Pointless Optical Illusion

[Vicarious Reality]

You with a really thin dagger like blade (i used a cold steel large ti-lite) go ahead and stick that blade through one side of a new paper towel roll, making sure that the tip touches the other side inside the tube.
Now stare into the tube with one eye and have the other eye on the side with the knife. Look at the computer screen or whatever gives you contrast.
Wiggle the knife up and down while keeping your eye straight down the tube looking at something further away.