The Moon is Earth's only natural satellite and is the fifth largest satellite in the Solar System. It is the largest natural satellite in the Solar System relative to the size of its planet, a quarter the diameter of Earth and 1/81 its mass, and is the second densest satellite. It is in synchronous rotation with Earth, always showing the same face; the near side is marked with dark volcanic Maria among the bright ancient crustal highlands and prominent impact craters.

It is the brightest object in the sky after the Sun, although its surface is actually very dark, with a similar reflectance to coal. Its prominence in the sky and its regular cycle of phases have since ancient times made the Moon an important cultural influence on language, the calendar, art and mythology. The Moon's gravitational influence produces the ocean tides and the minute lengthening of the day. It governs the rhythms of the  waters, and rain, the fertility of women, of animals, and of vegetation. For this reason, a close affinity exists between its periodic rhythms between all life.

The Moon's current orbital distance, about thirty times the diameter of the Earth, causes it to be the same size in the sky as the Sun--allowing the Moon to cover the Sun precisely in total solar eclipses.

The Full Moon, New Moon, and eleventh day of the New Moon are very auspicious days for fasting, meditation, ritual and celebration in many cultures. For example, if you check your calendar, you'll find that all major Jewish Holidays fall on one of these three phases of the moon. The Chinese New Year is celebrated on the second new moon after the winter solstice. Vaikunta Ekadasi, a sacred Indian holiday, falls on the 11th day of the Sukla Paksha (the waxing phase of the moon) in the ninth month of the Hindu Lunar Calendar. Hindus consider it a very auspicious day and observe it as a day of prayer and fasting. This is also the SAME day of Yom Kippur, the highest holy day of the Jewish people which also involves prayer and fasting.