Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Moon is the only natural satellite of the Earth, and the fifth largest satellite in the Solar System. The Moon is the brightest object in the sky after the Sun, although its surface is actually very dark, with a reflectance similar to that of coal. The Moon's gravitational influence produces the ocean tides and the minute lengthening of the day, while its prominence in the sky and its regular cycle of phases have, since ancient times, made the Moon an important cultural influence. Learn more about Moon, its history, geology and topography in this book.