Thanks to Skillshare for supporting this episode
of SciShow.
[♩INTRO]
For researchers studying objects younger than
60,000 years or so,
carbon dating is one of the most valuable
tools out there.
It involves analyzing the ratio of two kinds
of carbon atoms.
And with it, scientists have figured out the
ages of everything
from mummies to old manuscripts.
Carbon dating has transformed fields like
archeology and paleontology.
And it’s helped us get a much better understanding
of what the world
was like thousands of years ago.
The problem is, carbon dating might also be
in danger,
thanks to fossil fuels, of all things.
The idea of carbon dating was first proposed
in the 1940s,
and it was important enough to win its discoverer
a Nobel Prize.
It relies on two kinds, or isotopes, of carbon:
one called carbon-12, and another called carbon-14.
Carbon-12, or C-12 for short, is basically
normal carbon.
It has six protons and six neutrons, and it’s
stable,
so it doesn’t change and decay into different
atoms over time.
Carbon-14 is rarer, and it does decay.
C-14 has two extra neutrons, which makes it
unstable.
Over about 5730 years, half of the atoms in
any sample will
turn into a more stable form of nitrogen.
That’s called its half life.
Carbon-14 is produced when radiation from
objects like the Sun interacts
with those stable nitrogen molecules
as they’re floating around in Earth’s
atmosphere.
Then, the C-14 ends up in carbon dioxide,
and works its way into plants
and animals through photosynthesis and the
food chain.
Historically speaking, the amounts of C-12
and C-14 in the atmosphere
have been roughly consistent over the years.
So scientists can expect to find a predictable
ratio in most organic materials.
That ratio is what carbon dating is based
on.
So, say researchers were trying to figure
out
how old some frozen animal tissue is.
If their sample has less C-14 than normal,
that suggests
that it’s been around long enough for that
carbon to decay, so it’s older.
But if they have a sample where the ratio
is normal, it’s probably relatively new.
By tracking exact ratio changes and knowing
the half life of C-14,
scientists can usually pin down an object’s
age to within a few decades.
Carbon dating has worked for years, but now,
there’s a problem:
That consistent carbon ratio is changing.
Admittedly, it has changed before.
But those changes were small enough that they
weren’t a huge deal,
and the results could be easily calibrated
with other measurements.
Now, things are getting more dramatic.
Over the years, as we’ve burned fossil fuels,
we’ve launched a lot of extra
carbon dioxide into the air.
And since those fossils fuels are so old,
almost all of their carbon-14 has decayed.
That means we’re adding a bunch of carbon-12
to the atmosphere
so much that it’s really messing with the
ratio
that scientists use for carbon dating.
Officially, this is called the Suess effect,
after the scientist
who first noticed this pattern in the 1950s.
And it’s not great news.
According to one 2015 paper, if we keep burning
fossil fuels at this rate,
we’ll add so much extra C-12 to the atmosphere
that
new materials in 2050 will seem 1000 years
old.
There will be so much C-12 in them that the
amount of C-14
will look tiny and decayed by comparison.
And without an outside reference,
it will be almost impossible to figure out
how old they really are.
Many groups are already working to reduce
the rate at which we burn fossil fuels
and that’s good for everyone, not just archeologists.
But we probably won’t stop using them completely
any time soon.
Thankfully, one researcher came up with a
solution to help us sort through this mess.
Or at least, it’s a reliable way to tell
if fossil fuels have skewed measurements.
In a 2016 paper published in the journal Environmental
Research Letters,
he suggested we just look at a different isotope
of carbon.
Carbon-13, or C-13, has just one extra neutron.
And like carbon-14, it forms naturally, but
it’s pretty rare.
Plants don’t really store it, so there isn’t
much of it in fossil fuels
or in current living things.
And it only makes up 1% of the Earth’s atmosphere,
so it’s also getting
overshadowed by all the extra C-12 we’re
putting out there.
But unlike carbon-14, C-13 is stable.
That means the amount in a sample should be
predictable and shouldn’t change over time.
Researchers should see a constant percentage
of C-13
that is, unless there’s a skewed amount
of carbon-12.
In his 2016 paper, this scientist suggested
that researchers should always
check on that C-13 percentage during the carbon
dating process.
If it’s unusually low, they’ll know the
sample is affected by extra carbon-12,
so traditional carbon dating won’t be reliable.
They’ll have to use another method.
For example, if an organic object was found
in a hard rock layer,
researchers can estimate its age by dating
the rock,
which doesn’t always require carbon.
Ideally, we’ll be able to stop this problem
by reducing our fossil fuel usage.
But since that might not happen soon,
this carbon-13 strategy will definitely be
helpful.
All this week, we’re turning our attention
at the end of each video
to a Skillshare class we think you’ll get
a lot out of.
We try to make them relate to the topic of
the episode,
which is pretty easy because there are over
20,000 classes on skillshare.
There aren’t any Skillshare classes on carbon
dating though.
Which, I guess isn’t too surprising.
So instead, I wanted to tell you about this
class taught by
award-winning designer Mirko Ilić.
It’s called Making Art to Drive Change,
and that still feels kind of related.
Mirko Ilić is a world class artist and designer,
who teaches master’s degree illustration
at the School of Visual Arts in New York and
runs his own studio,
which is famous for its strong visual concepts.
He’s captivating to listen to, and the project
for the class is inspiring.
As he points out in the class, no matter what
your background,
everyone has something they’re passionate
about and can make art.
Right now Skillshare is offering SciShow viewers
2 months of access
to all of their classes for free.
So you could take a poster design class from
an expert like this for free!
Check it out as well as any other class you
like
by following the link in the description.
Thanks for watching and for supporting SciShow.
[♩OUTRO]
