We take time for granted as it passes during every moment of our existence. Other things may change, but time remains constant and predictable. The past, the present, and the future exist within a harmonious, reliable, and never-changing system. Or at least thats how it seems It was Albert Einstein who, in 1905, first theorized that time might not be quite as straightforward as that. In one of the most influential papers on physics ever published, he proposed something called time dilatation. This suggested that time was neither fixed nor constant and that the passage of time was related to the relative speed of the observer. Long before the advent of modern science and Einstein's theory of relativity, people have contemplated time traveling, and there are still debates about the concept today. During the 20th century, new theories of the multiverse suggested that our world isnt discrete and separate but perhaps one of an unimaginable number of other universes, separated by membranes that may be possible to see or even pass through. These ideas are difficult to grasp, but as theoretical physicist Werner Heisenberg put it succinctly, Not only is the Universe stranger than we think, it is stranger than we can think. Despite so many popular depictions in literature and movies, it is widely assumed that nobody has built a working time machine, but ordinary people have insisted that theyve experienced odd events during which they found themselves in another time. Some of these experiences have been reported by seemingly rational individuals, and some have involved more than one witness. The conventional view is that all these people are either deluded or mistaken, even though others have found some of these accounts strangely compelling.
