EVERYDAY SCIENCE

Detailed explanation-1: -Believe it or not, it actually is just a coincidence-and a happy one at that. The Moon and Sun have virtually the same angular size in our sky because the Sun is about 400 times wider than the Moon, but it’s also about 400 times farther away.

Detailed explanation-2: -Click here to enlarge. Given the Earth’s greater size, it naturally appears larger in the lunar sky. From the perspective of an astronaut standing on the Moon’s surface, Earth varies from 1.8° to 2° in apparent diameter as the Moon travels from perigee (closest approach) to apogee (farthest) during its 27.3-day orbit.

Detailed explanation-3: -The Moon happens to be about 400 times smaller than the Sun, but the Sun happens to be about 400 times further from the Earth than the Moon is. So simple geometry tells us that the apparent disk of the Moon is almost exactly the size of the apparent disk of the Sun.

Detailed explanation-4: -The sun and the moon are about the same size when you look at them in the sky, though that’s just thanks to the coincidence that the sun is about 400 times farther away than the moon and also about 400 times bigger. Another fun coincidence is that the radius of the sun is about twice the distance to the moon.

Detailed explanation-5: -The Moon is always the same size, and the distance varies by only a small amount during its orbit. As a result, the Moon is roughly the same size in the sky every night. Even though it looks huge on the horizon, it’s identical to when it’s directly overhead.