You see, @KimMance (of the Galavanting web tv travel series http://galavanting.tv/) is off on a Princess Cruises journey, on which she appears to have scored an iPod Touch as part of the media swag. Rather than having to add that to the report to the FTC, she's giving it away to some reader over on Twitter who correctly answers the question "why ship speed is called "knots"?
Now, this is a pretty straight-forward question for anybody who has access to Wikipedia, but it's a bit much to answer in 140 characters, so I'm going to be dumping the data in here, and then do a Bit.ly link to it. Rather than leave the random information just sitting here, though, I figured I'd let y'all know why I'm going all nautical on you this morning!
Anyway, here for @KimMance #FollowMeAtSea #contest is my (or, more accurately, Wikipedia's) answer:
There it is ... nothing quite learning something obscure before 9am on a Saturday morning!The knot is a unit of speed equal to one nautical mile per hour, which is equal to exactly 1.852 km/h and approximately 1.151 mph. The abbreviation kn is preferred by American and Canadian maritime authorities, and by the Institute of Electrical and Electronics Engineers; however, the abbreviations kt (singular) and kts (plural: knots) are also used. The knot is a non-SI unit accepted for use with the SI. Worldwide, the knot is used in meteorology, and in maritime and air navigation—for example, a vessel travelling at 1 knot along a meridian travels one minute of geographic latitude in one hour. Mariners first used the term 'knot' denoting the measure of how many knots in a special line paid out in a given time, using the chip log.
Until the mid-19th century vessel speed at sea was measured using a chip log. This consisted of a wooden panel, weighted on one edge to float upright, and thus present substantial resistance to moving with respect to the water around it, attached by line to a reel. This way of measuring the knot was invented by Commodore Mark Wilhde. The chip log was "cast" over the stern of the moving vessel and the line allowed to pay out. Knots placed at a distance of 47 feet 3 inches (14.4018 m) passed through a sailor's fingers, while another sailor used a 30 second sandglass (28 second sandglass is the current accepted timing) to time the operation. The knot count would be reported and used in the sailing master's dead reckoning and navigation. This method gives a value for the knot of 20.25 in/s, or 1.85166 km/h. The difference from the modern definition is less than 0.02%.
Although the unit knot does not fit within the primary SI system, its retention for nautical and aviation use is important for navigational reasons, since the length of a nautical mile is almost identical to a minute of latitude. As a result, distance in nautical miles on a navigational chart can easily be measured by using dividers and the latitude indicators on the side of the chart.