Electrons don’t spin the way a basketball spins on a fingertip, but they do have a property called “spin” that behaves remarkably like rotation. This is one of the most genuinely strange things in physics: electrons carry angular momentum and generate magnetic fields exactly as if they were tiny spinning charged balls, yet treating them as literally rotating objects creates serious contradictions. The real answer is more interesting than a simple yes or no.
Why Electrons Can’t Be Spinning Like Tops
Electrons have angular momentum, which is the same property that keeps a bicycle wheel upright or makes an ice skater spin faster when they pull in their arms. They also behave like tiny magnets, and magnetic fields naturally arise from rotating charged objects. So far, so good for the “spinning ball” picture.
The problem is size. If you try to model an electron as a small solid sphere that physically rotates, you can calculate how fast its surface would need to move to produce the angular momentum physicists actually measure. The answer: faster than the speed of light. Since nothing with mass can reach the speed of light, a tiny spinning ball simply can’t account for what we observe. This is the central reason most physicists say electrons aren’t “really” spinning.
What Spin Actually Is
Spin is an intrinsic property of electrons, meaning it’s built into what an electron is, not something it does. Every electron has a spin quantum number of exactly 1/2. This value never changes, can’t be sped up or slowed down, and doesn’t depend on anything happening around the electron. It’s as fundamental to an electron as its charge or mass.
What makes spin so counterintuitive is that it has no direct equivalent in everyday experience. A planet orbiting a star has orbital angular momentum because it’s physically moving through space. An electron in an atom also has orbital angular momentum for similar reasons. But spin angular momentum exists on top of that, even for an electron sitting perfectly still. It’s angular momentum without anything visibly rotating.
When physicists measure an electron’s spin along any direction, they only ever get one of two results: spin “up” or spin “down.” There’s no in-between, no gradual change. This two-state nature is what makes spin a quantum mechanical property rather than a classical one. A spinning top can rotate at any speed you like. An electron’s spin is locked to exactly two possible orientations.
The Experiment That Revealed Spin
In the early 1920s, physicists Otto Stern and Walther Gerlach sent a beam of silver atoms through an uneven magnetic field. If atoms behaved like classical objects, they’d fan out smoothly across a range of positions on a detector. Instead, the beam split cleanly into two distinct bands.
This was so striking that Gerlach sent a telegram to Niels Bohr: “Bohr was right after all.” He even mailed a postcard with the now-famous photograph of the split beam. At the time, both experimenters thought they had confirmed a prediction about how electrons orbit the nucleus. They were wrong about the reason. Silver atoms, it turned out, have no net orbital angular momentum. The splitting came entirely from electron spin, a property that wouldn’t even be proposed until 1925, several years after the experiment. In retrospect, Stern and Gerlach had demonstrated something they didn’t know existed.
Where Spin Comes From
In 1928, physicist Paul Dirac wrote an equation that combined quantum mechanics with Einstein’s special relativity. He wasn’t trying to explain spin. He was trying to describe how electrons behave at speeds approaching the speed of light. Spin fell out of the math automatically.
The Dirac equation showed that any particle with the electron’s properties must have exactly two internal states, corresponding to spin up and spin down. It also predicted antimatter, which was confirmed a few years later. The fact that spin emerges naturally from combining relativity with quantum mechanics, rather than being tacked on as an extra assumption, is one of the strongest hints that spin is deeply fundamental to the structure of reality.
A New Argument That Electrons Really Do Rotate
Not everyone accepts the “spin is just an abstract property” line. Caltech philosopher of physics Charles Sebens has published arguments that electrons genuinely rotate, just not as tiny solid balls. His proposal: an electron isn’t a point particle but a spread-out blob of charge, more like an ice skater with arms extended than a compact spinning marble.
With the electron’s charge spread over a larger region, no part of it needs to move faster than light to produce the observed angular momentum. This also solves another nagging problem. If an electron is a point particle, the electric field it creates is infinitely strong at its own location, making force calculations break down. A spread-out electron has finite, well-defined forces everywhere. Sebens’ view is a minority position, but it’s a serious one, published in peer-reviewed journals.
Why Spin Matters for Atoms and Chemistry
Spin governs one of the most important rules in chemistry: the Pauli exclusion principle. This rule says no two electrons in the same atom can share all the same quantum properties. Since each orbital in an atom is defined by three quantum numbers (related to energy, shape, and orientation), the only remaining difference between two electrons sharing an orbital is their spin. One points up, the other points down. That’s it. A third electron simply cannot fit.
This is why the periodic table looks the way it does. Electron orbitals fill up two at a time, with paired spins, and once an orbital is full, the next electron must move to a higher energy level. Without spin, atoms would behave completely differently, chemical bonds would change, and matter as we know it wouldn’t exist. When two electrons pair up with opposite spins in the same orbital, their tiny magnetic fields cancel each other out, which is why most everyday materials aren’t magnetic.
Spin in Modern Technology
Electron spin isn’t just a curiosity for physicists. It’s the basis of a growing field called spintronics, which uses the spin state of electrons (rather than just their charge) to store and process information.
The foundation was laid in the 1980s when Albert Fert and Peter Grünberg discovered that layered magnetic materials change their electrical resistance dramatically depending on how the layers’ magnetizations are aligned. This giant magnetoresistance effect earned them the 2007 Nobel Prize in Physics and led to far more sensitive read heads in hard disk drives starting in 1997. That technology is a big part of why hard drive storage capacity exploded in the late 1990s and 2000s.
More recently, Samsung demonstrated the first in-memory computing system based on magnetic random access memory, or MRAM. Traditional computer memory stores data using electric charge, which leaks away when power is cut. MRAM stores data using electron spin orientations, so it retains information without power and can potentially perform calculations right where data is stored, eliminating the bottleneck of shuttling information between memory and processor. Spintronics is also being explored for logic circuits and sensors, making electron spin one of the more practically consequential quantum properties in modern engineering.