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Hey hermit kings and queens, Trace here for DNews.

So the Democratic People's Republic of Korea, AKA North Korea, has reportedly tested their

5th nuclear device.

They want us to know they did it.

We know they want us to know they did it.

And they know that we know that they want us to know what we know.

But how can we know it was a nuclear bomb?

We're not just going to take Kim Jong-un's word for it.

There's actually an organization called the Preparatory Commission for the Comprehensive

Nuclear-Test-Ban Treaty Organization.

Or the CTBTO…

Though technically I guess it should be the PCCNTBTO.

Since 1996, the CTBTO has had it's ear to the ground around the world, listening for

any rumblings.

That's not just a metaphor, they literally have 42 primary and 107 secondary stations

around the world monitoring seismic activity.

Usually they just pick up earthquakes, but if there's a nuclear test underground, like

all the North Korean ones have been, they'll pick up the seismic waves through the earth's

crust and mantle.

Based on the direction, speed and type of waves each station picks up, the location

of the test site can be deduced.

But what if the tests are conducted underwater?

That scenario has been planned for too, and the CTBTO has an array of 10 hydroacoustic

monitoring stations globally.

Why only 10?

Because sound travels amazingly well under water, particularly 1000 meters down, at a

depth known as the Sound Fixing and Ranging channel, or SOFAR.

With just a handful of stations, they can still hear nuclear tests in the earth's

oceans, even when they're SOFAR away…

Get it?

And if the tests are conducted in the atmosphere, the CTBTO can catch that too.

Again the method is to use sound, this time at frequencies so low we can't even hear

them, or infrasound.

These longer wavelengths travel farther but they still don't move as efficiently as

sound in water, so there are 49 infrasound stations in use right now to listen to the

breeze.

As a bonus, underground tests generate infrasound too, so the data can be combined with the

seismographs for more accurate information.

You'll notice all these methods of detection have something in common: they can be tripped

by non-nuclear means.

Volcanoes, earthquakes, and conventional explosions can cause seismic activity and sound waves.

There's only one way to know for sure the bomb was an A Bomb:

radioactive fallout. When a nuclear bomb explodes, it creates radioactive xenon isotopes. And,

because xenon is a gas, it can seep through layers of rock until it reaches the open air.

This means that unless tests are conducted deep underwater or underground, the CTBTO

can forensically prove when someone tests a nuclear bomb.

So then what? Well that's where the bulldog loses its teeth, I'm afraid. The Comprehensive

Test Ban Treaty has been signed and ratified by 164 countries but still needs 8 more before

it can enter into force. Hence why the organization is still technically called the “Preparatory

Commission” for the CTBTO. So currently when a country sets off a bomb, all the rest

of the world can really do is wag a finger at it and impose more sanctions for the test

that was unsanctioned. North Korea, perhaps unsurprisingly, has not signed or ratified

the treaty, but to be fair the USA has signed it but hasn't ratified it either. Still,

until every country is on the same page about nuclear weapons, at least the CTBTO has the

tools to warn the rest of the world that someone's not being chill.

Guys, if you love DNews in English -- gracias! Now, we've got a new sister

show, "DNews en Español" -- It's DNews, but in Spanish! Check it out here.

In early 2015 North Korea set off what they

claimed was a hydrogen bomb, but was it? How is an H bomb even different from an A bomb?

Julian covers all that here.

What's your stance on nuclear weapons? Inexcusable superweapon or necessary evil?

Let us know in the comments, make sure you subscribe,

So you get more DNews and thanks for watching.