I’m back home from my brief travels, and I returned to find the latest outbreak of quantum woo infection, followed immediately by a heap of silliness about anthropic twaddle.

“Too soon,” I thought. “I need to go back on vacation.”

So, instead of complaining at great length about things I’ve already complained about, I’ll just share one quick observation and then head out into the outside world, shopping for art supplies.

Yesterday, I flew into Boston. In my laptop I carried a hardback of Lois Lowry‘s *The Giver* (1993) and, to recapture a more innocent time, Feynman and Weinberg’s *Elementary Particles and the Laws of Physics* (1987). In between reading these two, I happened to glance at the pamphlet-type thing which the airline clerk had given me to hold my boarding passes in. Here’s the puzzling part, under the “Free Baggage Allowance” heading:

**Carry-on Baggage** is limited to one piece per passenger, plus a personal item such as a purse, briefcase or laptop computer. The carry-on cannot exceed 51 inches (11″ × 14″ × 26″) and must fit under the seat or in an overhead compartment.

Why are the three linear dimensions *added*? The frame device the airline positions at each gate for testing whether or not your carry-on will fit rejects your baggage if *any* dimension exceeds the threshold set. Your baggage is deemed invalid even if the total volume is *less* than 11″ × 14″ × 26″ = 4004 in^{3} (just try carrying on something long and skinny). The longest diagonal of an 11″ × 14″ × 26″ box is

[tex]\sqrt{14^2 + 26^2} \approx 29.5[/tex]

inches long. So, you can have a carry-on item the sum of whose edge lengths is, say, thirty-one inches, and which won’t fit the *actual* airline restrictions no matter how you try to wedge it in sideways. The sum of the height, width and depth is a meaningless number.