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Our world,
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our solar system, our universe.
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None of it would exist without
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a ghostly particle
called the neutrino.
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They can pass right
through a wall,
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right through a planet,
right through a star,
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without even noticing.
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They are our early
warning system.
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Whenever there's trouble
in the universe,
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you can expect
a flood of neutrinos.
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00:00:28,895 --> 00:00:32,598
Neutrinos trigger
star-killing explosions,
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00:00:32,699 --> 00:00:33,699
supernovas.
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00:00:35,668 --> 00:00:39,905
Neutrinos can answer
so many questions, from why
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do we exist to, how was
the universe created?
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These tiny particles
saved the infant cosmos
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from annihilation.
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They cause destruction.
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They, you know, sometimes
they blow up a star.
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But, at the end of the day,
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they can be the very reason
that we exist at all.
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Neutrinos are the key
to how the universe works.
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In the 1960s, our sun
appeared to be dying.
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There was
tantalizing evidence that
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our sun might be shutting down.
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This question was
a biggie for astronomers.
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If the sun isn't undergoing
nuclear fusion at the rate
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we thought it was,
then that's a big deal.
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Was the sun's nuclear
core shutting down?
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Stars, including our own sun,
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are giant nuclear
fusion reactors.
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Inside these fusion reactors,
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hydrogen atoms smash together,
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producing heat and light in
the form of photons.
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All the light
and all the heat that
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we receive on Earth
comes from the sun.
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If the sun were to suddenly
start cooling off,
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that would be seriously bad
news for us.
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How do we check if
the sun is shutting down?
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We have a spacecraft
monitoring the solar surface,
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but they can't see into
the heart of the reactor,
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the sun's core.
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You can see the surface,
and the sun is very bright.
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That makes it very easy
to study.
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Sadly, the core of the sun is
under 400,000 miles of sun,
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and that makes it pretty hard
to look at.
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Studying the light made
in the core doesn't help.
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By the time it gets to us,
it's old news.
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Imagine a photon
or this particle of light
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that's born in the center
of a star,
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and now imagine that it wants to
reach the surface of the star.
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It turns out that the star is
so dense in the center,
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and the star itself is so
physically large that it will
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take it 30,000 years
to escape the core.
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It's like being
at a cocktail party,
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where you're trying to leave,
and every time that you
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make another step
towards the door,
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another group of people want
to talk to you, and you also
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want to talk to them,
and then it just takes
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30,000 years to leave
your cocktail party.
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Any information
we get from sunlight
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about what's going on
in the core
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is tens of thousands
of years old.
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If you want the current
events, the news headlines of
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what's going on in the sun's
core right now,
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photons are not
the way to do it.
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You want neutrinos.
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So what are these
mysterious particles?
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Neutrino literally means
tiny neutral one, right?
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We think they carry no net
electrical charge,
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and they're really,
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really small,
so we call them neutrinos.
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Neutrinos don't like to
interact with matter.
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They fly through
almost everything.
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The sun itself is generating
enough neutrinos to
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send 60 billion of them
through your thumbnail
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every single second,
and you will spend...
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This is the craziest thing...
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You will spend your entire
life without feeling
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a single one.
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Neutrinos form during
nuclear fusion reactions
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inside the core of stars...
Hydrogen atoms collide,
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fuse into helium, and release
photons of light and neutrinos.
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In the core of the sun,
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nuclear bombs are going off,
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and all of these nuclear
reactions release neutrinos.
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That's about
10 trillion, trillion,
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trillion neutrinos being
created every second.
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The trillions of
neutrinos shoot out of the core
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and up through 323,000 miles
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of the sun to the surface.
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A neutrino basically
doesn't even notice
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the sun is there.
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It sails out at very close
to the speed of light.
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If you imagine
a gridlocked highway,
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the neutrinos would be
the motor bikes that are just
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zooming through the traffic.
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The solar neutrinos
race towards Earth.
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Most pass straight through.
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All the neutrinos,
the trillions upon
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trillions of neutrinos
passing through the Earth
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every single second,
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the entire Earth
will only interact
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with one neutrino
out of 10 billion.
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Because they pass
through anything,
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they're hard to detect.
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I consider neutrino physicists
to be the ghost hunters of
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the particle physics realm,
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because we study something
so elusive, and they're really,
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really hard to nail down
and study.
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Hard, but not impossible.
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While most neutrinos pass
through Earth,
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a few collide with atoms in
the planet, and we can detect
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those collisions.
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To spot these tiny impacts,
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we built underground
neutrino detectors
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with giant sensors
full of chlorine.
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When a neutrino strikes
this chlorine atom,
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it transforms into argon.
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And then we can pick out
the argon atoms from
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the detector and count them up
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to see how many neutrinos
actually struck our atoms.
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The sensors detected
neutrinos from the sun,
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but the numbers were
lower than expected.
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Detectors were only
detecting about a third of
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the number of the neutrinos that
their models predicted.
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This is called
the solar neutrino problem.
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That is a big deal...
That either means
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we're doing something wrong
or our physics is wrong.
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Where were the missing
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two-thirds
of the solar neutrinos?
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They weren't AWOL.
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The detector had missed them,
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because neutrinos can
change identities.
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It turns out neutrinos can
change what kind
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of neutrino they are as
they're flying through space,
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and we call this
flavor changing.
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Neutrinos come in
three different flavors.
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Think of them as different
types of playing cards.
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The king is
the electron neutrino.
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The muon neutrino is the queen,
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and the jack
is the tau neutrino.
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The sun produces
electron neutrinos,
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but by the time
they reach Earth,
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they could be
a different flavor.
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As they travel to the Earth,
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they constantly wave back
and forth,
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trading their identities.
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So you never know exactly
what you're gonna get
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until it arrives at the Earth,
and we observe it.
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It could be... anything.
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The detectors weren't
seeing the different flavors.
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But when we fine-tuned
the sensors,
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we saw all the solar neutrinos.
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So there were actually
enough neutrinos coming from
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the sun, but we were only
detecting a third of them.
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Flavor-changing neutrinos
showed the sun was healthy.
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The changing identities
also answered
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an important question
about neutrinos.
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Do they have mass?
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Einstein showed that only
particles without mass can
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travel at the speed of light,
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and these particles
don't experience time.
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But neutrinos
can change their flavor,
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so that must happen over time.
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And that means neutrinos can't
travel at the speed of light,
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and so they must have mass.
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When scientists first started
thinking about neutrinos,
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they thought that
they were massless,
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and if a neutrino has no mass,
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then it's bound to be one flavor
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or one type of neutrino forever.
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Experiments proved that
neutrinos have mass.
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And if they have mass,
they must produce gravity,
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which means they can influence
other things around them.
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Neutrinos are also involved
in moments of huge
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cosmic violence.
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Whenever there's trouble
in the universe,
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you can expect
a flood of neutrinos.
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These floods of neutrinos
are the key to
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some of the biggest bangs in
the cosmos.
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And new research suggests
that without them,
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there would be no solar
system, no planets, and no us.
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Neutrinos are one of
the smallest particles in
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the cosmos.
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However, new research
suggests they play
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a role in some of
the universe's biggest events.
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Exploding stars
called supernovas.
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The deaths of giant stars.
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But there is a mystery
surrounding
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their explosive ends.
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Why do these giant stars
end their lives so violently?
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This is a major puzzle
in astrophysics.
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We got a lead when we detected
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a huge flash of light in
the large Magellanic Cloud,
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a satellite galaxy of
the Milky Way.
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The light was
a supernova explosion.
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But three hours
before the flash,
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astronomers spotted
something else
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a burst of neutrinos coming
from the same region of the sky.
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This was the first time
we have seen neutrinos
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coming from a source
other than the sun,
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so there must be some sort of
connection between neutrinos
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and supernovae,
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but... but what is
that connection?
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When a star runs out of fuel,
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its core crushes
down to a neutron star.
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Then the rest of the star
collapses inwards,
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hits the neutron star,
and bounces out,
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triggering a supernova.
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But computer models of
supernovas reveal a problem.
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The star doesn't explode.
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When we run computer
simulations of how supernova
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might work, after this bounce,
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the explosion stalls,
it peters out.
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The supernova isn't so super.
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It needs another source of
energy to
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propel it to become
an actual explosion.
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Could the neutrinos
that appeared before
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the explosion be that
energy source?
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First, we need to understand
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what created
the burst of neutrinos.
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The core of the star
collapses inward and eventually,
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the outer layers of the star
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fall in toward that star at
an appreciable fraction of
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the speed of light.
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As the core rapidly collapses,
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the intense pressure squeezes
atoms together.
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That core of iron gets
squeezed down
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to become a neutron star.
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The electrons and the protons
that are part of this core are
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under so much pressure that
they fuse together to form
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neutrons and neutrinos
in the process.
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The neutrinos shoot out
from the newly formed
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neutron star core,
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carrying an enormous amount
of energy.
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99% of the energy is
carried by the neutrinos.
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Neutrinos are the main event.
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Trillions of neutrinos
smash into
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the remains of the dying star.
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And when those neutrinos are
flying out of that core region,
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a very tiny fraction of them
interact with the gas,
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and that fraction heats the gas.
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00:13:48,794 --> 00:13:50,428
Everything that's hanging around
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this newborn neutron star
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get heated to
an unimaginable degree.
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The heat creates pressures
in the surrounding gas.
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00:14:00,239 --> 00:14:02,740
It builds and builds
until it triggers
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00:14:02,842 --> 00:14:04,242
an enormous shock wave.
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00:14:07,012 --> 00:14:09,180
And then the actual explosion,
250
00:14:09,315 --> 00:14:11,683
the actual fireworks show,
begins.
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The star explodes
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in one of the brightest events
in the universe,
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powered by neutrinos.
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We think that if
it weren't for neutrinos,
255
00:14:25,898 --> 00:14:28,399
supernovas might not even exist.
256
00:14:29,869 --> 00:14:32,270
And we might not exist either.
257
00:14:32,371 --> 00:14:35,373
Our bodies contain heavy
elements, like calcium
258
00:14:35,474 --> 00:14:39,210
in our bones
and iron in our blood.
259
00:14:39,311 --> 00:14:42,847
These elements form in
supernovas and are
260
00:14:42,948 --> 00:14:46,184
scattered across
the cosmos by the blast.
261
00:14:46,285 --> 00:14:51,389
Neutrinos are what
kindle the fire
262
00:14:51,490 --> 00:14:54,392
in the forages of
these elements.
263
00:14:54,493 --> 00:14:57,161
And without the neutrinos,
you don't have the elements.
264
00:14:57,263 --> 00:14:58,329
And without the elements,
265
00:14:58,430 --> 00:15:00,465
you don't have planets
like the Earth.
266
00:15:00,566 --> 00:15:03,902
And without planets like
the Earth, you don't have life.
267
00:15:04,003 --> 00:15:07,171
There's this common phrase,
you know, we are stardust,
268
00:15:07,273 --> 00:15:09,307
which is true,
but I like to think
269
00:15:09,408 --> 00:15:12,010
we're more like neutrino dust.
270
00:15:14,446 --> 00:15:17,916
Neutrinos reveal
how supernovas explode,
271
00:15:18,017 --> 00:15:21,519
and they also warn us when one
is about to detonate.
272
00:15:21,620 --> 00:15:23,421
So neutrinos can even be these
273
00:15:23,522 --> 00:15:26,457
ghostly signposts for
something very violent
274
00:15:26,558 --> 00:15:28,036
that's happened in
the universe, right?
275
00:15:28,060 --> 00:15:30,395
We detect a sudden burst
of neutrinos.
276
00:15:30,496 --> 00:15:33,431
It could be that a star has
gone supernova somewhere.
277
00:15:35,367 --> 00:15:38,736
Neutrino bursts
are cosmic watchdogs,
278
00:15:38,837 --> 00:15:40,972
alerting us to danger.
279
00:15:41,073 --> 00:15:44,142
Neutrinos are definitely a sign
280
00:15:44,243 --> 00:15:47,712
that something
troubling is happening.
281
00:15:47,813 --> 00:15:50,982
And in 2017, a single neutrino
282
00:15:51,083 --> 00:15:54,485
told us about something
very troubling,
283
00:15:54,586 --> 00:15:57,221
one of the most intense
sources of radiation
284
00:15:57,323 --> 00:16:01,059
in the universe, and it was
pointing right at us.
285
00:16:10,803 --> 00:16:13,171
Spring 2017.
286
00:16:13,272 --> 00:16:15,506
Scientists at the South Pole
are on the lookout
287
00:16:15,607 --> 00:16:16,607
for neutrinos.
288
00:16:18,010 --> 00:16:21,946
These ghostly particles are
extremely hard to detect.
289
00:16:23,515 --> 00:16:25,984
Neutrinos are the biggest
introverts in the universe.
290
00:16:26,085 --> 00:16:28,786
They just don't like
interacting with anything, so if
291
00:16:28,887 --> 00:16:30,231
you want to detect
one of these things,
292
00:16:30,255 --> 00:16:31,456
you need a lot of stuff.
293
00:16:31,557 --> 00:16:34,525
You need a lot of atoms
in one spot.
294
00:16:34,626 --> 00:16:36,627
So scientists built a facility
295
00:16:36,729 --> 00:16:38,796
with lots of available atoms.
296
00:16:38,897 --> 00:16:41,599
It's called IceCube,
with neutrino
297
00:16:41,700 --> 00:16:45,770
detectors buried deep beneath
sheets of ice.
298
00:16:45,871 --> 00:16:48,673
It turns out
that water is a very,
299
00:16:48,774 --> 00:16:52,377
very good detector of neutrinos.
300
00:16:52,478 --> 00:16:54,679
To catch neutrinos,
you need to build
301
00:16:54,780 --> 00:16:57,782
a very large target for
a reasonable cost.
302
00:16:57,883 --> 00:17:02,754
Large areas of ice
checks both boxes.
303
00:17:02,855 --> 00:17:06,057
So you need a lot of water
that's very, very clean.
304
00:17:06,158 --> 00:17:08,593
What's the cleanest source
of water on the planet?
305
00:17:08,660 --> 00:17:11,729
The Antarctic Ice Sheet.
306
00:17:11,830 --> 00:17:14,265
The Antarctic detector IceCube
307
00:17:14,366 --> 00:17:18,803
measures 3,280 feet across.
308
00:17:18,904 --> 00:17:22,407
That's about the length of
nine football fields.
309
00:17:22,508 --> 00:17:27,011
It contains 5,000 sensors,
surrounded by more water
310
00:17:27,112 --> 00:17:30,048
atoms than there are
stars in the universe.
311
00:17:33,018 --> 00:17:35,820
September 22nd, 2017.
312
00:17:37,623 --> 00:17:42,226
IceCube detects a neutrino
colliding with a water atom.
313
00:17:42,327 --> 00:17:45,530
When a neutrino hits an ice
atom inside of IceCube,
314
00:17:45,631 --> 00:17:47,565
a charged particle flies out,
315
00:17:47,666 --> 00:17:49,867
and it's this charged particle
that makes a signal
316
00:17:49,968 --> 00:17:50,968
we can detect.
317
00:17:51,070 --> 00:17:53,971
The ejected particle
appears to fly out
318
00:17:54,073 --> 00:17:56,207
faster than the speed of light.
319
00:17:56,308 --> 00:17:58,676
At first glance, this
looks like it violates
320
00:17:58,777 --> 00:18:00,011
something very, very important
321
00:18:00,112 --> 00:18:03,281
about physics, that nothing
can travel faster than light.
322
00:18:03,382 --> 00:18:07,185
But light slows down when
traveling through a medium like
323
00:18:07,286 --> 00:18:11,355
air or water, and it is possible
324
00:18:11,457 --> 00:18:15,426
for other things,
other particles, to outrun light
325
00:18:15,527 --> 00:18:17,261
in a medium.
326
00:18:17,362 --> 00:18:20,431
As it hurtles through the ice,
327
00:18:20,532 --> 00:18:24,168
the particle generates a burst
of blue light called
328
00:18:24,269 --> 00:18:26,104
Cherenkov radiation.
329
00:18:26,205 --> 00:18:27,839
It's almost like a sonic boom.
330
00:18:27,940 --> 00:18:29,700
If you travel faster than
the speed of sound,
331
00:18:29,775 --> 00:18:32,376
there's a boom, right?
- When you hear that boom,
332
00:18:32,478 --> 00:18:35,813
you also see this cone of wind.
333
00:18:35,914 --> 00:18:38,916
It's the same thing
with Cherenkov radiation.
334
00:18:39,017 --> 00:18:40,518
You get this cone of light.
335
00:18:42,521 --> 00:18:44,989
Neutrinos carry
different amounts of energy.
336
00:18:45,090 --> 00:18:49,427
Some, like the 2017 neutrino,
337
00:18:49,528 --> 00:18:51,696
carry quite a punch,
338
00:18:51,797 --> 00:18:55,800
and the energy of the neutrino
depends on its source.
339
00:18:55,901 --> 00:19:00,037
High-energy neutrinos come
from high-energy events,
340
00:19:00,139 --> 00:19:02,507
so we're looking for stuff
blowing up.
341
00:19:02,608 --> 00:19:04,208
We're looking for
stuff colliding.
342
00:19:04,309 --> 00:19:06,878
We're looking for stuff
colliding and blowing up.
343
00:19:06,979 --> 00:19:08,880
We're looking for
awesome things.
344
00:19:08,981 --> 00:19:13,951
The blue burst
of Cherenkov radiation
345
00:19:14,052 --> 00:19:16,387
gives us a clue about
the fearsome origin of
346
00:19:16,488 --> 00:19:18,122
the neutrino.
347
00:19:18,223 --> 00:19:21,859
We can follow the path
of that blue light,
348
00:19:21,960 --> 00:19:26,898
and we can look backwards to see
where the neutrino came from.
349
00:19:29,201 --> 00:19:30,535
We track the neutrino to
350
00:19:30,636 --> 00:19:33,838
a galaxy nearly six billion
light-years away.
351
00:19:35,207 --> 00:19:36,841
At its heart sits one of
352
00:19:36,942 --> 00:19:39,744
the most powerful objects in
the universe,
353
00:19:44,016 --> 00:19:45,249
a blazar.
354
00:19:46,518 --> 00:19:52,456
A blazar is the biggest,
baddest form of feeding
355
00:19:52,558 --> 00:19:55,493
active, supermassive
black hole out there,
356
00:19:55,594 --> 00:19:58,629
where material isn't just
falling into the black hole,
357
00:19:58,730 --> 00:20:00,865
it's swirling around,
creating a high-energy
358
00:20:00,966 --> 00:20:02,867
accretion disk.
359
00:20:02,968 --> 00:20:06,470
The blazar's
accretion disk spins at millions
360
00:20:06,572 --> 00:20:08,973
of miles an hour,
361
00:20:09,074 --> 00:20:11,108
charging particles of gas
and dust.
362
00:20:11,210 --> 00:20:14,645
The disk also generates
magnetic fields
363
00:20:14,746 --> 00:20:18,182
that twist and tangle as they
swirl around the black hole.
364
00:20:20,986 --> 00:20:23,454
Because you have
magnetic fields that are
365
00:20:23,555 --> 00:20:24,789
twisted around,
366
00:20:24,890 --> 00:20:27,024
they also generate
electric fields.
367
00:20:27,125 --> 00:20:29,760
The electric fields can then
accelerate the charged
368
00:20:29,861 --> 00:20:32,129
particles along
the magnetic fields
369
00:20:32,231 --> 00:20:35,132
and thus produce
a lot of both particles
370
00:20:35,234 --> 00:20:38,102
and radiation
coming out along jets.
371
00:20:38,203 --> 00:20:40,304
The jets blast out
372
00:20:40,405 --> 00:20:41,939
of the poles of the black hole.
373
00:20:44,910 --> 00:20:50,047
These are the most
intense sources of radiation
374
00:20:50,148 --> 00:20:52,383
that the cosmos can
ever produce,
375
00:20:52,484 --> 00:20:56,153
and they are pointed right at
us from billions of
376
00:20:56,255 --> 00:20:57,355
light-years away.
377
00:20:57,456 --> 00:21:00,825
Do the jets create
the powerful neutrinos?
378
00:21:02,227 --> 00:21:03,694
It's a bit of a mystery.
379
00:21:03,795 --> 00:21:05,196
For a while, it was thought that
380
00:21:05,297 --> 00:21:07,865
neutrinos are produced
directly by the jet.
381
00:21:07,966 --> 00:21:09,667
But now we think that matter,
382
00:21:09,768 --> 00:21:12,570
like protons, come in from
the accretion disk,
383
00:21:12,671 --> 00:21:14,071
and they slam into each other,
384
00:21:14,172 --> 00:21:17,275
and that's what produces
the neutrinos.
385
00:21:17,376 --> 00:21:19,644
Particles racing around
the accretion disk
386
00:21:19,745 --> 00:21:22,046
crash into the base of the jet.
387
00:21:22,147 --> 00:21:25,683
The enormous energy there
smashes the particles together,
388
00:21:25,784 --> 00:21:27,985
producing neutrinos.
389
00:21:28,086 --> 00:21:30,221
The jets focus the stream of
390
00:21:30,322 --> 00:21:34,392
neutrinos and fire them
straight towards Earth.
391
00:21:34,493 --> 00:21:36,294
By just detecting one neutrino,
392
00:21:36,395 --> 00:21:39,230
we get to see a lot of
information from
393
00:21:39,331 --> 00:21:42,600
the inner workings of
an object outside of our galaxy.
394
00:21:42,701 --> 00:21:44,902
And that's what's really
exciting about neutrinos
395
00:21:45,003 --> 00:21:48,439
is that it could peer
into the unknown.
396
00:21:48,540 --> 00:21:52,810
Now we use neutrinos
to probe even further
397
00:21:52,911 --> 00:21:54,312
into the universe,
398
00:21:57,149 --> 00:22:01,285
back towards the first second
of the Big Bang
399
00:22:01,386 --> 00:22:04,622
to answer the biggest question
of them all...
400
00:22:04,723 --> 00:22:08,125
How and why do we exist?
401
00:22:20,772 --> 00:22:23,307
Neutrinos are key
to our understanding
402
00:22:23,408 --> 00:22:25,042
of how the universe works.
403
00:22:26,411 --> 00:22:29,280
They show us that
the sun is healthy.
404
00:22:31,483 --> 00:22:35,086
They are the trigger that
makes supernovas explode,
405
00:22:35,187 --> 00:22:39,824
and they reveal the location
of lethal blazars.
406
00:22:39,925 --> 00:22:42,927
And now they may solve
something that still
407
00:22:43,028 --> 00:22:47,598
puzzles physicists...
How we exist.
408
00:22:47,699 --> 00:22:50,935
The fact that our universe
appears to be filled
409
00:22:51,036 --> 00:22:53,738
with matter is puzzling.
410
00:22:53,839 --> 00:22:55,740
There should have been equal
amounts of matter
411
00:22:55,841 --> 00:22:57,742
and antimatter in the beginning,
412
00:22:57,843 --> 00:22:59,710
and they should have
annihilated one another,
413
00:22:59,811 --> 00:23:01,912
producing just pure energy.
414
00:23:02,013 --> 00:23:03,647
So why do we exist?
415
00:23:03,749 --> 00:23:05,716
This is a fundamental question,
416
00:23:05,817 --> 00:23:09,220
because this is a question
about why is there something
417
00:23:09,321 --> 00:23:10,821
rather than nothing?
418
00:23:12,290 --> 00:23:15,092
To answer that question,
we have to
419
00:23:15,193 --> 00:23:16,427
rewind the clock back
420
00:23:16,528 --> 00:23:21,866
nearly 14 billion years to
the birth of the universe.
421
00:23:21,967 --> 00:23:25,970
A speck of energy sparks
into existence.
422
00:23:26,071 --> 00:23:28,806
This energy cools
and forms tiny,
423
00:23:28,907 --> 00:23:33,077
primitive particles of matter,
including neutrinos,
424
00:23:33,178 --> 00:23:36,781
the building blocks of
everything we see today.
425
00:23:36,882 --> 00:23:40,584
The early universe
appears chaotic,
426
00:23:40,685 --> 00:23:43,554
but it quickly establishes
some ground rules,
427
00:23:43,655 --> 00:23:45,456
including symmetry.
428
00:23:45,557 --> 00:23:49,627
Our universe is full
of symmetries.
429
00:23:49,728 --> 00:23:52,029
There are positive
electric charges
430
00:23:52,130 --> 00:23:53,898
and negative electric charges.
431
00:23:53,999 --> 00:23:55,433
There's the yin and the yang.
432
00:23:55,534 --> 00:23:59,837
Well, there's also matter
and antimatter.
433
00:23:59,938 --> 00:24:02,873
The Big Bang stuck to
the rule of symmetry
434
00:24:02,974 --> 00:24:07,211
and made the same amount
of both forms of matter.
435
00:24:07,312 --> 00:24:10,681
The mechanisms that we have
for creating matter in
436
00:24:10,782 --> 00:24:14,285
the early universe create
an equal amount of antimatter.
437
00:24:14,386 --> 00:24:19,190
That symmetry is baked into
the laws of physics.
438
00:24:19,291 --> 00:24:21,692
The laws of physics also say
439
00:24:21,793 --> 00:24:25,596
that when matter
and antimatter meet...
440
00:24:25,697 --> 00:24:27,698
sparks fly.
441
00:24:27,799 --> 00:24:29,867
So matter and antimatter,
442
00:24:29,968 --> 00:24:31,769
when they touch,
they annihilate.
443
00:24:31,870 --> 00:24:34,472
They just disappear
in a flash of energy.
444
00:24:34,573 --> 00:24:37,408
And as far as we understand,
the earliest moments of
445
00:24:37,509 --> 00:24:40,177
the universe, matter and
antimatter were created in
446
00:24:40,312 --> 00:24:41,178
equal amounts.
447
00:24:41,279 --> 00:24:44,081
So they should have annihilated,
448
00:24:44,182 --> 00:24:46,984
leaving nothing but energy.
449
00:24:47,085 --> 00:24:51,088
Which means, no matter,
no antimatter, no gas,
450
00:24:51,189 --> 00:24:54,358
no dust, no stars,
no galaxies, no life, nothing.
451
00:24:54,459 --> 00:24:57,995
Somehow matter won the battle
452
00:24:58,096 --> 00:25:00,331
over antimatter
in the early universe.
453
00:25:03,401 --> 00:25:04,568
In some ways,
454
00:25:04,669 --> 00:25:06,570
the universe ignored
the rule of symmetry.
455
00:25:07,906 --> 00:25:12,409
Something has to drive
the universe off balance.
456
00:25:12,511 --> 00:25:14,879
There has to be a violation
457
00:25:14,980 --> 00:25:18,516
of this fundamental balance
in our universe.
458
00:25:18,617 --> 00:25:21,585
That way, when
the matter and antimatter met
459
00:25:21,686 --> 00:25:24,588
and annihilated,
because there was more matter,
460
00:25:24,689 --> 00:25:27,558
there would be a residual of
leftover matter,
461
00:25:27,659 --> 00:25:31,295
and there would be
no antimatter.
462
00:25:31,396 --> 00:25:33,430
How did the Big Bang break
463
00:25:33,498 --> 00:25:36,567
the symmetry between matter
and antimatter?
464
00:25:36,668 --> 00:25:39,670
So we're looking for
any interaction,
465
00:25:39,771 --> 00:25:44,174
any process whatsoever
where matter behaves slightly
466
00:25:44,276 --> 00:25:46,043
differently than antimatter.
467
00:25:46,144 --> 00:25:50,714
We're trying to find
a flaw in physics.
468
00:25:50,815 --> 00:25:54,451
We can't look
for that flaw directly,
469
00:25:54,553 --> 00:25:56,453
because we can't see
the Big Bang,
470
00:25:56,555 --> 00:25:59,156
but we can recreate it,
471
00:25:59,257 --> 00:26:01,959
and we think neutrinos
are involved.
472
00:26:03,228 --> 00:26:05,296
This is incredibly complicated.
473
00:26:05,397 --> 00:26:09,166
I'm... we are diving deep
into the bowels of
474
00:26:09,267 --> 00:26:12,102
fundamental physics,
and it is not a pretty sight.
475
00:26:15,106 --> 00:26:17,474
Japanese scientists
conducted an experiment
476
00:26:17,576 --> 00:26:19,910
called TK2.
477
00:26:20,011 --> 00:26:22,546
They re-created part of
the Big Bang by
478
00:26:22,647 --> 00:26:24,281
studying neutrinos
479
00:26:24,382 --> 00:26:28,819
and their symmetrical twin,
antineutrinos.
480
00:26:28,920 --> 00:26:32,089
The goal... to see if
antineutrinos change their
481
00:26:32,190 --> 00:26:36,627
identity or flavor at the same
rate as regular neutrinos.
482
00:26:37,696 --> 00:26:42,466
Matter and antimatter should
behave exactly the same,
483
00:26:42,567 --> 00:26:44,969
but we found something very
interesting with
484
00:26:45,070 --> 00:26:46,870
this experiment.
485
00:26:46,972 --> 00:26:49,373
The particles broke symmetry.
486
00:26:49,474 --> 00:26:52,876
Neutrinos and antineutrinos
changed flavor at
487
00:26:52,978 --> 00:26:54,178
different rates.
488
00:26:55,680 --> 00:26:57,615
This was a clear-cut example
489
00:26:57,716 --> 00:27:01,051
of matter behaving differently
than antimatter.
490
00:27:02,320 --> 00:27:04,955
And that has
revolutionized our understanding
491
00:27:05,056 --> 00:27:07,458
of the formation of particles
during the Big Bang.
492
00:27:08,927 --> 00:27:10,972
What could have
happened in the early universe
493
00:27:10,996 --> 00:27:14,398
is that more of the neutrinos
converted into matter
494
00:27:14,499 --> 00:27:18,435
than there were antineutrinos
became into antimatter,
495
00:27:18,536 --> 00:27:21,739
and in this way, you end up
with a surplus of matter
496
00:27:21,840 --> 00:27:23,040
over antimatter.
497
00:27:28,246 --> 00:27:29,947
Even though
that surplus was just
498
00:27:30,048 --> 00:27:32,116
one particle in a billion,
499
00:27:32,217 --> 00:27:34,084
it was enough to build
the cosmos.
500
00:27:36,121 --> 00:27:38,155
So neutrinos
in the early universe
501
00:27:38,256 --> 00:27:40,457
could possibly solve the matter,
502
00:27:40,592 --> 00:27:42,660
antimatter asymmetry problem
we have.
503
00:27:45,563 --> 00:27:47,498
Yes, they cause destruction.
504
00:27:47,599 --> 00:27:49,767
They... you know, sometimes
they blow up a star,
505
00:27:49,868 --> 00:27:52,870
but, at the end of the day,
they did save
506
00:27:52,971 --> 00:27:54,571
the entire universe.
507
00:27:56,508 --> 00:28:00,444
Now, scientists hope
that neutrinos may solve
508
00:28:00,545 --> 00:28:03,647
one of the biggest mysteries
in the cosmos...
509
00:28:03,748 --> 00:28:06,583
The identity of dark matter.
510
00:28:18,363 --> 00:28:20,831
Neutrinos have been around since
511
00:28:20,932 --> 00:28:22,433
the birth of the universe.
512
00:28:22,534 --> 00:28:28,105
They may even be responsible
for the formation of matter.
513
00:28:28,206 --> 00:28:30,808
Now we investigate
if they play an even
514
00:28:30,909 --> 00:28:34,311
larger role in the development
of the universe,
515
00:28:34,412 --> 00:28:37,514
the formation of the cosmic web.
516
00:28:39,984 --> 00:28:43,487
At the very largest
scales in our universe,
517
00:28:43,588 --> 00:28:48,058
galaxies are arranged in
a very peculiar pattern.
518
00:28:48,159 --> 00:28:51,662
We see long, thin threads
of galaxies,
519
00:28:51,763 --> 00:28:55,065
and at the intersections, we
see dense clumps of galaxies
520
00:28:55,133 --> 00:28:56,133
called clusters.
521
00:28:56,234 --> 00:28:57,935
In between them,
we have these vast
522
00:28:58,036 --> 00:29:01,238
empty regions called
the cosmic voids.
523
00:29:01,339 --> 00:29:03,474
For a long time, how the cosmic
524
00:29:03,575 --> 00:29:06,343
web formed and held together
was a mystery.
525
00:29:06,444 --> 00:29:09,980
One of the real mysteries
about our existence is
526
00:29:10,081 --> 00:29:12,983
why the universe was able to
hold together at all.
527
00:29:13,084 --> 00:29:15,586
All the matter was simply
spread apart
528
00:29:15,687 --> 00:29:18,655
to sparsely to ever form
galaxies or stars.
529
00:29:18,757 --> 00:29:21,925
Instead, something helped
to hold it together.
530
00:29:22,026 --> 00:29:26,597
We now think
the glue binding the cosmic web
531
00:29:26,698 --> 00:29:31,401
is a mysterious substance
known as dark matter.
532
00:29:31,503 --> 00:29:34,571
If it wasn't for dark matter
in the very early universe,
533
00:29:34,672 --> 00:29:36,740
there might be no structure
at all.
534
00:29:39,511 --> 00:29:42,412
But what is this
architect of the universe,
535
00:29:42,514 --> 00:29:43,514
this dark matter?
536
00:29:44,816 --> 00:29:47,618
Dark matter is
invisible matter that we can't
537
00:29:47,719 --> 00:29:51,488
see... so you, me, all of
the particles, everything that
538
00:29:51,589 --> 00:29:56,460
we see is actually only 5% of
actual matter in the universe.
539
00:29:56,561 --> 00:29:58,428
The rest is dark matter.
540
00:29:59,998 --> 00:30:03,467
Dark matter is a fancy name
541
00:30:03,568 --> 00:30:05,769
for something
we don't understand.
542
00:30:05,870 --> 00:30:07,871
What we do know is that there
543
00:30:07,972 --> 00:30:10,774
is much more stuff
than we can see.
544
00:30:10,875 --> 00:30:13,277
But we have no idea what it is.
545
00:30:13,411 --> 00:30:17,281
It's one of the greatest
open mysteries in science.
546
00:30:19,083 --> 00:30:21,718
Dark matter hardly
interacts with anything,
547
00:30:21,820 --> 00:30:26,123
a bit like neutrinos...
Also like neutrinos,
548
00:30:26,224 --> 00:30:30,360
dark matter was abundant and
active in the infant universe.
549
00:30:30,461 --> 00:30:34,798
So could neutrinos and dark
matter be the same thing?
550
00:30:36,334 --> 00:30:38,335
We don't know
what dark matter is,
551
00:30:38,436 --> 00:30:40,637
but we kind of know
how it behaves.
552
00:30:40,738 --> 00:30:43,607
And neutrinos sound like
a pretty good candidate for it
553
00:30:43,708 --> 00:30:45,576
because, hey, they are dark.
554
00:30:45,677 --> 00:30:47,077
They are everywhere
in the universe,
555
00:30:47,111 --> 00:30:49,346
and they do have a little bit
of mess.
556
00:30:50,548 --> 00:30:54,651
And by little,
we do mean little... neutrinos
557
00:30:54,752 --> 00:30:58,155
weigh around 10 billion,
billion, billion
558
00:30:58,256 --> 00:31:02,192
times less than a grain of sand.
559
00:31:02,293 --> 00:31:06,029
But neutrinos are also
exquisitely abundant, and so
560
00:31:06,130 --> 00:31:08,565
because they're so abundant,
561
00:31:08,666 --> 00:31:12,970
their individual tiny mass can
actually add up to a large
562
00:31:13,071 --> 00:31:16,473
diffuse mass
on very large scales.
563
00:31:22,981 --> 00:31:24,014
To investigate
564
00:31:24,115 --> 00:31:26,516
if neutrinos and dark matter
are the same thing,
565
00:31:26,618 --> 00:31:28,185
we must return to the Big Bang.
566
00:31:30,855 --> 00:31:34,892
As the universe expands and
cools, primitive matter forms,
567
00:31:34,993 --> 00:31:39,162
including dark matter
and trillions of neutrinos.
568
00:31:39,264 --> 00:31:43,166
The dark matter clumps
together, forming regions of
569
00:31:43,268 --> 00:31:47,437
higher gravity,
which pulls in regular matter.
570
00:31:47,572 --> 00:31:51,842
It formed a structure,
a scaffolding, that allowed
571
00:31:51,943 --> 00:31:54,244
regular matter to
gravitationally begin to come
572
00:31:54,345 --> 00:31:56,947
together and collapse
into galaxies,
573
00:31:57,048 --> 00:31:58,548
stars, and planets.
574
00:31:58,650 --> 00:32:01,985
Could the combined mass
of neutrinos in the early
575
00:32:02,086 --> 00:32:05,489
cosmos have produced the extra
gravity to help
576
00:32:05,590 --> 00:32:07,024
structures form?
577
00:32:09,193 --> 00:32:11,995
Could it be possible that
this really is dark matter?
578
00:32:12,063 --> 00:32:13,297
These tiny little particles,
579
00:32:13,398 --> 00:32:15,165
but in abundance across
the universe.
580
00:32:15,266 --> 00:32:18,101
And we know more...
581
00:32:18,202 --> 00:32:21,038
Not all... we know more
about neutrinos than we do
582
00:32:21,139 --> 00:32:22,572
about dark matter,
583
00:32:22,674 --> 00:32:28,111
but there's still a question
around whether or not neutrinos
584
00:32:28,212 --> 00:32:31,381
can be a specific type
of dark matter.
585
00:32:33,351 --> 00:32:36,286
To answer this question,
we have to work out what
586
00:32:36,387 --> 00:32:41,491
specific type of dark matter
was around in the Big Bang...
587
00:32:41,592 --> 00:32:43,894
Hot or cold.
588
00:32:43,995 --> 00:32:46,530
People talk
about hot dark matter
589
00:32:46,631 --> 00:32:47,965
and cold dark matter.
590
00:32:48,066 --> 00:32:49,766
And really,
what you're saying is
591
00:32:49,867 --> 00:32:51,702
the speed of
the particles themselves.
592
00:32:51,803 --> 00:32:53,737
The cold dark matter
is moving slowly,
593
00:32:53,838 --> 00:32:56,340
and the hot dark matter
is moving fast.
594
00:32:56,441 --> 00:33:00,410
This speed difference
is an important clue
595
00:33:00,511 --> 00:33:03,046
to whether neutrinos
make up dark matter.
596
00:33:05,016 --> 00:33:06,550
With hot and cold dark matter,
597
00:33:06,651 --> 00:33:08,685
the way they interact with
regular matter has
598
00:33:08,786 --> 00:33:10,554
a lot to do with how fast
they're going.
599
00:33:10,655 --> 00:33:12,889
So it's a good analogy to
think about a river.
600
00:33:12,991 --> 00:33:15,525
With hot dark matter,
you'd have a torrent.
601
00:33:15,626 --> 00:33:17,294
Basically, it's going so fast,
602
00:33:17,395 --> 00:33:19,006
it doesn't actually connect
with anything.
603
00:33:19,030 --> 00:33:20,397
It just goes right on past.
604
00:33:20,498 --> 00:33:22,699
So there's no chance to form
that larger structure.
605
00:33:24,369 --> 00:33:26,970
If you have relatively
slow-moving dark matter,
606
00:33:27,071 --> 00:33:29,740
cold dark matter, think about
a slow-moving river.
607
00:33:29,841 --> 00:33:32,275
A slow-moving river begins
to deposit silt.
608
00:33:34,078 --> 00:33:35,946
Think of that silt as
the billions
609
00:33:36,047 --> 00:33:39,483
of galaxies that make up
the cosmic web.
610
00:33:39,584 --> 00:33:42,019
We observed that
galaxies formed very early in
611
00:33:42,120 --> 00:33:43,587
the universe, and this is good
612
00:33:43,688 --> 00:33:45,622
for cold dark matter,
but it doesn't work for
613
00:33:45,723 --> 00:33:46,723
hot dark matter.
614
00:33:46,758 --> 00:33:47,935
So we think cold dark matter is
615
00:33:47,959 --> 00:33:49,926
really dominating
structure formation
616
00:33:50,028 --> 00:33:52,262
in the early universe.
617
00:33:52,363 --> 00:33:56,533
But cold and slow does
not describe neutrinos.
618
00:33:56,634 --> 00:33:59,736
They move very fast,
close to the speed of light.
619
00:33:59,837 --> 00:34:02,773
This is a problem
with neutrinos,
620
00:34:02,874 --> 00:34:04,975
because neutrinos
would be hot dark matter.
621
00:34:05,076 --> 00:34:09,112
That rules out neutrinos
as cold dark matter.
622
00:34:11,416 --> 00:34:13,683
The idea that neutrinos
are dark matter
623
00:34:13,785 --> 00:34:17,020
hit another setback
when we weighed the universe.
624
00:34:19,490 --> 00:34:22,225
If you add up the total mass
of all the neutrinos in
625
00:34:22,326 --> 00:34:24,127
the universe, it would wind up
626
00:34:24,228 --> 00:34:27,664
being about a half a percent
to 1.5% of
627
00:34:27,765 --> 00:34:29,666
the total mass of dark matter.
628
00:34:31,402 --> 00:34:33,170
Neutrinos were
a good candidates for
629
00:34:33,271 --> 00:34:36,373
dark matter because they exist,
630
00:34:36,474 --> 00:34:38,875
and they're very shy,
just like the dark matter
631
00:34:38,976 --> 00:34:40,677
particles are.
632
00:34:40,778 --> 00:34:43,780
But then we were able to
measure more accurately how
633
00:34:43,881 --> 00:34:47,484
much dark matter there is and
how much neutrinos there are,
634
00:34:47,585 --> 00:34:49,853
and there's just way
less neutrinos
635
00:34:49,954 --> 00:34:51,088
than there is dark matter.
636
00:34:52,757 --> 00:34:54,658
It sounds like game over,
637
00:34:54,759 --> 00:34:57,961
but the neutrino hunters
aren't giving up.
638
00:34:58,062 --> 00:35:01,331
The search is on for
a mysterious new kind
639
00:35:01,432 --> 00:35:02,599
of neutrino,
640
00:35:02,700 --> 00:35:05,435
one that could solve the riddle
641
00:35:05,536 --> 00:35:06,937
of dark matter.
642
00:35:17,982 --> 00:35:20,550
Neutrinos played a huge
role in shaping
643
00:35:20,651 --> 00:35:22,352
the early universe.
644
00:35:24,322 --> 00:35:28,725
They helped matter
defeat antimatter,
645
00:35:28,826 --> 00:35:31,128
and the cosmos
develop structure.
646
00:35:32,597 --> 00:35:36,566
This led us to wonder if
neutrinos might be dark matter.
647
00:35:38,970 --> 00:35:41,438
But when we weighed
the universe,
648
00:35:41,539 --> 00:35:43,240
the numbers didn't add up.
649
00:35:43,341 --> 00:35:46,977
Neutrinos do have mass,
and there are a lot of them
650
00:35:47,111 --> 00:35:49,079
out there,
so it might be some tiny,
651
00:35:49,180 --> 00:35:52,048
tiny fraction of dark matter
is made up of neutrinos.
652
00:35:52,150 --> 00:35:54,084
But we know that these things do
653
00:35:54,185 --> 00:35:55,919
not make up the bulk
of dark matter.
654
00:35:56,020 --> 00:35:58,155
It must be something else.
655
00:35:58,256 --> 00:36:01,424
So neutrino scientists
hunt for a different
656
00:36:01,526 --> 00:36:03,293
contender for dark matter,
657
00:36:03,361 --> 00:36:06,830
a completely new kind
of neutrino.
658
00:36:06,931 --> 00:36:10,567
We know about three flavors
of neutrinos...
659
00:36:10,668 --> 00:36:13,103
The electron neutrino,
660
00:36:13,204 --> 00:36:15,972
the muon neutrino,
and the tau neutrino.
661
00:36:16,073 --> 00:36:19,943
But there could be a hidden
fourth flavor of
662
00:36:20,044 --> 00:36:23,813
neutrino that could solve
the riddle of dark matter.
663
00:36:27,685 --> 00:36:30,787
We call this a sterile neutrino.
664
00:36:30,888 --> 00:36:32,923
So-called because they interact
665
00:36:33,024 --> 00:36:36,593
even less than
regular neutrinos.
666
00:36:36,694 --> 00:36:41,031
A particle so tiny, so hard to
detect could actually turn out
667
00:36:41,132 --> 00:36:43,567
to have lots of the secrets
wrapped up inside it
668
00:36:43,668 --> 00:36:45,168
as to how the universe works.
669
00:36:47,838 --> 00:36:49,739
The first step to find out if
670
00:36:49,840 --> 00:36:52,342
sterile neutrinos
are dark matter
671
00:36:52,443 --> 00:36:54,544
is to prove they exist,
672
00:36:54,645 --> 00:36:56,479
and that's tough.
673
00:36:56,581 --> 00:37:00,417
Even though sterile neutrinos
are almost impossible
674
00:37:00,518 --> 00:37:03,486
to detect,
we can still hunt for them.
675
00:37:03,588 --> 00:37:06,156
Back in the day,
neutrinos were also said
676
00:37:06,257 --> 00:37:09,526
to be difficult to detect.
677
00:37:09,627 --> 00:37:11,995
Trying to find dark
matter, trying to find
678
00:37:12,096 --> 00:37:13,330
these sterile neutrinos,
679
00:37:13,431 --> 00:37:15,632
it's almost like
using one invisible,
680
00:37:15,733 --> 00:37:18,301
undetectable thing to find
another, using a ghost
681
00:37:18,402 --> 00:37:19,970
to find a goblin.
682
00:37:20,071 --> 00:37:23,473
We are definitely
pushing the limits of science.
683
00:37:23,574 --> 00:37:28,378
A team at Fermilab
has an ingenious idea.
684
00:37:28,479 --> 00:37:33,049
They can't spot sterile
neutrinos directly, because
685
00:37:33,150 --> 00:37:36,586
they don't interact with atoms
in the detectors.
686
00:37:36,687 --> 00:37:38,688
So they're looking
for neutrinos as
687
00:37:38,789 --> 00:37:42,492
they change flavor
into sterile neutrinos.
688
00:37:42,593 --> 00:37:46,162
We know that normally,
neutrinos change type as they
689
00:37:46,264 --> 00:37:47,464
move through space,
690
00:37:47,565 --> 00:37:50,400
but they have to move far enough
before that change happens.
691
00:37:52,436 --> 00:37:54,537
So tracking neutrinos
over a short
692
00:37:54,639 --> 00:37:57,274
distance shouldn't show
any flavor changing.
693
00:37:59,443 --> 00:38:01,088
In this experiment,
they've constructed
694
00:38:01,112 --> 00:38:03,246
only a half-mile-long path.
695
00:38:03,347 --> 00:38:04,867
It's not enough time from
the neutrinos
696
00:38:04,915 --> 00:38:06,916
to change flavor
in the normal way.
697
00:38:07,018 --> 00:38:10,520
If they do see something,
if they see something change,
698
00:38:10,621 --> 00:38:13,790
this could be some interesting
aspect, perhaps evidence
699
00:38:13,891 --> 00:38:15,091
for sterile neutrinos.
700
00:38:15,192 --> 00:38:17,627
So is it possible that,
over short distances,
701
00:38:17,728 --> 00:38:19,529
regular neutrinos can
oscillate into this
702
00:38:19,630 --> 00:38:20,730
sterile neutrino?
703
00:38:26,370 --> 00:38:28,838
The team shoots beams
of muon flavor
704
00:38:28,939 --> 00:38:31,007
neutrinos along the detector.
705
00:38:33,644 --> 00:38:36,313
In theory, they won't have
time to change flavor.
706
00:38:40,985 --> 00:38:44,054
We can see whether
or not these muon neutrinos
707
00:38:44,155 --> 00:38:48,491
morphed into
a different type of neutrino.
708
00:38:48,592 --> 00:38:51,361
They shouldn't change,
but if they do,
709
00:38:51,462 --> 00:38:54,497
that points us towards
sterile neutrinos.
710
00:38:56,901 --> 00:38:58,335
The team compare the number
711
00:38:58,436 --> 00:39:01,871
of muon neutrinos
reaching the detectors
712
00:39:01,972 --> 00:39:04,908
to those fired along the beam.
713
00:39:05,009 --> 00:39:09,512
Fewer muon neutrinos
hit the detectors.
714
00:39:09,613 --> 00:39:12,716
Some neutrinos had
changed flavor.
715
00:39:14,719 --> 00:39:17,787
So we are seeing
that oscillation of
716
00:39:17,888 --> 00:39:21,224
neutrinos changing
from one type to another.
717
00:39:21,325 --> 00:39:26,496
We had an idea of how many
we should have seen,
718
00:39:26,597 --> 00:39:27,897
but we're seeing more,
719
00:39:27,998 --> 00:39:32,469
and that could be
sterile neutrinos.
720
00:39:32,570 --> 00:39:35,205
If sterile neutrinos do exist,
721
00:39:35,306 --> 00:39:38,975
would they be dark matter?
722
00:39:39,076 --> 00:39:40,944
Right now,
we don't know the mass
723
00:39:41,045 --> 00:39:42,912
of the sterile neutrino,
724
00:39:43,013 --> 00:39:48,118
but if it's heavy enough,
it could be a contender.
725
00:39:48,219 --> 00:39:53,123
If it exists, it's prevalent
enough to account
726
00:39:53,224 --> 00:39:56,359
for all the dark matter
in the universe.
727
00:39:56,460 --> 00:39:59,062
Fermilab's results
haven't been verified by
728
00:39:59,163 --> 00:40:01,464
other scientists.
729
00:40:01,565 --> 00:40:03,633
So it's too soon to say
730
00:40:03,734 --> 00:40:06,369
definitively that sterile
neutrinos are real
731
00:40:08,038 --> 00:40:10,540
or that they make up
dark matter.
732
00:40:10,641 --> 00:40:12,942
Dark matter is probably one of
733
00:40:13,043 --> 00:40:15,345
the biggest questions of
our time.
734
00:40:15,446 --> 00:40:17,313
And the fact that Fermilab
735
00:40:17,415 --> 00:40:21,651
may be one of the places to
answer that question,
736
00:40:21,752 --> 00:40:25,522
and the fact that I am working
here is really fantastic,
737
00:40:25,623 --> 00:40:27,924
because we're attempting
the impossible.
738
00:40:30,694 --> 00:40:34,164
We have to wait to see if
the impossible is possible.
739
00:40:37,301 --> 00:40:39,636
We know neutrinos
have played a vital
740
00:40:39,737 --> 00:40:41,838
role in the history of
our universe,
741
00:40:43,507 --> 00:40:47,877
and even now, they refresh it
by powering supernovas.
742
00:40:51,115 --> 00:40:55,718
Without them, our sun,
our world,
743
00:40:57,188 --> 00:41:00,089
and even our bodies
would not have formed.
744
00:41:01,459 --> 00:41:05,295
Neutrinos are pesky little
particles, super elusive,
745
00:41:05,396 --> 00:41:08,565
difficult to study,
but when you can catch them,
746
00:41:08,666 --> 00:41:12,535
they offer secrets
to the universe.
747
00:41:12,636 --> 00:41:15,839
A story of neutrinos
has been really interesting.
748
00:41:15,940 --> 00:41:16,973
It's like reading a book,
749
00:41:17,074 --> 00:41:18,452
and you think you're on
the last page, and then
750
00:41:18,476 --> 00:41:21,544
you turn it, and then suddenly
there's 100 new pages.
751
00:41:21,645 --> 00:41:24,681
Neutrinos are teaching us
that the universe is,
752
00:41:24,782 --> 00:41:27,650
in many ways, subtle
and hard to figure out.
753
00:41:27,751 --> 00:41:29,786
And the more we learn
about these things,
754
00:41:29,887 --> 00:41:32,222
the more we learn
about the universe.
755
00:41:32,323 --> 00:41:35,592
Neutrinos are the universe's
great escape artists,
756
00:41:35,693 --> 00:41:37,293
the Houdini of particles.
757
00:41:37,394 --> 00:41:39,429
In fact, they may have
helped us to
758
00:41:39,530 --> 00:41:42,532
escape the Big Bang
and end up existing.
759
00:41:42,633 --> 00:41:46,002
At the end of the day,
they're what saves us.
760
00:41:46,103 --> 00:41:49,806
The more we understand
these elusive particles,
761
00:41:49,907 --> 00:41:55,111
the more we can gain insight
into how the universe works,
762
00:41:55,212 --> 00:41:57,580
so it's really cool.
763
00:41:57,604 --> 00:41:59,604
764
00:41:59,654 --> 00:42:04,204
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