Chapter 3-4 Parallel Universes
The thought experiment "Schrödinger's cat" could originally be seen as a joke among physics giants like Schrödinger. It's likely that Schrödinger himself didn't take it too seriously when he first proposed it. However, this thought experiment unexpectedly opened up scientists' imaginations and explorations of introducing quantum properties of the quantum world into the macroscopic world. One of the most heated discussions that arose from this is the "Parallel Universe (Multiverse) Theory".
Figure 3.7: The Concept of "Parallel Universes"
In 1957, American quantum physicist Hugh Everett proposed the "Parallel Universes" theory based on "Schrödinger's cat". He suggested that there are originally two universes inside the opaque box containing the cat, and the situation in these two universes is entirely consistent with the world outside the box. However, in one universe, the cat is alive, while in the other universe, the cat is dead, and the cats in these different universes cannot perceive the existence of the other universe. Initially, the two universes are in a superposition (or entangled) state. At the moment the box is opened, the two universes split, but which universe we observe cannot be determined in advance.
According to the theory of "Parallel Universes", even if we see the cat as dead, the "cat" might still be alive in another universe, in a state completely different from the one we observe now. Furthermore, since all matter in the universe has both macroscopic states and quantum microscopic states, the cat is "more than just one". Any possibility could occur, just in different universe spaces. This means that in the quantum state, the universe is likely not just one, but rather there are N parallel universes in superposition. (Figure 3.7)
The deeper meaning of "Parallel Universes" is that the universe as a whole is a single entity, so it does not require signal transmission. The individual particles and all things we see are actually just different "phases" of the same origin, which can coexist in parallel, with infinite possibilities, simultaneously. Take the famous "Goldfish Experiment" as an example: two cameras are used to film a goldfish in a tank from different angles. Suppose these two cameras are very far apart; each camera sees a different goldfish. However, no matter how far apart they are, the cameras cannot understand how, when one goldfish eats water plants, the other does so simultaneously. How do these two goldfish move so synchronously? In reality, it is actually the same goldfish, but each camera only sees it presenting different "phases". (Figure 3.8)
Figure 3.8: "Quantum Entanglement" Goldfish Experiment
Science fiction films often use this hypothesis to create various fantastical and mind-bending stories. Movies like "Interstellar" are brilliant interpretations of the "Parallel Universes" theory. In these films, we find ourselves in this originally familiar universe, but as we explore further, this state extends into countless parallel worlds, each facing an equal probability of outcomes. Humanity opens the door to an unknown world... Unfortunately, like metaphysical plots, these intriguing and challenging "scientific" discussions are still in the "unproven" stage.
At times like these, the pioneers of physics can only look to the heavens and sigh deeply, expressing their regret: What a pity! To ordinary people, it seems that there is not much difference between scientists and metaphysicists. When the common folk see these descriptions, they simultaneously oppose feudal superstitions and marvel incredulously, saying: "The end of science is Metaphysics." To quote a line from Bertrand Russell: "If men could control their environment or if they were always lucky, there would be no superstition."
Reflecting on the previous chapter, if "each choice we make splits into another parallel universe", how many dimensions are we talking about? Yes, if we reach beyond the fifth dimension, it is highly likely that we can "see" different choices in different "Parallel Universes" simultaneously. Upon graduating from middle school, you could choose to attend high school, go to college, become a teacher, or dive into business. Different choices lead to different life paths and different life outcomes. If you could take a peek or ask a being in the fifth dimension, that would be impressive, and you would undoubtedly choose the path most beneficial to yourself.
Of course, acknowledging the existence of unseen spaces and dark matter does not mean the academic world accepts the "Parallel Universe" theory. As carbon-based beings, humans are constantly undergoing metabolism. Human consciousness and thoughts are always in flux; are we always in a "superposition" state like "Schrödinger's cat"? It is still inconclusive to what extent different people's consciousness can reach different dimensions. "There are a thousand Hamlets in a thousand people's eyes", so which one is the real Hamlet?
