Answers to Go with Susan Smith
SAN MARCOS PUBLIC LIBRARY 625 E. HOPKINS ST. 512-393-8200
Q. What is the origin of the word knot as used to describe speed at sea? How do knots compare to miles per hour?
A. According to the “World Book Encyclopedia,” a knot is a unit of speed used for ships and aircraft. It equals one nautical mile an hour. A ship with a 20- knot speed can travel 20 nautical miles in an hour.”
Is a nautical mile per hour the same as miles per hour used on land? Approximately. According to the National Ocean Service, a branch of the National Oceanic and Atmospheric Administration, a knot equals 1.151 miles per hour.
The “World Book” continues: “The international nautical mile equals one-sixtieth of one degree, or a minute of arc, of the earth’s circumference. Navigators use the nautical mile because of its simple relationship to the degrees and minutes by which latitude and longitude are measured. The international nautical mile equals exactly 1,852 kilometers or 6,076.115 international feet, or 1.151 statute miles.
“The term knot came into use in the earlier days of sailing, when ships carried a speed measuring device called a log chip and line. The line was wound up on a reel. The chip, a piece of wood, was allowed to drag in the water behind the ship. The chip caused the line to unreel as the ship moved. The line was knotted at intervals of 47 feet 3 inches (14.4 meters). At the end of the first interval was one knot. Two knots marked the end of the second, and so on.
“The line was allowed to run for 28 seconds. An interval of twenty-eight seconds is to one hour approximately what a distance of 47 feet 3 inches is to 6,076 feet. Therefore, if the log had pulled out 5 intervals of line in 28 seconds, the sailors knew the ship was moving at 5 knots, or 5 nautical miles an hour.”
Q. I know that strange things happen during tornadoes, but I’ve got a small wager that tornadoes do not actually drive straws into boards. Can you help me win my bet?
A. Not this time. I pulled out “Why Do Some Shoes Squeak? And 568 Other Popular Questions Answered,” a reference book by George W. Stimpson. Stimpson writes, “The
Stimpson writes, “The velocity of the wind in the whirl of a tornado is terrific. It sometimes attains a speed of more than 300 miles an hour. That such wind frequently drives quills, straws, and splinters into solid boards and tree trunks is well established.
“‘Straws,’ wrote the director of the U.S. Weather Bureau in 1925, ‘have been driven by tornadoes short distances into the bark of trees and in some cases into the surface of wooden boards.
“According to the National Geographic Society, tornadoes have been known to drive planks all the way through the trunks of trees. A tornado-like waterspout at Calcutta, India, once drove a bamboo cane completely through a wall faced on both sides with brick.
“These phenomena are no mystery to physical science. The velocity of a straw, splinter, or other small object may be so great that it will penetrate a harder body before it is crushed itself. It is the energy with which a body strikes another that determines its piercing effect.
“A small fast-moving object may possess far greater kinetic energy than a large slow-moving body. The straw hurled through space at a tremendous speed expends its kinetic energy in penetrating the harder object. This happens so quickly that the inertia of the straw prevents it from crumpling until it has penetrated some distance.”
If you would like more strange weather stories, I recommend a book by Randy Cerveny: “Freaks of the Storm: The World’s Strangest True Weather Stories: From Flying Cows to Stealing Thunder.”
