Particle physicists might seem like a dry bunch, but they have their fun. Why else would there be such a thing as a “strange quark”? When it comes to the fundamental nuclear forces, though, they don’t mess around: the strongest force in nature is known simply as the “strong force,” and it’s the force that literally holds existence together.
Zoom in on the Elementary Particles
To find out what the strong force is, you need to have a basic understanding of what physicists call the elementary particles. Let’s start with an atom—helium, for example. A helium atom has two electrons zipping around a nucleus made up of two neutrons and two protons. For most high-school chemistry classes, that’s where the tiny particles end.
But you can zoom even further into the atom: those protons and neutrons are a class of particle called hadrons (à la the Large Hadron Collider!), which are made up of even smaller particles called quarks. Quarks are what’s known as an elementary particle, since they can’t be split up any further. They’re as small as things get. There are two types of elementary particles; the other is the lepton. Quarks and leptons each have six “flavors”, and each of those have an antimatter version. (The electrons in our helium atom are a flavor of lepton, so we’re as zoomed in on them as is possible.) Heady stuff! Check out the diagram below if you’re getting lost.
Forces of Nature
Following so far? There are four more parts to this puzzle we call the Standard Model, which is the theory of all theories when it comes to particle physics. Those parts are the fundamental forces. Two are probably familiar: gravity is the force between two particles that have mass, and electromagnetism is the force between two particles that have a charge. The two others are known as nuclear forces, and they’re less familiar because they only happen on the atomic scale. Those ones are known as the weak force and the strong force. The weak force operates between electrons and neutrinos (another kind of lepton), but of course, it’s the strong force we’re here to talk about.
The strong force is what binds quarks together to form hadrons like protons and neutrons. Physicists first conceived of this force’s existence to explain why an atom’s nucleus can have more than one positively charged proton and still stay together — if you’ve ever played with magnets, you know that a positive charge will always repel another positive charge. Eventually, they figured out that the strong force not only holds protons together in the nucleus, but it also holds quarks together in the protons themselves. The force actually comes from a type of force-carrier particle called a boson. (Surely you remember the 2012 discovery of the Higgs boson?) The particular boson that exerts this powerful force is called a “gluon”, since it “glues” the nucleus together (we told you that physicists were a fun bunch).
Here’s what makes the strong force so fascinating: unlike an electromagnetic force, which decreases as you pull the two charged particles apart (think of magnets again!), the strong force actually gets stronger the further apart the particles go. It gets so strong that it limits how far two quarks can separate. Once they hit that limit, that’s when the magic happens: the huge amount of energy it took for them to separate is converted to mass, following Einstein’s famous equation E = mc2. That’s right—the strongest force in the universe is strong enough to turn energy into matter, the thing that makes up existence as you know it. We learned some particle physics, everyone. Who needs a snack?