It’s hard to believe that anything as jaw-droppingly futuristic could be 57 years old, but the lava lamp (or astro lamp as it was originally known) has been around that long.

Invented by a British accountant named Edward Craven -Walker in 1963, the lava lamp quickly became an icon of 1960s psychedelia, with news of the product spread by worth-of-mouth.

The lamps work by using a light bulb to heat a bottle containing coloured oil and water (and some other minor chemicals – but those are the main two). The oil and water have similar densities but are insoluble to one another, meaning they don’t mix.

When the bottle is heated the oil absorbs the heat first, expanding in size as it does so. The expansion means that it becomes less dense and begins floating upwards.

As it floats up it cools, contracts and falls back to the bottom of the bottle, starting the chain of events all over again.

This continual slow motion process is based around very slight differences in density between the oil and water – the balance between them is like a very sensitive pair of scales, with small amounts of heat tipping the balance back and forth.

Bizarrely, the assembly line robots who help the humans have come from Detroit’s collapsed motor industry.

via Made in England for 50 years: the lava lamp celebrates its birthday – The Independent.