Astronomical Units Content from the guide to life, the universe and everything

Astronomical Units

8 Conversations

Simply stated, an astronomical unit is the mean distance1 between the Earth and the Sun.

For those of you keeping score, that's about 1.49×1011m, or 149,000,000,000 metres.

The Astronomical Unit (AU) is what is known as a Natural Unit. It is a relic of the ancient days of astronomy when no one had any absolute measurements to any other object in the solar system. In those times everything was measured with relative units (eg Mars is 1.5 times farther from the Sun than the Earth is) and later, when absolute measurements were deciphered, no one wanted to give up this unit.

This unit is useful to get a sense of scale for distances that are tough to comprehend. Can you really imagine 1.49×1011m? Thought not. Neither can astronomers.

1Despite the illustration, the Astronomical Unit is actually measured from the centre of the Earth to the centre of the Sun.

Bookmark on your Personal Space


Edited Entry

A201790

Infinite Improbability Drive

Infinite Improbability Drive

Read a random Edited Entry

Categorised In:


Written by

Edited by

h2g2 Editors

Write an Entry

"The Hitchhiker's Guide to the Galaxy is a wholly remarkable book. It has been compiled and recompiled many times and under many different editorships. It contains contributions from countless numbers of travellers and researchers."

Write an entry
Read more