The Earth appears relatively small when viewed from the Moon due to the vast distances involved and the difference in sizes between the two celestial bodies. Here are a few key reasons why the Earth appears small from the Moon:
Distance: The average distance between the Earth and the Moon is about 384,400 kilometers (238,900 miles). This considerable distance causes the Earth to appear far away, and as a result, its size appears diminished when observed from the Moon.
Size comparison: The Earth has a diameter of about 12,742 kilometers (7,918 miles), while the Moon has a diameter of approximately 3,474 kilometers (2,159 miles). Therefore, the Earth is approximately four times larger than the Moon in terms of diameter. When you view an object that is significantly larger or smaller in comparison, it can create an illusion of size difference.
Lack of atmospheric cues: When we observe the Earth from the Moon, we don't have the presence of Earth's atmosphere to provide visual cues. On Earth, the atmosphere scatters sunlight, creating an apparent halo around the planet and making it appear larger. However, without the atmospheric scattering effect, the Earth appears as a relatively small, sharp-edged sphere against the blackness of space.
Field of view: When astronauts are on the Moon's surface, they usually have a limited field of view due to the constraints of their helmets and spacesuit designs. This narrower field of view can contribute to the perception of the Earth appearing smaller.
Overall, the combination of distance, size comparison, lack of atmospheric cues, and field of view contribute to the Earth looking small when observed from the Moon.