Russian cosmonaut Sergei Krikalev is the world’s most accomplished time traveller. Due to his 803 days in orbit aboard the Mir Space Station, he has travelled a total of 23 milliseconds into the future (compared to Earth-bound humans). According to Einstein’s special and general theories of relativity, Krikalev lost a small amount of time due to the microgravity of space, but gained substantially more through time dilation from the 550 million kilometres he travelled. In other words, he is now 0.023 seconds younger than he would have been if he had chosen a different profession.
The effects of motion and gravity on time were experimentally demonstrated by Joseph Hafele and Richard Keating in 1971 by flying an atomic clock on a commercial aeroplane eastward around the world. In accordance with theory, the clock gained 273 nanoseconds compared to its stationary twin. These effects need to be adjusted for in the Global Positioning System. The clocks on GPS satellites are set to run fractionally slower than Earth clocks to correct for the effects of general relativity. Without correction, the GPS would accumulate an error of 10 kilometres per day.
When Edwin Aldrin returned from the moon in 1969, he reported a strange phenomenon. While inside the command module, Aldrin saw unexplained flashes of light. Since then, many astronauts have reported similar observations with patterns varying from points and arcs to more complex displays resembling fireworks.
These light flashes are caused by high energy cosmic rays, the majority of which are blocked by Earth’s magnetic field. Three theories exist as to how cosmic rays create light flashes:
1. Interaction with molecules in the eye to produce light, known as Cherenkov radiation.
2. Stimulation of photoreceptors in the retina to produce the sensation of light.
3. Stimulation of the visual cortex of the brain. The consequences of this are substantial – potentially, any part of an astronaut’s brain could be impinged upon by cosmic rays, affecting perception, decision-making or psychology.
A similar phenomenon, known as the prisoner’s cinema, has been reported by individuals kept in low light conditions for long periods. The appearance of coloured lights, often forming discernible shapes, is attributed to a combination of heightened awareness of phosphenes and the psychological effects of isolation.