World's oldest light bulb turns 125 and the conspiracy theory about it gets physics wrong

Theory Briefing

• The Centennial Light in Livermore, California has been burning for 125 years, making it the world's longest-running light bulb.
• Conspiracy theorists cite it as proof that manufacturers deliberately design short-lived bulbs to force repeat purchases.
• A key physics fact about low-wattage filaments explains the bulb's longevity — and why it can't simply be mass-produced as a modern replacement.
• The planned obsolescence theory assumes durability is suppressed by choice, but the trade-off between brightness and lifespan is a real engineering constraint.