51吃瓜

Austrian physicist Erwin Schr?dinger won the 1933 Nobel Prize in Physics for his work in quantum mechanics, a branch of physics that studies the nature and behavior of subatomic particles. In 1935, Schr?dinger came up with a famous thought experiment, now eponymously referred to as Schr?dinger’s cat, as a criticism of what’s known as the Copenhagen interpretation of quantum mechanics. The Copenhagen theory stated, essentially, we can’t know what state or place an atomic particle is in until it’s observed, and so that particle could hypothetically be in all possible states or places until then.

Schr?dinger found this theory flawed, and to demonstrate why, he asked his colleagues to imagine a “ridiculous case” where a cat, a tiny bit of radioactive material, a Geiger counter, a hammer, and a glass vial of poison were all locked inside a single box. Over the course of an hour, there is a chance that the radioactive substance might emit a particle (specifically, an alpha particle), and an equal chance that it might not. If the particle is emitted and hits the Geiger counter, a relay is set in motion whereby the hammer shatters the flask, releasing the gas and killing the cat. Thus, after an hour, there is equal probability of the cat being alive or dead, and an observer can open the box and see which state the cat is in.

Now, if we scale up the Copenhagen theory from the quantum level all the way up Schr?dinger’s scenario, then all outcomes simultaneously exist in all possible configurations until one opens the box, which, according to the complex mathematics of quantum mechanics, forces only one outcome: the cat is either alive or dead. The problem is that this would mean that until the very last moment before someone opens the box, the cat is somehow both alive and dead at the same time.

Obviously, a cat can’t be both alive and dead—vampire cats excluded—which was exactly Schr?dinger’s point. The Copenhagen theory is a paradox. At what precise moment do the mathematical probabilities give over to physical reality?

Complex scientific theories don’t tend to become online memes, but Schr?dinger’s cat is an exception, perhaps due to its rather visceral nature. References to Schr?dinger’s cat have been featured in webcomics, images, YouTube videos, in poems, and T-shirts saying that “Schr?dinger’s cat is dead” (as some physicists like to joke). The popularity of the LOLcats meme, which depicts house cats in various cute or amusing poses, has also inspired humorous depictions of Schr?dinger’s cat, with many images of cats in cardboard boxes serving as a chance to reference the famous theory. For example, there is an image of a cat angrily clawing its way out of a cardboard box, with the caption “Schr?dinger’s cat is alive … and very pissed off.”