Question

Both moon and earth are the same distance away from the sun. Then why the temperature variation is moderate on earth but violent on the moon?

Answer 1

Temperature variation:

1. Most of the sun's radiation is absorbed by the heat-trapping greenhouse gases and some of them are reflected by the earth and the atmosphere.
2. Some infrared radiation is absorbed and re-emitted in all directions by greenhouse gas molecules, while others pass through the atmosphere. This has the effect of warming the earth's surface and lowering the temperature.
3. But in the case of the moon, there is no atmosphere so the sun's energy directly affects the moon, as a result, the temperature variation is very violent there. For example, $-200°\mathrm{C}$ to $120°\mathrm{C}$.

Therefore, the temperature variation is moderate on earth because of the atmosphere.