Because sailors in the 15th century did not have GPS ......
Adventures and history books are full of tragic stories of sailboats capsizing at sea, stories of sailors running low on food and fresh water, dying of scurvy, getting stranded, or stranded in the tropics during storm season. Unless the sailors knew how fast they were sailing, they could be a few days later than planned, endangering those on board and worrying their loved ones waiting for them in port.
With no landmarks to measure their progress on the high seas, sailors could not judge the speed and distance of their voyage. However, when the nautical mile (1852 km) was introduced in the 15th century, they had a convenient standard for measuring speed and, as needed, created a log, the world's first offshore speedometer. "They use the materials they have at hand," she explains. "A wedge of wood, a small glass timer, and a very long rope. ”
But not just any rope will do. Depending on the length of the nautical mile, every 144 meters to tie a knot. One end is fixed to the stern and the other end to the plank, which is then lowered into the water. "As a sailor watched through the glass for 30 seconds as the sand emptied, his shipmate pulled the rope behind the boat and counted the knots of the rope passing between his fingers," Caballero said. Will 14Divide 4 meters by 30 seconds, and they learn that a section is equal to 185166 km/h or one nautical mile.
By calculating by using the number of knots actually released, the sailors were able to measure the speed of the boat.
Frequently measured averages throughout the day have proven to be highly accurate reflections of the speed at which the ship is moving. This data was used to help them navigate by dead reckoning, a method used before the advent of modern instruments.
Nowadays, speed at sea is determined by ultrasonic sensors or Doppler measurements, and the 30-second divisor in the rate equation has been replaced by 28. But the instruments used to measure the speed of ships are still called logs, and sea and aviation distances are still measured in nautical miles.
Maps used at sea and in the air are based on the circumference of the Earth, and their size varies with latitude, and nautical miles, which are about 500 feet longer than land miles, can reconcile these differences.
In today's wheelhouses and cockpits, speeds equal to one knots per hour are still called, a term that echoes echoes the echoes of the times when the crews of square booms and caravans were creative with a few simple materials and crafted a basic and important gadget.
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