Why Can’t You See the Dark Side of the Moon in the Daytime?

During the daytime on Earth, we can only observe the side of the Moon that faces us, but a common misconception is that you cannot see the dark or far side of the Moon during daylight. This article aims to clarify why we can see at least some parts of the Moon's dark side when the Moon is not full, and why it is always facing away from us due to tidal locking.

Finding the Dark Side of the Moon

First, it’s important to distinguish between the 'dark side' of the Moon, which can be seen in phases other than a full Moon, and the far side of the Moon, which is always hidden from Earth. The term 'dark side' here refers to the unilluminated part of the Moon as viewed from Earth. This part appears faintly lit due to Earthshine when the Moon is not full.

If your query is about the far side of the Moon, the answer lies in tidal locking. The Moon's rotation period is synchronized with its orbital period around the Earth, meaning it always shows the same face to us. Therefore, the far side of the Moon is always turned away from Earth. However, if you look closely, you can see at least some of the dark side during any phase except a full Moon.

Observing the Dark Side

When the Moon is not full, parts of its unlit side can be seen by the faint reflection of sunlight off the Earth, a phenomenon known as Earthshine. This occurs because the illuminated part of the Moon reflects enough light back towards Earth to light up the dark side, making it faintly visible but not completely dark. The visibility of these parts depends on the Moon's position in its orbit and the angle of sunlight illumination.

Phases of the Moon

The Moon's phases are a result of its position relative to the Sun and Earth. As the Moon orbits the Earth, different portions of its surface appear illuminated by the Sun. When the Moon is almost full, the entire side facing Earth is illuminated, and the opposite side is in darkness from our perspective on Earth. However, for other phases, such as gibbous, quarter, or crescent moons, you can see some portion of the dark side, which is illuminated by Earthshine.

Observing a Lunar Eclipse

A solar eclipse, visible during the daytime, involves the alignment of the Sun, Earth, and Moon. If you have ever seen a lunar eclipse, you might notice how the Moon can appear dark or even take on a red color, which is often referred to as a "blood moon." During a total lunar eclipse, the Moon is in Earth's shadow, and the light we see is due to Earth's atmosphere bending and filtering the sunlight, which can be quite fascinating to observe.

In summary, you can see parts of the dark side of the Moon during its phases when it is not full. However, due to tidal locking, the far side of the Moon, which is always facing away from Earth, is never visible from our planet. The key to understanding this phenomenon is to differentiate between the dark side, which can be faintly seen due to Earthshine, and the far side, which is perpetually hidden.

For more information on astronomy and the Moon, you can explore other resources like NASA's official website or the JPL Moon fact-sheet.