According to many of the ancients, the heavens are what we see about the earth. These consist of the sun, the moon, the planets, the stars, and other objects occasionally, like comes and meteors. Even in early times, the planets were distinguished from the stars by their motion. They moved relative to the stars, and the name "planet" in Greek means "wanderer"
One of the earliest civilizations to have ideas about the universe was the Babylonian, located in What is now Iraq. We know from ancient writings that by 1700 BCE the Babylonian knew the length of a year to within a few minutes. The Babylonians divided the year into twelve lunar months. A lunar month is the time for the moon to go from full moon to full moon, as observed on earth, a time of somewhat more then 29 days. Because a year is a little longer than 12 lunar months, the Babylonians included a leap month every few years.
The Babylonians divided the circle into 360 degrees, each degree into 60 minutes, and each minute into 60 seconds. We still use these units of angular measurement, but we also use others. In Figure 1.1 we show a circle with angles of 30 degrees and 90 degrees marked off. A degree is abbreviated