When we first started to leave Earth's atmosphere, strapping test pilots into spacecraft and blasting them into the vacuum of space, we expected there to be a few surprises in store. And we were not disappointed. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

For instance, dating back to the Apollo program, many astronauts have reported mysterious bright flashes of light in their eyes. One survey of 59 astronauts found that 47 had seen these flashes while on spaceflights, which were most often noticed before sleep, sometimes disturbing it. The flashes were predominantly described as appearing white and having elongated shapes, usually going in a sideways or diagonal direction but never in the vertical.

The flashes have long been be

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