Name: We Found Radioactive Traces From Nuclear Bombs in the Mariana Trench
Uploaded: 2020-03-30T03:52:36.000Z
Duration: 7 min 46 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

The Mariana Trench is the deepest, darkest part of our ocean.

At a maximum depth of 11,000 meters, it's an extreme place that's home to borderline

Scientists like to visit the trench to understand how life could possibly survive

and on one trip, a group found something unexpected inside the muscle tissues of deep sea crustaceans.

There were traces of bomb carbon, or carbon-14; a special radioactive isotope that surged

into the atmosphere after decades of nuclear weapon tests.

While it's a surprise that a human signature somehow found its way that far down -- there

are actually traces of bomb carbon everywhere, even inside you.

During the Cold War, we tested a lot of nuclear weapons.

When a bomb goes off, you had nuclear reactions of either fission or fusion occurring, with

a large amount of neutrons being basically blasted in all directions from the center

Those extra neutrons in the atmosphere made extra carbon-14.

Carbon-14 is a naturally produced radioisotope.

It's made in the upper atmosphere from cosmic ray interactions with gas atoms.

But during that period of time when we set off hundreds of nuclear bombs...

the concentration of carbon-14 in the atmosphere almost doubled.

tests, the concentration in the atmosphere started to go down.

It hung out in the atmosphere until it combined with oxygen to make carbon dioxide and then

that carbon dioxide started to get pulled out of the atmosphere, getting incorporated

So everything that's alive at that time was labeled with this extra carbon-14 and that

Everyone who's alive now has some of the bomb pulse in them.

It may sound concerning, but the amount of bomb carbon you have in you isn't harmful.

There is natural radioactivity everywhere.

Everything that's alive is radioactive as well as have carbon-14.

In a surprise twist from the atomic testing era, Bruce and his colleagues uncovered a

way to use traces of that bomb carbon to clock the age of human cells and tissues.

I was at an American Chemical Society meeting where there was a special focus session on

the use of accelerators in nuclear chemistry.

Another speaker in that session was looking at metals in Alzheimer's plaques.

He said, "We don't really know how old the plaques are."

And I thought, hmm, I think I know a way where we could actually measure that.

And that was my start of doing bomb pulse biology

Every tissue turns over at different rates.

Different types of cells are being born and replaced, some turn over very, very quickly.

You may be a certain age, but your skeleton is likely a different one.

So how do you measure the amount of bomb carbon in something as small as a cell to find a

First, an understanding of how to do radiocarbon dating, a technique that's been around since

Carbon comes in basically three different flavors.

99% of carbon is carbon-12, it has six protons and six neutrons.

Carbon-13 has again six protons, but now seven neutrons.

Carbon-14 has six protons and eight neutrons.

All that chemistry is the same, but we can actually trace the different atoms by mass.

Because carbon-14 is radioactive with a half-life of about 5,730 years, the concentration of

And that decrease in carbon-14 concentration is what's used to do radiocarbon dating.

By measuring the ratio of carbon-14 in a sample to the amount of carbon-14 in the atmosphere,

But figuring out how much there is in tissue requires skills in advanced chemistry and

The chemistry that goes into doing a sample prep is really the hardest thing to do.

We need about 10 million cells to get enough DNA to do an analysis.

Once you've separated the different type of cell that you want, then you have to harvest

the DNA and clean it up We add some copper oxide to it and evacuate

We then combust that material to convert all that carbon to carbon dioxide again.

That carbon dioxide gets reduced to elemental carbon in ion powder and that's actually

Once they've got that down, they'll put the samples into targets for the mass spec

The targets are little aluminum sample holders that have a little hole in them about a millimeter

It then goes into a sample wheel and put in the ion source.

We use a cesium sputter ion source and it makes negative ion we set up an electric field

to extract the negative ions out of that through the plasma mass that's right in front of the

We have this negative ion beam that's coming out of the ion source.

We then put it through a low energy magnet to select the mass that we want.

The accelerator has a very high positive voltage at the center, it's called the terminal.

We then have a couple of focusing elements, a couple more magnets, and then we measure

carbon 14 counts in a particle detector at the end.

This precise atom counting technique has uncovered some incredible things about our bodies.

Ever wonder why an Achilles tendon injury takes so long to heal?

It's because the tissue turnover is practically nonexistent.

This finding is just one of many other discoveries thanks to bomb pulse forensics.

Cardiomyocytes are the muscle cells of the heart.

We saw that there was turnover, relatively low like 1% turnover, but it did occur.

Why that's important is that you might be able to clinically stimulate an injured heart

This was huge because previously, we didn't know adult heart cells could replenish.

We found that the only place there seem to be any turnover of neurons was in the hippocampus.

Hippocampus is where our short term memories become long term memories.

And in another study using the bomb pulse, they uncovered that fat cells are forever.

People get new fat cells through adolescence, and then the body seems to maintain that number.

So when you swing through weight gain and weight loss the number of fat cells is staying

But, with all this investigative potential, there's a catch.

The bomb pulse is essentially going away.

But there's another factor that's actually pushing the C-14 lower because we've been