Megameter
A megameter (Mm) is a unit of length in the metric system, equal to 1 million meters (1 Mm = 10⁶ meters or 1,000 kilometers). Megameters are used to measure very large distances, typically on a global or planetary scale. For example, the Earth’s diameter is about 12.7 megameters. Although it’s a valid metric unit, the megameter is rarely used in everyday life or science, as kilometers or other astronomical units are more common for such distances.
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.