Losev’s diodes

As a PhD student I took a course in inorganic photochemistry. One of the opening soundbites – ‘photons are expensive’ – chimed with my parents’ endless exhortation to switch off the lights, especially when visiting my grandmother in Italy.

As a species, we are addicted to light. The harnessing of fire was the means by which humans increased their food security, but flickering firelight also extended the day and strengthened social bonds. Lighting also had a profound intellectual impact by allowing reading and writing indoors and at night. Yet it took 5000 years to move from the use of a simple wick and some oil to something a little brighter.

Crucial to this was the rise of chemistry. The 18th century closed with the idea that combustion required both fuel and oxygen, an idea triumphantly exploited by François-Pierre-Amédée Argand, whose idea of a chimney around a large whale oil-soaked wick significantly increased air flow, the temperature of the flame and its brightness. Such combustion lamps combined with coal gas would reach their apogee with Karl Auer’s invention of the incandescent gas mantle around 1889. But the writing was on the wall for flames.