Geoff Brumfiel

This year, deep inside a mountain, North Korea detonated a giant nuclear bomb.

The intercontinental ballistic missile that North Korea launched on Wednesday appears to be significantly larger and more powerful than previous versions, according to independent analysts.

North Korea says a new intercontinental ballistic missile tested on Wednesday proves it has a nuclear deterrent that can reach any target in the United States.

According to a statement from the Korean Central News Agency, the ICBM is capable of carrying a "super-large heavy warhead, which is capable of striking the whole mainland of the U.S."

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DAVID GREENE, HOST:

The tiny nation of Denmark has just three stations for monitoring atmospheric radiation. Each week, scientists change out air filters in the detectors and take the used ones to a technical university near Copenhagen.

There, Sven Poul Nielsen and other researchers analyze the filters. They often snag small amounts of naturally occurring radioactivity, radon for example.

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