Ummm, What?

As I've said many times I'm a skeptic. I don't believe things unless I see them in front of my own eyes.  Well today something happened out of nowhere.  We were sitting at the dinner table in the kitchen when we heard the mirror in the entry way rattle.  My girlfriend and I both thought this was because of the cat. He often sits on the bench in front of it and bumps into it when he moves.

However when we glanced at the mirror there was no cat. Looking at the mirror I said, "That's weird." and it happened again.  It happened right in front of me!  The mirror rattled and moved as if something has bumped into it.  I was staring right at it, not out of the corner of my eye, not something I heard but didn't see.  The mirror moved right before my eyes.

No cat, no wind, no furnace running, no tremors or Canadian earthquakes.  I really have no explanation for this.  I'm a bit baffled.

The mirror is pictured in this post.  As you can see it's just hanging on the wall.  Nothing really touches it.  I don't know if I'd say it was paranormal, but it sure was strange.