The following information appeared on the NASA website in regards to its tracking of Cyclone Yasi which was at the time off the coast of Queensland. "It was centered about 1,400 kilometers (875 miles) east of Cairns, Australia, moving west at about 19 knots per hour (35 kilometers per hour, or 22 mph). Cyclone-force winds extend out to 48 kilometers (30 miles) from the center." Spot the error.

davejacobs

A knot is a unit of velocity. Knots per hour is an acceleration, but plainly that was not what they meant. http://en.wikipedia.org/wiki/Knot_(unit) Feb 02 11, 6:15 PM

gtho4

"knots" is not a measure of distance, it is a measure of speed The device that sailors used to make their speed measurement was called the "chip log." Chip as in chip of wood, and log as in to record in a log. The chip was a wedge of wood about 18" in size; it was tied to one end of a rope on a large spool. The rope had knots tied into it about every 47'3" (more about how that was calibrated below). The wooden chip was thrown overboard at the ship's stern (back end). Because of its wedge shape, it would "grab" the water and start pulling out rope as the ship moved forward at some yet unknown speed. One man would hold the spool of rope as it played out; another man would start a sandglass filled with 30 seconds of sand; and a third man would count the knots as they passed over the stern board. When the 30 seconds of sand expired, the time keeper would call out and the counting of knots would stop. The faster the ship was sailing, more knots and a longer length of rope were played out. The number of knots in the rope that were counted in 30 seconds, then, was equal to the speed of the ship in nautical miles per hour. A "knot", therefore, is not a nautical mile, it is a nautical mile per hour. Thus 1 knot was equivalent to 1 nautical mile per hour; 5 knots were equivalent to 5 nautical miles per hour; etc. The similar sound of "knot" and "naut" is entirely coincidental. http://www.onlineconversion.com/faq_07.htm Feb 02 11, 6:21 PM