It was supposed to be easy, a few googles, maybe a peer reviewed paper or two, and I would be able to answer the “Ask a Scientist” question “what is a Higgs boson?” Unfortunately — or fortunately, depending on how you look at it — answering that particular question became somewhat complicated, and entailed a little bit more effort than that.
To properly answer the question we have to establish some atomic background, briefly ask what mass is and talk a little bit about the world’s largest machine.
The idea that the universe is composed of discrete and tiny units of matter dates back to the ancient Greeks, who named these particles atomos, which roughly translates to “un-cut-able,” paying homage to the idea that atoms were the smallest unit of matter. This theory competed with others for several hundred years until an Englishman proposed atomic theory in the early 19th century and demonstrated that matter was indeed made up of tiny particles.
John Dalton, born in England, to a Quaker family in 1776, was one of the first modern scientists to propose a modern atomic theory, which he based on observations of gasses as they were heated or cooled. Radical at the time, Dalton proposed that all matter was made out of atoms, all atoms of a single element are the same, all elements are composed of unique atoms, atoms can combine to form chemical compounds and finally atoms cannot be created or divided into smaller particles.
Today we know that some of Dalton’s laws were flawed, for example; all the atoms of an element are not always identical, ions for instance are elemental atoms, which have different compositions, however Dalton’s laws provided a basic foundation on which modern chemistry is built.
Dalton viewed the atom as a solid particle, a theory that held for many years, until a New Zealander scientist named Ernest Rutherford started firing radiation at very thin sheets of gold foil. Rutherford noticed that a majority of the dense radioactive particles passed right through the foil, but occasionally a particle would be deflected, leading Rutherford to propose that atoms were composed mostly of empty space surrounding a dense, positively charged nucleus.
Rutherford’s discovery also indicated that atoms might not be discrete and indivisible units, but were composed of parts which were smaller than atoms themselves, or subatomic.
Today modern atomic theory proposes that atoms are composed of electrons orbiting around a dense nucleus, which is made up of neutrons and protons and orbited by electrons. Neutrons and protons can be further divided into particles called quarks, which are held together by gluons.
Modern atomic theories define four fundamental forces. They are: weak nuclear force, strong nuclear force, gravity and electromagnetism. These fundamental forces do things like hold atomic nuclei together, hold atoms together and hold you to the earth, and we understand them pretty well. However one question that is related to the fundamental forces that keeps modern scientists up at night is, “What is mass?”
Mass is a tricky concept mainly because we tend to use it interchangeably with the word weight, however, while related, the two terms are very different.
As a thought experiment, which illustrates the difference between mass and weight fairly well, imagine yourself here on Earth and on the moon. On the earth you might weigh 80 kg, while on the moon, since it is smaller than the Earth, and the force of gravity is weaker, you would only weigh 13.3kg. Paradoxically though, your mass would remain the same.
Removed from gravity — such as in outer space, an objects mass can still be detected. For example if you had an elephant and a mouse floating in space, it would require more force to move the elephant than the mouse. This is because the elephant has more atoms, and therefore more mass.
But what gives an atom mass? This is the question that has confounded scientists for decades, and no one has been able to give a scientifically supported answer yet.
The Higgs field and the Higgs boson
To answer the question posed above, Peter Higgs proposed the theory of the Higgs field and the Higgs boson.
To understand the theory a little better, it helps to compare it with an idea we are all familiar with: light. Light is the result of a particle called a photon interacting with a field, which we call the electromagnetic field. Manipulations of this field can give us different colours of light, X-rays and radio waves.
Higgs postulated that bosons interact with the related Higgs field, which is what gives an atom mass.
The only problem? Nobody has ever seen a Higgs field or a Higgs boson.
Finding the Higgs boson
Atoms are generally measured in angstroms, which is the equivalent of 1×10-10 metres (that’s a one with 10 zeros in front of it). A hydrogen atom — the simplest atomic element, with one proton and one electron — measures one angstrom across. Because they are so tiny we cannot see atoms, let alone the subatomic particles that make them up. This means that scientists have to come up with interesting ways of visualizing the particles that make up an atom.
One machine that is used to investigate sub atomic particles is the particle accelerator, which collides streams of subatomic particles — such as protons — into one another. The resulting impacts destroy the particles, the resulting fragments are measured and from the data gathered, physicists can make educated guesses in regards to the make up of the particles.
If the Higgs boson exists, physicists believe they will be able to see it in this manner. However, to date, a particle corresponding to what a Higgs boson should look like has never been seen despite the concerted effort of scientists and particle accelerators around the planet. To this end the world’s largest machine — at more than 26 km in circumference — the large hadron colider (LHC) has been built, with one of its goals being to collide protons with such force as to free a Higgs boson from its subatomic bonds.
What’s the big deal?
Modern physics is divided into two camps, each with their own laws and areas of expertise. Physicists who study the very large things in our universe — such as planetary motion and supernovas — speak of phenomena in terms of Einstein’s theory of relativity and Newtonian physics, while scientists studying the very small — such as atoms and sub atomic particles — adhere to a theory called quantum mechanics.
Unfortunately both theories are radically different from one another and neither do a very good job of explaining things beyond their own narrow scope.
Quantum mechanics follows something called the standard model, which outlines all of the particles and forces required to make up the universe. The Higgs boson is one glaring hole in that theory, and its discovery is considered so important in some circles that it has been dubbed “the God particle.”
The discovery of the Higgs boson also has the potential to help physicists with what is perhaps the loftiest goal in all of science; to unify quantum physics with the Newtonian/Einsteinium variety. The discovery Higgs boson, and it’s explanation of the origin of mass, would help apply quantum mechanics to the larger universe, and be a point at which the two camps could converge.
So that’s what all the fuss is about — an infinitesimally small particle, which, if found, would help physicists understand the universe a little better. And with the LHC currently being cooled almost to absolute zero — the temperature at which all molecular motion stops — it might not be long before we find it.