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Centennial Light
Light bulb burning in Livermore, California
A bulb in a fire station in Livermore, California, has been lit almost continuously since 1901. Its filament is thick and it burns at a low power.
The Centennial Light is a hand-blown bulb with a carbon filament. According to the local fire department's history, it was donated to the fire station around 1901 and has been hanging in a station ever since. It was moved with the department when its home changed, and the bulb was kept powered during the moves, apart from a few short interruptions.
It has been recognised by Guinness World Records as the longest-burning light bulb. Its glow is dim, comparable to a small night light, because it runs at a low wattage. That low power, plus the thick filament and a gentle, steady use, are commonly cited as reasons it has lasted so long.
The exact manufacturer and date are not fully certain, and the claim of continuous operation rests on local records rather than laboratory testing. Several engineers have studied it informally and consider the story believable.
It also lends itself to the idea of planned obsolescence, since ordinary bulbs made today are designed to trade longevity for brightness and efficiency.
The bulb is now reported to draw only about four watts, which is far less than a typical modern household bulb, and a webcam run by the fire department lets people watch it online.