Cos(yt)
Over the last couple of weeks my wife has been knitting a tea cosy as a present for a friend. A tea cosy is an insulating jacket to keep the tea pot warm. I’ve always been amazed at the effectiveness of these little woollen gadgets but now I’ve watched one being built I’m beginning to see why. They’re not simply a layer of knitting, they’re knitted in a special way so that there are air pockets trapped along the sides, these pockets vent downwards so that as the hot air travelling upwards gets trapped. I have to admit though; I can’t understand the physical significance of the bobble.