Even if you’ve never set foot inside a physics classroom, you probably have a pretty solid grasp of the laws governing how objects move and behave.
Throw a basketball against a wall and it bounces off. If a coin flipped in San Francisco comes up heads, that won’t cause a coin flipped in Los Angeles to come up tails. If you’re sitting on your couch, you’re not also on the treadmill at the gym. (Alas!)
These same rules apply to something as big as a galaxy or as small as a grain of sand. But once you zoom in even further — to the protons, neutrons and electrons that make up atoms, for instance, or the photons that make up light — our familiar concepts fade away, and new, much weirder behaviors emerge.
Physicists studying the atomic and subatomic realms have discovered that particles can pass right through walls. Observing a particle in one location can determine the state of another particle, even if that particle is miles away. And one particle can be in two places or states at the same time.
An extremely short introduction to quantum mechanics
Physicists have a name for these baffling behaviors. They call them quantum states, a reference to the fact that, on atomic and smaller scales, properties like energy or momentum go up or down in a stepwise fashion, rather than along a smooth curve.
For instance, if you have set foot in a physics classroom, you might remember that electrons orbit the nucleus of an atom along set paths, called shells, that form concentric shapes around the nucleus. An electron can gain energy and jump to the next shell out, or lose energy and fall to the next shell in. But it can’t be in the space between shells. All electrons in a given shell have the same amount, or quantum, of energy.
In the century or so since humans began to observe and describe quantum states, these theories have had huge impacts on society, says Steve Kahn, dean of the Division of Mathematical and Physical Sciences at UC Berkeley. “Quantum mechanics formed the basis for the invention of the laser, the transistor, and essentially all of modern electronics.” Still, Kahn says when it comes to reaping the benefits of quantum theory, we’re just getting started.