FOR much of human history, it was at best nerve-wracking and at worst a torment to enter an unfamiliar room at night holding a guttering candle or an oil lamp. The incandescent electric light bulb changed all that.

The American inventor, Thomas Edison, and Sunderland-born Joseph Swan were the leading rival figures who independently invented the glass vacuum-bulb in which a carbon filament glows with the heat released by an electric current under resistance.

The filament (as you will have noticed) does not burn away, it just goes on shining. Edison and Swan came head-to-head on the matter of patent priority for their light bulbs, but settled out of court in 1882, confounding their lawyers by sensibly merging their companies, improving mass production and making even more money.

The light bulb was a very bright idea which upended an accepted wisdom. Before that, electrical light was produced by the arc lamp, in which a continuous fountain of sparks, powered by high-voltage batteries, passed between two contacts.

Edison and Swan showed how a much cheaper light could come from their new gadget, with its high electrical resistance, when connected to a moderate voltage and a trickling current.

This led rapidly, in the powerful late 19th-century economies, to the wiring and lighting of single houses and hotels, and spread on, through ever-widening circuits, to the illumination of larger communities and eventually to whole towns and cities.

Now, when we go into a dark room, we flap a hand at the wall and take it for granted that at about shoulder height there will be a square of plastic with a flipper on it, and lo! There is light.

The electric light bulb has spread its influence from this now universal human gesture that leaves sticky fingermarks on new paint, to some of the most profound art that the 20th century has produced. Picasso’s Guernica (1937) juxtaposes an oil lamp held in the dark by a terrified woman, with a blazing incandescent light bulb shining on a screaming horse and a weeping mother, and bearing witness to an unforgettable act of human barbarity.

• James Hamilton is the author of Turner— A Life and Faraday — The Life.