Think about what a circle is, a single line bounding a figure equidistantly from a single point, called the centre. The line itself is, however, unbounded. Do you see a way in which the circle might represent a kind of Little Infinity?
Think about the single straight line. Could this be a way of representing Big Infinity stretching out in both directions for eternity?
This looks an awful lot like a line to me. So now, if a circle is representative of Little Infinity and a line is representative of Big Infinity they seem like they might be very much alike indeed.
Do you buy into this? What do you think? Is this convincing you of something more about infinity? Does it make you think maybe there is something interesting at work here that we need to look at more closely?