If parallel universes exist, then there is at least one way to get to a place that is different from our reality. So far, the existence of parallel universes is mostly associated with science fiction. But there are scientific theories that suggest that other universes exist. If so, how can we get there? Physicist Paul Sutter believes that such a possibility exists, but it is a very difficult journey, writes Space. Theories suggesting the existence of parallel worlds The existence of parallel universes is suggested by at least two well-known theories in physics. One of them is called the inflation theory and describes an extremely early universe. Soon after the Big Bang, not one, but a huge number of universes could have been created, which began to expand at an accelerated rate. Moreover, each universe has different physics and distribution of matter. But getting to other universes is extremely difficult, because they are beyond the visible space and are moving away from us faster than the speed of light. Another theory, known as the many-worlds interpretation of quantum mechanics, says that when some random quantum process occurs, one universe gets one of the possible outcomes, while other universes get other outcomes. This creates a multiverse with all possible quantum outcomes. How to get to a parallel universe? To get into one of these parallel universes, you need to create a time machine to go back to the past. Usually, such time travel leads to the emergence of various paradoxes. For example, if you go back to the past and destroy the time machine, it will not exist, which means that you cannot go back in time. But the journey has already taken place. According to Stephen Hawking’s chronology-protection hypothesis, it is impossible to travel back in time. On the other hand, Novikov’s self-consistency principle suggests that traveling to the past is possible, but changing the past is impossible. But how can you travel to the past without changing it? This is possible if you go back in time, but not to your own past. Instead, you get into an alternate history and you can change things there. If you go back to the future, the past in this reality will remain unchanged. The many-worlds interpretation of quantum mechanics offers a natural platform for creating such alternative histories. If the universe is constantly splitting anyway, then time travel simply moves you from one reality to another. On the other hand, going back to the future can create a new reality that did not exist before. But no one knows exactly how it works. It is not known how this process unfolds or by what mechanism an alternative history arises. To get into one of these parallel universes, you need to create a time machine to go back to the past. What does quantum physics say? Attempts to understand this question by studying quantum mechanics have yielded mixed results. Quantum fields tend to break down when time machines are involved. They can be stabilized by giving up some of the theory’s core principles, such as the correspondence principle, which states that quantum processes eventually lead to macroscopic behavior and that fundamental reactions are reversible. No one is willing to give these up, since they seem central to the theory. But even classical, non-quantum systems face problems. Suppose you have a switch that can turn a time machine on and off, perhaps by opening or closing a wormhole. We don’t know how alternate histories can accommodate such changes in their space-time structures, regardless of what quantum processes are going on at the subatomic level. If we could build a time machine, we could easily test whether alternative histories are created. All we would have to do is change something in our own past. If we can’t do that, then there is only one timeline. If we can, then alternative histories exist and the many-worlds interpretation of quantum mechanics is correct. It is not known whether any of these are possible, but such possibilities cannot be completely ruled out. So, although traveling to a parallel universe may be a very difficult process, it is not completely impossible. The post How to get to a parallel universe: the answer from physicists may surprise appeared first on Anomalien.com.