In 1923, a comet passed very close to Earth, very close to a town in Finland, which caused disorientation in people, some were lost and never returned home, others temporarily lost their memory.
A woman went to the police very scared to tell them that the man who was in her house was not her husband. When the police went to her house they told her that indeed this was her husband, the woman told them that her husband had died many years ago. But the police were unable to arrest the man because he was her husband as recorded in the public record.
In 1935 a scientist tried to explain the phenomenon. He locked a cat in a box with poison. The animal had a 50% chance of living and a 50% chance of dying, that is, when two possibilities were created, two realities were created in different universes. If parallel universes really existed, the cat would still be alive in one universe and dead in another parallel universe.
The woman died saying that this was not her husband. While the man simply said that she was his wife.
Eversince we're born, we have known only one reality - in which we live - but according to some scientists there could be several. This implies that what does not happen in our world, may be happening in another. There may even be many versions of ourselves in other universes.
Other tests:
In 1954 a man arrived at Tokyo Airport with a passport from a non-existent country: "Taured". The man was arrested for using false papers, but he continued to explain that he was from that country and that he had other papers to prove it. They arrested him in a hotel, but he disappeared without a trace.
The "déjà vu" is the feeling that you have already experienced something, but there is also the "déjà vecu", the feeling that you know what will happen next. But even stranger is the "alter vu", that is, when someone remembers his story differently, and is aware that the events are unfolding differently. Many believe that this kind of sensation has to do with memories of other versions of ourselves, in other parallel universes.
Some believe that the "ghosts" that we think we see, are actually people who live in other universes and who are inadvertently reflected in ours, although they cannot do it completely.