How many people does it take to invent a light bulb? The answer is less straightforward than you might think. Thomas Edison is generally credited with its invention, but it was an Englishman, Joseph Wilson Swan, who demonstrated the first incandescent light bulb to an audience in Newcastle upon Tyne in February 1879 - nine months before Edison switched on in New Jersey.
It's not clear if Edison knew of Swan's experiments with electricity or whether it was a case of synchronicity, but Edison was the first to make it work - and he made a lot more money. In his lifetime, he registered more than a thousand patents and founded the company that became a multinational - General Electric.
His famous "1 per cent inspiration, 99 per cent perspiration" formula for genius might have been an exaggeration, but it had a grain of truth. He tried out 6,000 materials before he found a filament - carbonised cotton thread - that worked. Legend has it that his moment of enlightenment came when he threw a broken fishing rod on to a camp fire and watched it glow.
The science of light bulbs is simple - current passes through a resistantfilament, making it heat up and give off light. But the problem Edison and others had was finding a filament that didn't burst into flames at high temperatures. Putting the filament in a vacuum helped because it removed the oxygen needed to burn.
The invention of electric light started a second industrial revolution. Previously, candles and gaslight were the main sources of illumination. But they were dirty and inefficient and most work had to finish at dusk. Picasso liked to work by artificial light, and a blazing bulb is prominent in his famous painting from the Spanish civil war, "Guernica".
But the future's not looking bright. Although light bulbs have built-in obsolescence - to make us buy more of them - their lifespan might be a lot more limited than their designers intended. In the next century light emitting diodes - cheaper and more efficient - are predicted to supplant the humble bulb. They have been around since the Sixties, but only in 1995 was a way found of producing white LEDs. The inventor - Japanese researcher Shuji Nakamura - could be the Edison of the next millennium.