Fathom to Astronomical Unit Converter

A fathom is a unit of length primarily used for measuring the depth of water, equal to 6 feet or approximately 1.83 meters. It represents the span of a person's outstretched arms.

The fathom derives from the Old English 'fæthm' meaning 'outstretched arms' or 'embrace'. It was originally based on the distance between the fingertips of a person's outstretched arms, typically about 6 feet. It has been used for measuring water depth since ancient times.

Fathoms are still used in some maritime contexts for measuring water depth, particularly in traditional sailing and fishing communities. However, meters are increasingly preferred for official nautical charts and modern navigation systems.

An astronomical unit (AU) is a unit of length approximately equal to the average distance from Earth to the Sun, defined as exactly 149,597,870.7 kilometers or about 93 million miles.

The astronomical unit was originally defined as the semi-major axis of Earth's orbit around the Sun. It was first estimated by Giovanni Cassini in 1672 and has been refined over centuries. In 2012, the International Astronomical Union redefined it as an exact value rather than a measured quantity.

Astronomical units are primarily used for measuring distances within the solar system, including distances between planets, asteroids, and comets. They're standard in planetary science, space mission planning, and solar system astronomy.