The Crime Wave We Can Blame on… Neutron Stars? (1)
There's a crime wave sweeping the world right now.
- [Newsreader] The troubling trend
targeting a key car component.
- [Newsreader 2] Thieves targeting cars
for their catalytic converters.
- These thefts that take just minutes to carry out.
- And a thief can remove one from your car
in 60 seconds or less.
- You feel violated.
- [Joe] The thieves are on the hunt for something
that fetches big bucks on the black market.
- [Newsreader 3] A nearly $7 million theft ring.
- [Newsreader 4] They want the valuable metals
inside the converters.
- [Interviewee] This would be a very quick way
for them to make a quick buck.
- [Joe] Numbers are absolutely skyrocketing
and public officials are scrambling for answers.
- We're trending in the wrong direction.
- And people are getting tired of it.
- This is a growing problem, there's no excuse for it.
- Turns out we can blame it all on this:
(stars whirring)
(curious music)
Hey smart people, Joe here.
So back in the '70s, air pollution was out of control.
Many U.S. cities were completely blanketed in smog
and people were getting sick,
all these warnings about acid rain,
and one of the big culprits was car exhaust.
So the U.S. passed these huge, new environmental laws
like the Clean Air Act,
which led to one of the most monumental innovations ever
in cleaning up the way that we drive:
the catalytic converter.
A catalytic converter is basically
an extra little chamber along your car's exhaust pipe,
EV owners, this doesn't apply to you.
This magical little box
takes dangerous chemicals and engine exhaust
and transforms them into relatively harmless gases
that are better for the environment and public health.
I mean, car exhaust still causes global warming
but at least this solved that whole smog thing.
But in recent years, catalytic converters
have become one of the most stolen items on cars.
Thefts have risen almost 4000% since 2018
(burglar cackles)
and numbers are still on the rise
and that's all because of what's inside.
That little thing on your exhaust
that you've probably never looked at,
is a literal treasure chest full of valuable metals,
platinum, palladium and this one, rhodium,
the most expensive metal on planet earth.
But why do we need this crazy-expensive metal
in something that cleans literally
the dirtiest stuff that comes outta your car?
Well, because of the very unique chemistry
that happens inside of a catalytic converter.
Rhodium belongs to a family of metals
that are extremely resistant
to oxidation and corrosion and heat.
So it can stand up
to conditions inside your car's exhaust system
and all of the junk that comes through it,
but it also has another super important property:
it's a catalyst,
which means it can speed up certain chemical reactions.
Here's an example:
burning gasoline creates harmful chemicals
like nitrogen oxides, which can damage the ozone layer,
contribute to acid rain, and warm up our planet.
But the rhodium in a catalytic converter
turns it into harmless nitrogen and oxygen gas
and it can do this over and over and over again,
as long as nobody saws it off your car
in the middle of the night.
A catalytic converter
has something like a couple of grams of rhodium in it,
which has a street value of almost $1,000.
To put this in perspective,
right now, a one kilogram bar of gold
is worth around $57,000.
That's a lot of money, but that same amount of rhodium
would be worth more than half a million dollars.
Here's a little periodic table I have
that has actual samples
of all of the non-dangerous, non-deadly elements.
This little microscopic piece of rhodium I have in here,
hold on, we're gonna need to enhance.
Let's move... Grab the macro lens or something.
So this tiny little piece is worth almost $10.
So why is this stuff so expensive?
When we look at rhodium
and it's neighbors on the periodic table
we find a lot of stuff that's ridiculously rare,
at least in Earth's crust where we can get to it easily.
If we represent the total
of all the elements in Earth's crust
by a roll of toilet paper stretching from here to London,
rhodium would make up just this much.
To figure out why these precious metals are so rare,
we have to talk about how elements are made.
And to understand how elements are made
and where they come from,
we have to spend a little bit of time with this.
Every box on the periodic table represents one element.
And the type of element you are
is determined by the number of protons you have.
If you're an atom with just one proton,
you're hydrogen, here at the upper-left corner.
If we add a proton, we have element two, helium, instead.
Six protons, carbon.
Eight, you're oxygen, and so on.
Protons are positively charged,
but like charges repel each other
like identical ends of a magnet.
So why doesn't that repulsion make a nucleus fall apart?
Well, because there's another fundamental force
at play inside a nucleus, the nuclear force.
You can think of the nuclear force as Velcro
that only works when protons or neutrons
are pushed very close together.
See, atoms contain both protons and neutrons.
Neutrons also have this sticky nuclear force Velcro,
but unlike protons they're uncharged,
they don't repel other stuff.
So neutrons act like an atomic glue
that can help hold a nucleus together.
Adding or subtracting neutrons can change an atoms mass
but not what type of element it is.
It's only when we add or take away a proton
along with enough neutrons
to keep a nucleus from falling apart
that we make a new chemical element.
And to get protons and neutrons close enough together
for that nuclear Velcro to do its thing
requires a lot of heat and energy.
Amounts that we only find in special places
and at special times.
The hot, dense universe that existed just after the Big Bang
created the perfect conditions
to squish protons and neutrons together.
That's how the lightest,
most abundant elements on the periodic table were created.
Stuff like hydrogen and helium.
In fact, all of the hydrogen that exists in the universe
was created in those first few minutes after the Big Bang.
But to create heavier and heavier nuclei,
you need more and more energy.
Unfortunately, the Big Bang only happened once,
13.8 billion years ago.
And all of its energy has been spreading out
as the universe continues to expand.
So where else can we find enough energy
to squish nuclei together?
The fusion reactions that make stars burn
turn lighter elements into heavier ones
by smashing nuclei together.
Two atoms of hydrogen make one atom of helium,
smash three helium nuclei together, you get carbon,
add one more helium nucleus, you get oxygen,
you get the idea.
But cooking up these different elements gets harder
as we move down and across the periodic table.
If a nucleus gets big enough, even the immense pressures
and energies inside the core of a star
aren't enough to keep sticking on new protons.
It turns out that iron is the heaviest element
that can be made in a star.
So what about the rest of the periodic table?
Well, everything after uranium was made by humans
but we still need a way to make all of these.
Luckily, there is one more way to add protons to a nucleus:
by adding neutrons.
Because neutrons don't have a charge,
it takes less energy to get them to stick to a nucleus
but adding neutrons can also make a nucleus unstable.
That's why radioactive isotopes spontaneously decay
and eject subatomic particles and radiation in the process.
Sometimes a neutron that's been captured by a nucleus
can decay into a proton.
And since that's one more proton that wasn't there before
we've created a new element.
If that seems weird and confusing,
well, welcome to physics.
This way of adding protons to a nucleus
by actually adding neutrons
is how most elements on the periodic table are born.
But in this story,
every answer seems to bring us to one more problem.
Where do you go to find big piles of neutrons
just waiting to get smashed onto nuclei?
Before I answer that,
first I wanna take a quick moment to thank our patrons,
because while we're on the subject of making new things,
your support helps us make these videos.
We can't thank you enough.
And if you wanna join our community of supporters,
just check out the link down in description.
I also wanna let you know
that another great way to support the show for free
is by watching new episodes when they're first released.
This helps spread the show
to other subscribers and to new viewers.
If you are already part of the early squad, thank you.
And if not, hit the bell icon next to the subscribe button,
our whole community of curious learners will thank you.
So where do you go to find big piles of neutrons
waiting to get smashed onto nuclei?
Well, one place is dying low-mass stars.
The ones that don't go out in those violent explosions
like their more massive cousins.
They've got lots of free neutrons floating around
so every so often a nucleus can grab one,
it decays into a proton
and becomes a slightly heavier element.
That new element can grab neutron after neutron,
some occasionally decaying into protons along the way,
forming heavier and heavier elements.
This is a slow process
that basically walks box by box along the periodic table.
But it takes billions of years for these stars to die
so it's not like they've got anything better to do.
But there's another way to add a bunch of neutrons at once.
And one place that we find it is in a supernova,
the explosive end of a massive dying star,
which is full of free neutrons
and a whole bunch of stellar junk.
In the immense energy of a supernova explosion,
lots of neutrons can be slapped onto a nucleus at once
before they have time to decay.
Then when that decay finally does happen,
you've effectively added
a whole bunch of protons all at once.
So instead of tiny steps,
we can take big leaps across the periodic table
and end up with really heavy elements, super quick.
We used to think a supernova was the only place
that this rapid neutron capture could happen.
Today, we know that's not true.
After they collapse and go boom, exploding stars
often leave unthinkably dense neutron stars in their wake.
Unsurprisingly, neutron stars are full of neutrons
and if two neutron stars come close enough together,
spiral together and merge,
they release tidal waves of these free neutrons.
Exactly the ingredients
to take those big leaps across the periodic table.
Creating new elements and merging neutron stars
used to be purely theoretical,
but in recent years
we've actually witnessed these collisions
and felt their gravitational aftershocks.
The light given off by one merger
900 million light-years away confirmed
that heavy elements like gold
do form during these violent events.
Sometimes enough to make 10 Earth's worth of gold
in a single merger.
Is this same process true for rhodium too?
Well, we don't really know, but scientists think
that it's likely colliding neutron stars could,
in fact, be where most of the heavy metal end
of the periodic table is born.
But there's still much about these processes
that scientists don't fully understand.
Rhodium and some of its rare neighbors,
they likely form in other ways too,
perhaps somewhere in between these rapid and slow processes.
But even in a universe
that's experienced several generations of dying stars
across nearly 14 billion years of existence,
these explosive atomic nurseries are rare
and pretty spread out.
Across the universe, elements made in these processes
are about a million times more scarce
