To learn how I made the vacuum pump used to operate this cannon, take a look at this video: https://www.youtube.com/watch?v=UkPLu6mgdWA A vacuum cannon is an interesting physics demonstration that shows how much atmospheric pressure there is at the earths surface, though we do not feel it because our bodies have the same amount of pressure both inside and out. By removing air pressure from inside of a length of pipe the balance with atmospheric pressure is removed, and if the seal is broken on one end air pressure will rush in quickly enough to throw a projectile with a good deal of force. I first learned of vacuum cannons thanks to this article on Instructables: http://www.instructables.com/id/Vacuum-Cannon-drives-ping-pong-ball-at-supersonic-/ #NightHawkInLight ~-~~-~~~-~~-~ Check out my latest video: "How To View Invisible Air Currents With Lasers" https://www.youtube.com/watch?v=K94Cc21KEIA ~-~~-~~~-~~-~