"Place a penny on the middle of one of your tables in space, and, leaning over it, look down from the top of it. It will look like a circle. But then, draw back to the edge of of the table, and gradually lower your head and thus your eye (...) and you will find the penny appearing more and more oval; and at the last (...) a straight line."
After reading this short paragraph of Edwin Abbott's Flatland I never looked at the world as I saw it before. Nothing is fixed. Everything has the potential to be something else at all time.