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.	2010 HPS Midyear Topical Meeting Radiation Risk Communication to the Public 24-27 January 2010 Albuquerque, NM
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07 November 2009

Answer to Question #4581 Submitted to "Ask the Experts"

Category: Radiation Effects — Hiroshima and Nagasaki

The following question was answered by an expert in the appropriate field:

I heard once that the bombs exploded on Hiroshima and Nagasaki had a very strange effect: when the bombs exploded, dark shadow-like images of people doing whatever it was they were doing when the bombs went off were "photographed" (if you will) onto buildings and other surfaces. Is this true? If so, in scientific terms, how did this happen?

The "shadow" images you refer to were created as a result of the thermal effects of the bomb. These images might appear to be a dark "shadow" on a light background or a light-colored "shadow" on a dark background. In the vast majority of cases, they were of inanimate objects rather than of people.

Heat from the explosion could char, discolor, and/or alter the texture of surfaces, e.g., wood, paint, concrete. In some cases, an object positioned between the explosion and the exposed surface would protect it from the heat and result in the shadow image.

The angle of the images was used to help estimate the center of the explosion.

Paul Frame, CHP, PhD

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