Egyptian solar system. Coloured historical artwork of the Earth-centred (geocentric) Egyptian model of the solar system. This model tried to retain a stationary Earth and still account for the erratic movements of the planets Mercury and Venus. The frequent retrograde (backwards) movement of these planets in the sky is (correctly) explained by them orbiting the Sun. Such an example of heavenly bodies orbiting each other was first discovered by Galileo in 1610, who observed Jupiter's moons and Saturn's rings through his telescope. However, the model still (incorrectly) had the Sun and the remaining known planets orbiting the Earth. From Bilder Atlas by Johann Georg Heck, 1860.