As a matter of fact, yes, planes can be tied in knots. Here's a page from "Knotted Surfaces and Their Diagrams" by J. Scott Carter: http://i.imgur.com/2rIKJ8E.

As a matter of fact, yes, planes can be tied in knots. Here's a page from "Knotted Surfaces and Their Diagrams" by J. Scott Carter: http://i.imgur.com/2rIKJ8E.png http://i.imgur.com/2rIKJ8E.png