Did you get it?

I'm afraid yesterday's post was a bit self-indulgent.  I found it amusing, but I imagine that there will be plenty of you who will have wondered what it was all about.  So - Heisenberg was a German physicist who is best known for his "Uncertainty Principle" which says (among other things) that as far as sub-atomic particles are concerned, you can know their velocity (how fast they are going) or their position (where they are) but not both at the same time.  Now read the joke again.