Brain Games

There is a television show on National Geographic and also on Netflix called Brain Games.  There have been a bunch of episodes on sight perception and illusions, and more specifically for this post, how we perceive motion.  When looking at a basketball, we are able to know what it is from our past experiences.  Once our brains have figured out what the object is, it has to figure out how the object is positioned.  We are able to know this by the shadow that the object casts.  The television show has a illusion of a basketball moving across the screen.  They put a shadow directly underneath/next to the ball which makes it look like it is being rolled across the floor.  Now, when the shadow is moved and placed parallel to the ball still moving in the same direction, our perception of the ball is that it is being throw into the air with the shadow underneath it.  They change the shadow's placement once more and have it move in a zig-zag format from next to the basketball to underneath it which gives in the illusion of the ball bouncing.  This shows us that our brain has completely trusted shadows to tell us where objects appear to be in space. 

https://www.youtube.com/watch?v=PN1NAiM55hU