Anything in the universe takes a certain amount of time if it wants to travel through space. Even moving forward at the speed of light— the fastest speed we know — the light emitted by the sun still takes more than eight minutes to reach Earth due to the vastness of the solar system. But how can even the fastest thing stand up to the most distant places humans can imagine? Answering such questions is what Unveiled meant. Now we are answering another particular question: How long does it take light to reach the edge of the universe? Are you fascinated by the facts of the universe? Do you maintain a constant curiosity?
The speed of light isn't just the fastest speed in the universe as we know it—it's also the limit of universal speed. According to Einstein's equations, matter cannot exceed the speed of light. The speed limit can be accurate to 299,792,458 meters per second (or about 186,000 miles per second), and because of this, our space travel is severely limited. Even moving at 99% of the speed of light (the highest speed that matter can reach), it will still take years or decades to reach distant galaxies. Science, especially quantum physics, does offer some potential solutions... Quantum entanglement seems to bypass the speed of light, as the two particles seem to be able to communicate at once over a long distance. But there are still many unknowns, and some researchers believe that quantum entanglement doesn't really break the speed of light because, curiously, entangled particles don't transmit real information between them.
So today we're going to expand on a more traditional light-speed understanding. The speed of light is fixed, but the size of the universe is by no means static. Back in the 1990s, scientists were shocked to find that the universe was expanding. They observed that the light of galaxies reaching Earth was redshifted, meaning they were moving away from us at high speeds. The question has been further puzzled by recent Hubble measurements, which have shown that not only is the universe definitely expanding, but it's expanding faster. Not only that, but it also expands much faster than previously thought. In fact, today's research even suggests that we may need entirely new physics to help us understand this manifestation of the universe.
However, in terms of today's problem, the question is: If the universe has been expanding, where are its edges? Let's start with the observable universe, because by definition, it has a definable edge. From the Big Bang to the present day, about 14 billion years ago, in such a long time, only light could reach us through the vast starry sky. In the process of considering the universe expanding at a constant rate, light begins to travel in our direction, and the farthest star we can observe is the edge of the observable universe, about 47 billion light-years from Earth. So if we just want to know how long it takes for light to reach Earth from the edge of the observable universe, the answer is 47 billion years, which is also the farthest time for light to reach Earth that humans know.
The problem, however, is that the edge of the observable universe is not the edge of the entire universe. We know that there is still a lot of space in the universe that we can't observe at the moment, and that's simply because light doesn't have enough time to travel to Earth. So, where exactly is the edge of the universe? Answering this question for a variety of reasons is much more complicated than it may seem. Of all the reasons, the dominant one is that we don't even know if our universe has edges. When we stand on Earth and look up at the stars, it feels like the light of the whole universe is coming towards us, and we are at the very center of the whole universe.
However, this is only an illusion, because if you can be teleported to the edge of this universe or to any corner, you will still find in the same way that your position will be the very center of this universe. Astrophysicist Paul Sutter explains the shape of the universe using the analogy of ants crawling on beach balls. Ants are galaxies, beach balls are the universe, and the universe expands when filled with air. The beach ball is circular, with no edges and no center, because the surface of the ball itself is the universe. It depends on whether you agree with the theory of the multiverse, the edge of which is likely to exist in another dimension... But as far as humans know at the moment, or as they predict, the universe may have no edges or even no edges at all. But even if there is a rim, when will the light reach the edge of the universe if a beam of light is emitted from Earth? The answer is obvious, never.
This is because the universe is already expanding very fast, even faster than the speed of light. If the universe had boundaries, it was moving away from us at a speed faster than the speed of light, so as the light got closer, it expanded farther and farther. Matter in the universe can't exceed the speed of light, but the universe itself seems to be able to do it! Then in the universe, the only viable way to reach the boundary is to travel faster than the speed of light, which is naturally impossible for light. But wait! Doesn't this mean that the obvious cosmic speed limit has been broken? The answer is yes and no.
The universe seems to be breaking the apparently indestructible rules through its own expansion, but at no time can matter itself travel faster than the speed of light—only the space around it can. The voids between substances do not follow the same rules at all and are therefore not restricted. The elaborate theory of using wormholes to travel through space essentially follows the same logic, only in reverse direction — wormhole travelers don't travel faster than the speed of light, they just shorten the distance between two points in space by compression. In such a case, the space between any two points always inevitably expands. Turning this idea upside down again, this means not only that light will never reach the edge of the universe, but that light from the edge of the universe will never come to us.
The entire galaxy is filled with stars and planets, but with the universal limit of the speed of light, they are always out of our field of vision. There are always vast areas of the universe that we will never be able to touch—and perhaps even far more expansive than anything we have known so far. As far as we know, there has always been extraterrestrial life "outside"... But we are too far apart from each other to communicate or even know each other's existence. If we just say "visible universe," it will take about 47 billion years for light from anywhere to reach the edge of the universe. If we're talking about "the whole universe," then we may never be sure how long it will take. The edge of the universe is likely to remain an unsolved mystery forever... For unless we are one day able to use the same cosmic techniques that the universe itself uses to bypass the cosmic speed limit, nothing— not even light— will come any closer to us! That's how long it takes light to reach the edge of the universe.
By: Adam, Wei, ET Alien