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2. The Universe / General Astronomy
3. Everything / Maths, Science & Technology / Astronomy

Astronomical Units

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

For those of you keeping score, that's about 1.49x1013cm.

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 these 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 1.49x1013cm? Thought not. Neither can astronomers.


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Entry Data
Entry ID: A201790 (Edited)

Written and Researched by:
SetupWeasel

Edited by:
Orinoco


Date: 15   November   1999


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Referenced Guide Entries
Natural Units
Astronomy for Amateurs
Mars
What's the Point of Astronomy?
The Sun
Earth
An Amazing A-Z of Space


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