A Higgs boson walks into a Catholic church
with a troubled look. After indecisively looking at the confessional, he seems to gather his
courage and enters, where a priest is waiting. The priest says "Higgs, me lad, what seems
to be boddering ya?" The Higgs boson takes a deep breath and says "Father Flanagan, I’m
thinking of leaving the church." The priest replies "Me son, you con’t do tot." The
Higgs boson says "But - but Father, I’m - I’m having a real crisis of faith. I have
to leave." To which Father Flanagan replies "No, Higgs me boy, you don’t understond.
You can’t leave the charch. Widdout ya, how con we have mass?"
OK, so you may have heard that one. Now, before I go on, I’d like to apologize to any Catholics
who might be offended. But even more- and this is important- I’d really like to apologize
to anyone who actually knows what an authentic Irish brogue sounds like.
This story illustrates very nicely a common idea, which is that the origin of all mass,
including the mass that keeps us firmly on the ground stems from the Higgs boson. There’s
just one problem. It isn’t true. Now, I don’t mean that we physicists have been
lying to you. The statement that the Higgs boson gives mass to fundamental subatomic
particles and that it is a crucial discovery in our quest to understand the rules that
govern our universe is an entirely true one. It’s just that the particle’s impact is
probably different than you have imagined. In fact, the origin of the kind of mass that
makes up you and me is from something else and the real source is actually pretty mind
blowing. So you guys know that you are made of atoms
and, if you add up all the mass of the atoms inside you, you’ll find that they equal
your mass. There’s no controversy there and we can conclude that atoms are the origin
of mass. But the story goes deeper than that. We know that atoms are composed of protons
and neutrons at their center and electrons that swoop around at great distances, kind
of like electron planets orbiting the nuclear sun. Purists will bring up the idea of quantum
mechanics and electron clouds, but the fact is, that for our purposes, the planetary model
of the atom is good enough. Given that the atom has three components,
it’s probably true that one or more of them is the true source of mass. As it happens,
protons and neutrons have about the same amount of mass, so for our purposes, we can treat
them as the same thing and simply call them nucleons, which identifies them as the particles
in the nucleus of the atom. In contrast, the electrons are relatively light. Each electron
has only about 0.05% of the mass of the nucleons. So in our search for the origins of mass,
we can ignore the electrons. To all intents and purposes, they don’t matter. So can
we conclude that your mass comes from nucleons? Well, actually yes. We can. However we also
know that nucleons are made of even smaller particles called quarks. In fact, each nucleon
contains three quarks. And here’s the good thing- to the best of our knowledge there
is nothing inside quarks. That’s the end of the line. So it stands to reason that the
ultimate origin of your mass is the quarks, and since there are three quarks in each nucleon,
each quark carries about a third of the nucleon’s mass. And that’s the final word. However,
there’s only one problem. When we measure the mass of the quarks and add them up, we
find that they actually make up only about one or two percent of the nucleon’s mass.
So where is the other 98%? To understand that, we need to have an idea about what a proton
would look like if you had a magic magnifying glass and could study it. What you’d see
is the three quarks furiously orbiting around each other in a sphere with a radius of a
quadrillionth of a meter. (That’s 10-15 meters for us scientific types.) Further,
these quarks aren’t just lollygagging about. They are moving at nearly the speed of light,
almost 300,000 kilometers per second…that’s 186,000 miles per second, or almost fast enough
to orbit the earth eight times in a single second. Objects moving that fast have a lot
of kinetic energy, which is the energy of motion. In addition, if something is moving
that fast in such a tiny volume, there have to be some crazy big forces holding the nucleon
together. Therefore, huge forces have to exist in the nucleon and whenever you have huge
forces, you have a lot of binding energy or what scientists call potential energy. So
this is the first important point, quarks inside nucleons have a very small mass but
a huge amount of kinetic and potential energy. The second important point involves this guy
here. In 1905, Albert Einstein worked out his famous equation, which we now write as
E = mc2, where E stands for energy, m stands for mass and c for the speed of light. Basically
this equation says that energy and mass are identical. That’s what the equal sign means.
And now we can pull it all together. It turns out that your mass isn’t what you think.
The idea that we are made of some kind of "stuff" is wrong. Instead, your mass comes
from countless little balls of energy spread throughout your body. Weird, huh? So that
brings us back to the Higgs field and the Higgs boson. How does that fit in? Well the
Higgs field does give mass to the quarks themselves and the electrons that we’ve neglected.
In short, the Higgs field is only responsible for about 2% of your mass. So does that mean
that the Higgs field is unimportant? No, not at all. If it didn’t exist, electrons would
have no mass. And if electrons didn’t have any mass, then atoms wouldn’t exist. And
then we wouldn’t exist and be here to wonder about it. So it matters a lot. Luckily, the
Higgs field does exist, so I’m still here. However, when it comes to the origin of the
kind of mass that makes up you and me, there is a different cause. Your mass comes mostly
from a single source, the energy stored inside nucleons. In fact, to very good approximation,
there is no mass in the way we usually think about it, there is only the kinetic and potential
energy of the quarks orbiting in nucleons, like a swarm of hyper-caffeinated bees. And
that is incredibly cool.
