WHAT WAS THE STORY BEHIND OF INVENTION

 The Mercury completes own year in 86.25 days of earth. and the Pluto completes own year in 90,462.5 days of earth. It seems very easy in write and hear. but what is the story behind it. perhaps do not knows you. that how did hard work the former people to find out the year of each planet. and gathered the all data of days to us. and we should always keep remember their hard work. you well knows that to do gather all data shall be spend the time. to which cost we cannot pay. 

ALWAYS KEEP REMEMBER MY WORDS. 

That after the earth. to the find out days of year of  Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. did the hard work countless generations. and we cannot compute these generation. unusual you knows about the number of events of one person. So what you can imagin the events of all generation. which are include in this mission. we seems very simple in read. but what was the story behind it. perhaps we do not knows.