May the Fourth Be With You!

Today, May 4, is International STAR WARS Day. I’m here to talk about the Force. No, not that force; I’m talking about the fundamental forces of the universe. If you don’t know what those are, they are the four fundamental forces which we experience every day: Gravity, Strong Nuclear Force, Weak Nuclear Force, and Electromagnetism. Today, using STAR WARS, I will explain each of these forces for you.

First, let’s start with one of the more well-known forces: Electromagnetism. This encompasses electricity, magnetism, and what happens when you convert one into the other. We talk about them all together because electricity and magnetism are two sides of the same coin; sort of like the dark side and light side of the force. And like the force, you can convert electricity to magnetism and magnetism to electricity. Three of the four forces have carrying particles which carry the force. For electromagnetism, it is the photon.

The magnetism side of electricity is… complex.  Many things have to go right if there is to be a magnet. First, the atoms have to have half filled shells so the electron's intrinsic magnetic fields won’t cancel out. Next, all the atoms in the crystals have to align all their electromagnetic fields the same way. Finally, all the different ‘domains’ in the magnet have to align their magnetic fields either naturally or by an outside force. If all this works, then you have a magnet.

Electromagnetism works a bit differently. They rely on special relativity. Here’s some background information. When an object is moving, it experiences time slower relative to an object not moving and also contracts. This contraction is crucial for electromagnetism. Let’s say we have a copper wire. It is not a magnet. The amount of freely drifting protons and electrons even out, so there is no magnetic field. There is a balance(sort of like the force). Run a current through the wire and nothing should happen. Let’s say you get a positively charged object and place it next to the wire while the current is running. Nothing happens. But what happens if you push the object in the same direction as the current and at the same speed? The object gets repelled. How? From your perspective, It makes no sense. But let’s look from the object’s perspective. From the object’s perspective, the electrons are not moving at all. In fact, according to the object, it’s the protons which are moving in the opposite direction! And because a moving object contracts slightly, the protons contract slightly. This allows for there to be more protons than electrons, creating a ‘disturbance in the force’. The abundance of protons pushes away the positively charged object. From our perspective, we think that the current in the wire generates a magnetic field.

Next, a lesser-known force: the Weak Nuclear Force. This is the force responsible for the radioactive decay of the nucleus of atoms. It also plays a crucial role in nuclear fission. As the least-known force, it is carried by W and Z bosons. It also allows quarks to change states. Quarks come in six states: up, down, strange, charm, top, and bottom. The weak force allows the quarks to swap their state for another one. The change is mediated by W and Z bosons.

The strong force is an extremely crucial force in the universe. Carried by gluons, it only acts over extremely small distances, but it is extremely powerful. It is what holds the quarks inside protons and neutrons together, and some extra “leakage” is what holds the protons and neutrons in the nucleus together.

And finally, there’s Gravity. Gravity… is different from the other forces. The other three forces are forces carried by quantum particles. They are described by quantum mechanics. These particles are like fluctuations in a field. Gravity is different. Gravity is described by special and general relativity, the most famous theories of Albert Einstein himself. Gravity is merely the warping of the space time continuum. Relativity is a theory of geometry, of absolute predictions. But in quantum mechanics, there are no absolute predictions, only probabilities of what might happen, so they don’t work with each other. To add to the mess, there is no carrying particle for Gravity. Think of it like the three Sith next to the entire Jedi order of the prequel era.

In the end, the four forces can be a bit mind boggling to comprehend. But don’t try to think about them. As a famous Jedi once said: “Do or do not. There is no try.”