字幕列表 影片播放 列印英文字幕 The Comprehensive Nuclear-Test-Band Treaty prohibits all nuclear explosions anywhere on Earth 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.