The earth is constantly moving in its orbit around the sun so the angular relationship between the sun and the earth's equatorial plane is always changing. This is because the earth's axis remains oriented toward the same part of the sky all the way through its orbit. Since this relationship determines the length of a shadow it too must constantly change.
More specifically, the height of the sun changes from day to day. In the summer it is highest and in the in winter lowest. So as the the days go by from say, winter to summer, the sun gets a little higher each day,and thus your shadow shorter
More specifically, the height of the sun changes from day to day. In the summer it is highest and in the in winter lowest. So as the the days go by from say, winter to summer, the sun gets a little higher each day,and thus your shadow shorter
