2012-07-21
Explanation
This comic shows a teacher standing in front of a class saying: "How do I remember? I just look at my hand, and there's five fingers, and that's about the value of pi." The caption below reads: "Physics professors shouldn't teach geometry."
The joke plays on the stereotype that physicists are notoriously cavalier about mathematical precision compared to mathematicians. The actual value of pi is approximately 3.14159, but the teacher is rounding it to 5 -- the number of fingers on a hand. This is an absurd exaggeration of the well-known physics joke that "pi equals 3" (or sometimes "pi equals 1" for order-of-magnitude estimates). In physics, approximations are common and often acceptable when exact values are unnecessary, but confusing pi with 5 takes this tendency to a ludicrous extreme. The mnemonic device the teacher uses -- counting fingers -- is also a parody of the kinds of memory tricks teachers share, except this one gives a value that is off by nearly 60%.