Nautical League
A nautical league is a unit of distance once used at sea, mainly by sailors and navigators. It equals 3 nautical miles, which is about 5.56 kilometers or 3.45 miles. Nautical leagues were used to measure longer distances during voyages before modern navigation tools became common. While the nautical mile is still widely used today in maritime and aviation navigation, the nautical league is mostly obsolete and rarely used.
X-unit
The X-unit (symbol: xu) is a very small unit of length used primarily to measure wavelengths of X-rays and gamma rays. It was introduced in the early 20th century for precision measurements in X-ray crystallography.
1 X-unit ≈ 0.1 picometers (pm) or 10⁻¹³ meters
It allows scientists to express extremely small wavelengths typical of X-rays, which are on the order of atomic spacing
The exact definition has varied historically, but the unit remains useful for comparing wavelengths in X-ray spectroscopy and crystallography
Though largely replaced by the picometer or ångström in modern usage, the X-unit played a crucial role in early developments of atomic-scale measurement.
No conversions available for length.