From the dawn of history until the beginning of the 17th century the knownuniverse consisted of only 8 planets:
1. Earth, 2. Sun, 3. Moon, 4. Mercury, 5. Venus, 6. Mars, 7. Jupiter,8. Saturn and the "fixed" stars. These are the ones that can be seen easily withoutany optical instruments. In Europe, the prevailing view was the Ptolemaic system withthe Earth at the centre and the other bodies revolving around it.
In 1610, Galileo first turned a telescope on the heavens and the universe wasexplored. By the end of the 17th century, 9 new planets had been discovered andCopemmican’s heliocentric theory was widely accepted. The total number of knownplanets had more than doubled to 17. In 18th Century, only 5 new planets (not counting
comets) were discovered, all by William Herschel , bringing the total to 22. Thenumber of planets in the solar system increased dramatically in the 19th century more...