I spent the afternoon of New Year's Day pleasantly with my friend Katie and her five-year-old, Quinn, at Lawrence Hall of Science. I'd never visited before, though Quinn was an old regular there.
I spotted the shirt below in the gift shop.
I don't recognize the equation, though I can hear C.P. Snow roaring in my ear, Have you read a work of Shakespeare's?.
The humor of the shirt lies in the deformation of a set linguistic phrase, in this case, the faintly aggressive "What part of [X] don't you understand?" In its usual context, X is something very simple, such as "no." Ideally, it's something that doesn't have parts in the first place. This makes the question rhetorical: there's nothing to debate, because X is so very self-evident. If you understand X, as you must, then the conversation is finished.
The phrase is aggressive because it suggests that the reader/listener must be very stupid to have disagreed with the speaker; it suggests that such disagreement can only result from an inability to understand some part of the very simple X.
The phrase on the shirt deforms the template phrase by making X something visually complicated, with many parts. The humor turns precisely on our receiving the equation as complicated, difficult to understand. But it retains the aggressivity of the original template phrase, even as it undercuts itself. You must be very stupid not to understand X, which I am positioning as not at all simple; that is, you must be very stupid relative to me.
Indeed, we are not meant to be able to understand the equation, or even see it: unlike the template into which it is inserted, X is here rendered in small close-set type. It is the aggressive template that is emphasized by the shirt's typography; of the equation, we are only meant to catch enough of a glimpse to see that it is complicated and contains line integrals. It doesn't matter whether the reader can see or read the equation; it's assumed up front that the reader wouldn't understand it anyway.
The wearer of the shirt thereby lays claim to membership in a contemptuous literati, whose aggressivity is both incited and justified by the difference between the wearer's ability to understand X and reader's presumed, typographically enforced, and culpable inability to understand it.
This is one popular understanding of what it means to be a scientist.