Summer of Science: Hole In Your Hand

Despite the fact that I almost forgot to post this Summer of Science experiment, it was one of the most fun ones we’ve done so far thanks to its simplicity. 

So here’s how it goes, the next time you’re sitting on the toilet with an empty roll, yelling for someone…anyone to bring you a full one, look through it.  Yes, put it up to one eye and look through it like you’re a pirate scouting out distant treasures to loot.  Just make sure you keep your other eye open at the same time. 

Now hold up your opposite hand.  i.e. If you're holding the roll to your right eye hold your left hand up in front of you.  Place your hand close to the roll and near, if not past, the end of it. (Really a paper towel roll would do better but we don’t use paper towels.) 

With both your eyes open you should see a hole in your hand (as if you were looking through it). 

Why do you see a hold in your hand? Simple.  Usually, we see with both our eyes at the same time but we’re not aware of this because our brain takes the images from each eye and puts them together.  In this experiment when your brain puts the images together you end up with the hand from your left eye and the hole in the roll from the right.  Put that together and whaddya get?  A hole in your hand.