According to the Theory of Special Relativity, time slows down at extremely high speeds.

I’m sitting outside Penny Black’s pub on Boat Quay, looking at a sign that says “Happy Hour: 11:30am to 8pm”. Assuming that the sign is accurate, how fast is Penny Blacks moving?

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Well, it doesn’t really make sense for them either way. Because no matter how fast the pub is moving, one hour will still be one hour for the people inside. However, if you want to know how fast they would have to go for one of their hours to take 8:30 of ours, I think the answer is 99.3% of the speed of light. That’s 298 million meters per second.

Ding ding ding, we have a winner.

(And yes, I probably should’ve been a bit more specific about whether we’re measuring the length of happy hour from the point of view of an observer inside or outside the pub. But that would’ve ruined the joke.)