What does the word planet mean?

Planet - is the word planet comes from the Greek planetes meaning "the wanderer". Originally the term was applied to the seven heavenly bodies which changed their places by revolving so men believed round the earth. The seven were Mercury, Venus, Mars, Jupiter, Saturn, the moon and the sun. While we now realize that the planets including the earth revolve round the sun the distinction between planet and star is still valid. Planets are too cool to give off any light of their own. We can see the other planets only because they reflect the light of the sun which is now known to be not a planet but a star. The planets are only a few million miles away but distances to the stars are so vast that they have to be calculated according to the time taken for their light to reach the earth. Three more planets joined the list in comparatively recent times. In 1781 William Herschel discovered Uranus. Neptune was added in 1846 and Pluto in 1930.

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