This unique phenomenon can be easily reproduced in a pool on a sunny day. If you liked this video check out these: How to Make a SQUARE Vortex Ring! https://www.youtube.com/watch?v=N7d_RWyOv20 Why Hawaii's volcano is so UNUSUAL https://www.youtube.com/watch?v=k0tnqPmwWvk Subscribe - http://www.youtube.com/subscription_center?add_user=physicswoman http://instagram.com/thephysicsgirl http://www.physicsgirl.org/twitter http://www.physicsgirl.org/facebook http://www.physicsgirl.org/ Help us translate our videos! http://www.youtube.com/timedtext_cs_panel?c=UC7DdEm33SyaTDtWYGO2CwdA&tab=2 Many thanks to the Vlogbrothers for their sponsorship of this video! Also thank you to Daniel Walsh for answering many fluid dynamics questions, to Jacob Schalch for filming the burning penny, and to Justin and Brendan for their donations to support Physics Girl!