for any purpose, period.

Though as of 2015, it still remains to be signed and/or locally ratified in a few important places.

In spite of this, the Test-Band preparatory commission has already developed a monitoring system

that can detect pretty much any nuclear explosion that takes place anywhere on, above, or inside the Earth.

Here's how it works

Nuclear explosions release a lot of energy

much of it in the form of blast waves that radiate outwards through the air, water, or ground.

These waves travel at the speed of sound in the air, water, or rock

so if you detect them in multiple places you can triangulate exactly where and when the blast occurred.

Simple in principle, complicated in practice.

Atmospheric explosions are monitored by a global network of infra-sound detectors.

They detect the super-long wavelength, low frequency sound waves generated by

storms, glaciers, volcanic eruptions, meteor impacts, rocket launches, space shuttle disasters

and yes, nuclear explosions.

However, nuclear explosions are so much more intense than pretty much anything else

that happens in the atmosphere, that an atmospheric blast is pretty easy to detect.

Underwater detonations are monitored by hydro-acoustic sensors.

Basically, super sensitive underwater microphones floating above the ocean floor.

And like in the atmosphere, underwater nuclear blasts are pretty easy to detect

because there's just nothing else that violent that happens in the oceans.

Underground explosions are the tough ones.

They're monitored using seismometers, the same tools that detect earthquakes

and as you might expect, they mainly detect earthquakes.

Big earthquakes, small earthquakes, and lots of tiny earthquakes

and volcanic eruptions, and mining explosions, and even airplane crashes

Scientists have gotten to know these non-nuclear blasts pretty well

so when they saw large unusual disturbances beneath North Korea in 2006, 2009, and 2013

they concluded correctly, that these were nuclear explosions.

However, while all three wave techniques

waves in air, waves in water, and waves in earth

can triangulate the location of a major disturbance and even give some insight into its nature

a fourth technique is critical in order to know, for sure, if an explosion was nuclear or not:

Radionuclide Detection.

AD stations around the world sample the air for radioactive dust and gases

that are smoking gun signals of nuclear activity

which, combined with sophisticated atmospheric air flow modeling allows us to both

predict where fallout will disperse, and retrodict the general location of its source.

But in the case of a perfectly contained secret underground or deep ocean explosion

there might be no radioactive fallout.

So if seismographs and hydro-acoustic sensors pick up a suspicious signal

There's one final weapon in the international monitoring system's arsenal:

sending on the ground inspection teams to the actual location.

Except, inspection teams won't actually be legal until the treaty is fully signed and ratified.

*cough cough*

That's you, U.S., China, Israel, Egypt, Iran, India, Pakistan, and North Korea.

The world is waiting.

This video was made possible by the comprehensive test-ban treaty organization

though any political views expressed are my own.

Come on America, let's ratify the treaty now.

The CTBTO preparatory commission developed and implemented

the international monitoring system I described

and they're constantly seeking to improve the sensitivity of their sensors

and the sophistication of their data analysis.

They also make all their data available to the worldwide scientific community

so that other researchers can, for example

predict and monitor tsunamis, study the structure of the Earth, search for downed airplanes

do their own analysis of nuclear blasts, or track whale migrations, or meteors in the upper atmosphere

or radioactive fallout from nuclear power plant failures.

In short, the CTBTO is a collaborative endeavor of people around the world

using science to help prevent people from doing horrible things to each other with science.

And in the process they happen to be generating a lot of positive scientific side effects.

The CTBTO didn't ask me to say this, but after learning about their work

I want to thank them for making the world a safer place for millions, if not billions of people.