Which of the following best defines an astronomical unit ($au$)?

• A. The average distance between the Earth and the Sun, approximately $1.496\times {10}^{11}m$
• B. The distance from the Earth to the Moon
• C. The distance light travels in one year
• D. The radius of the Earth

Answer: (A)

Verified step by step guidance

1. Understand that an astronomical unit (AU) is a unit of length used primarily to measure distances within our solar system.
2. Recall that the AU is defined based on the average distance between the Earth and the Sun, which provides a convenient scale for planetary distances.
3. Recognize that the average Earth-Sun distance is approximately \$1.496 \times 10^{11}$ meters.
4. Compare this definition with other distance measures such as the Earth-Moon distance, the light-year, and Earth's radius to see which matches the AU.
5. Conclude that the astronomical unit is best defined as the average distance between the Earth and the Sun, approximately \$1.496 \times 10^{11}$ meters.