There were 9 planets when I was in school. Today my son is studying that there are 8 planets in our solar system. It is really fascinating to travel the space and learn about the sun and planets. Today is dedicated to Neptune.
At times we use things in our lives, but never think from where they actually came from. Who thought of this first and why. Someone must have understood a problem and tried to solve it in a way or the other. The whole story inside is somewhat like that.