Mobius belt is a by-product discovered by German mathematician Mobius when he studied "Four-color Theorem" in 1858. "Mobius circle", as one of the "interesting figures to understand and appreciate", has been written into the mathematics curriculum standard and incorporated into the compulsory education curriculum standard experimental textbook "Mathematics".
If we cut a Mobius ring along the midline, what will we get? After cutting, it actually didn't split in two, but became a big ring. If you cut the Mobius paper ring along the bisector, what will you get? If you cut along the bisector of Mobius ring, you will return to the original point after cutting two rings, forming two rings with a big ring and a small ring nested with each other. The circumference of the big ring is twice that of the original Mobius ring, and the circumference of the small ring is the same as that of the original Mobius ring. If we further experiment and cut the Mobius ring along the bisector, we will find the following phenomenon: we actually cut out two interconnected paper rings, unfold them and straighten them, and we can see that the two paper rings are the same length. By cutting Mobius ring along the bisector, three interconnected paper rings can be cut, and the three paper rings can be unfolded and straightened. You can see that two of them are the same length, and the other is half the length of the other two rings. Three interconnected paper rings can be cut along the bisecting line of Mobius ring. When the three rings are unfolded, it can be seen that the lengths of the three rings are the same. The newly obtained longer paper circle itself is double-sided, and its two boundaries are not knotted, but nested together. Then cut the paper circle along the center line. This time, you really split it in two. You get two paper circles nested with each other, and the original two boundaries are contained in two paper circles respectively, but each paper circle itself is not knotted.