You may think scientists stationed in Antarctica
are just playing with penguins or studying
leopard seals.
But some of them are down there to fly balloons
or watch ice cubes.
Special balloons and special ice cubes.
Like the balloon-based experiment ANITA, which
has seen things we thought weren’t possible,
and could show us that our current knowledge
of particle physics is just the tip of the
iceberg.
ANITA, short for the Antarctic Impulsive Transient
Antenna, was designed to study ultra-high-energy
cosmic neutrinos by taking advantage of the
ice sheets that blanket Antarctica.
Now I know you are already an expert in neutrinos
because you watch all my videos, right?...
Right??
Okay then, quick refresher: neutrinos are
ultra lightweight and chargeless particles
that almost never interact with other matter.
Because of those properties, they can travel
through entire planets without being affected.
At least that’s true for the low energy
neutrinos we usually talk about.
That variety mostly comes from atomic decay
deep inside the sun act like me at a party;
rarely interacting with anything.
These are the same neutrinos we use massive tanks
of ultrapure water like the Super-Kamiokande
detector to spot.
But there are other types of neutrinos, and
the ultra-high energy variety is something
of a different animal.
They have wider “cross sections” meaning
they’re more likely to collide with other
particles as they pass.
They’re made during high-energy collisions
like when cosmic rays and photons interact.
Then they zip along through the universe until
they reach us here on Earth.
Because of that bigger cross section, they
don’t penetrate very far before they interact
with something, causing a cascade of particles
that gives off what scientists describe as
a “snap” of radio frequencies.
To pick up these fairly faint signals, known
as Askaryan pulses, scientists need somewhere
without a lot of other radio signals.
They also need a lot of a radio transparent
medium so the high-energy particle interaction
can occur, but the Askaryan pulses can still
propagate.
A medium like ice.
And that is why the ANITA experiment was flown
over Antarctica.
Attached to a NASA long Duration Balloon,
the antenna flew a total of four missions
from 2006 to 2016, staying aloft between three
and five weeks at a time.
While it was up there it picked up the refracted
radio signals coming from the ice below.
Scientists basically turned an entire continent
into a scientific instrument.
That is some comic-book villain logic.
And it totally worked.
Actually, it worked so well it spotted something
we can’t explain with our current particle
physics.
On multiple occasions, ANITA detected signals
coming straight up from beneath it, meaning
in theory they must have traveled through
the earth as opposed to just skimming through
the ice at an angle.
Since ultra high-energy neutrinos interact
much more frequently than their low-energy
counterparts, they shouldn’t be able to
travel through the entire Earth.
To double check there was no mistake, they
looked through the results of another Antarctic
based neutrino detector, IceCube.
Not the rapper-turned-actor, he's not down there.
Making use of stable ultra-clear ice, IceCube’s
sensors monitor a cubic kilometer of ice for
neutrino interactions starting 1500 meters
below the surface.
Sure enough, the data revealed three other
events where particles seemed to come straight
up from below.
Three detections may not sound like a lot,
but mathematically it’s way more than they
should be seeing.
It shouldn’t even happen once.
This is potentially huge news for particle
physics.
If we can rule out the idea that these are
neutrinos that are blasting at us from one
specific place so intensly that the detectors
can see them –– what’s called the ‘point
source hypothesis’ –– then these can’t
be ultra-high energy neutrinos at all.
Which means NOTHING in the standard model
explains it.
This means it could point to other theories
that could supplant or expand the standard
model one day.
But scientists aren’t ready to throw out
the standard model just yet.
More data is necessary, so ANITA’s proposed
successor, the Payload for Ultrahigh Energy
Observations, may continue the hunt for these
inexplicable interactions.
The resulting data from it, and experiments
like ANITA and IceCube could help tell the
Large Hadron Collider where to look as it
searches for particles outside the standard
model.
Of course, we can’t discuss Antarctic research
without acknowledging the giant penguin in
the room: the climate crisis.
Check out this episode of Focal Point about
scientists creating an “Ice Vault” in
Antarctica to store glaciers’ “memories”
before they’re gone forever.
And for more stone-cold-stunning science news,
subscribe, and I’ll see you next time on Seeker.
