Behold the mighty power of rapatronics

Rapatronics. Sounds like science fiction, doesn’t it – or maybe a berserk new music style. Except it isn’t.

In fact, rapatronics – ‘Rapid Action Electronics’ – was a technology for taking ultra-high speed photographs, invented by Harold Edgerton in the 1940s. That’s right – around 70 years ago. The system used oscillating magnetic fields to polarise and then depolarise a Faraday cell made typically of flint glass, turning it briefly transparent and acting as a shutter with exposure times down to 4 millionths of a second.

Rapatronic picture of an atomic explosion. Spikes are extensions of the fireball into the guy ropes stabilising the testing tower. Mottling effect is caused by the bomb casing, already vapourised and reflecting off the shock front of the fireball.
Rapatronic picture of an atomic explosion, milliseconds after detonation. Spikes are extensions of the fireball into the guy ropes stabilising the testing tower. Mottling effect is caused by the bomb casing, already vapourised and reflecting off the shock front of the fireball. Public domain, via Wikimedia.

Pretty cool tech even by today’s standards, and what’s even cooler is that the principle of using magnetic fields to polarise material was discovered by Michael Faraday in 1845.

Thing is, with a shutter speed of 1/4,000,000 of a second you need a pretty bright flash to properly expose the film. An atomic flash, in fact.  In 1947, Edgerton and two friends set up a company, EG&G, to make rapatronic cameras capable of photographing the first microseconds of nuclear test blasts. Each camera was good for one shot – there was no way of transporting roll film fast enough, so Edgerton typically ganged up a rack of them to take a series of shots at millisecond intervals. They were in operation by 1950 and used, for the last time, in 1962. By then the US, Britain and Soviet Union were already talking about a nuclear test ban treaty; and it was signed the following year – ending all nuclear tests except those held underground.

Edgington was also able to use his shutters to photograph hummingbirds in flight for the first time, at much slower shutter speeds, photographed bullets passing through playing cards, and was still working on camera systems in the 1980s – notably a strobe system that could take motion pictures of creatures that normally moved too slowly to be detected.

But his ghostly monochrome images of those atomic weapons tests remain perhaps the iconic demonstration of his inventiveness – and a sobering reminder of the wider mind-set of that age. The mid-twentieth century was still the age when humanity believed nature could be conquered. The atomic weapons and cameras used to photograph them ran to the edges of the laws of physics. It was an age when all things ‘atomic’ symbolised high-tech, superiority and power. When bigger was better – including, for a while, atomic bombs.

I still wonder how we got away with the twentieth century – why the world didn’t dissolve into armageddon, probably by accident. But we did get away with it. The dangerous stand-off was defused. Sanity prevailed.

Next time, of course, we may not be so lucky.

Copyright © Matthew Wright


11 thoughts on “Behold the mighty power of rapatronics

  1. Asimov wrote a short story titled Hell Fire (published in the collection Earth is Room Enough). In it a group of scientists gather to watch high speed video of a test-explosion at Los Alamos and see an evil-looking horned face grinning at them from within the fireball. I quickly read the story again (it’s just two pages) and I’m pretty sure what you describe here was his inspiration for that tale.

    1. I was thinking of that story as I wrote this post. I have the same book. Asimov was very good with his jabs like that. There was another super-short he did where the aliens were about to welcome humanity into the galactic club but then realised they had nuclear weapons and sadly ruled them out, as tbey were inevitably going to destroy themselves.

    1. Ditto. And looking back, it was amazing how the Cold War standoff was all looked on as normal and permanent. I remember doing an undergrad course on the politics in 1982 which pivoted on the notion. Luckily the world saw sense… And the other amazing thing was the speed with which the standoff shut down.

  2. If I didn’t know what the fireball photos were, I would have thought they were micro-photography of some simple organisms. Between the lack of recognisable elements, the simple structure, and the familiar monochrome of classical electron microscopy, the similarities are striking to me.

    1. It’s fascinating how these similarities emerge in so many different contexts. I guess the broad context of all being within the wider realms of the same laws of physics helps, but down at the detail level the application is quite distinct. Interesting.

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