December 3, 2019 45

How Wiretapping Helped Transform Astronomy

How Wiretapping Helped Transform Astronomy


This episode is sponsored by The Ridge. Go to ridge.com/scishow and use promo code
“scishow” to get 10% off your next order. [♪ INTRO] For better or worse, World War I saw tons
of technological advancements. And one of the especially effective ones was
a method of early, remote wiretapping. During the war, militaries ran telephone lines
from their command centers to the battlefield, and the opposition did their best to intercept
those signals. To do this, they stuck two prongs into the
ground hundreds of meters away, then ran attached cables to a device called
an amplifier. The prongs could pick up signals from the
phone lines, and from a relatively safe distance, soldiers would be able to listen in on sensitive
conversations. The goal here was pretty obvious: that sweet,
sweet intel. But occasionally, those soldiers also picked
up signals that were a little more alien-sounding. Things like twangs and hisses and [whistle
sounds]. These were sounds that telegraph operators
had heard for years, and no one was quite sure what they were. But once researchers started studying them
more closely, they were able to turn those noises into one
of astronomy’s most important tools. Although soldiers continued to hear these
sounds until the end of the war, we didn’t understand what caused them until
1953. That year, researchers at Cambridge conducted
a study tracking when these noises occurred, and they realized that those sounds, which
they called whistlers, are caused by lightning. Or, more specifically, they’re caused by
the stuff that makes up lightning: plasmas. These are extremely hot, electrically-charged
gases. And because they’re charged, they can interact
with magnetic fields and form waves. When lightning strikes, these plasma waves
travel along Earth’s magnetic field lines, changing speed and pitch as they go. They vibrate at really low frequencies, and
can be heard as radio waves by field amplifiers, telegraph lines, or any
magnetic device. With this discovery, scientists could finally
explain where the weird telegraph and wiretapping
noises came from! But as they kept researching, they also realized
that whistlers weren’t the only plasma phenomenon
like this. Instead, plasma could make a bunch of sounds
depending on how it behaved. And together, these noises were named whistler-mode
instabilities or whistler-mode waves. Today, we know they aren’t just caused by
lightning. Auroras can make whistler-mode waves, too,
which sound equally bizarre. But regardless of where they come from, these
noises are more than just neat: They’re also really useful tools. Since each sound is produced by a distinct
phenomenon, we can use whistler-mode waves to understand
what’s happening in Earth’s atmosphere, on the Sun, and around other planets; really
anywhere we find charged gases. And there’s a lot we’ve learned from them! Take what we discovered with the Van Allen
Probes mission, which wrapped up operations in July 2019. It used whistler-mode waves to study the Van
Allen belts, two big lobes of plasma trapped in Earth’s
magnetic field. And it discovered that the shape of the belts changes
all the time in response to conditions on the Sun. The Van Allen belts are a major point where particles
from the Sun interact with Earth’s magnetic field. And since those interactions can affect things
like electronics, and satellites, and astronauts on the Space Station, they’re
pretty important to understand! Whistler-mode waves have also helped us understand
the gas giants in our neighborhood. For example, the 1970s Voyager probes heard
whistlers while flying by Jupiter and Neptune. And in 2006, the Cassini spacecraft heard
whistlers on Saturn. That allowed researchers to infer that those
planets have lightning storms, which opened up new areas of research. The Voyagers also gathered data on other whistler-mode
waves, and that gave us insight into how Jupiter
and Saturn interact with their moons. For example, Jupiter’s moon Io emits tons
of gases, which form an electrically-charged disk that
orbits the planet. This disk is pretty important to know about
when you’re planning a mission to Jupiter, at least, if you want to keep your spacecraft
functional. And whistler-mode waves have helped us figure
out how thick it is. Meanwhile, on Saturn, Voyager 1 heard specific
types of whistler-mode instabilities called hiss and
chorus waves. And analyzing them produced evidence that Saturn was pulling plasma from the atmosphere
of its moon Titan. It was siphoning the gases up along its magnetic
field lines. And although we’re not quite sure what the
implications of that are, it’s a really cool observation, because
the Earth and our Moon are totally different. Since these discoveries, probes have continued
to monitor whistler-mode waves to better understand these planets’ moons,
magnetic fields, and atmospheres. And since gas giants have a lot of atmosphere
to study, we’re really just scratching the surface. So early telegraph operators, and WWI spies
were listening to plasma, and from that we could learn about things
like gas giants! Science is so cool! Thanks for learning about this with me, and thanks to Ridge for sponsoring this episode
of SciShow Space! The Ridge make wallets and other products
to help you streamline your life. Their flagship product is The Ridge Wallet,
which launched on KickStarter in 2013 and today sits in the pockets of over half
a million people. And now they also have backpacks, phone cases,
and more, all intended to help you carry less extraneous
stuff. Like, their Commuter Backpack comes with a
power bank holder so you can charge your phone or laptop on
the go. There’s also a lifetime warranty on all
products, and free returns if you don’t love them. If you want to learn more, you can go to ridge.com/scishow. If you use the promo code “scishow,” you’ll
get 10% off and free worldwide shipping. [♪ OUTRO]

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