Most incandescent light bulbs last anywhere from 1,000 to 2,000 hours, and modern LED bulbs can have an impressive lifespan of 25,000 to 50,000 hours. However, nothing beats the Centennial Light, which, as the name suggests, has been burning for over a century! First turned on in 1901, the Centennial Light hangs from the ceiling of the Livermore-Pleasanton Fire Department in Livermore, California. General Electric calls it the “Eternal Light,” and rightfully so since the bulb has outlived all of the firefighters that worked in the building at that time. The reason behind the bulb’s longevity is still shrouded in mystery.

The Centennial Light is a carbon-filament, hand-blown, common light bulb which was manufactured by the once-famous Shelby Electric Company. The bulb’s origin and rich history were uncovered as recently as the early 1970s.

Adolphe Chaillet, the founder of Shelby Electric Company, was a genius electrician. Famous for his contribution to filament technology, Chaillet, and his company gained a widespread reputation for manufacturing the brightest and the most durable light bulbs in America. At its peak, Shelby produced up to 4,000 bulbs per day. The Centennial Light, one of their products, was originally a 30-or 60-watt bulb. Today, it emits a dim glow, almost as bright as a 4-watt nightlight. The carbon-filament, hand-blown, light bulb was manufactured sometime in the late 1890s. Many similar light bulbs of that time can be found functioning today.

Although the bulb had always been a bit of a legend at the fire station, nobody knew for sure where it came from or how old it was until 1972 when a reporter named Mike Dunstan took an interest in it. He spent weeks interviewing locals who had spent their entire lives in Livermore. Through numerous written documents and oral narratives, he was able to piece together the origin and history of the light bulb, and it turned out to be a fascinating tale!

Dennis Bernal, the owner of Livermore Power and Water Company (the city’s first power company), purchased the bulb in the late 1890s and donated it to the city’s fire department in 1901 after he sold his company. Back then, only 3% of American homes had electricity. That is why the Shelby bulb was a highly sought-after product. Zylpha Bernal Beck and the firefighters of that time support that story.

In the early years, the bulb was moved around many times before it found a permanent spot at the fire station. In its century-old existence, the bulb has been turned off only momentarily a handful of times.

Before being used to illuminate the Livermore fire station, the Centennial Light was installed in a hose cart. It also served a brief stint at City Hall and in a garage. The fire department would keep the light on 24 hours a day, however, in the 1930s, President Roosevelt’s WPA (Works Progress Administration) remodeled the station. That is when the light was turned off for about a week.

Then again in 1976, the department was moved to Station #6, and the bulb needed to be moved too. Instead of unscrewing the bulb and risking damage to this antique gem, they cut the power cord. The bulb was packed in a specially designed box and moved with a fire truck escort. It remained without electricity for only 22 minutes. An electrician was asked to be ready at the new fire station, and upon the bulb’s arrival, he installed it onto the emergency generator.

Since the move, the bulb has been kept running using an uninterruptible power source. In 2013, a dedicated webcam captured what was thought to be the bulb’s last few moments. Everyone including the online viewers thought that the Centennial Light had officially burned out. An electrician was called the next morning to confirm the status, and to everyone’s surprise, he found that the bulb was fine. It got turned off because of a faulty power supply. After about seven hours, electricity was restored, and the bulb was turned back on.

The Centennial Light has been recognized by General Electric, Ripley’s Believe It or Not, and the Guinness Book of World Records. The bulb has garnered considerable popularity for its uniqueness.

In 1972, Mike Dunstan’s story, titled  “Light Bulb May Be World’s Oldest,” got published in the Tri-Valley Herald. After that, the bulb generated quite the buzz. Dunstan contacted General Electric, Ripley’s Believe It or Not, and the Guinness Book of World Records, all of whom agreed that it was the longest-burning bulb known to exist. In 1972, the Centennial Light was officially listed as the “the most durable light” in the Guinness Book of World Records.

The fire chief at the Livermore Fire Station states that every time a news outlet publishes a story on the bulb, it generates a lot of interest. The fire station even attracts some visitors. Major news channels such as CNN, WB, CBS, Fox, ABC, NBC, and NPR have run stories on the Centennial Light. The bulb has also been featured in many renowned newspapers and magazines.

The Centennial Light completed its 100th birthday in 2001, and it continues to be functional up to this day.

In 2001, the community celebrated the bulb’s 100th birthday with live music and a barbeque. Sandia National Laboratories, Lawrence Livermore National Laboratories, Livermore Heritage Guild, and Livermore-Pleasanton Fire Department partnered to form the Centennial Light Bulb Committee which is responsible for caring for the bulb. The Livermore-Pleasanton Fire Department is fully committed to housing and maintaining the bulb for the rest of its life, no matter the duration. For now, neither the fire department or the Centennial Light Bulb Committee has no plans for the bulb’s future when it does go out. However, Ripley’s Believe It or Not! has requested to keep the bulb at their museum.

Though no one can conclusively point out the reason behind the bulb’s long life, it is suggested that the low power, dedicated power source, and continuous operation have contributed significantly to its longevity. The Centennial Light has also been used as an example when discussing conspiracy theories such as planned obsolescence.

[Sources: 1, 2, 3, 4]