Brooks (brooksmoses) wrote,

Book Meme

This one's come around again (via umprof), only mutated rather a bit from the original -- now it's wanting a blue book, and a full paragraph. The rules this time:
1. Grab the nearest book with a blue cover.
2. Open the book to page 86.
3. Find the first full paragraph.
4. Post the text in your journal along with these instructions.
5. Don't search around and look for the coolest book you can find, just the closest blue book.
In my case, I didn't have to cheat -- I knew what blue book I was hoping to find when I turned around, and indeed it was the closest (though I had to pass over a couple of dark navy books as being insufficiently blue): The Wonder Book of the Air, by Allen and Lyman, from 1936. It's an "everything a boy would want to know about airplanes" book, and thus a quite delightful view of what flying in the late 1930s was like -- including a whole chapter on a typical flight from New York to San Francisco.

For instance, one of the things I'd never really thought about was what an "airway" was, back before modern air traffic control. In 1936, it was a physical and tangible pathway -- a chain of small airports, spaced 30 to 50 miles apart, stretching from (for example) Chicago to San Francisco, with revolving light beacons every 10 to 20 miles, so that a nighttime flight was possible simply by flying from beacon to beacon all the way across the country.

In any case, page 86 starts off the chapter on "Why an Airplane Flies", which is usually one of my pop-science pet peeves. The common explanation invokes Bernoulli's law, which although perfectly applicable is somewhat complicated and doesn't really move towards something more obvious, and it ignores Newton's lawsthat would provide the obvious explanation of "the airplane gets lift because the wings push air down". This book, however, takes a quite different approach. The initial paragraph, which is the one to quote according to the rules of the meme, is:
Every boy knows that if a flat stone is skipped across the water, it will go quite a distance before it finally loses speed and falls to the bottom. If there were only some way of keeping up its momentum, the stone could be made to go on indefinitely without sinking, just as a surfboard bearing a man's weight may be kept on top of the water as long as a speedboat has it in tow.
The book then goes on to talk about this, but in a manner that doesn't reference physical laws at all in any obvious way. Air is a substance, just like water, only much less dense. And so in much the same way, an airplane that's heavier than air can keep aloft in air, just as a stone can stay on top of the water, but only if it keeps moving. The book then describes taking a paper fan, and moving it through the air, and feeling how it gets lift if one inclines it a bit while moving it. It's a very experiential sort of explanation, which relates the effect to everyday experiences and things that one can directly feel and touch and play with, and so it feels like a quite complete explanation even though it never mentions reactions or Newton or Bernoulli at all. There's probably an important lesson in there, that I often forget when trying to explain the physics of the things that I'm working on.

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