July Iridescence 2
August 17, 2015
While the rainbow colors of a more mature film of Leptothrix discophora, such as the one shown in last week’s post, may be more spectacular, I think there’s also something to say for the younger, more subtle, manifestations of this iron bacterium—especially when it’s housed in attractive shale formations. In the first photo, notice how the film seems to disappear when it’s in the shadow of the piece of shale. Sometimes the film becomes invisible in the shade, and sometimes the film can be seen only if a shadow falls across it. Whaaa??? I know the visibility of these films has something to do with the angle of the sun relative to the viewer’s eyes, but the phenomenon must be more complicated. Where is a physicist with special expertise in optics when you need one?