Have you ever stared in the bathroom mirror and flicked the light on and off and watched what happens to your pupils? They get bigger, then smaller, then bigger, then smaller, right? One of our listeners was wondering what happens to our pupils when we close our eyes. Since we can’t see through our own eyelids, we called on Sasha Strul, University of Minnesota Pediatric Ophthalmologist, to help us discover the answer.

Do you have a Moment of Um question for us? Send it to us at BrainsOn.org/contact, and we’ll help open your eyes to the answer.