Hole in the Hand Experiment (Vision Science)

"Look at your hand. Can you see through it?"

"Uh ... no," was the reply I got from our 10-year-old (with a hint of attitude, mind you).

"What if I told you that you were going to look through a hole in your hand without us harming your hand in the least bit?"

(puzzled expression)

And thus our experiment began. It took barely any supplies and only a few minutes but the effect was something we were still talking about an hour later.

What You Need
An empty cardboard paper towel tube (or a rolled up piece of paper)
Two hands
Two eyes

What to Do
Place the tube over one eye and look down it. Bring the other hand (the one that isn't holding the tube), beside the end of the tube, palm toward your face, so it touches the tube. As you look down the tube, you'll suddenly see a hole in your palm! 

Don't see it? Try moving your palm forward and back, closer and further away from the tube.

How It Works
Your eyes see the same thing but from slightly different vantage points. In order to see dimension, your brain combines these images. With the tube in front of one eye, we are suddenly giving the brain two very different images. When it combines them, it appears that you hand suddenly has a hole through it.