Technology & Medicine › Electric age › Electric power and the grid
Incandescent light bulb
1878–80 (Swan, Edison; priority disputed)· Invention or discovery· Tools, energy & materials
DebatedHistorians or scientists disagree about what happened, when, or why.
A thin filament heated by electric current until it glows, sealed inside an airless glass bulb so it does not burn up.
See it on the Technology & Medicine map →How it works
Inventors had made filaments glow since the early 1800s, but they burned out fast; better vacuum pumps changed that. Joseph Swan in England showed a carbon-filament lamp in 1878–79. Edison's team, testing thousands of materials, ran a carbonized cotton thread for about 13 hours in October 1879, then carbonized bamboo that lasted over 1,000 hours. The rivals merged their British interests as 'Ediswan' in 1883. Tungsten filaments, introduced from 1904 to 1910, became the long-term standard.
Why it mattered
Electric light was cleaner, safer and brighter than gas and oil lamps, lengthening the working and reading day. Selling it created the first big demand for electric power.
How we know
Edison's US patent 223,898 (January 1880) and lab notebooks; Swan's demonstrations to the Newcastle Literary and Philosophical Society; the British patent fight settled by the 1883 Ediswan merger.
Still unknown or debated
Priority is disputed: Swan, Edison and earlier inventors such as Warren de la Rue and Hiram Maxim all have claims. Edison's real edge was a complete, sellable system.
Inside this (1)
Connections (4)
▸Glassmaking enclosed the glowing filament of the Incandescent light bulbWell documented
The connection
A hot filament burns up in air, so it must sit in a sealed vacuum. Glassblowers made the bulbs, and platinum lead-in wires were used because they expand with heat at nearly the same rate as glass, keeping the seal tight. Corning's 1926 'ribbon machine' later made bulbs by the millions.
When and how
Menlo Park, New Jersey, 1879, where Edison's glassblower Ludwig Boehm made the bulbs; Swan's bulbs in Newcastle, England; Corning Glass Works in New York supplied Edison from 1880.
How we know
The Edison Papers document Boehm's bulb-making at Menlo Park; Corning's company records cover its bulb contracts and the ribbon machine.
Debates and open questions
Little is debated; the main question is how much the breakthrough owed to better vacuum pumps, such as Hermann Sprengel's mercury pump, rather than to the glass itself.
▸Incandescent light bulb created demand for Electric power and the gridWell documented
The connection
Edison designed his bulb to sell electricity: he chose a high-resistance filament so many lamps could run side by side on thin, affordable copper wires. Lighting was the first mass market for electric power, and utilities sold mainly light until motors and appliances caught up between the 1890s and 1920s.
When and how
Menlo Park, 1878–80, where Edison and mathematician Francis Upton worked out the economics; Pearl Street Station, New York, opened September 4, 1882, to light offices in lower Manhattan.
How we know
Edison's notebooks and Upton's calculations compare gas-light costs with copper and lamp needs; early customer lists show lighting dominated demand.
Debates and open questions
Whether electrification spread from lighting outward or from industrial motors varies by country; in some places factories drove demand as much as lamps did.
▸Incandescent light bulb led, via the Edison effect, to the Vacuum tubeWell documented
The connection
Around 1880–83 Edison noticed his bulbs blackening inside and sealed in a metal plate to investigate; current flowed from the hot filament to the plate, but only one way. He patented it but found no real use. Fleming, a former adviser to Edison's London company, used this 'Edison effect' in 1904 to build the diode, the first vacuum tube.
When and how
Menlo Park, New Jersey, 1880–83 (Edison); London, 1904 (Fleming, then working for the Marconi company).
How we know
Edison's 1884 patent for an electrical indicator uses the effect; Fleming published studies of it in the 1880s and 1890s, and his 1904 diode patent built directly on it.
Debates and open questions
Frederick Guthrie in Britain saw a related effect in 1873, so the name arguably over-credits Edison; nobody understood it until the electron's discovery in 1897.
▸Thomas Edison commercialised the Incandescent light bulbWell documented
The connection
Edison did not invent the first electric lamp, but his Menlo Park team made a long-lasting, high-resistance carbon bulb plus everything needed to sell it: screw sockets, switches, fuses and meters. He raised money from J. P. Morgan and others, set up companies to make bulbs, and publicized them brilliantly, lighting Menlo Park for visitors on New Year's Eve 1879.
When and how
Menlo Park, New Jersey, 1878–80, with Francis Upton, Charles Batchelor and glassblower Ludwig Boehm, financed by the Edison Electric Light Company, formed in 1878.
How we know
Notebooks, patents, company records and press coverage in the Edison Papers; the Edison screw base remains the world's most common bulb fitting.
Debates and open questions
Credit remains argued: Swan's earlier lamps forced the 1883 British merger, and US rival William Sawyer's backers fought Edison's patent in court for years.