Why is the light from the moon called cool light and the light from the sun called hot light?

The moon does not produce its light; rather, it reflects the light coming from the sun. In contrast, the sun produces its light through nuclear fusion and emits it in the form of electromagnetic radiation, including visible light.

Sunlight consists of a broad range of electromagnetic waves, from ultraviolet (UV) to infrared (IR) light, including the full spectrum of visible light. Meanwhile, moonlight is just the sunlight that is reflected from the moon's surface, filtered, and partially absorbed so that it loses some energy and has less intense radiation.

The energy of the light can be related to its temperature. Higher energy light waves mean increased temperatures and vice versa. Since the sun's light has a higher energy level than the moon’s light, sunlight is said to be hot light as it can increase the temperature of the objects it falls upon, while moonlight is referred to as cool light since it has lower levels of energy and doesn't affect the temperature as much.

The human body is sensitive to temperature, and, as a result, we perceive sunlight as hotter and more intense than moonlight. The heat we experience from direct sunlight is absent in moonlight, even though both types of light are still coming from the same source and are essentially the same kind of electromagnetic radiation. The difference lies in the intensity and the levels of energy, leading to our perception of sunlight as hot and moonlight as cool. In conclusion, the light from the moon is called cool light because it reflects sunlight with lower energy levels, and it does not cause the same increase in temperature as direct sunlight. On the other hand, the light from the sun is called hot light because it has higher energy levels and can cause a noticeable increase in temperature upon objects it falls upon.