Knots.
Discuss.
And I don't mean tying your shoelaces. Or tying up the body before disposal.
This is a good one :
Until the mid-19th century, vessel speed at sea was measured using a
chip log. This consisted of a wooden panel, attached by line to a reel, and weighted on one edge to float perpendicularly to the water surface and thus present substantial resistance to the water moving around it. The chip log was cast over the stern of the moving vessel and the line allowed to pay out.
[6] Knots tied at a distance of 47
feet 3
inches (14.4018 m) from each other, passed through a sailor's fingers, while another sailor used a 30-second
sand-glass (28-second sand-glass is the currently accepted timing) to time the operation.
[7] 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%.
Derivation of knots spacing:
, so in
seconds that is
metres per knot.
