The Force Behind Mass

The Large Hadron Collider at CERN in Switzerland.

On July 4, 2012, an announcement rocked the science world. A discovery had been made, and it would revolutionize the world forever. It answered a simple question: Why do particles have mass?

At first glance, this question seems unnecessary. A truck has more mass than a tennis ball, and that’s all we need to know. In fact, on our planet, we can measure mass in multiple ways. One could use a scale on Earth, which measures weight and then divide by g (9.81). If one wanted to be more accurate, they could analyze the acceleration of an object after a known force is applied on it, and using the famous equation F=ma, solve for mass. With these accurate methods, why would we possibly have to know more about mass?

The Story

There are three force bosons in this story. The photon, the W boson, and the Z boson. All three are mathematically symmetrical, and that essentially means that they should all have no mass. For the photon this is true. But for the W and Z boson? They both are heavy (in quantum terms), which breaks the math. There has to be something that physicists are missing, which is the key to solving this problem!

Rewind 50 years prior to this discovery, in 1964. A man named Peter Higgs writes a pair of scientific papers that theoretically predicts the Higgs boson. This is groundbreaking in itself, but he has no concrete evidence to support this hypothesis. Without evidence, this claim was simply speculative. Luckily, hundreds of labs around the world were with Higgs to help him prove his theory correct.

The Discovery

The discovery finally took place in Switzerland at CERN, a particle physics laboratory famous for its massive underground ring, the Large Hadron Collider (LHC), with 17 miles in circumference. The purpose of this collider is to, well, collide particles at incredibly high speeds. A quick note about the LHC’s size: the reason it has to be so massive is because of how fast the particle is moving and how limited the magnets are. Particles moving faster and faster in a circle have two options. Either they somehow receive more centripetal force that allows them to maintain a certain radius, or they increase their radius of motion. Magnets can only provide so much force, and after a point, the only way to speed up the particles without them bashing into the walls was to increase the radius of the track. Keep in mind though, that while the magnets cause the particles to move in a circular path, it is actually electric fields that accelerate the particles and increase their speed.

As physicists like to do, they bash things together. When protons were the victim of physicists’ focus, that is exactly what physicists did to them; bash them together. Protons were accelerated to almost the speed of light and then collided, recreating conditions similar to shortly after the Big Bang. With enormous amounts of data, scientists detected something interesting. For a split second, there was something new in the collision, a new particle. This particle was the Higgs boson. Detecting the Higgs boson was important because it provided evidence for something even more fundamental: the Higgs field.

The Higgs field behaves like any other field. For example, take the electromagnetic field. It is everywhere, yet we don’t always feel it around us. The important fact is that all the cool things happen through disturbances in these fields. Excitations in the electromagnetic field generate electromagnetic waves, which can appear as light. Likewise, excitations in the Higgs field appear as Higgs bosons. These excitations are caused by interactions with the field. In a way, the Higgs field can be thought of as a syrup. Some particles, like the W and Z bosons, interact with this field, are slowed down, clump up, and have mass. Photons, on the other hand, glide through this field unaffected, and therefore have no mass. Note that the Higgs boson itself is not what gives particles mass, but is instead simply evidence that the Higgs field exists. In summary, particles that interact with the Higgs field strongly have a lot of mass, while particles that pass through the Higgs field easily have little to no mass at all. Without the Higgs field, atoms and matter could not exist as they do today.

The Consequences

A photo of Peter Higgs.

The discovery of the Higgs boson and confirmation of the Higgs field won Peter Higgs the 2013 Nobel Prize in Physics, but more importantly, confirmed a major part of the Standard Model. In simple terms, the Standard Model says that everything around us is built from a small set of fundamental particles interacting with each other through fundamental forces like the strong and weak nuclear force. This theory is incredibly accurate, and has agreed with experiments up to 10 decimal places. However, there are some flaws. The Standard Model does not explain gravity or antimatter, and if it really is as accurate as it is, then we may need a new theory that includes the two.