It is because when we fold the paper to a certain extent, the thickness of the paper is already very thick, so it will be difficult to continue folding down, and there is no way to continue folding down, because it is completely impossible to fold together. This is a kind of paper in itself. No matter how big the paper is, it can only be folded in half nine times at most.

When we fold the paper in half, the thickness of the paper increases by a multiple of 2. After the 1 fold, the thickness of the paper is twice that of a single sheet of paper; After the second folding, the thickness of the paper is twice that of 1 folding, that is, four times that of a single sheet of paper. By analogy, after the eighth folding, the total thickness of paper is 256 times that of single sheet, and after the ninth folding, the thickness of paper is 5 12 times that of single sheet. But if you want to continue, that's the 1024 floor. No matter how thin the paper is, the layer of 1024 is still very thick. The paper must be hard and cannot be folded in half.

And at this time, the thickness is much greater than the width (the width has changed to the original 5 12 1), so it is impossible not to break (tear) this piece of "paper" because of the bending and elasticity of the material mechanics. Moreover, there is a rebellious tension in paper, which will make it more difficult to fold in half.

Theoretically, if the thickness of paper is zero, it can be folded in half countless times. However, due to the actual thickness of paper, this theory does not exist, because the width of folded paper cannot be less than or equal to the thickness of paper, that is, a piece of paper with a thickness of 1 mm should be greater than 1mm?

However, the teachers and students of St. Mark's Middle School in Texas once folded a piece of toilet paper nearly 4 kilometers in half 13 times, perhaps because the paper was long enough and thin enough. However, we can never do it with ordinary paper.