your naked fingers. So you grab an oven mitt, and remove the hot tin and cake. Why do the air, cake and metal cake tin all have different abilities to burn you? Welcome back to our friend, heat conductivity. Heat conductivity measures how rapidly heat energy can flow out of an object. 'Conductivity' and 'insulation' are opposites. If an object is a good conductor, it's a bad insulator -- and vice versa. Air is a bad conductor, and a good insulator. So the flesh of your hand can 'touch' the hot air in the hot oven and not get burnt. The same goes for the cake. Even though the cake has a lot of heat energy stored in it, its poor conductivity stops the heat from getting into your hands. There is a lot of heat energy in the cake, but it can't flow quickly into your naked hand. Mind you, if you lay your hand on the hot cake for more than a few seconds, you'll get a nasty burn. But the cake tin has both a high heat content and a high conductivity. Touch the tin for a second or two with your naked flesh, and you'll get burnt immediately. But what about hot coals? They turn out to be very bad conductors of heat. A hot coal has a moderate amount of heat energy, but is incredibly bad at passing that heat energy to anything else. Back in 1997, Kjetil Kjernsmo, a Norwegian scientist from the University