The Heisenberg Uncertainty Principle was discovered in 1927 by Werner Heisenberg.  The idea itself is decently simple to understand.  It states "The more precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa."  That is, one can never know the exact position and momentum of a particle.

The hypothesis originally stated takes Heisenberg's work and applies it to larger bodies, in this case Chuck Norris's foot while in route to roundhouse kick someone in the face.  As far as physics is concerned, this   implies that Norris's foot is one giant particle behaving in it's own fashion.