QUESTION: Why can some sailboats go faster than the speed of the wind?
ANSWER: We usually like to ask questions that you've always wondered about, and sometimes we like to ask questions that you've never wondered about but should have wondered about, but today we're in short supply of both so we'll ask you a question that you've never wondered about, needn't wonder about, and probably might even refuse to wonder about on the grounds that you don't think the predicate is true. But it is. Some sailboats go faster than the wind.This is because a sail, when full of air, functions like an airplane wing.
Which also explains why sailboats go fastest at an angle to the wind, not directly with the wind.
Let's say the wind is blowing north. We aim our sleek yacht northwest. As the sail billows out, it takes on a curved shape. Air molecules passing from the front to the back of the boat are forced to take either the long voyage around the outer convex surface of the sail, or the shorter trip along the inside.
Either way, the air molecules arrive at the back of the boat at the same time, but the ones on the outside have to go faster to get there. Faster air is thinner air, and thinner air means less pressure on the sail. A suction effect takes place, with the sail pulled, or lifted, toward the northwest. There's your extra speed.
This is discussed in a book called "Rainbows, Curve Balls and Other Wonders of the Natural World Explained," by Ira Flatow, part of the burgeoning Infotainment market.
We have often wondered, "Why are trees able to suck water from their roots, against the force of gravity, even though they don't have moving parts?" and Flatow gives the answer. Water molecules are shaped in such a way that they bind to each other like magnets, and form long, one-molecule-wide chains that extend from the roots up through the narrow veins, or capillaries, of the tree, all the way to the leaves. As a molecule of water evaporates from a leaf, it pulls up the rest of the chain. The tree doesn't need moving parts, because water does all the work.
Water, frankly, is a little weird, and to that we owe our lives. It has physical properties unlike other elements with similar chemical structures. For example, most substances grow denser when they freeze. Water grows denser only until it drops down to 39 degrees, at which point it starts to expand, even when it freezes. This is why ice cubes swell up in their trays, and why ice floats on liquid water.
It is also why the ice forming at the surfaces of rivers and lakes doesn't sink to the bottom and gradually freeze them solid, which would have dire consequences for the biosphere. Water also maintains a liquid state at unusually high temperatures, conveniently in the same range as is commonly found at the surface of our planet. And the aforementioned magnetism allows water to pull apart the atoms from almost every substance it encounters, which is why water is called the universal solvent, and why we're made almost entirely of water. Though why we don't sink to the floor in a runny blob, we haven't figured out yet.
We just received the latest edition of The Food Insects Newsletter, put out by the University of Wisconsin. You may remember that recently we explained why humans don't eat bugs, and it had something to do with cultural prejudice.
But the real problem was that we lacked decent recipes, and The Food Insects Newsletter is helping to solve that with the instructions for a lip-smacking dish called Crispy Cajun Crickets: "To prepare, place 1 cup of healthy Cajun Crickets into a large, clean and airy container (add a pinch of oatmeal for food). After 1 day, remove sick crickets and freeze the remainder. Wash frozen crickets in tap water, spread on cookie sheet and roast in oven at lowest setting. When crickets become crunchy, sprinkle them with butter sauce and serve . . . Mmmmm - Good."
The newsletter claims this will be "a tasty and unique addition to any social occasion, with a crunchy-tangy flavor all their own."
Send questions to Joel Achenbach, Tropic Magazine, The Miami Herald, 1 Herald Plaza, Miami, FL 33132.
The Why Things Are column is happy to receive questions, complaints, arguments, accolades, briefcases stuffed with cash, lunar eclipse tables, solutions to complex mathematical formulae, anatomically correct dolls, cake recipes, and so on. But, please, nothing weird. Write to Why Things Are, c/o Tropic Magazine, 1 Herald Plaza, Miami FL 33132.)