While the title of “most famous force” clearly goes to the one that has a light side, a dark side, and binds us all together, gravity probably comes in a close second. From the infamous fall of Newton’s apple centuries ago to the gravitational waves that were detected sweeping through Earth last year, the force that keeps our feet on the ground and our planet spinning around the sun gets all the glory. But the universe has three other forces, and they’re more Leia or Luke than they are Fett or Ackbar. The weak force and the strong force keep atoms in one piece, which is admittedly pretty essential, but in my opinion the real star of the show is the electromagnetic force. Electricity is well known as the stuff that powers our devices, while magnetism is much maligned as an ineffable mystery (How DO they work??), but electromagnetism is so much more than that.
1. It’s really strong
Gravity might seem strong. After all, it’s what we give into when we collapse onto the couch after a long day and what makes sending stuff into space so expensive. But did you ever do that experiment where you rub a balloon with a wool blanket, and suddenly it can pick up little pieces of paper via static electricity? In that case, the charge (caused by an excess or lack of electrons) in that tiny ballon is winning a battle against the mass of the whole earth to attract those pieces of paper. Or consider a fridge magnet. The earth tries to pull it down all day long but it never budges, because the magnetic force keeps it in place.
2. It’s everything you’ve ever known
We’re made of atoms, which are each composed of a nucleus containing protons and neutrons, with electrons orbiting outside. In other words, our outermost layer is mostly electrons, be it clothing, skin, or hair. The same is true of chairs, walls, and other people. Electrons repel each other, and the closer they get the stronger that repulsive force becomes. To get two electrons to touch directly would require infinite energy to overcome the infinite force repelling them, which just doesn’t happen.
The upshot is that we go our entire lives without ever directly touching any other matter. Our shoes levitate a tiny bit above the floor, and our feet hover a little bit inside our socks. It’s a shame that we can never truly hug our loved ones, but on the other hand you never really have to touch the subway handles either.
3. The Relativity Connection
What is magnetism, and what does it mean when people say that electricity and magnetism are “two sides of the same coin”? Of the four infamous Maxwell equations, which describe everything there is to know about electromagnetism, two basically say that changing electric fields can create magnetic fields and vice versa. One really common type of changing electric field is a current, which changes because it moves. From Maxwell’s laws (and observation of compasses near wires) people realized that wherever there’s magnetism going on, somewhere deep down there is electric current at the heart of it.
“But isn’t motion relative?” Galileo would ask, appalled. What if we the observer start moving along with the current at the same speed. The charges look like they’re motionless so where does the magnetism come from? The answer is special relativity trickery. It’s kind of long to go into here, but basically when our motion perfectly matches the motion of the electrons creating the “magnetic field”, we find that the magnetic field has disappeared and been replaced by an identically strong electric field. It’s an incredible trick, and you can read about it in more detail here.
So if electricity and magnetism are two sides of the same coin, the common part holding them together is relativity, and if that’s not amazing I don’t know what is.
4. Let there be Light
As if it weren’t enough that electromagnetism is responsible for all the interactions you’ve ever had, it’s also to thank for light. Light is what happens when there’s no charge, but somehow a changing electric field gets going, which creates a changing magnetic field, which creates a changing electric field, which… well you get the point. One waxes while the other wanes, and it doesn’t stop until it runs into something. As an aside, there’s really nothing quite like it in the field of waves. Sound waves move in air, and ocean waves move in water, but light doesn’t move in anything but itself. Strange stuff.
Of course this phenomenon doesn’t just describe visual light. If those waves wave more frequently, they are x-rays or gamma rays. If they wave less frequently they are radio waves and microwaves. In addition to allowing us to see the world around us, electromagnetism is also responsible for all of the information we get about the world not around us via the internet, phone networks, and radios.
5. It’s an atomic world, we just live in it
It turns out that electromagnetism binds us together even more than The Force does. We spend all our time living in a world full of people and buildings, walls and chairs, solids and gravity. But when you really take a close look at electromagnetism, the scales fall from your eyes and you see that that world is nothing but a Matrix-like illusion spun by our brains out of electron clouds and self sustaining waves of electricity and magnetism. Thinking about electromagnetism forces us to confront the atomic nature of our world in every aspect of our lives.
The Insane Clown Posse had it backwards. Magnets aren’t the question, they’re the answer.
Water, fire, air and dirt. How do they work? Electromagnetism.
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