The astronomical unit is defined as the average distance between which objects?

The astronomical unit is defined as the average distance between which objects?

• A. The distance light travels in a year
• B. The distance between Earth and the Moon
• C. The distance between Earth and Mars
• D. The average distance between the Sun and Earth

Answer: (D)

An astronomical unit is a unit of length used to express distances within our solar system, tied to the Earth’s orbit around the Sun. Because Earth's orbit is an ellipse, the distance to the Sun varies over the year. The AU is defined as that average distance, essentially the semi-major axis of Earth's orbit. In numbers, it’s about 149.6 million kilometers (roughly 93 million miles). This provides a convenient scale for comparing planetary distances. The other options aren’t used as the AU: a light-year is the distance light travels in a year and is far larger; the Earth–Moon distance is a specific, much smaller value; the Earth–Mars distance changes a lot with orbital positions and isn’t a fixed unit.

An astronomical unit is a unit of length used to express distances within our solar system, tied to the Earth’s orbit around the Sun. Because Earth's orbit is an ellipse, the distance to the Sun varies over the year. The AU is defined as that average distance, essentially the semi-major axis of Earth's orbit. In numbers, it’s about 149.6 million kilometers (roughly 93 million miles). This provides a convenient scale for comparing planetary distances.

The other options aren’t used as the AU: a light-year is the distance light travels in a year and is far larger; the Earth–Moon distance is a specific, much smaller value; the Earth–Mars distance changes a lot with orbital positions and isn’t a fixed unit.