That’s just silly, right? It’s crazy that the act of measurement changes the outcome. Does this mean that physics experiments can change reality? Maybe.

What About That Zombie Cat?

I mentioned Erwin Schrödinger above. He was one of the pioneers of quantum theory, but he couldn’t bring himself to accept this idea of superposition. Using his macro-world common sense, he insisted there must be a flaw in the model, and that a complete theory of quantum mechanics would eventually be deterministic like classical physics.

When scientists don’t like something, they make up absurd scenarios to invite mockery of its proponents. So Schrödinger created a famous thought experiment you may have heard of. It’s called Schrödinger’s Cat, and it goes like this:

There is a cat in a box. This box also contains a radioactive atom, a detector, and a vial of poison. If the atom decays and produces radiation, the detector will open the vial and the cat will die. But if the box is closed, the atom is in a superposition state, being both decayed and not decayed—meaning the cat is both dead and alive. Only when you open the box and observe the cat will its wave function collapse into either dead or alive.

Nice try, but Schrödinger’s scenario was easily dismissed. First, no one was saying superposition translated to big objects like cats. Second, there was already a measurement before the box was opened: The device that releases the poison was monitoring the state of the atom.

In fact, Schrödinger was wrong—as was Einstein, who agreed with him. Since then, numerous experiments have proved that superposition is real and that uncertainty is fundamental to the universe. And a good thing it is, too, even if it makes no sense. Superposition is what gives quantum computers their immense parallel processing power.

Heads and Tails

It’s important to understand that superposition of states isn’t the same as saying we don’t know. If you flip a coin and cover it up when it lands, the coin is already either heads or tails—you just don’t yet know which. In the double-slit experiment, we know: It goes through only one slit and it goes through both slits.

Quantum systems have other properties that will scramble your brain if you try to grok them, like entanglement, where measuring the state of one particle determines the state of another, no matter how far away it is. This happens instantly, with no time for a signal to travel between them.

But by now these are well-established phenomena, so is it fair to call them bizarre? Are we only exposing the limitations of our human minds? Clearly, the level of reality we inhabit is only part of the story, so we should be skeptical of our intuition. If nothing else, quantum mechanics teaches humility. We keep doing science—and the farther we go, it seems, the greater the mystery.