Thomas Alva Edison (1847–1931) was born in Milan, Ohio, and grew up in Port Huron, Michigan. He had only a few months of school; his mother taught him at home. As a teenager he sold newspapers on trains and then worked as a telegraph operator, which taught him electricity. He became partly deaf young, and later said it helped him concentrate.
Key idea
A first lesson
Edison's first patent, in 1869, was an electric vote recorder for lawmakers. It worked, but nobody wanted it: lawmakers liked slow voting. Edison said later that he learned to invent things people would buy.
The phonograph, 1877
Working on telegraph and telephone devices, Edison wondered whether a needle moved by the voice could scratch a groove, and the groove later move a needle to play the voice back. In late 1877 he had a machinist build a cylinder wrapped in tinfoil, with a needle on a diaphragm. He recited "Mary had a little lamb," and the machine played it back. It made him famous.
The light bulb: trying thousands of materials
Electric arc lights already lit some streets, but they were blinding and needed constant care. Many inventors had made glowing bulbs, including Joseph Swan in England. The problem was a bulb that would glow softly for hundreds of hours, cheaply, and a way to deliver power to homes. In 1878 Edison promised to solve it.
- Why a vacuum: a hot thread glowing in air burns up, because it reacts with oxygen. With most of the air pumped out, it lasts much longer. Better vacuum pumps were a key step.
- Why a thin, high-resistance filament: Edison planned to wire many lamps side by side (in parallel) from one supply. A thin filament with high resistance needs less current, so the copper wires could be thinner and cheaper.
- What they tried: platinum first, which melted or cost too much; then carbon made by baking cotton thread, paper, wood and more. In October 1879 a carbonized cotton thread glowed for more than 13 hours. Carbonized cardboard did better. Then the team tested thousands of plant fibers, and in 1880 found that carbonized bamboo could last over a thousand hours.
The first step is an intuition—and comes with a burst, then difficulties arise … 'Bugs' as such little faults and difficulties are called show themselves and months of anxious watching, study and labor are requisite before commercial success—or failure—is certainly reached.
Worked example: Hours to days
- $1200 \div 6 = 200$.
Answer: 200 nights.
A system, not just a bulb
A bulb is useless without power. Edison's team designed dynamos, wiring, fuses, switches, meters and sockets. On September 4, 1882, the Pearl Street Station in Lower Manhattan began sending direct current to customers. In Britain, Edison and Swan joined their companies in 1883.
Story or history?
Some popular sayings about Edison are hard to trace, such as that he "found 10,000 ways that won't work." His team really did test thousands of materials, as the notebooks show. But be careful with famous quotations: check where they come from, the way historians do.
| When | What happened |
|---|---|
| 1847 | Born in Milan, Ohio |
| 1863 | Works as a telegraph operator |
| 1869 | First patent: the electric vote recorder |
| 1876 | Opens the Menlo Park laboratory |
| 1877 | Phonograph: "Mary had a little lamb" |
| 1879 | Carbonized cotton filament glows for more than 13 hours (October) |
| 1880 | Carbonized bamboo filaments last over 1,000 hours |
| 1882 | Pearl Street Station powers lamps in New York |
| 1887 | Moves to a larger laboratory in West Orange, New Jersey |
| 1931 | Dies in West Orange, holding over a thousand U.S. patents |
Worked example: Team speed
- $6000 \div 100 = 60$.
Answer: About 60 a week, more than 10 every working day.
What it led to
The research lab, where a team works on problems full time, became the model for companies around the world. The electric light changed when people could work and read. Edison's direct current system was soon challenged by alternating current, which brings us to Tesla.
Common mistake
Build it yourself
Read more: Thomas Edison, Incandescent light bulb and Phonograph.