Marshall Brain
Hi, I’m Marshall Brain with today’s question – What is a nautical mile and what is a knot, and how do they differ from normal miles and kilometers? A nautical mile is based on the circumference of the planet Earth. If you were to take the Earth and cut it in half at the equator, you could pick up one of the halves and look at the equator as a circle. You could divide that circle into 360 degrees. You could then divide a degree into 60 minutes. A minute of arc on planet Earth is one nautical mile. This unit of measurement is used by all nations for air and sea travel.
A knot is a unit to measure speed. If you are traveling at a speed of one nautical mile per hour, you’re said to be traveling at a speed of one knot. A kilometer is also defined using the planet Earth as a standard of distance. If you were to take the Earth and cut it in half along a line passing from the North Pole through Paris, and then measure the distance of the curve running from the North Pole to the equator of that circle, and then divide that distance by 10,000, you would have the traditional unit for the kilometer as defined in 1791 by the French Academy of Sciences.
A nautical mile is therefore 1,852 meters or 1.852 kilometers. In the English measurement system, a nautical mile is 1.15 miles or 6,076 feet. To travel around the Earth at the equator, you would have to travel 21,600 nautical miles, which is 360 times 60, or you’d have to travel 24,857 normal miles, or you’d have to travel 40,003 kilometers. Do you have any ideas or suggestions for this podcast? If so, please send me an email at Podcast@HowStuffWorks.com.
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