John Conway Ties an Impossible Knot

When I take my students to the Center for Mathematical Sciences in Cambridge for Lectures we always stop to see the Gates that have the chiral reflections of two knots with the same polynomial knot form, a Conway discovery.

While watching a video tribute to Martin Gardner, I came across Conway doing one of his mathematical tricks that I thought was interesting. See if you can do it. What he says is, "You know, it is impossible to tie a knot without leaving go of the ends of the string the way I just did."