first, I don’t have the precise numbers off the top of my head, but here’s an easy way to get a first pass…. google the massses of the up and down quarks. Then google the mass of a proton or a neutron. Multiply the first number by three and compare it to the second. That’s your percentage. (protons and nuetrons are made of three quarks from the “up” and “down” variety)
Best,
-cvj
that’s fascinating about the Higgs being (theoretically) responsible for only a tiny portion of the mass. can you say what percentage?
also, not sure if I understand it correctly, but would the Higgs be the first thing to “create” mass after the big bang? in other words, is the idea that the emergence of the Higgs field be the first time that particles felt drag, and thus began to slow down and coalesce into massive objects?