Dr Kelvin Kemm: Alice in Hydrogen Land

At a shopping mall or amusement park one can see vendors selling balloons filled with Helium. Kids love them and dance around trailing their balloons, which float above them. From time to time some kid accidentally lets go and you see the balloon soaring high into the sky, to the delight of many watching, but to the heartbreak of the kid. The balloon soars up into the sky because it is filled with Helium, and Helium is a gas much lighter than the Oxygen and Nitrogen which make up most of the atmosphere.