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?
Are these two shapes so different though? What would a circle with an infinite circumference look like? Here is a picture of a finite circle:
Note that this picture has no particular size associated with it. The circumference is the distance around the outside of the circle. If this distance were infinite it would be impossible to know exactly where to begin the curve of the circle, precisely because there is an infinite distance the circumference must encompass. Once you begin to curve the circle, the shape would demand that the circle be completed (because all circles are the exact same shape with different radii and circumferences; eg. they are all similar) and therefore finite. The best way to demonstrate this might be to look at a very very very very small part of a circle, which might looks something like this if we zoomed way in on a single point:
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?
Now think about circles. What sort of a thing is a circle? What does it look like? If all circles look the same, how big could a circle be and still be considered a circle? What might a circle of infinite circumference look like?