11 January 2011

Things I learned recently

Handmade paper does not have a grain. The fibers stretch out in random directions. But factory-made paper uses a process where water flows across the surface of the paper as it forms. Take any sheet of printer paper and you'll find that you can curl up the long vertical edge over using less force than the shorter horizontal edge. Even though you're bending more paper the long way, you're bending fewer of the paper's fibers by going with the grain.

According to the Wikipedia article on shmoon, “The word ‘shmoo’ has appeared in nearly 700 science publications since 1974; it is used in labs studying the bread-and beer-making species Saccharomyces cerevisiae.”

The geoid is the shape of the mean sea level of the earth. It is not an ellipsoid. Gravitational forces due to variations in the earth's density subtly distort the geoid. This is why a GPS device can tell you you're 20 meters underwater when you're at the beach: GPS measures your altitude above a reference ellipsoid, not the true geoid. The difference can be much greater in magnitude than the tides.

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