There are many astronauts experiences that are well understood.
Everyone knows about “weightlessness,” or floating in a microgravity environment, (which is actually perpetual free-fall around the Earth, but that’s a technicality for another post.)
Everyone has heard about the problem of space sickness that hits some astronauts and not others. Disruptions in our sense of orientation (i.e., up and down,) are likely to blame.
However, what many do not know about are the strange “flashes” of light astronauts see while in space and what it might mean for their future heath. With commercial space travel on the horizon and space tourists and commercial astronauts lining up to take part, the realities of space travel must be explored and disclosed.
The Earth’s atmosphere normally acts as a shielding layer, protecting the surface from cosmic and solar radiation. However, when we travel beyond the atmosphere, (i.e., space,) we increase our exposure to such radiation. In truth, these “flashes” reported by astronauts are actually electrochemical reactions occurring in astronauts’ eyes as a result of high-energy radiation striking their retinas. A radiated particle passes through the lens of the eye, strikes the retina, and fakes out the optic nerve, which in turn interprets the signal as light.
So, aside from being strange, what are the potential effects of these flashes?
There appears to be a relationship between this radiation exposure and later development of cataracts, a disease characterized by a clouding of the lens of the eye. According to a 2001 study, a total of 39 astronauts have developed cataracts later in life, and 36 of them flew on high-radiation missions, such as those to the Moon.
Scientists are currently working on nailing down the genetic link between radiation exposure and cataracts, but until then, it simply appears that exposure to space radiation increases your risk of cataracts later in life. Advances in and the regularity of surgically-implanted interocular lenses make cataracts less of a concern, but effects like these are something for the aspiring casual spaceflight participant as well as for future planetary and deep space explorers to be aware of.