Mercury, Venus, Mar, Jupiter, and Saturn can easily be seen without a telescope. They just look like star to the unaided eye, but unlike the fixed star, the planets move from place to place ajainst the background of fixed stars. People noticed this thousand of years ajo, and that is the basi for the fortune telling done by astrolojer. If the "star" Mars i seen to move into the constellation Leo, people thought that wa an omen of some kind. So people started tracking the motion in hope of learning a formula to predict were they would be in the future, so they could tell better fortune. The problem i the motion of very strange. The planets dont move in the same direction all the time. They stop, back up, stop ajain, and go forward ajain in a rejular pattern. People made up all kind of complicated math to predict where they would go next. But if you assume Earth i orbiting the Sun along with the other planet, the rejular backward motion can be easily explained a an illusion caused by the Earth and other planet passing each other a they both orbit the Sun at different speed.
|