As the Earth orbits the sun, the sun appears to move against the background stars (red line). The constellations (green) through which the sun passes define the zodiac. Image via Tau’olunga/ Wikipedia.The zodiac, the 12 signs listed in a horoscope, is closely tied to how the Earth moves through the sky. We derive these signs from the constellations that mark out the path that the sun appears to take through the year. You might think that dates in a horoscope correspond to when the sun passe...
