I thought this was a really cool video that may intrigue some people here. It gives a nice visualization to what a "sound wave" is. All these experiments are real. For a quick breakdown: [spoiler]The salt on the plate moves because the tone vibrates the plate a specific frequency. This vibration causes the salt to move accordingly. The water is being ran through a hose that rests outside a subwoofer, and so the oscillations from the subwoofer cause perturbations in the water's flow. Again, at a certain frequency you get the helix effect. The flames are from a holes in a pipe that has a flammable gas flowing through it. By placing a speaker at one end, the sound waves travel through the pipe, effecting the distribution of gas, thus effecting the height of flames. These specific frequencies are causing "standing waves." Because of the nature of standing waves, the flames raise and lower consistent heights and distances from each other. When they turn the tesla coils on, they all wear chain metal, because electricity will only travel on the outside if they are completely enclosed in a conductor. If they weren't wearing chain metal, their chances are pretty slim, especially when he jumps in the air. We can see from this, that a hollow body does not feel external forces from the inside, which is an interesting scientific distinction to make, in my mind at least. [/spoiler] Anyone have any similar videos? I find this stuff super interesting.