Articles

This Is What Neutrinos Look Like When Scientists Catch Them


Does this image look familiar? You may know it as an album cover for the
famous post-punk band ‘The Strokes’, but I’ve got a surprise for you. It’s really a picture of charged subatomic
particles inside a giant bubble chamber. Yeah, you heard me right. This artistic, iconic image is a visualization
generated by one of the many interesting ways we’ve tried to ‘see’ the subatomic particles
in our world…which is harder than it sounds. And that’s because subatomic particles can
be…tricky. Take neutrinos, for example. They’re a fundamental particle of the universe,
and they are quite literally everywhere around us, all the time–you have neutrinos passing
through you right now! But the catch is they have no charge and a
miniscule mass–some even say no mass at all. This means they interact so little with the
matter around them, we don’t notice them zinging through the earth and our bodies at
nearly the speed of light all day long. And that’s also what makes them so hard
to find, measure and understand! How do you look at a thing that doesn’t
interact with anything? ‘Very creatively’ is the answer. Which brings us back to this album cover. Like I mentioned, this dreamy image was generated
by the equally dreamy-sounding bubble chamber. The Gargamelle, for example, was a bubble
chamber used at CERN in the 70’s, consisting of a muon-neutrino beam and nearly 12 cubic
meters of heavy-liquid freon. Using Gargamelle, researchers could observe
the charged particles set in motion by the neutrinos…kind of like seeing the ‘shadow’
of the neutrino. This is the reason the neutrino is sometimes
referred to as the ghost particle–you can’t see the neutrino itself, but you can see them
knocking stuff around if you arrange things properly. Not only did this instrument help us ‘see’
neutrinos, but also provided crucial early evidence that quarks exist, . And even though
it was short-lived due to some cracks in its structure, this particular bubble chamber
played a pretty important role on the road to our current understanding of particle physics. That image is an actual picture of the real
interaction. It’s not a visualization generated abstractly
from some other data, it’s the real picture of the real thing in real time. Since then we’ve moved on to some more sophisticated
methods of neutrino detection, which you can learn more about here. But what about some more of the ones that
just look cool? Like liquid argon time projections, for example! Remember how Gargamelle used heavy-liquid
freon? Well, after that we moved on to argon, which
can be kept in its liquid phase more easily than the rest of the noble gases. In a liquid argon time projection chamber
(TPCs), one charged particle produces 55,000 electrons with every centimeter it travels. The way the electric and magnetic fields in
a TPC are set up allows the electrons to travel uniformly through the argon, and there are
tons of them. Both of these things mean that TPCs give really
clean, crisp high-resolution details of neutrino interactions and they’re able to capture
lots of them simultaneously. And last but not least, my favorite: Cherenkov
radiation. Which just looks like something out of a movie,
honestly. Nothing travels faster than the speed of light,
right? Well, that’s only true in a vacuum. Here on earth, light actually travels a bit
slower than its peak speed through transparent media like water, for example. When other subatomic particles, like electrons
given off as radiation from a nuclear reactor, travel through water faster than light does…it
produces this radically cool blue glow. Some of the neutrino observatories we use
today incorporate what we call water Cherenkov detectors. Like the Sudbury Neutrino Observatory, a neutrino
detection facility that happens to also be the deepest clean room in the world at 2 kilometers
below the earth’s surface! In this detector, a neutrino passing through
a special water tank sets a muon or an electron in motion, producing Cherenkov radiation. Scientists can see and reconstruct the moment
that light begins, therefore essentially ‘seeing’ the moment the neutrino hit that muon or electron. Sometimes science imitates art, I guess. Which one is your favorite? Fun fact, that Strokes album is called ‘Is
This It’, which kinda melds perfectly with the whole concept behind the cover. I can picture scientists standing around looking
at each other asking themselves…’is this it? Is this the neutrino?’. To keep up with all the developments on the
quantum level, subscribe to Seeker, and check out this video on quantum computing. Thanks for watching.

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