One of the big challenges facing journalists writing about science is to summarize a scientific subject accurately, clearly and succinctly. Sometimes one of the three requirements is sacrificed, and sadly, it is often the first one.
So here is my latest (but surely not last) attempt at an accurate, succinct, and maybe even clear summary of why the Higgs business matters so much.
`True’ Statements about the Higgs
True means “as true as anything compressed into four sentences can possibly be” — i.e., very close to true. For those who want to know where I’m cutting important corners, a list of caveats will follow at the end of the article.
- Our very existence depends upon the Higgs field, which pervades the universe and gives elementary particles, including electrons, their masses. Without mass, electrons could not form atoms, the building blocks of our bodies and of all ordinary matter.
- Last July’s discovery of the Higgs particle is exciting because it confirms that the Higgs field really exists. Scientists hope to learn much more about this still-mysterious field through further study of the Higgs particle.
Is that so bad? These lines are almost 100% accurate… I’m sure an experienced journalist can cut and adjust and amend them to make them sound better and more exciting, but are they really too long and unclear to be useable?
Some False Statements about the Higgs
Meanwhile I would like to suggest we avoid the following statements, or anything like them.
- The Higgs field and/or the Higgs particle were crucial to the Big Bang. [On the contrary, there's no evidence that the Big Bang would have been stymied in the absence of the Higgs field and particle, or of anything directly related to them... despite what Professor Michio Kaku said earlier in the week on CBS news, to the embarrassment and annoyance of the physics community.]
- All mass in the universe comes from the Higgs field and/or Higgs particle. [There are many things in the universe which don't get their mass from the Higgs field, including atomic nuclei, the black holes at the centers of galaxies, and (probably) dark matter. Meanwhile, the Higgs particle cannot give mass to anything.]
- The Higgs field and/or Higgs particle gives ordinary matter its mass. [Nope; although the Higgs field, by giving the electron its mass, makes ordinary matter possible, it doesn't provide most of ordinary matter's mass. Most of an atom's mass is in its nucleus, and thus in protons and in neutrons, particles which are not elementary and do not get most of their mass from the Higgs field. Protons and neutrons get their masses from effects involving the strong nuclear force; they'd still have mass if there were no Higgs field. And again, nothing gets its mass from the Higgs particle.]
- The existence of the Higgs particle confirms Einstein’s theories. [Einstein had nothing to do with these ideas, which were developed after his death.]
Oh, and please let’s stop using “God Particle”. Aside from the fact that it is the field, not the particle, that’s so important, the term makes it sound as though important religious questions can be answered by science, using experiments. Science is a powerful tool, but it has its limitations, and it cannot address questions of this sort. No one benefits when scientists and/or the media confuse non-scientists into thinking that it can.
Addenda, Subtleties and Caveats
Now, in the interest of accuracy and precision, and so that any journalists and other non-scientists reading this understand exactly where I’m taking short cuts, here are some caveats and addenda to the two nearly-accurate statements that I gave above.
A first small caveat: I said the Higgs field “gives elementary particles” mass; I avoided saying “gives all elementary particles their mass” because it is likely that there are elementary particles that we haven’t yet discovered that don’t get their mass from the Higgs field. This is probably true of the particles of dark matter, assuming that dark matter really is made from particles in the first place. (In fact it is arguably true of the Higgs particle itself, but I don’t want to argue about this, because semantic issues immediately come up.)
The most important subtlety left out of the two statements above is that not only does the Higgs field exist, it is “on”, in a sense. If you could measure the Higgs field at any point in space (which we can’t actually do directly), you’d find it isn’t zero, because it is “on”; in fact it has just about the same value everywhere throughout the universe (at least in that part that we can observe.) By contrast, if the Higgs field were “off”, you’d measure it to be zero in most places. This is similar (though different in a couple of key ways) to another field you may know about, the electric field; it too can be “on” or “off” on average. If it were “on” in your vicinity then your hair would stand on end, just as when lightning is about to strike nearby, or when you’ve just taken off a wool hat in winter and static electricity is at work. On the other hand, the electric field exists (i.e., it is something real that can be measured) even when it is “off”, as it probably is where you’re sitting right now, with nicely behaved hair.
And so an important addendum to the second statement is that discovery of a Standard Model-like Higgs particle doesn’t just confirm the Higgs field exists; it confirms that the field is “on” — which is crucial, since if it were off, it wouldn’t be able to provide masses for elementary particles.
We must also now add an asterisk to the statement that electrons would be massless if there were no Higgs field. If the Higgs field did not exist at all, the statement is correct: electrons would be massless. However, if the Higgs field existed but were simply turned off somehow, and nothing else were changed, electrons would still have a very, very tiny mass, due to a funny quantum interplay of the strong nuclear force and small interactions between electrons and the (off) Higgs field. (Thanks to George Fleming for reminding me of this some time ago.) But this is really a small asterisk, because it remains true that atoms could not form at the current epoch of the universe; the warmth left over from the Big Bang would blow them apart. The correct statement in this case would be that electrons would have tiny, tiny masses compared to what they do in nature, and this would cause atoms to become extremely fragile and easily fall apart. So the basic idea is still right.
Another addendum: if the Higgs field were off, not just the electron’s mass but many other aspects of the world would be very, very different. It isn’t clear exactly what would happen, actually… it turns out that, for subtle reasons, it is rather hard to calculate the impact. (Professor Chris Quigg recently mentioned to me that he and his colleagues tried to compute the main effects, but found some important issues are too close to call.) It appears likely that there would be no atomic nuclei, and/or the proton would be unstable, and/or stars couldn’t shine. What is certain is that the world would be unrecognizable, even if electrons managed through some alternative magic to keep their masses. So the electron’s mass is only a part of the story — the part that is easiest to understand, but not the only part — of why the Higgs field is crucial.
That’s important because there is yet one more asterisk about the electron and the Higgs. In the so-called Standard Model (the equations that we use to describe the known particles and forces) there is only one Higgs field and one Higgs particle, of the simplest possible type, and in that case my statements about the electron mass are true (still with the previous asterisk). But if the Standard Model isn’t quite right, there might be more than one Higgs field and more than one Higgs particle. If this turns out to be the case (and the experimentalists at the Large Hadron Collider are trying to find out), then we do not actually know yet that the Higgs field associated to the recently discovered Higgs particle — the field which definitely gives the W and Z particles much or all of their rather large masses — is truly the same as the Higgs field that gives the electron its relatively small mass. So the caveat here is that although at least one of the Higgs fields in nature must be responsible for the electron’s mass, we don’t yet know that the Higgs particle we’ve just discovered is associated to that particular field. (The field associated to the newly-discovered Higgs particle would still be crucial to our lives, however, because of its other important roles mentioned in the previous paragraph. Moreover, evidence is already rising that this field interacts with the heaviest cousin of the electron, a particle called the “tau”, which for technical reasons makes it more likely that it interacts with the electron too. Still, strictly speaking the jury is out, and will be for a while.)
Despite these caveats and addenda (and maybe there are more I should add), I still think the above two statements are about as accurate as you can get without becoming technical and long-winded. And again, they are far more accurate than what often appears in print!
Colleagues: please feel free to suggest further improvements, and please point out further addenda, subtleties and caveats that I’ve overlooked; I’ll add them to this page.