Where the light comes from
- High-energy particle
- Passes through the eye
- Excites cells
- Brain sees a flash
Vision is wired so that any excitation of the retina or visual pathway is interpreted as light. The particle doesn't need to glow: it's enough for it to hit cells along the way.
Other mechanisms may also be involved. A fast-moving particle in the eye's transparent tissues can produce a faint glow, or it may directly excite nerve cells. The contributions of the different pathways have not been fully separated.
Crews on lunar missions were the first to report this: in the quiet, with their eyes closed, they noticed dots, streaks, and little clouds. The phenomenon proved so repeatable that separate experiments were conducted to study it.
How it was tested
Observations confirmed by measurements: detectors were worn on the station, and reports of flashes coincided with particles passing through
Experiments were conducted in orbit with a detector helmet: a participant pressed a button after seeing a flash, while instruments recorded whether a particle had passed through their head at that moment. The events did coincide.
Flashes occur noticeably more often in certain parts of the orbit, where Earth's magnetic-field protection is weaker, and during solar events. This is another argument that radiation is the cause.
The phenomenon itself is harmless and stops after returning home. The bigger concern is that the same particles also pass through other tissues, and the total dose is one of the main unsolved problems for long-distance missions.
Where do astronauts' flashes of light come from?
How was this confirmed?
Sources
- Visual flashes during spaceflight were first described by crews of the Apollo program and confirmed by subsequent observations on orbital stations
- experiments with individual particle detectors showed that reports of flashes coincided with particles passing through. The mechanisms under discussion include direct excitation of the retina and light emission in the eye's transparent tissues
Next in the “Body in Space” series
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