![](https://adamfronteras.net/wp-content/uploads/2020/11/Retrogradation-scaled-1-1140x641.jpg)
The word planet comes from the Greek, planetes, meaning ‘wanderer’ and this is because no one really understood planetary movement until Kepler’s theory of planetary motion in the 17th Century.
![](https://www.adamfronteras.net/wp-content/uploads/2020/11/Retrogradation-766x1024.jpg)
The word planet comes from the Greek, planetes, meaning ‘wanderer’ and this is because no one really understood planetary movement until Kepler’s theory of planetary motion in the 17th Century.