Relative Sizes and Distances Between the Earth, Moon and Sun

The Size of the Earth, Moon, and Sun

The Earth is approximately 12,742 kilometres in diameter.
The Moon is roughly one-quarter of the Earth’s diameter, around 3,476 kilometres.
The Sun, by contrast, is much larger, with a diameter of approximately 1.39 million kilometres.

Distances Between the Earth, Moon, and Sun

The average distance between the Earth and the Moon is about 384,400 kilometres, a distance that light travels in just over a second.
The distance between the Earth and the Sun, often referred to as one astronomical unit (AU), is about 149.6 million kilometres.
Because of the elliptical shape of the Earth’s orbit, the distance to the Sun varies throughout the year, from about 147.1 million kilometres at perihelion (closest approach to the Sun) to about 152.1 million kilometres at aphelion (farthest retreat from the Sun).
Light from the Sun takes approximately eight minutes to reach Earth.

Relative Sizes and Distances

The distances between these celestial bodies are all incredibly large compared to their sizes. For example, if the Earth were the size of a pea, the Moon would be a tiny seed about 30 centimetres away, while the Sun would be over 100 metres away.
The Moon is about one-fourth of the Earth’s diameter and about 1/80th of the Earth’s mass.
The Sun, despite being much farther away, appears roughly the same size as the moon in the sky because it is about 400 times larger but also about 400 times further away. This is why we can observe total solar eclipses.

Remember, these facts will help you calculate other aspects of the Earth-Moon-Sun system, such as their gravitational forces, their effect on tides, and the occurrence of solar and lunar eclipses.