This moon phases astronomy diagram depicts the various lunar phases visible from Earth. From one full Moon to the next, it takes 29.5 days. This is also referred to as a lunar month. Have you noticed how much longer this is than the time it takes to orbit the Earth? This is because of the Earth's rotation around the Sun. The Moon must travel a little further to return to the same position. Every 27.3 days, the Moon completes an orbit around the Earth. We can only see the portion of the Moon that is illuminated by the Sun. The other half is still dark. As it orbits the Earth, the Moon receives sunlight from various angles.