xkcd.WTF!?

Explanation ➲

In this comic, Randall is cooking a recipe found online. It took him much longer than the recipe said it would, and he concludes that this was due to time dilation as described in the theory of special relativity; that is, the recipe author was moving at 94% of the speed of light, causing relativistic effects, so that only 35 minutes passed for the author while 105 minutes passed for Randall. To calculate the 94% figure, he takes the recipe’s official duration (t’) and his actual duration (t), and then calculates what speed of light fraction would account for the cooking time difference.

This is absurd^{[citation needed]} and therefore humorous primarily because the most likely cause of the difference in time is that Randall is less skilled in making the recipe than its author, rather than relativistic effects. The recipe author would report the time in their own frame of reference, not Randall's, no matter what the difference in motion between the two.

Randall is poking fun at online recipes that state an optimistic cooking time. The recipe author may assume an ideally equipped kitchen, a skilled chef, and the availability of prepared ingredients, such as canned or frozen cooked black beans instead of dried beans which take over an hour to soak and cook.[1]

The title text takes the relativistic theory even further, saying that because of Lorentz contraction caused by the recipe author moving close to the speed of light, Randall should use different sizes of ingredients. If the recipe author calling for 1/4" onion slices is indeed traveling at 94% of the speed of light relative to Randall, he wonders whether his onions should be cut to 3/4" slices to match their size in his frame of reference. This is similarly absurd and therefore humorous.