2015 marked the 100th anniversary of Albert Einstein's 'General Theory of Relativity'. The theory suggested we lived in a 4-dimensional world (the 3-space dimensions: up and down, left and right, forward and backward and space-time dimension in which space and time were said to be inextricably linked).
"According to Einstein," it was explained, "2 people observing the same event in the same way could see the one event occurring at 2 different times, depending upon their distance from the event in question. These types of differences arose from the time it took for light to travel through space. Since light traveled at a limited and same speed, an observer from a more distant point would see an event as occurring later in time; however, the event was 'actually' occurring at the same instant in time. Thus, 'time' was dependent on space."
Albert Einstein died in 1955. In 1957, Hugh Everett III introduced the parallel universe theory in which it was said, "Our universe was not the only one, but that many universes existed parallel to each other."
In 1980, parallel universe was discussed in the children's program 'SuperFriends' when in a freak accident Superman was switched from his home universe into an opposite one in the episode 'Universe Of Evil'.
And in 1998, parallel universe was the subject of the movie 'Sliding Doors' starring Gwyneth Paltrow. Writer and director Peter Howitt started the 'Sliding Doors' project in 1991. Some 20 script rewrites later, he recounted, "The nervous breakdown occured about (1996). All I could do was stay in my flat in Fulham (England) and cry and write the script for 'Sliding Doors'. The worst lasted about 3 months. Then I slowly began to get better. Now I'm really glad it happened..."
'Sliding Doors' "has an independent sensibility, in that it has its own ideas, its own rhythms, its own point of view. It has an edge. It doesn't pander to audience expectations or their intellectual shortcomings," Gwyneth pointed out. "If you trust the film, you will be rewarded. But you have to keep on your toes. If you’ve ever had your heart broken, you remember and connect with ('Sliding Doors' and 'Great Expectations') so palpably. But out of heartbreak always comes the most interesting evolutions, the most interesting changes: When you wake up and say, 'I will never make those mistakes again. I will never make the same choices.'" Peter added, "I was just after a film that makes sense, that people enjoy and maybe have a little think about what’s going on."