What a consonant set of options to choose from today. I went with these two because we all know alliteration is the best literary device.

A yard is, by definition, exactly three feet. (That’s about a meter, more or less.) But “exactly three feet” is only helpful if you know how long a foot is, which historically wasn’t a given. So people would estimate a yard as the distance from their nose to their outstretched fingertips. (Of course, this meant different people had different “yards”, but generally they’d be close enough—unless you were buying from a giant. Then: Bonanza.) (Self-promotion time: If you’re really into units and measurements, I’ve scripted a number of videos about them.)

For me, one of the most interesting parts of all this is that, subjectively, stretching out an arm feels like pushing a hand away from our body—even though that’s not what happens. Our muscles can’t push on our bones; they can only pull on them. When you extend your arm, muscles in the back of your arm (your triceps) pull your forearm toward your elbow, swinging your hand away from your body as a result.

There’s a similar (for a very specific idea of “similar”) misconception that surrounds sails. People think they’re pushed by the wind (like bouncy castles), but that’s only true sometimes. If it were the only option, sailboats wouldn’t be able to go anywhere but downwind. To go upwind, though, sails act more like wings than anything else, propelling the ship below along more through lift than direct wind-on-sail impact. Sails are wings turned on their sides.

Skirting around the mechanics of lift for the second post in a row, this was just as true for the ships of the Spanish Armada as it is for today’s yachts.

At least, as long as those yachts have sails instead of motors. But motors are a story for another time, too.