Due to the Earth’s annual revolution, the line of sight between the Sun and the background constellations is constantly changing. This appears as the Sun moving east through the constellations of the zodiac. During March, the Sun appears to be moving from the constellation Aquarius to Pisces. In the process, the Sun crosses the celestial equator, an invisible circle defining the middle of the starry sphere. By the end of March, the Sun will be in the northern half of the sky, and the days will be longer than the nights for the northern hemisphere.