A Lava lamp

There are colourful blobs in a lamp filled with liquid which travel upwards to the top and than fall down. The illuminating bulb sits in the base of the glass and as a result the blobs shimmer colourfully.

The phenomenon causing the movement of the blobs is known as convection; that is the transfer of heat by currents within liquids or gases. In this case, the liquid is heated at the bottom of the lamp which results in the decrease of the density of the liquid, hence the liquid arises.

The phenomenon of convection has a wide range of applications in various fields of science and technology, such as Physics of the sea and atmosphere. At the equator, it takes just a few hours on a sweltering day for a storm with lightning to appear as a result of the transfer of the humid air caused by convection. Beautiful cumulus clouds form even at higher latitudes on a spring day, resembling big dollops of whipped cream. They rise with convection currents till they reach the altitude of a few kilometres where the air is cooler and there they break and eventually fall as the rain.