The concept of the perfect circle continually repeats across multiple observers thereby making the perfect circle infinite.
It is the continual repetition of a phenomenon which makes it infinite.
For example a continually progressive function of the number line necessitates 1 existing in perpetual variation given each number is the number one repeating itself. Under this number line progression 1 exists as perpetually changing thus 1 is repeating in newer and newer variation through the numbers which follow from it.
1 as perpetually changing is 1 as an action. One as a continual action is 1 as infinite.
Infinity is perpetual change as action and can never be observed in its entirety except through the source which repeats itself under newer and newer variation. Infinity can be observed in the number 1 given 1 is infinite through perpetual change.
Infinity thus can be observed through the finite where the finite is the point of change from one phenomenon to another. Each finite object is infinite through its continual change with this change from one finite phenomenon to another being multiple infinities.