Blogpost #3 (everything moves up a number)

We were learning about Kenimatics.  We are learning all of the equations for gravity such as: d=1/2at2)+Vot, V=Vo+at, and V(2)=Vo(2)+2ad.  I don't get why the formulas work but I know how to plug in all of the different variables to find the answer to the problem.  I always wondered how people were able to find out the acceleration for earth.  For people to test that how did they factor in all of the different variables that would affect the path of an object when dropped?  To find out how scientist found the acceleration of earth would be interesting to find out.  Since this is late I hope that I will be able to fully understand the next unit and how to plug in all of the information needed in the next chapter.