Can the deceased continue to exist in the universe? This question may sound like a plot from a science fiction novel, but it is actually a serious scientific inquiry.
In physics, this question corresponds to a deeper inquiry: Do the past, present, and future truly exist? While many may think this idea is unlikely because the past has already occurred and the future has yet to arrive, only the present seems real. However, Einstein’s theory of relativity informs us that time and space are interconnected and their alterations depend on the observer’s speed.
According to relativity, time slows down relative to us when we move quickly. This theory reveals the nature of time’s passage and raises our thoughts about the relationship between the past, present, and future.
Einstein’s theory of relativity tells us that time and space are interconnected. (Illustration: ZME).
Some scientists have proposed the concept of non-linear time, wherein the past, present, and future may appear in different orders to different observers. This perspective suggests that time is not linear; rather, it resembles a series of snapshots of moments, each existing independently.
To better visualize this, we might liken it to our experience of sitting in a movie theater watching a film on the screen. We assume that the frame being shown at this moment is the present, and only this frame is real, rendering both the past and future as non-existent.
In reality, the entire film—past, present, and future—is condensed within the film reel. It unfolds frame by frame, continuously perceived and recognized by our consciousness as the present. This means that both the past and future are real; they are simply perceived and experienced in different ways. To understand this better, we can imagine each moment of the universe as a painting.
Both the past and future are real; they are just experienced differently. (Illustration: CNN).
From the Big Bang 13.8 billion years ago to the formation of the Milky Way, the entire history of the universe resembles a gigantic photo album, chronicling the state of countless moments. Each photograph represents the state of the universe at a specific point in time.
Therefore, we now need to ponder a simple yet profound question: What is the present? We can understand the present as the moment we are experiencing, as well as the events occurring elsewhere in the universe. It consists of countless moments merging to create what we perceive as the present.
It can be said that the present is the picture of the universe at a specific time. If we assume that space and time are absolute and that time passes at the same pace for everyone, we can define an absolute present. Under this assumption, the present is the same for all observers in the universe. No matter where you are in the universe—whether on Earth, on other planets in the Solar System, or in distant galaxies—the present you experience is the same.
However, Einstein disagreed; according to relativity, different observers in different reference frames will have different present moments. Although the speed of human movement on Earth is relatively low and the spatial distances are relatively short, we may assume that everyone on Earth shares the same “present.”
However, the situation changes if we consider the perspective of someone situated 10 billion light-years away from Earth. Suppose there is a person sleeping on Earth, while simultaneously, an alien 10 billion light-years away is also at rest. In this case, their clocks would tick at the same rate, so their present would be consistent.
If the alien begins to move toward Earth, their motion will cause time to pass more slowly for them. This means their clocks will no longer tick at the same frequency, and their present will diverge from the present on Earth. Although the alien moves slowly and has a negligible effect on time’s speed, there will be a significant difference in time when crossing the vast distance of 10 billion light-years.
(Illustration: Zhihu)
This implies that the alien’s “present” will slightly lean toward Earth’s past. In other words, the present the alien perceives corresponds to a past moment on Earth. Hence, for the alien, our current moment is their future.
This suggests that for different observers, the future is real, while what we perceive as the past may appear to them as happening right now. Thus, according to this theory, what we refer to as the past, present, and future is real for different observers.
This means that the deceased may still be alive for other observers, a concept that is quite difficult to believe but also raises a series of profound philosophical questions about the nature of the world we live in. If the past, present, and future all exist simultaneously, are we living in a real world? Or are we living in a simulated world?
