Geometry,physics,and philosophy?

In day while i was in cl, the teacher told us that the perimeter of an object is indefinite bacause when we use smaller units of measurement the perimeter increases......so one day as I was thinking in came the idea to my mind that we live in a approximate world in which all of our calculation are approximate because are measurements of space and time are not perfect....having in account this we cannot solve a general formula of the universe like string theory because we use approximate measurements and we dont have the technology to make them perfect..am I right?