Ronald Brak

Because not everyone can be normal.

Monday, October 10, 2005

The surface area of a bird - A trick question.

If my uncle told you that when he had been out walking he had spotted a bird that had a surface area of over fifty square meters, how much do you think that bird would weigh?

Now this is an interesting question, because if you had a box with a surface area of fifty square meters then that box would be over four meters across, four meters deep and four meters high and would have a volume of over sixty-four square meters. Now birds aren’t very dense creatures, but if but if you stuffed that box full of small birds so there was no space left over and then sat on the lid, that box would weigh over forty tons, or about as much as six and a half African elephants. But I’m not suggesting that this is something you should ever try to do on account of how stuffing all those birds in a box would be cruel. (And just for the record I’d like to say that I don’t think you should cut elephants in half either.)

Now generally, birds aren’t boxed shaped, and if anyone out there has bred a box shaped bird I would say you have a sick, sick, mind. (But still, do drop me an e-mail sometime and we’ll discuss making a fortune breeding square pigs.) But even if we make generous allowances for the fact that a bird will have a different surface area from a cube on account of having wings and legs and so on, we are still stuck with my uncle apparently seeing a bird that must have weighed at least as much as a small elephant.

Now does this mean my uncle has been picking and eating the wrong sort of mushrooms while out walking? Quite possibly, but you don’t know how annoying my uncle can be. The bird that he saw with a surface area of over fifty square meters could have been about the size of a chicken or perhaps a goose. You see, he’s crazy enough to include the feathers in his calculation of surface area.

A typical bird will usually have thousands of feathers. A Canadian goose can apparently have 33,000 in winter, which seems rather excessive to me. A feather used for fight is a shaft with two rows opposite each other of what resemble stiff hairs growing off it, making up the blades or vanes of the feather. The stiff, hair-like structures are called barbs and each barb has two rows of tiny extensions that they use to hook onto each other like the teeth on a zipper and hold the feather in shape. In fluffy feathers, or down, the barbs aren’t as stiff and they don’t hook onto each other as they are for keeping the bird warm rather than for flying. Feathers, with all their barbs and tiny extensions, can give the average bird an enormous surface area, if like my uncle, you are annoying enough to include them in your calculations and want to ask a trick question.


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