It can be quite difficult to comprehend the vast distances between planets in the solar system. To help make these distances more intuitive and easier to work with, scientists often use a unit of length called the astronomical unit, which is equal to the average distance between Earth and the Sun. The astronomical unit (au) describes solar system distances more conveniently than using numbers that are in the millions or billions.
For example, instead of saying Mars is about 228,000,000 kilometers (142 million miles) away from the Sun, the distance can be described as 1.5 au—about 1.5 times the distance between Earth and the Sun.
Video: Measuring Distance in the Solar System
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
Watch the video on the left about the use of astronomical units.
Do astronomical units help make the size of the solar system more understandable for you? Explain why or why not in the notes box below.