Originally Posted by hellosailor
Is that one as old as the Sphinx?
It is used as a test of cognitive skills because if you can rearrange the relationships to a logical order, it becomes father-son-(who is also a father therefore his son is) grandson (son of speaker).
Now for a true mystery, how is it that a random length of twine or rope can tie itself in knots, but if you held the same piece in your hands all day and flipped it around, you couldn't get it to tie itself up in knots at all?
That is called Speers Law: "Rope or wire left to it's own devices will tied itself in knots"