For almost the entire time that scientists have been examining electricity and magnetism, they have believed that the two were different. But actually, magnetic and electrical phenomena are not just connected, they are facets of the same thing. That’s why physicists now call this fundamental force of the universe the electromagnetic force. “Magnetism and electricity are not independent things . . . they should always be taken together as one complete electromagnetic field,” Richard Feynman said. The two, he said, waxing lyrical, have a “very intimate relationship.”
To understand the electrical force, we have to go back to electrons and protons. The electron is negative. The proton is positive. These electric charges are the sources of the electrical field. Like the magnetic and other fields, the electrical field is the stuff of the universe, stretching out through it in fluidlike lines that can move in peculiar ways. Electric and magnetic field lines tend to go hand in hand. But there are a few differences between the two fields. While magnetic field lines run in unending loops, electrical field lines can end. And while electric charges can exist as solo particles that are either negative or positive—like electrons and protons—every magnet known in nature has two poles, north and south, just as Petrus Peregrinus discovered in the thirteenth century. No matter how small a magnet gets, those two poles are always present. (Scientists keep looking for a magnetic monopole but have not yet found one.) That means there are no independent magnetic charges.
So where does the magnetic field come from, if not from magnetic charges? Here’s where things get a little more complicated than the unpaired spinning electron. It turns out that the magnetic field depends on electrical charges. While the Earth is the source for the Earth’s gravitational field and electrically charged particles are the source for the electrical field, it’s the electrically charged particles themselves that create the magnetic field, but only when they are moving. In other words, a stationary charged particle makes an electrical field but not a magnetic one. A moving charged particle makes an electrical field and an electrical current, which makes a magnetic field. That can mean a bunch of moving charged particles in a current, or it can be the spin of an electron within an atom. You can take the idea down to the scale of a single atom of iron. Its negatively charged unpaired spinning electrons are creating a tiny circulating electrical current. That means the atom itself is also creating a tiny magnetic field. If you put enough of these atoms together so that the tiny magnetic fields arrange themselves to amplify one another instead of canceling one another out, you get a magnetic substance. In effect, as Feynman said, all magnetism is produced from currents of one sort or another.
Albert Einstein realized that what constitutes “movement” here depends on one’s frame of reference. If you are at rest with respect to an electrical charge, you will see an electrical field. If you are moving with respect to the same electrical charge, you will see a moving charge, which is producing an electrical current as well as a magnetic field. The same is true when you are stationary with respect to an electrical charge that is moving. It’s all about perspective. It’s all, as Einstein would say, relative.
The journey to entwine electrical and magnetic forces culminated with Einstein. But it has scampered across thousands of years, winding through myth, dogma, experimentation, and, finally, mathematics. The fact that these phenomena are facets of each other came as a surprise. Consider this: The name “electromagnetic,” one of the many words that Ørsted coined, contains within it William Gilbert’s cranky christening five hundred years ago of the word “electricity” from the Greek word for “amber” as well as Homer’s telling of the tale of the ancient hero-king Magnes nearly three thousand years ago, patched onto the evolution of those ideas in the centuries since. Were we to magically erase all that rich history and metaphor embedded in the current label and name the electromagnetic force anew, knowing what we know about physics today, we would give it a label that clearly indicates that magnetism and electricity are the same thing.
The electromagnetic force is one foundation on which the whole universe rests, at play in each single small piece of each atom. The electromagnetic field can manifest itself as waves, or vibrations, that can be any length. We see some of the tiny waves in the form of light and color, which means, by definition, that light is also electromagnetic. By a pleasing symmetry of nature, the charges all seem to balance one another out most of the time, making the universe electromagnetically neutral. Most of the time, we aren’t even aware of the electromagnetic force that is so powerfully at work.
So, the electrical force is produced by charged particles. Electricity, on the other hand, is electrons in motion. The earliest forms of electricity that scientists became aware of were what today we would call static electricity. A spark is static electricity, and so is lightning and so is the emanation from rubbed amber that attracts a piece of fluff, the phenomenon that led Gilbert to name electricity in the first place.
You’re making static electricity when you rub a balloon on your hair. The balloon steals a few electrons temporarily from your hair, making the balloon slightly negatively charged and your hair slightly positively charged. If you hold the balloon overtop your head, your hair will fly up to meet it. The hair’s positive charge wants to be reunited with the balloon’s negative, and the force between them is strong enough to lift your hair. Eventually, the electrons drift away from the balloon and the hair falls back down. The rubber in the balloon is called an insulator because it doesn’t easily conduct electrical charges. Insulators used to be called “anti-electrics,” and include other things such as glass and wood and plastic. When insulators capture extra electrons, they store them, like the balloon does, rather than pushing them somewhere else. Insulators can also isolate pockets of opposite charges from one another.
The revelation for scientists in the late eighteenth and early nineteenth centuries was that they could make electricity flow. At that time, they believed that electricity was a fluid that ran through wires and so they called it “current” electricity, as if it were a running river. Today, we say that electrical current is the one that moves from the socket through the wires into your lamp. What makes that happen? The electromagnetic field can be harnessed to push electrons through substances known as conductors and make them travel from one place to another. The human body is a conductor. Others include metals that have at least one unpaired electron in an outermost filled orbital, like copper, which is often used in electrical wiring. The old incandescent bulbs used to have a metallic tungsten strip in them where the electrons collected and heated up the metal, producing heat and light. New LED bulbs, like the ones in the art display at the Niels Bohr Institute, shine because electrons are forced into shedding some of their energy in the form of tiny units of light called photons, which are extremely short electromagnetic waves.
A key to all of this is that while the electromagnetic force is fundamental to the universe and will live as long as the universe, the process for harnessing that force into making a current is only about two hundred years old. And forcing immense amounts of current into a vast, interconnected transmission system, like the modern electrical infrastructure we rely on, is only about one hundred years old. As a society, we devote significant amounts of time, thought, and money into keeping these systems going. But as the planet’s magnetic field undergoes its restless contortions inside the Earth’s core, the transmission systems themselves are put at the kind of risk no one imagined when they were created. Under certain circumstances that scientists are just beginning to track, the planet’s human-built electrical transmission system could be switched off.