I was watching Apollo 13 in IMAX format in Bangkok and noticed that one of the astronauts takes with him a Walkman type cassette player to play Country and Western music on the trip. Later after the accident as Apollo 13 is slowly dying the cassette player is shown floating in the frigid air of the cabin playing very slowly as it's battery is dying. It's a very effective symbol of their situation. But how can this be true?

The Apollo 13 accident happened on April 13,1970. Sony introduced the original Walkman cassette player in 1979, eight years after the event.