Megameter to Astronomical Unit Converter

A megameter (Mm) is a unit of length in the metric system equal to one million meters (10⁶ m). It is commonly used to measure very large distances, particularly in astronomy and geography.

The megameter was introduced as part of the metric system's decimal-based approach to measurement. The prefix 'mega-' comes from the Greek word 'megas' meaning 'great' or 'large', and was officially adopted in 1960 as part of the International System of Units (SI).

Megameters are primarily used in scientific contexts, particularly in astronomy for measuring distances between celestial bodies within our solar system, and in geography for measuring very large terrestrial distances such as the diameter of planets or the distance between continents.

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.