Robert McNees
Engineer and photographer Harold Edgerton was born #OTD in 1903.
Edgerton pioneered various forms of high-speed photography using specialized cameras, strobe lighting, and other techniques. You’ve probably seen many of the images he created!
Images: MIT; H. Edgerton
Robert McNees
While working at EG&G, Edgerton and his colleagues developed the “Rapatronic” camera. Its shutter had no moving parts and could capture exposures as short as 2 microseconds.
This new camera allowed for high speed photos of atomic bomb tests. Notice the silhouettes of the Joshua trees in this photo.
Robert McNees
What’s going on in these photos?
The roughly spherical blob is the shockwave from the blast, and the white splotches are bits of bomb casing catching up with it.
What about the protrusions emerging from the sides and bottom of the blast?
Images: Public Domain
Robert McNees
In these tests, the bomb sat at the top of a support tower and was held in place by steel mooring cables. (You can see the tower if you zoom in.)
Those glowing protrusions are the cables vaporizing. This phenomenon is known as the “rope trick effect.”
Image: Public Domain
Robert McNees
The rope trick effect is visible in this fascinating but very unnerving footage of various bomb tests.
https://www.youtube.com/watch?v=KQp1ox-SdRI
Robert McNees
Here is a gif of the rope trick effect from a video recorded with Edgerton's Rapatronic camera.
The vaporization races down the cables, outpacing the shockwave from the blast. At the end you can also see bits of bomb casing catching up with the blast.
Nick Ulivieri
@mcnees - The 'splatter pattern' aside, is the weird non-sphere, globular shape due to differences in the bomb casing density? Relatedly, how did later bombs seemingly achieve a much more spherical appearance?
mmby
@mcnees I always wonder whether these exposures can be calibrated retroactively, i.e. whether there is enough data to get approximated luminance values for every pixel, so one could have a comparison, e.g. looking at the sun vs. that
they look just so unreal
Robert McNees
You can see loads more Edgerton photos (including some cool images produced with the Schlieren Method) here:
http://edgerton-digital-collections.org/galleries/iconic
Images: H. Edgerton, MIT
arclight
@mcnees Edgerton is the "E" in EG&G, the scientific instrument supplier. EG&G was born out of the AEC's need for high-speed photography of nuclear weapons tests.
Robert McNees
@arclight I don't know how I forgot to mention that part!
Robert McNees
@arclight In the late 60s (way before my time), EG&G acquired ORTEC. Their office was between my house and my schools in Oak Ridge, so I'd drive by it every day and see the EG&G logo on their sign.
arclight
@mcnees I've got your back ;) #LandfillOfWeirdEngineeringTrivia
JP Mattia
@mcnees
It was late in the day, and as I walked past, he was standing with his hands clasped behind his back, reading the bulletin board with job opportunities. Being the grad-student smartass that I was, I piped up and said "Looking for a career change Doc?" He smiled at me and replied "It's never too late, you know!"
He passed away a couple of weeks after that. I prefer to think of it as a career change. 2/
JP Mattia
@mcnees Doc Edgerton was quite a fixture on MIT's campus, pretty much until the end. The last time I ran into him was in front of the old MIT Career Office, on my way home from the TA ghetto in building 26. 1/
JP Mattia
@mcnees
Doc Edgerton achieved larger-than-life status culturally, but he was a down-to-earth inspiration for many of us, and it was an honor to have known him, even a little. 3/3
Robert McNees
@jpmattia This is a great story.
Anne Louise Merrill
I got to meet him when I toured MIT!
Garrett Wollman
@va2lam @mcnees While Edgerton is best known for high-speed photography, EG&G was also a major supplier of detonator components for nuclear weapons.
Robert McNees
@wollman @va2lam The EG&G Ortec offices were right down the road from where I grew up!
Garrett Wollman
@va2lam @mcnees Building 34, home of the big lecture hall 34-101, is the "EG&G Education Center". Edgerton, Germeshausen, and Grier were all associated with Course VI, and Joel Moses liked to tell the story of how each man was convinced to give money for the building's construction by telling him that the other two had agreed. (Building 34 was designed as part of the 36–38 complex but the money ran out and 34 was deferred until additional funds could be raised.)
Patrick Lam
@mcnees I lived in Edgerton House, a graduate residence, when I studied at MIT.
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