Science is all about asking questions and
then running carefully controlled experiments to find the answers. Most of the time, it doesn’t take too long
to actually run those experiments — maybe a few years at most. But some experiments can take way longer,
to the point where the original question is almost forgotten, and the researchers who
originally asked the question are long gone. From an electric bell that refuses to shut
up to lead-sealed microbial time-capsules, here are some of the world’s longest-running
experiments. Most mechanics will tell you that to keep
your car running smoothly, you should change the battery every four years. But in a corner of the physics department
in the University of Oxford, there is a battery that’s been running for 177 years. And no one knows how it’s lasted that long. In 1840, Oxford physics professor Robert Walker
bought a weird-looking contraption consisting of two long, sulfur-covered cylinders attached
to two bells. A metal ball slowly vibrates back and forth
between the bells, propelled by the charge propelled by the charge from the battery. The type of battery it uses is called a dry
pile, because unlike most modern batteries, the electrolyte, which is the stuff that actually allows
electricity to flow, is a paste rather than a liquid. The bells were built only 40 years after the
very first battery was invented, and the batteries powering the metal ball were only expected
to last 4-5 years. So it’s pretty weird that this thing has
lasted almost two centuries, and physicists would love to know more about how its batteries
work. But unfortunately, the cylinders are sealed,
and the records of their manufacture were lost long ago. We do have some clues about these batteries. Other dry piles made at the time had layers
and layers of metal discs stacked on top of each other, with sulfur sealing everything
in. The discs were usually coated with zinc sulfate
on one side, and manganese dioxide on the other. These days, zinc sulfate is mostly used as
a dietary supplement, but manganese dioxide is still used in modern dry-cell batteries. But something about the way this thing’s
batteries were made has let them last a ridiculously long time. The thing is, until we open up the cylinders, we won’t know for sure that’s what’s inside. And at this point, scientists don’t really
want to crack it open and investigate — they’d rather see how long it keeps going first. Once it stops though, I imagine they’ll
organize the autopsy pretty quickly. Talk to a farmer, and they’ll probably tell
you that one of their biggest challenges is weeds. Sometimes it seems like they’re fighting
a never-ending battle against them. That’s because weeds have this annoying
property where they can lie dormant, chilling out just under the surface. They lull you into a false sense of security
until you get complacent and then BAM! They’re all over the place again. There have been plenty of studies by agricultural
scientists trying to find out how long weeds can hang around in the soil. But the oldest, and longest-running, of these
experiments can be found on the grounds of Michigan State University. There are 5 whiskey bottles, filled with sand,
buried upside down in a top-secret location. And no, they aren’t the leftovers of some
19th century rave. They’re the legacy of botanist William James
Beal. He filled 20 of these bottles with seeds from
21 different species of weeds, plus moist sand. He buried them angled down so they wouldn’t
fill up with water, and then planned to dig one up every five years and plant the seeds
to see which survived. At least, that was the plan. In 1919, there was an early frost and the
bottle couldn’t be excavated without a jack-hammer, so they waited until 1920, and decided to
extend the interval to ten years from then on. In 1990, instead of digging up a bottle, the
researchers who’d taken over the project extended the interval again to 20 years. The most recent one was opened in 2000, and
there are five left. Which means the last bottle will be unearthed
in 2100. When researchers planted the seeds from the
bottle they dug up in 2000, seeds from only two of the original species sprouted into
plants. That’s pretty much what they expected, since
the last time seeds from more than three species sprouted was in 1930. But they’re curious whether seeds from the
hardiest species will keep sprouting when they dig up future bottles. By now, the point of the experiment has kind
of flipped. The researchers aren’t trying to figure
out how to kill weeds — they want to know more about how seeds stay viable to help save
plants that might be going extinct. Thousands of people all over the world have
decided to sit and watch something that flows even slower than paint dries. All for the chance at witnessing the next
big moment in a 90-year-old experiment. It’s called The Pitch Drop Experiment. In 1927, Thomas Parnell, a physics professor
at the University of Queensland in Australia, set up a demonstration to show that pitch,
aka asphalt, actually flows. Even though it looks and acts like a solid. And it turns out that it does flow … just,
very slowly. The experiment consists of a large funnel
filled with black pitch that slowly drips into a beaker. It took 8 years for the first drop to fall,
and in the ninety years since, there have been 8 more drops. Based on these drops, researchers found that
pitch has a viscosity 30 billion times greater than water — meaning, it flows about 30
billion times more slowly than water does. In the 1980s, scientists at the university
debated taking down the experiment, since they figured it had served its purpose. But then, two things happened. First, they realized that no one had ever
actually seen the drop fall. They’d just found another drop in the beaker
the next morning. And second, the pitch started acting… weird. The drops had been falling at a semi-consistent
rate up until this point, but the 8th drop took a lot longer to fall than the previous
ones. It fell in 2000, but a really badly timed
blackout meant the cameras set up to record the drop failed. The 9th drop fell in 2014, and was caught
on camera. But now, it seems like the pitch is flowing
faster, and scientists aren’t sure exactly why. So the experiment is still going, and researchers
hope the pitch’s behavior will give us insights into other super-high viscosity materials
like plastics and silicone. According to the Centers for Disease Control,
cardiovascular disease is the leading cause of death in the United States, claiming over
600,000 people a year. And scientists back in the 1940s wanted to
know more about how to prevent it. In 1948, about 5,000 people in Framingham,
Massachusetts volunteered to be a part of a massive, long-term study. Researchers picked healthy adults that showed
no signs of heart disease and started monitoring their lifestyle and physical health. The study linked cholesterol, high blood pressure,
and other factors like smoking to heart disease and stroke. And it’s still going, even though there
are very few of the original participants left. In the 1970s, the adult children of the first
subjects were enrolled and, more recently, a third generation was added to the study. And as the study continues, it’s helping
us learn more about the role of genetics in heart disease. Evolution happens very slowly. It can take generations for a single change
to spread through a population. And it can be hard to study exactly how those
changes spread. When you’re dealing with nature, you can’t
just re-wind the clock and see if the same adaptations will happen again. Which is why, in 1988, American biologist
Richard Lenski decided to grow 12 cultures of E. coli bacteria. The thing about bacteria is that they don’t
live very long. So over the nearly 30 years that Lenski’s
team has been growing these cultures, they’ve cycled through tens of thousands of generations. And the group has had a front-row seat the
way the populations have changed under different conditions. Since it’s a laboratory experiment, they
can grow multiple cultures at the same time and see if they do the same thing. Over time, the E. coli have gotten bigger,
started mutating more often, and gotten better at digesting the sugar in the solution they’re
grown in. And around 33,000 generations in, one strain
evolved a more complex mutation that allows it to digest citrate, a compound in the solution, in a way that E. coli aren’t normally able to do. From our point of view, this experiment has
only been running since 1988 — which, compared with some of the other experiments I just
mentioned, basically makes it a tiny baby experiment. But from the E. coli’s perspective, they’ve
been growing and evolving over 60,000 generations. Which sort of makes it the longest-running
experiment in history, right? Technically, this one isn’t a long-term
study … yet. Microbiologists have been studying life in
tough places on our planet for decades, and they’ve learned that some microbes have
a special ability: When conditions get too extreme, they can
survive, dormant and dried out, while they wait for things to improve. Then they just wake up and go about their
lives. They might be able to survive this way for
thousands of years, but we’re still not totally sure how they do it. So a group of researchers from around the
globe have set up what they’re calling the 500-year microbiology experiment. They’ve dried out and preserved microbes
in two sets of 800 glass vials different boxes. One box is lead-lined to protect the microbes
against radiation, and the other’s just using glass to keep them isolated. It’s a little bit like the seed experiment,
but with less sand, and microbes instead of weeds. For now, every other year, they’re opening
up three vials from each box to rehydrate them and see if they’ve survived, and to
analyze their DNA for damage. Starting in 2038, they’ll only open new
vials every 25 years, which means that assuming the microbes survive that long and there’s
no zombie apocalypse, the experiment will finish up in 2514! Researchers are hoping the results of these
experiments will help us understand the extremes of life: how long can some of the simplest
organisms survive being preserved and then reanimated? Knowing more about life in the most extreme
conditions on Earth will also help us learn more about where life could have evolved on
other planets. But there’s another side to this experiment,
too: the vials of preserved microbes are a sort of time-capsule. Researchers investigating them in the 26th
century will have a unique snapshot of microbial communities from 500 years ago. It’ll be interesting to see what’s changed
and how they’ve evolved. Not that we’re going to get to see those
changes, though. Lucky future scientists. We’ll all be dead. This episode of SciShow was brought to you
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