You can hardly hear the sound of the Oxford Electric Bellso faint it is. Despite this, the bell – which is also known as the “Clarendon Dry Pile” – began to ring well before 1840, and so for almost two centuries. It has seen the whole of the old century and the first twenty years of the new one, and although it is considerably aged and increasingly “tired”, it still goes on thanks to the two batteries that power it. How they are made inside, however, is still a mystery to scientists: if they were opened the bell would break, and at that point goodbye to one of the longest-running scientific experiments ever. But everything has an end: according to experts it will take about ten years before this battery system also reaches its end, and they can finally be opened and studied.
According to scholars, the ringing of the bell occurred at least 10 billion times, and for this very reason it holds the Guinness World Records as “the world’s longest-lasting battery.”
Where the Bell Comes From and the Enigma of Batteries
This long-running scientific experiment consists of two brass bells, each placed under a dry cell battery, and a small metal sphere with a diameter of 4 millimeters that oscillates perpetually between them thanks to electrostatic force and which produces a sound (oscillation frequency of 2 Hertz).
The Reverend Robert Walkerwho was also professor of physics at Oxford University at the time, purchased the bell from the instrument makers Watkin and Hill who had made it in 1825 and brought it into the classroom to show it to his students. The object is now in the Clarendon Laboratory of the university – from which it took the first part of its name – protected by two layers of glass.
We understand why it is called Clarendon, but instead Dry Pile? Translated from English it means “dry battery”. This second part of the name was attributed to it because the two batteries look very similar to those “with dry moss” created by the Italian priest and physicist Joseph Zamboni. These batteries were made of at least 2000 pairs of tin foil discs glued to paper impregnated with zinc sulphate and coated on the other side with manganese dioxide. The cells are not dry, but contain just the right amount of water to provide the electrolyte without causing short circuits.
The Oxford Bell batteries are also sealed on the outside with a coating that is believed to be sulfurand this makes them look like candles (don’t worry, it’s all just appearances: it’s impossible that they are candles, otherwise the bell wouldn’t work).
However, it is not certain that they are batteries of this type, and to know exactly what they are made of we have to wait for the batteries to die: as we wrote previously, if we were to open them now the experiment would end, and scientists want to make it last as long as possible.
Why has it been running for so long?
It is thought that at least part of the reason the bell has been ringing for so long is due to the fact that It doesn’t require much energy and that doesn’t waste much of it.
The doctor Robert Taylor of Oxford University explained:
As it moves back and forth, the small lead bell touches the two batteries on both sides, and as it does so it is continuously charged and discharged.
A small amount of charge leaks between the two ends and the only loss is air resistance.
When will it stop working?
The bell has rung for a long time, but it will not do so forever, and sooner or later it will stop working. According to Taylor, it will take between 5 and 10 years at mostas it has slowed down more and more over the last 40 years. Because sooner or later all batteries run out, and when they run out the bell will stop ringing, making Oxford University a little quieter.
