Since Einstein's general theory of relativity, many physicists have created different metrics (distance functions) to express different space-time geometries. These include the well-known Schwarzschild metric (a description of the geometry of space-time around a black hole) and the Friedman-Lemaître-Robertson-Walker metric (a description of the geometry of the expanding universe). These are different from the Minkowski space in special relativity. The space-time of the former is curved due to the uneven energy distribution, while the latter is under the uniform energy distribution.
If some energy distribution results in a closed time-like curve, then causality will become meaningless under Novikov's self-consistency principle, as depicted in the movie. That is, if there is a single closed time-like curve, the probability of changing an event at any one spacetime point is zero. That's why Adam said to Noah in Season 2: You don't know how to play this game yet, because all events that take place in this plane are fixed and unchangeable. In other words, this cycle cannot be broken from within spacetime. Unless there is the entanglement of other time and space (here is a personal guess), that is to say the other world is at the end of the second season.
From a physics perspective, the show does nothing more than introduce a very interesting and very precise discussion of time travel and causality. At present, such a space-time structure is not yet possible to exist. Because a closed time-like curve requires negative energy, which is nowhere to be found in the universe as we know it (at least we haven't found it yet, in fact, the space-time geometry of wormholes also requires negative energy). Of course, this does not mean that closed-time-like curves are not theoretically feasible.
The film discusses the causal theory of time travel to a large extent, and also reveals the changes in the human nature of its observers at different time and space points in this space-time. Thus, it has evolved from a physical fictional world into a literary work that reflects social issues such as human nature, religion, ethics, family and so on. It was an unprecedented and wonderful trip for me.
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