|The Higgs Boson: What Does It Mean?|
On July 4th, newspapers around the world announced the discovery of “the God particle” by teams of scientists at CERN. Both the appearance of the word “God” and the excitement with which it was presented convinced many readers that this had to be a tremendous leap forward in an area of physics with fundamental importance to theological questions and the daily lives of ordinary people.
In this brief essay, I would like to explain what was actually achieved, why it is of technical importance to people doing physics research, but also why I believe that “hype” surrounding it is unfortunate.
Why was anyone looking for a Higgs Boson Anyway?
Particle physics today is not, as many people would imagine, about tiny spheres of matter flying around in empty space. Rather, it is dominated by quantum field theories (QFTs), which are about waves in space that satisfy complicated mathematical relationships.
As its name implies, “the Standard Model” stands out as one of the most widely accepted of the many QFTs. Its fame derives from the fact that it incorporates so much of what we know about particles and the ways they interact into a compact and beautiful form. (Here, I am using a mathematical notion of “beauty” in which the complicated algebraic relationships between the different fields are interpreted as being like the symmetries of an intricate design.)
In addition to capturing so much of what we already know from experiments in a neat form, the Standard Model made one prediction which had never been experimentally verified, namely the rest energy of the boson for the Higgs field. Let me explain what that means.
The Standard Model describes what we would normally think of as forces in terms of the exchange of tiny ripples of the waves that are the fields. The ripples come in discrete chunks, called quanta (the source of the word “quantum” in QFT) and the quanta responsible for the forces are called “bosons”.
For example, as you know, if you are pulling a magnet off of the refrigerator you have to tug pretty hard -- harder than you would have had to have pulled if the object had not been magnetized. According to the Standard Model, this is because of an exchange of photons, the boson of the electro-magnetic field.
Prior to the recent attention to the Higgs Boson, the photon was the only boson that many non-experts had heard of, but, it is not the only one. The Standard Model has a bosonic description for every force except for gravity and “dark energy”. (I’ll say more about those two exceptions later.)
Now, imagine that you have to push a car along a flat road. Because of the wheels (and because the car is in neutral), friction really is not much of an issue. And because you are pushing it slowly, air resistance is not a problem either. Nevertheless, it takes some effort to push the car. The amount of effort depends on the mass of the car (e.g. it would be easier to push if you take all of the gold bars out of the trunk first). It is this force that is explained by the exchange of the boson for the Higgs field in the Standard Model. In other words, the Higgs boson gives inertia to the other particles just as the photon is responsible for the pull of a magnet.
However, the algebraic relationships between the fields in this QFT puts a restriction on the amount of energy in the Higgs boson itself. It was known that it had to be in a certain range, not too low, not too high. No particle with that energy had ever been observed in an experiment, making the Higgs boson into a prediction of the Standard Model that had yet to be verified. Because the energy level in question was quite high, it was not the sort of experiment that could be done on just any lab bench. And so, the quest for the Higgs boson was a goal for those scientists with access to a high energy particle collider.
What was really announced on July 4th?
Put bluntly, but accurately, the scientists at CERN were smashing particles together at huge speeds and looking at the debris that flew out, hoping to spot a boson with energy in the range predicted for the Higgs. After conducting many such experiments and analyzing the data carefully, they made the following cautious announcement on July 4th:
“CMS observes an excess of events at a mass of approximately 125 GeV with a statistical significance of five standard deviations (5 sigma) above background expectations.”
Translated into English, this means they found something that looks like a particle with the right energy, and the probability that they are wrong is really very, very small.
However, in contrast to the less restrained claims in many newspapers, they did not say that this was the Higgs boson or that they had confirmed the standard model. What they actually said was:
“Within the statistical and systematic uncertainties, results obtained in the various search channels are consistent with the expectations for the SM Higgs boson. However, more data are needed to establish whether this new particle has all the properties of the SM Higgs boson or whether some do not match, implying new physics beyond the standard model.”
In other words, what they found is consistent with the Standard Model’s predictions for the Higgs boson, but that does not mean that this particle has any of the other important properties expected of the Higgs boson.
“The God Particle” was the title of a popular 1993 book by physicist Leon Lederman about the Higgs boson. He has been quoted as saying that he originally wanted to call it the “Goddamn particle” but that the publisher would not allow it. The name (either way) was presumably only intended to capture the intensity with which he and his fellow researchers were looking for evidence of the Higgs boson (and to increase sales of the book).
However, the fact that it is now regularly referred to as “the God particle” in news articles is somewhat misleading. Obviously, “God” plays a rather unique role in theology: the all-powerful creator and cause of everything. Yet even in the Standard Model, the Higgs boson is no more fundamental nor more powerful than any of the other particles. It is just one little piece of an intricate puzzle.
The Higgs field does have some implications for the cosmology of the early universe according to current theories. The interesting thing is that it would have behaved differently in the small and hot universe that would have existed immediately after the Big Bang, and so inertial mass would not have been a factor at first until after some expansion. When cosmologists describe the evolution of the early universe, they often make use of this feature which does seem to help explain some of what we see around us today.
This must be what physicist Lawrence Krauss was referring to when he wrote in a Newsweek piece about the CERN announcement “If we can describe the laws of nature back to the beginning of time without any supernatural shenanigans, it becomes clear that you don’t need God.”
However, one should not conclude from Krauss’ statements either that a definitive discovery of the Higgs field will prove once and for all that creation without a deity is possible, nor that its absence would somehow be disastrous for such claims. Even with the Higgs mechanism in place, there are plenty of gaps remaining in our understanding of physics and cosmology. (The failure of QFTs like the Standard Model to account for gravity, and our complete ignorance at this point of the phenomena called “dark energy” and “dark matter” are only some of the more famous ones.) And, as gaps go, the one filled by Higgs seems relatively small and technical. Apparently, some questions about the distribution of matter in the universe become easier to answer if the Higgs field kept inertia from being relevant during the earliest moments in the universe...but even if it was found that the Higgs field does not work as supposed, this hardly seems like something that would require us to resort to a supernatural explanation. I mean, this phenomenon does not seem like something requiring intellect or intention (as the distribution and diversity of animal species seemed to prior to our understanding of natural selection). If not the Higgs field, then some other natural phenomenon, an inertia canceling property of “dark energy”, could be hypothesized to replace it.
The experimental verification of the existence of a particle with the right energy to be a Higgs boson is of interest to particle physicists (in that it lends support to the Standard Model) and to cosmologists (for whom the Higgs field makes computer models of the evolution of the universe turn out more like what we actually observe today). For the rest of the world, however, I think that the attention it received was quite out of proportion to its actual importance.
One could argue that the fact that this announcement turned into a PR-palooza can only be good for science, because it grows public support and funding for future research. However, I think that this sort of argument overlooks the damage that it can do to science.
The worst situation would be if it turned out that this had to be retracted. Do you remember earlier this year when similar hype surrounded an announcement of “faster than light neutrinos”? Peer review and attempts to replicate their results showed, in the end, that they had misinterpreted their data; there were no faster than light neutrinos. It could similarly turn out that the CERN announcement was based on a mistake, or (more likely) that the particle seen really did have the right mass but did not have the other properties of a Higgs boson. This would be seen by many who read the articles in the popular press as a failure of science, when in fact it would be an instance of the scientific method working as it should. Peer review, reproducibility and ongoing research are part of the scientific process. Of course, I have no real reason to think such retractions will be necessary in this case, but I think that the press coverage ought to occur after we have had a chance to see how it plays out rather than before.
Yet, even if all of the claims turn out to have been justified, if this is a Higgs boson with the properties predicted by the Standard Model, it has little hope of living up to the hoopla surrounding the announcement. Science has a (deservedly) wonderful reputation for objectivity and skepticism, but a media circus like this one leaves even me somewhat jaded. In the near future, if such instances of hype and exaggeration continue, I would not be surprised if people react to an announcement from scientists much as they would an e-mail from Nigeria asking for assistance in transferring millions of dollars.
In conclusion, there may or may not be a Higgs field like the one in the Standard Model. This announcement puts a bit more weight on the “pro” side of the debate, but is far from the last word on the subject. Quoting Lawrence Krauss on this topic again: “Humans, with their remarkable tools and their remarkable brains, may have just taken a giant step toward replacing metaphysical speculation with empirically verifiable knowledge.” I agree, would like to emphasize that the same would have been true had the announcement been that they were unable to find a particle with the specified energy level. The great thing about science is that every discovery, whether as we had hoped or not quite what we imagined, is a giant step towards replacing speculation with verifiable knowledge.