Phases of the Moon

You have an appointment with the Moon practically every day. It disappears from the sky only when it is facing the Sun. The Sun being located at the center of the solar system, it illuminates in the same way all the planets that revolve around it and all the satellites, including the Earth as the Moon.

On the other hand, the Moon also revolves around the Earth, and when it forms a right angle with the Earth and the Sun a half-moon is observed; It is the first or last quarter. When the Moon is located behind the Earth in relation to the Sun it is the Full Moon. When it is no longer seen, it is either because it arises much later or because it is hidden in the light of the Sun; This is the New Moon.

The Moon turns around the Earth in just over 27.3 days, it is its period or sidereal revolution. But as the Earth is also moving in its orbit around the Sun, it takes about 29 days and 13 hours for the Moon to be exactly in the same place in the sky, it is its period or synodic revolution, also called the lunar month. In practice it takes a month to see the same crescent Moon.