Apollo 11 crew reports cabin light flashes — translunar and transearth coast

Aldrin observed recurring light flashes inside the darkened cabin throughout the flight, eventually noting single and double flashes separated by roughly a foot, and streak-like appearances. He hypothesized penetration of a high-energy particle into the spacecraft. Armstrong independently observed approximately 90 flashes over an hour on the last night when deliberately looking. Armstrong and Aldrin speculated the cause was cosmic radiation (neutrons or atomic particles) interacting with the visual system. This is consistent with the well-documented cosmic-ray light-flash phenomenon.

“ALDRIN: "I could see double flashes, at points separated by maybe a foot...the only thing that comes to my mind is that this is some sort of penetration...some penetration of some object into the spacecraft that causes an emission as it enters the cabin itself." ARMSTRONG: "It could be something like Buzz suggested. Mainly a neutron or some kind of an atomic particle that would be in the visible spectrum."”

OCR has moderate noise from scan artifacts and classification markings. The light-flash phenomenon has a well-established scientific explanation (cosmic ray Cerenkov / direct stimulation of photoreceptors), recognized even by the crew. Included as a documented anomalous visual phenomenon. Aldrin's initial static-electricity hypothesis was considered and ruled out by further observation.