xkcd.WTF!?

Explanation ➲

This comic is a joke creating a humorously false synthesis, combining the principles of quantum superposition and the effects of reading a comic one panel at a time. Schrödinger's cat is a thought experiment that illuminates the notion that a particle only resolves itself to its state upon observation, and until such observation is made, it is in all of its possible states simultaneously. In the thought experiment, a cat is both dead and alive until observation; likewise, in this comic, Black Hat and Cueball are likening the last panel to the box with the cat: until you read it, it is in a mixed state (a superposition) of both funny and unfunny. Finally, in the last panel, both of them say "Shit." The joke is that after reading the last panel, the comic is both funny (as it is unexpected) and not funny (as the last line was a non sequitur and therefore there is no climax) at the same time, thus proving Black Hat and Cueball wrong, hence them expressing discontent with the word "shit."

The title text, which Randall here unusually calls "alt-text", implies that it might only come into existence when the mouse over action takes place. This is another reference to the Schrödinger's cat concept, where the user can't determine if the title text exists until they hover the mouse over it. So, prior to hovering, the title text might be absent or present.

Schrödinger's cat

Schrödinger's cat is a famous thought experiment proposed by Erwin Schrödinger to question the Copenhagen interpretation of quantum mechanics. Under the Copenhagen interpretation, any particle is described by a wave function that allows one to calculate the probability that it is any given state. A radioactive nucleus with a half-life of one hour, for instance, would have a wave-function that would split, showing two distinct states (decayed, undecayed) that change over time until some "observation" forced the wave-function into one state or another (called "collapsing the wave-function"). Before the wave-function is collapsed, it is incorrect to say that the atom has decayed or has not decayed; it is in a "superposition" of states, effectively both decayed and undecayed.

Schrödinger thought that the Copenhagen interpretation was absurd and devised a thought experiment to demonstrate it. The experiment consisted in putting a cat in a box with a device triggered by the decay of an atom with a half-life of one hour that would release a poisonous gas if triggered. Then, after waiting an hour, the Copenhagen interpretation would say that the atom is in a superposition of decayed and undecayed states, and thus, by extension, the cat would be in a superposition of alive and dead states. Only when the box is opened would the wave-function for the cat collapse into either alive or dead states. This thought experiment is not meant to be taken literally, as every interaction of a particle with another constitutes an observation, and many particles must interact for a cat to die, but still his argument was that since it is absurd for a cat to be both alive and dead, it is absurd for an atom to be both decayed and undecayed. If this experiment were to be performed, the cat would not be both dead and alive.