How much do you know about the Moon landings?

Most people can recite the phrase, "One small step for man, one giant leap for mankind", but other aspects of NASA's Apollo missions aren't common knowledge.

Strangely, every astronaut since the first Apollo 11 Moon landings in 1969 has reported seeing the mysterious flashes - whether their eyes are open or not.

On the Science Channel's show Nasa's Unexplained Files, it was explained: "Several of the Apollo astronauts reported seeing something strange as they approached the Moon."

One astronaut, Alan Bean, said: "I saw a flash and I thought 'did I really see a flash?"

Another, Charles Duke, explained: "I'm having these light flashes. I'm seeing this, like, light flashing in my eyeballs.

"It was like fireworks in your eyeballs. It was spectacular."

Strangely, the men were seeing the flashes when their eyes were open and when they were closed.

On Moon missions, the lights were reported as being white.

On other missions, different coloured lights - such as blue or yellow - were observed.

More worryingly, the astronauts continued to see the flashes when they returned home from space under various light conditions.