One very prominent mind twister in both science fiction and real-life science is the concept of parallel universes. This is hardly surprising, since the idea of multiple copies of yourself existing at the same time is both existentially disturbing and thrilling.
The idea of a multiverse is not considered a scientific theory but rather, as Ethan Siegel of Forbes puts it, “a theoretical consequence of the laws of physics as they’re best understood today.” The idea that space-time begins and stretches infinitely implies that existence is mathematically bound to repeat itself at some point—a notion sometimes called the “quilted multiverse.”
Or, forgetting the idea of repetitious cosmic clones, there’s the possibility that multiple big bangs begat multiple space-time bubbles, in a foamy multiversal sea of infinite potentialities. Here’s how it works:
But what we want to know is: could you ever get to another space-time?
That depends. The American theoretical physicist and string theorist extraordinaire Brian Greene, of Columbia University, argues that the plausibility of multiversal travel—conceding that parallel universes really do exist—hinges on which multiverse concept you subscribe to. If you are an advocate of a multiple big bang multiverse, then that would mean that leaving our universe to travel to another would be just as impossible as travelling back to the time before the big bang that resulted in our universe even happened.
Now, if you believe a quantum physics-dominated notion of parallel universes, then there’s no need to travel to other universes, because you are already inhabiting multiple alternate universes (though not necessarily all of them). Can’t decide which dress to wear? No matter—you’ve worn them both, in two separate parallel universes.
Meanwhile, theoretical physicist Michio Kaku believes that our universe will end up in a “big freeze,” and that technology can one day allow us to travel between universes.
Neil deGrasse Tyson, on the other hand, says that if you come from a universe with higher dimensions, then it could be as easy to move between dimensions as stepping from one room to another. And in string theory—one of the leading contenders in bridging the seemingly insuperable gulf sundering quantum mechanics and general relativity—the assumption is that we actually have far more dimensions in this universe than we previously thought and that we just fail to detect them because they are actually very small, curled up in the infinitely minute, trans-subatomic realms beyond the reach of our instruments.
But how can we prove (or disprove) any of these arguments without gaining first-hand experience of it? Much as many aspects of our universe still remain elusive to us, it’s currently impossible to acquire any proof to confirm which of these hypotheses is right. But while we don’t have the means to definitively prove whether alternate universes do exist, and whether we could traverse borders to move from one to another, it’s highly unlikely that a topic as stimulating as this will disappear anytime soon, either in science fiction or in real-life science.
Meanwhile, physicists are at it. Watch this brief video of physicists going head to head with each other on string theory, Math, and potentially embarrassing alien encounters.