My little sister is blonde, beautiful, and has a big brain. Theresa has a degree in mathematics, and formerly worked on the Mathematica program for Wolfram Research, and as a result, often speaks light years over my head.
Years ago, I heard a report on NPR about parabolas, and the report went on to say that the world's best known parabola is our St. Louis Arch. Impressed with my little math fun fact, I ran it by Theresa. As usual, she was able to correct me by stating the Arch was not a parabola, but a catenary curve. She described this by saying to think of it as the chain of a necklace. If you were to take the chain, and form a dip with the gravity, this would be catenarious (ironically, the Latin word for chain). A hanging chain carrying only it's own weight is a catenary curve. However, if you were to hang a pendant on the chain, or use the curve to suspend something heavy, like a suspension bridge, it would then become parabolic. Even still, our Arch is not a true catenary, as it is thicker at the base, and thinner at the apex. So it's really more of an approximate of a catenary.
Sure enough, a couple of weeks after the broadcast that I heard, NPR had "The Math Guy" on to correct their original report. He stated everything my sister said, and then went on to state that even Galileo got this incorrect. The parabolic equation is y2=ax2a, whereas a catenary equation is much more complicated, and would require calculus; something that had not even been invented in Galileo's time, and a class I have yet to take. So, he and I were both sadly incorrect. But how totally cool is it that I have something in common with Galileo?
Wednesday, May 19, 2010
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Hey Sweet Lady...you're behind on your blog. I miss reading your posts! Hope you're doing great.
ReplyDeleteLove and prayers ~ Leigh