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  • Detonating a nuclear bomb seems like a risky business in general,

  • but in the early 1960's, the US and the Soviet Union were busy trying to figure out

  • what would happen if you set one off in space.

  • The answer turned out to be something they didn't really expect.

  • A nuclear blast could cause a high-altitude electromagnetic pulse, or EMP,

  • a powerful man-made burst of electromagnetic energy that could

  • basically wipe out communications here on Earth.

  • It was a whole new way to use the bomb, and they kind of discovered it by accident.

  • It all started in 1958, when the US launched its first satellite Explorer 1.

  • NASA scientist James Van Allen equipped it with a Geiger counter,

  • because he wanted to measure radiation at different altitudes,

  • a project he'd already been working on using balloons.

  • The readings that came back were strange. Radiation levels seemed to increase with

  • altitude, then suddenly dropped to 0, then increase, and then suddenly dropped to 0 again.

  • More testing showed that readings that looked like 0 were actually

  • because the radiation levels were so high that the detector couldn't handle it.

  • But that spring Van Allen realized he made a new discovery: that there were at

  • least two belts around the planet between 1,000 and 60,000 kilometers up

  • with extra high concentrations of charged particles like electrons and protons.

  • Today we call these belts the Van Allen belts and we know that they're

  • mostly made of particles from solar wind and cosmic rays, held in place by Earth's

  • magnetic field. We also know that depending on solar activity there can be

  • more than two of them. In May of that year Van Allen presented his discovery

  • at a press conference at the National Academy in Washington DC. Later that day,

  • the US military asked for his help detonating nuclear weapons in the Van

  • Allen belts. US military officials suspected the Soviets were doing

  • high-altitude nuclear tests, and at the time nobody really knew how

  • high-altitude explosion would differ from one here on Earth. And the Van Allen

  • Belts added a whole new element because nuclear blasts release lots of charged

  • particles and here with these two huge bands of more charged particles. The US was

  • worried that interference from the Van Allen belts might hide incoming missiles or

  • that they could somehow be used to steer a blast. So they decided to learn more

  • about how atomic bombs behaved at high altitudes by detonating a bunch of them.

  • During those tests they ended up measuring electric signals so high they thought it

  • was a fluke caused by other flaws in the instruments they were using. But they had

  • to wait a while to figure out what was

  • really happening, because later that year the USSR called for a ban on

  • high-altitude nuclear testing, and the US agreed. Then in 1961 the USSR started

  • testing their own nukes at high altitudes anyway, and the US quickly

  • continued their own, including a test known as Starfish Prime.

  • Starfish Prime was humanity's first hydrogen bomb detonated at a high altitude.

  • It detonated 400 kilometers above a point near its launch from Johnston Island in

  • the Pacific Ocean. It was also the biggest bomb ever set off in space,

  • 100 times more powerful than the Hiroshima bomb and with a blast equal to

  • about 1.4 million tons of TNT. But with so little air around it, it didn't make a

  • fireball. Instead, the charged particles zooming away from Starfish Prime caused

  • a huge Aurora that could be seen for thousands of kilometers around Johnston Island.

  • And then, burglar alarms started going off in Hawaii more than a thousand kilometers away.

  • 27 rockets followed Starfish Prime to gather data and even they weren't equipped

  • to measure what happened. What the US learned was that the oddly high

  • measurement from earlier tests weren't glitches. High-altitude nuclear

  • explosions are just very different. In the near vacuum up there, the energy

  • from nuclear blast sends out lots of free electrons. Those electrons create a brief

  • but extremely powerful electromagnetic pulse: an EMP. Starfish Prime's EMP was so strong,

  • it affected the flow of electricity on Earth thousands of

  • kilometers from Johnston Island, causing blackouts and electrical malfunctions in

  • Hawaii and disabling at least six satellites. But that was in a relatively

  • isolated area. Today an EMP could be used to disable an entire country. A US

  • commission to study EMPs in 2008 estimated that an EMP attack could kill

  • 90% of the US population within 12 months, since so much of the

  • way we live depends on satellites and the electrical grid. The US military ran a

  • few more tests after Starfish Prime, but they kept things a lot smaller and the

  • data from those tests is still classified. Only a year later the

  • USSR proposed another moratorium on high-altitude nukes: the Limited Test Ban

  • Treaty of 1963, and we haven't set off any nukes in space since then.

  • So in the end humanity was probably right to be worried about the

  • consequences of detonating nuclear bombs in space, but mainly because they

  • accidentally stumbled upon a way to make the aftermath of the bomb even worse.

  • Thanks for watching this historical episode of SciShow Space and thanks

  • especially to our patrons on Patreon who help make this show possible.

  • If you want to help us keep making episodes like this just go to

  • to learn more,

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Detonating a nuclear bomb seems like a risky business in general,

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The Unexpected Effects of Nukes in Space

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    joey joey posted on 2021/04/18
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