Since ancient times the Moon has intrigued mankind. First and, I just guess foremost, because of its metaphysical influence on life on Earth. The Moon came into being, approximately four and half billion years ago, after the earth collided with Theia, a body about the size of Mars.
This impact caused material to blow away, form the Moon, and spiral around the Earth in an orbit. The fact that the Moon is circling around the Earth causes tides, and also because the Moon is rotating around the planet in the exact opposite way of the Earth rotating around it's axis is causing the Earth to speed down. It is measured that Earth's days are lengthening every year with fifteen microseconds.
The appearance of the Moon from Earth is depended on its position on the orbit, and whether it is lid by the Sun or not. However, the Matsya Purana, one of the oldest of the eighteen post-Vedic Hindu scriptures, tells another tale about the waxing and waning of the moon:
Chandra [Chandra is Sanskrit for Moon, ed] was born when the sea was churned by the gods and the demons. When Chandra came of age, he married the twenty seven lunar constellations, who were Daksha's Daughters.
One day the daughters complained to their father, "Our husband loves only one of our sisters, Rohini. He neglects the rest of us." In a fit of rage Daksha cursed the moon: "Chandra" said Daksha, "you will fade away and die."
Horrified, Chandra's wives begged their father to withdraw such a terrible curse. It was not possible to withdraw the curse. Daksha, however, agreed to change it. "Chandra, you will henceforth fade for a fortnight, and grow for a fortnight."
A beautiful tale. This explanation of the waxing and waning is probably not supported by science, but at least a good read!, and a proof that the moon continues to inspire people around the world. Inevitably, we see the Moon coming back in Hatha Yoga as well. The Moon for example, gives name to a number of asanas. Also, there is a nice short sequence of poses fully dedicated to the moon: Chandra Namaskar (the Moon Salutation). Indeed, as in Sun Salutation (Surya Namaskar). Curious how it goes? Watch this online video: