This is a model of a sculpture by Karel Vreeburg.[br]The mathematical physicist [url=https://en.wikipedia.org/wiki/John_C._Baez]John Baez[/url] paid some [url=http://math.ucr.edu/home/baez/week297.html]attention[/url] to the [url=http://www.karelvreeburg.com/kunstwerk/13285086_Hidden+Split+Torus+2.html#.WP1T3YVOKM8]sculture[/url] and[br]the European Mathematical Society has used it on a cover for a [url=http://www.ems-ph.org/img/journals/emss/emss-cover.gif]scientific journal[/url].[br][br]The torus is split by a triple twisted mobius band (3 times 180 degrees).[br]The resulting object is a trefoil knot.[br][br]N.J. Wildberger talks about Torus knots in his lecture[br][url=https://www.youtube.com/watch?v=xKvbGFrkx18]AlgTop26: Covering spaces[/url](Starting from minute 37)[br]If you are curious about what topology is:[br]See the total [url=https://www.youtube.com/playlist?list=PL6763F57A61FE6FE8]beginners course in Algebraic Topology[/url].