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physics.ox.ac.uk/Erin McCarthy
physics.ox.ac.uk/Erin McCarthy

What’s the World’s Longest Running Science Experiment?

physics.ox.ac.uk/Erin McCarthy
physics.ox.ac.uk/Erin McCarthy

Between our look at the longest prison sentences the other day and the 69-year-old pitch drop experiment finally getting caught on camera last month, reader Justin got curious and wrote in to ask, “What’s the longest experiment that scientists have filled their decades or lifetimes with?”

While the pitch drop gets the nod for longest uninterrupted duration, there are at least two projects that started before it and keep going today, but have had some stops and starts along the way. The older of the two, and grand champion for years-in-progress, is the Oxford Electric Bell, a.k.a. the Clarendon Dry Pile.

The bell, as the name suggests, is an experimental electric bell kept at the University of Oxford’s Clarendon Library. It was built by Watkin and Hill, an instrument-making firm in London, and purchased by Robert Walker, a professor at Oxford. In 1840, he set it ringing. Today the bell still tolls. 

The bell is actually two metal bells, with a metal clapper set between them. The clapper is powered by two “dry piles,” an early form of battery.  Dry piles were normally composed of alternating strips of metal foil and paper—sometimes hundreds or thousands of layers thick—like electric club sandwiches. A variety of metals could be used, but Watkin and Hill left no record of what their piles were made of. 

Scientists are eager to find out just how long the mystery battery can go, and then open it up and find out what it's made of, but the whole thing is a bit of a waiting game. Whatever its makers used, the device has some staying power. Guinness World Records called the bell’s dry piles the “world’s most durable battery,” and for one hundred and seventy three years, minus occasional interruptions, the bell has been ringing. 

The clapper oscillates between the two bells at a usual frequency of 2Hz, or two cycles per second, depending on the weather. High humidity can cause the clapper’s movement to slow and even stop, but when the humidity drops the bell can begin again without external intervention. As the clapper strikes and rings one bell, the corresponding dry pile charges and electrostatically repels it. The clapper then swings toward the other bell, and the same thing happens. 

Because there’s just little bits of energy being discharged through the process, the drain on the battery—whatever it's made of—is very small, so it can happen again and again and again, causing a continuous ring. If we fudge a little and say that the clapper has had a 2Hz frequency for the entire 173 years, that means it’s made a whopping 10,911,456,000 strikes against those bells. 

Eventually, the electrochemical energy of the dry cells will be exhausted and the bell will go quiet. Not knowing what powers the contraption, though, no one is sure when that will happen, and silence instead could come when the clapper or one of the bells wears out. Not that anyone can hear it, anyway: To keep the patrons of the Clarendon Library from going mad from the noise, the bell is kept encased in sound-damping glass. 

The second longest-running experiment is an experimental clock (called the Beverly Clock) in New Zealand that's been ticking since 1864 without needing to be wound, and is driven by variations in atmospheric pressure and temperature.

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Big Questions
What's the Difference Between Gophers and Groundhogs?
Gopher or groundhog? (If you chose gopher, you're correct.)
Gopher or groundhog? (If you chose gopher, you're correct.)
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Gophers and groundhogs. Groundhogs and gophers. They're both deceptively cuddly woodland rodents that scurry through underground tunnels and chow down on plants. But whether you're a nature nerd, a Golden Gophers football fan, or planning a pre-spring trip to Punxsutawney, Pennsylvania, you might want to know the difference between groundhogs and gophers.

Despite their similar appearances and burrowing habits, groundhogs and gophers don't have a whole lot in common—they don't even belong to the same family. For example, gophers belong to the family Geomyidae, a group that includes pocket gophers (sometimes referred to as "true" gophers), kangaroo rats, and pocket mice.

Groundhogs, meanwhile, are members of the Sciuridae (meaning shadow-tail) family and belong to the genus Marmota. Marmots are diurnal ground squirrels, Daniel Blumstein, a UCLA biologist and marmot expert, tells Mental Floss. "There are 15 species of marmot, and groundhogs are one of them," he explains.

Science aside, there are plenty of other visible differences between the two animals. Gophers, for example, have hairless tails, protruding yellow or brownish teeth, and fur-lined cheek pockets for storing food—all traits that make them different from groundhogs. The feet of gophers are often pink, while groundhogs have brown or black feet. And while the tiny gopher tends to weigh around two or so pounds, groundhogs can grow to around 13 pounds.

While both types of rodent eat mostly vegetation, gophers prefer roots and tubers (much to the dismay of gardeners trying to plant new specimens), while groundhogs like vegetation and fruits. This means that the former animals rarely emerge from their burrows, while the latter are more commonly seen out and about.

Groundhogs "have burrows underground they use for safety, and they hibernate in their burrows," Blumstein says. "They're active during the day above ground, eating a variety of plants and running back to their burrows to safety. If it's too hot, they'll go back into their burrow. If the weather gets crappy, they'll go back into their burrow during the day as well."

But that doesn't necessarily mean that gophers are the more reclusive of the two, as groundhogs famously hibernate during the winter. Gophers, on the other hand, remain active—and wreck lawns—year-round.

"What's really interesting is if you go to a place where there's gophers, in the spring, what you'll see are what is called eskers," or winding mounds of soil, Blumstein says [PDF]. "Basically, they dig all winter long through the earth, but then they tunnel through snow, and they leave dirt in these snow tunnels."

If all this rodent talk has you now thinking about woodchucks and other woodland creatures, know that groundhogs have plenty of nicknames, including "whistle-pig" and "woodchuck," while the only nicknames for gophers appear to be bitter monikers coined by Wisconsin Badgers fans.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
Why Does Santa Claus Give Coal to Bad Kids?
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The tradition of giving misbehaving children lumps of fossil fuel predates the Santa we know, and is also associated with St. Nicholas, Sinterklaas, and Italy’s La Befana. Though there doesn't seem to be one specific legend or history about any of these figures that gives a concrete reason for doling out coal specifically, the common thread between all of them seems to be convenience.

Santa and La Befana both get into people’s homes via the fireplace chimney and leave gifts in stockings hung from the mantel. Sinterklaas’s controversial assistant, Black Pete, also comes down the chimney and places gifts in shoes left out near the fireplace. St. Nick used to come in the window, and then switched to the chimney when they became common in Europe. Like Sinterklaas, his presents are traditionally slipped into shoes sitting by the fire.

So, let’s step into the speculation zone: All of these characters are tied to the fireplace. When filling the stockings or the shoes, the holiday gift givers sometimes run into a kid who doesn’t deserve a present. So to send a message and encourage better behavior next year, they leave something less desirable than the usual toys, money, or candy—and the fireplace would seem to make an easy and obvious source of non-presents. All the individual would need to do is reach down into the fireplace and grab a lump of coal. (While many people think of fireplaces burning wood logs, coal-fired ones were very common during the 19th and early 20th centuries, which is when the American Santa mythos was being established.)

That said, with the exception of Santa, none of these characters limits himself to coal when it comes to bad kids. They’ve also been said to leave bundles of twigs, bags of salt, garlic, and onions, which suggests that they’re less reluctant than Santa to haul their bad kid gifts around all night in addition to the good presents.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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