The God Particle
July 4th, 2012, was a significant day in the history of science. In a news conference in Geneva Switzerland, physicists at the Large Hadron Collider – a 16 mile long particle accelerator where matter is smashed together in an attempt to recreate conditions which existed fractions of a second after the Big Bang – announced that, after a 30+ year search, they have confirmed the existence of the Higgs boson. This is a really big deal. As I will explain, there is a reason the Higgs boson has acquired the nickname the “God Particle”. As usual, the mainstream media coverage on this dumbs down the science when reporting this story, assuming that the reader cannot possibly understand. This is just the type of gap in news coverage that I try to fill here in Common Science®. So fasten your seat belts and return your tray tables to their full, upright, and locked positions as we embark on a journey into particle physics.
To understand why the discovery of the Higgs boson is so important, we need to start with a review of the structure of matter and a summary of the Standard Model of physics. Early on in high school chemistry you were taught that atoms were made up of protons, neutrons, and electrons. Then most of the remainder of the course focused on the interactions of atoms. However, I expect that at least part of one of the lectures did mention that protons and neutrons are made up of even smaller particles called quarks, whose existence was first proposed in 1964. The concept of quarks gave rise to the development of the Standard Model (SM) of physics.
The SM attempts to explain the properties and interactions of all the elementary particles and fundamental forces in the universe. The four forces in the universe according to the SM are gravity, and the electromagnetic, strong, and weak interaction forces. Although everyone is familiar with the effects of gravity, its mechanism is still not fully understood. (For more detail see my earlier column “Gravity, Still a Mystery”). The electromagnetic force controls interactions between atoms and molecules. As such, it is the driver of all of the phenomena you observe in daily life, including light, electricity, weather, and chemical reactions. The strong interaction force is what holds the protons and neutrons inside of the nucleus of an atom together and the weak interaction force is what causes some nuclei to break apart in the process known as nuclear decay (think nuclear power or an atom bomb.) (You may be thinking “Hey it doesn’t make any sense that the weak interaction force can overcome the strong one to break apart a nucleus. I agree but I didn’t get to pick the names.)
The SM describes 12 elementary particles which make up all of matter. Six of these are quarks and six are leptons. Most people have heard of quarks. The six quarks are called up, down, charm, strange, top and bottom. Protons and neutrons are made up of combinations of up and down quarks. Charm, strange, top and bottom quarks are unstable and can only be created in very high energy situations like the big bang or in a particle accelerator. Leptons are much less familiar to the general public than quarks. I will not give a review of leptons here as it is not necessary for this column. You do know one of the six leptons, the electron. The other 5 are not stable.
The four fundamental forces act on the 12 elementary particles through force carrier particles known as bosons. For example, the strong force which holds nuclei together is mediated by the exchange of bosons which are rather appropriately named gluons. The electromagnetic force is mediated by the most familiar or the bosons, the photon (Many thanks to Star Trek for bringing this word into public consciousness with the “photon torpedo”). Photons are what make up electromagnetic radiation. You are familiar with some types of electromagnetic radiation such as light, ultraviolet rays and gamma radiation. For more on electromagnetic radiation see my earlier column, “Is your cell phone trying to kill you?” The weak interaction force is controlled by the less charmingly named W and Z bosons. The boson for gravity, named the graviton, has yet to be observed.
Simply stated, the SM tell us that the universe is composed of 12 elementary particles which interact with one another in 4 ways through the exchange of force carrier particles know as bosons.
Now that we have the basics down we can move on to the elusive and amazing Higgs boson. In the 1960s, Professor Peter Higgs of the University of Edinburgh published several papers addressing a key gap in the Standard Model. It could not account for the fact that elementary particles had mass. As gaps in theories go, not having an explanation for mass was a doozy. Without mass, the Big Bang would have generated a uniform field of energy expanding throughout the universe. Such a universe would be featureless and lifeless.
To fill this gap, Higgs predicted the existence of a force exchange particle, later named for him, that imparts mass to quarks and leptons, allowing them to attract one another via gravity. Therefore, the action of the Higgs boson eventually led to the coalescence of sub-atomic particles into protons and neutrons, then atoms, then molecules, then solar systems, then planets and then, eventually, us. Hence the “God Particle” nickname. Higgs, who is alive and kicking, is purported to dislike the name as being a bit sensationalistic, keeping alive the stereotype that physicists need a better sense of marketing.
Physicists searched for the Higgs boson for four decades by smashing small pieces of matter together at extremely high energy. Their goal was to create conditions similar to those which existed a fraction of a second after the big bang. This is the moment when, according to the Standard Model, the Higgs boson came into existence and began its task of imparting mass to nearby quarks and leptons. Our ability to recreate these conditions in the Large Hadron Collider is an amazing feat and it helps to confirm our understanding of the origin of the universe.
I am glad to see that physics can still garner headlines in the days of reality TV and insipid political commercials. I think part of the interest comes from the realization that there is still much about the universe that we still don’t understand. Even with the remarkable achievement of finding the Higgs boson, we still can’t account for 70% of the mass in the universe. So there is still quite a bit of physics left to be done.
I hope that that Mr. Higgs enjoyed the announcement on Wednesday. Forty years is a long time to wait to be proved right.
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