From Ben Haller, Ithaca, New York, US
You report that “odd radio circles”, or ORCs, have been detected (11 July, p 14). They are “symmetrical and their edges are brighter than their interiors”. I know nothing about radio astronomy, but I can tell you what that description reminds me of: a rainbow. Of course, I am not suggesting that reflection inside water droplets is responsible, but perhaps some analogous process might be. If so, the original source would be in the opposite direction from the ORC, as seen from Earth.
