Have you ever looked up into the sky and seen three suns? Did you think your eyes were playing tricks on you? Two out of those three suns were probably an optical illusion, known as sun dogs.

Ice crystals high up in the atmosphere are to thank for that beautiful phenomenon. The shape and size of the ice crystal, along with the angle of the sun, determine which optical illusions our eyes see. 

Johanna Wagstaffe explains the science behind sun dogs in this week's Science Smart.

If you have a science question you'd like answered, send Johanna Wagstaffe a tweet (@JWagstaffe) or an email to johanna.wagstaffe@cbc.ca.