Another "explain this xkcd strip" thread

That was my take on it, too.

The changing of the outlet is baffling. But notice in the third panel the whirring of the machine with ‘click’ is the exact opposite of it’s start-up indicating going back in time. Also, the character’s hands on on the bottom of the lever when it’s turned off rather than on top, indicating time reversal rather than willfully shutting it off.

Lesson: Don’t make a time machine that simply reverses the flow of time… it automatically shuts itself off.

Yeah, there are really subtle “action lines” in the third panel showing the switch being forced down. It’s just a “if you reverse time your time machine turns itself off” joke. The outlet changing is just a mistake, IMO.

Okay but if the punchline is “The trouble with time machines is that any change made in time will retroactively appear to be the way things always were so you’ll never the effects of a time machine” then it’s sort of funny in an ironic way.

But if the punchline is “The trouble with time machines is that they always turn themselves off” then I don’t see any humor here.

But the latter is more likely, since it is actually a funny take on a real phenomenon. If time travel is possible, it would be via wormhole, with one end being accelerated into the future, and thus there would be no way to go back to before the time machine was invented.

Plus the tooltip makes it quite clear that time is still running backwards, something that would not be happening if your first interpretation were correct.

A time machine can, however, cause you to accidentally a word.

ʇɥǝ oʇɥǝɹ dɹqoןǝɯ ʍıʇɥ ʇıɯǝ ɯɐɔɥıuǝs ıs ʇɥɐʇ ʎno,ןן ɹǝɐp ǝʌǝɹʎʇɥıuƃ ןıʞǝ ʇɥıs˙