My client, a science educator and speaker, wanted to write a beginner-friendly guide to quantum physics that would be accessible for everyday readers. While she wanted to include some references to New Age spiritual concepts, she wanted the book to primarily stay focused on science. It had to be accurate, well-researched, and fun to read. I’ll admit—this is one of the toughest projects I’ve taken on to date, but it was worth it! I learned so much and my client was thrilled with the result. This excerpt is from a chapter dedicated to the history of quantum physics.
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Alrighty, fellow cosmic adventurers, buckle up for a rollercoaster ride through the history of physics! Before we quantum leap into the nitty-gritty of tiny particles and wavy light, let’s take a quick spin through the evolution of classical physics and how it gave birth to the quantum realm.
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You remember the old story: It’s the 17th century, and Sir Isaac Newton, the OG physics superstar, is lounging under an apple tree, minding his own business, when bam! An apple conks him on the noggin. This fateful encounter got Isaac thinking about the force that pulled that apple down—and thus, Newtonian physics was born.
That story is probably just a legend, though Newton really might have sat there watching apples fall from trees. Scientists are a curious bunch. They like to sit around and observe things and study why they happen.
Newton’s observation and study led him to develop the theory of universal gravitation. He wrote about it in a book called Mathematical Principles of Natural Philosophy (a real page-turner, I’m sure), published in 1687. In the book, Newton said, “Every object in the universe attracts every other object according to their masses, and how far apart they are from each other.”
And everyone else said, “You mean like magnets?”
“No, no,” said Newton. “Well, a little bit like magnets. Objects with larger mass are more attractive. So the Earth and the Sun attract each other. But the Sun is bigger, so it’s pulling more on the Earth than the other way around.”
Newton also developed a whole set of predictable, deterministic laws that tried to explain how the world worked—and largely succeeded. Maybe you’ve heard of a few:
Newton’s First Law: Objects stay in one spot or keep cruising at a constant speed, unless some meddling force jumps in.
Newton’s Second Law: The force (F) acting on an object is equal to its mass (m) times its acceleration (a). In other words, F = m×a, baby!
Newton’s Third Law: For every action, there’s an equal and opposite reaction. It’s like the universe’s way of saying, “You push me, I push you back!”
Newtonian physics ruled our understanding of reality for centuries, explaining everything from gravity to how stuff moves. It’s so classic that we call it “classical physics.”
But—plot twist!—it wasn’t perfect.
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Fast-forward to 1800s Scotland, where botanist Robert Brown noticed pollen grains doing the jitterbug in water. They moved around in a random, zig-zaggy motion, and were constantly jiggling. Brown was like, “What the heck is going on? It’s like the pollen bits are bumping into other bits of . . . something I can’t see.” Brown sat down and had a think. Then a light bulb went off over his head. “Maybe these somethings are atoms!”
Brown was basically right. Those “somethings” were a ton of water molecules all vibrating at a rate relative to their temperature (thermal motion). Everyone thought that was a cool observation. (Haha, get it? “Cool?”) But they couldn’t see the atoms, so they weren’t convinced the atoms existed.
To this day, this motion is called “Brownian motion.”
Brownian motion: The random, erratic movement of particles in a fluid, arising from their constant contact with the molecules of the surrounding medium.
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James Clerk Maxwell was another brainy 19th century Scot. Building on the work of Faraday and others, he finalized the Theory of Electromagnetism.
Okay, what does that mean? Basically, he studied electric and magnetic fields, and how those fields interact with matter. One aspect of this theory says that when charged particles decide to bust a move and change their acceleration—speeding up, slowing down, or doing the Macarena—they send out electromagnetic waves.
Picture it this way: There’s a jump rope on the ground, stretched out in a straight line. You bend down and grab one of the handles. If you just hold the handle still, nothing happens to the jump rope. But if you shimmy the handle side to side really fast, what happens? A wave of motion goes down the jump rope. It looks like a wavy-wavy snake slithering across the floor.
The handle is a charged particle, like an electron. If it gets moved around a lot, it sends out waves. We call these waves electromagnetic radiation—lovingly nicknamed “light.”
Theory of Electromagnetism: A set of laws describing how charged particles interact via fields that combine electric and magnetic forces—aka, electromagnetic fields.
Electromagnetic radiation: Essentially, light. Light is a type of electromagnetic radiation that falls within humans’ visual spectrum, but the spectrum extends beyond what we’re able to see.
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Hold onto your hats, folks, because it’s 1911 and the physics world is about to get shook to its core, courtesy of one Ernest Rutherford and his epic gold foil experiment.
When I play around with gold foil, I’m lucky not to get it stuck all over everything it comes into contact with. When Rutherford did it, he discovered the atomic nucleus—the heart of the atom.
The nucleus was seen as holding most of the mass of the atom, and the electrons were seen as negatively charged particles. Now we have the concept of the atom and the birth of particle physics. Scientists popped a bottle of bubbly.
But then somebody threw a curveball. “Hey wait! What about the Theory of Electromagnetism?” Cue the record scratch. Everybody put a pause on that bubbly. After all, electromagnetism was a real thing. There was no room for it to be wrong. And according to the Theory of Electromagnetism, those charged electrons circling the atomic nucleus would sometimes emit electromagnetic radiation.
Okay, so what was the problem with that?
Well . . .
→ If an electron was emitting radiation, it was losing energy.
→ According to classical mechanics, if it was losing energy, it did not have enough strength to balance the mass of the nucleus.
→ Therefore, it shouldn’t stay in a stable orbit around the atomic nucleus.
→ It would be pulled into a spiral toward the nucleus. Because of gravity.
→ The atom would collapse on itself.
Hmm. According to classical mechanics, reality shouldn’t exist because everything should have already collapsed into itself.
You gotta hand it to physicists. Some people would see this math—the math that said atoms negated their own existence—and would think they’d made a mistake. They’d decide their math was bunk.
But physicists had double-checked their math. They knew it was right. It said that atoms should collapse on themselves . . . and yet when scientists looked around, they could clearly see that reality existed. Nothing had collapsed onto itself. That meant that classical mechanics itself wasn’t right. Or, at least, it didn’t account for everything.
Stuff was starting to get very weird.
