STEP 2 - Compare the football and modelling clay ball in size ... same time it is also orbiting the Sun. The Earth takes 365 and a quarter days to make one complete orbit of the Sun. This is why ...

We always see the same side of the moon, but part of it is in shadow, due to the moon's rotation. Only when the moon, Earth and the sun are perfectly aligned is the moon 100% full. And sometimes ...