Posted: December 24th, 2016

Take about 15 index cards and a flashlight that is opaque on all sides (so that light shines only through the front) into a very dark room.

Take about 15 index cards and a flashlight that is opaque on all sides (so that light shines only through the front) into a very dark room. After placing all 15 cards over the beam of light, slowly remove the cards one at a time until you can barely detect the light, and then count the number of cards that remain over the light. After a few minutes, the light should begin to look brighter. When this is the case, add a card and see if you can still see the light. Repeat this process of gradually adding cards over a 15 minute period. Were you able to detect an increasingly dim light the longer you spent in the dark?