Welcome to brain Stuff past him Marshall Brain. On the news, you'll often hear people, especially boat and airplane people, talking about nautical miles. Have you ever wondered why there's more than one kind of mile? A normal mile is five thousand, two d eight feet, and that's a totally random unit of measurement. A nautical mile is instead based on the size of the Earth. If you take the circle of the Earth at the equator, you can divide that circle
into three hundred sixty degrees. You could then divide each degree into sixty minutes. A nautical mile is a minute of the Earth's arc. If you travel one degree around the Earth, you've traveled sixty nautical miles. Three hundred sixty times sixty is one thousand, six hundred, so it's twenty one thousand, six hundred nautical miles around the planet. Coincidentally, a kilometer is also based on the planet Earth. Take the distance from the north pole to the equator, divide
that by ten thousand, and you have a kilometer. For more on this and thousands of other topics, go to how stuff works dot com. M