The idea of "time travel", once confined to the realm of science fiction, has sparked heated debate in the scientific community. If we can use a time machine to travel back in time or into the future, why haven't we seen any visitors from the future so far? Based on our daily life experience, time seems to have only one direction of flow – from the past to the future, which is exactly what we call the "arrow of time". However, we still know very little about this unidirectional nature of time.
Theoretically, time travel is not entirely impossible, but our understanding of the phenomenon is still at the stage of trying to grasp the smoke drifting away by the wind, and we can only perceive its edges. The laws of reversible physics show that the passage of time is not a rigid one-way street. However, in the real world in which we live, the dreams of traveling through time and space are still out of reach, and those wonderful ideas that cross time and space have not become reality.
In exploring the nature of time, physicists have discovered a perplexing phenomenon: the universe we observe exhibits only one-way passage of time, despite the fact that the laws of mathematical physics allow for the possibility of turning back time. This passage is like an arrow that will never look back, from the past to the future. If we have the ability to reverse this "arrow", then the broken glass may be restored to its original state. But this has never happened in the real world.
When we look up at the starry sky, going back in time to the beginning of time, we come into contact with the Big Bang theory. This cosmic origin event seems to be the starting point of the "arrow of time", and since then, time has begun its one-way journey. The ever-expanding state of disorder indicates that the end of time may not be far away. And this end point could be the evaporation of a black hole, or it could be the heat death of the entire universe. At that point, the concept of time may become vague or even meaningless altogether.
On the question of why we have not seen future man, we have to mention the theory of the expansion of the universe. The theory makes a compelling idea: the universe is expanding at an accelerated rate, which is causing distant galaxies to gradually move away from us at a faster rate. One day in the future, the light of these galaxies may no longer be able to touch Earth, making it impossible for later generations to observe their existence.
这种加速扩张引发了我们对宇宙未来的悲观预测。大约一千亿年后，银河系周边可能会变成一片虚无，星系的光芒被时空的遥远所吞没。这种宇宙景象与我们通常理解的时间流转和空间距离截然不同。如果时间的演进持续如此，未来人的可能性将极其微小，因为他们将无法穿越时空来访问我们这个时代。
In exploring the possible state of human existence in the future, we are confronted with a complex set of physical concepts. One of them is the theory of the end of time. According to this idea, the expansion of disorder after the Big Bang may herald the end of time. This endpoint may be the evaporation of the black hole, marking the final dissipation of matter and energy in the universe, leaving only randomly floating particles.
In this scenario, the notion of time becomes blurred, and the passage of time as we understand it will no longer apply. If future humans exist in such a universe, they may experience a slow stagnation of time, and may not even be able to perceive the forward or backward flow of time. In addition, as the universe expands, the disappearance of galaxies means that even if future people were able to time travel, they would not be able to observe enough of the past, because the rays of the past would no longer be able to reach their world.
Everyday experiences profoundly shape our perception of time, leading us to believe that time is evenly propelled. However, the in-depth exploration of science reveals a multidimensional reality that does not correspond to everyday experience. In this reality, the possibility of time travel is subject to a series of physical laws.
From a physical point of view, the properties of time and space can vary in extreme environments, such as the strong gravitational field around a black hole or the early days of the Big Bang. The expansion or contraction of time in such environments is very different from the passage of time that is perceived on a daily basis. Furthermore, the uncertainty principle of quantum mechanics states that the future of microscopic particles is unpredictable, which further complicates time travel.
While scientific advances do not necessarily preclude the possibility of time travel, the challenges of achieving it will be insurmountable. The constraints of the real world seem to warn us that time travel is more likely to be science fiction than real life.