Buzz
Following our recent discussion on the longest prison sentences and the momentous occasion when the 69-year-old pitch drop experiment was finally filmed last month, reader Justin became curious and asked, “What’s the longest experiment that scientists have been dedicated to for decades or even their entire careers?”
While the pitch drop experiment holds the record for the longest uninterrupted duration, there are at least two other projects that began earlier and continue today, though they’ve had occasional interruptions. The oldest of these, reigning champion for the most years in progress, is the Oxford Electric Bell, also known as the Clarendon Dry Pile.
As suggested by its name, the Oxford Electric Bell is an experimental device housed at the Clarendon Library at the University of Oxford. Built by the London-based firm Watkin and Hill, it was purchased by Robert Walker, an Oxford professor. He set the bell ringing in 1840, and remarkably, it continues to toll to this day.
The bell consists of two metal bells with a metal clapper positioned between them. The clapper is powered by two 'dry piles,' an early type of battery. These dry piles were typically made of alternating layers of metal foil and paper—sometimes stacked in hundreds or even thousands of layers—resembling an electric sandwich. While various metals could be used in their construction, Watkin and Hill did not document the specific materials of their dry piles.
Scientists are keen to discover just how long this mysterious battery can keep going before it finally depletes, and when it does, they plan to open it up and examine its composition. However, the process is largely a matter of waiting. Regardless of the materials used, the device has proven to be remarkably durable. Guinness World Records has even called the bell's dry piles the 'world’s most durable battery.' For 173 years, with occasional pauses, the bell has continued to ring.
The clapper swings between the two bells, typically at a rate of 2Hz (two cycles per second), although this depends on the weather. High humidity can slow or even halt the clapper’s movement, but once the humidity drops, the bell resumes ringing without any external assistance. As the clapper strikes one bell, the associated dry pile charges and repels the clapper electrostatically, which causes the clapper to swing toward the second bell, where the process repeats.
Since only small amounts of energy are discharged in each cycle, the battery's drain—whatever it's made of—is minimal, allowing the bell to ring continuously. If we assume that the clapper has been oscillating at 2Hz for the entire 173 years, it would have struck the bells a staggering 10,911,456,000 times.
Eventually, the electrochemical energy within the dry cells will run out, and the bell will fall silent. However, since no one knows for sure what powers the mechanism, it is uncertain when this will happen. The silence might also occur if the clapper or one of the bells wears out. But no one can hear it anyway: To prevent the patrons of the Clarendon Library from being driven mad by the noise, the bell is kept inside a soundproof glass enclosure.
The second longest-running experiment is the Beverly Clock, an experimental timepiece located in New Zealand. Since 1864, it has been ticking continuously without needing to be wound, powered instead by changes in atmospheric pressure and temperature.
