Way cool- an aluminium foil ship floating above ground on sulfur hexafluoride (gas significantly denser than air) at the Physikshow of the University of Bonn! [a href="http://www.youtube.com/watch?v=1PJTq2xQiQ0"]
(file:///C:/DOCUME%7E1/ENDUSE%7E1/LOCALS%7E1/Temp/moz-screenshot-18.jpg%22%20alt=%22%22%5D%5Bimg%5D/image/hexafluorid1.jpg)[/a]
This is Sulfur hexafluoride. It's 5.11 times as dense as air. It's non toxic, although it's byproducts can be extremely dangerous. Inhaling this gas will make your voice sound deeper. Sound does not travel as fast in this medium. Helium can transmit sound very rapidly, so it makes your voice squeaky.[/p][a href="http://www.youtube.com/watch?v=1PJTq2xQiQ0"]http://www.youtube.com/watch?v=1PJTq2xQiQ0[/a]