This paper takes part in the series essay competition of “great science” of Recordunkown.
When mankind with the help of science and technology, out of the earth, we found that the world outside the earth is so vast and wonderful. When human beings really see the vast universe, their enthusiasm for exploring the universe is constantly rising.
It is the infinite curiosity of the unknown that human civilization can enter the era of science and technology in a very short time and achieve rapid leap. Before human beings walked out of the earth, we explored and studied the secrets of the earth, and we could only look at the starry sky.
But when we really get out of the earth, the focus of scientists’ exploration is also on the vast universe. There are too many mysteries in the universe waiting for us to solve, and in many mysteries, exploring the origin of the universe is the earliest carried out by scientists. Through a lot of cosmic observation and research, scientists put forward the big bang theory.
Scientists believe that our universe originated from a singularity explosion 13.8 billion years ago. This singularity is a hot, dense thing full of matter particles and high-energy radiation. Its volume is infinitely small, but its mass is infinitely large. Although the big bang theory is a conjecture put forward by scientists, scientists have found more and more evidence to prove the correctness of the big bang theory.
Now, the big bang theory has been generally recognized by the scientific community, and under the big bang theory, another cosmic phenomenon has attracted great attention of scientists, that is the expansion theory. The original universe was very, very small. After the big bang, the universe was born and began to expand rapidly.
The temperature of the universe is also slowly cooling down in the process of the universe’s continuous expansion, and then there are stars, planets, galaxies and other celestial bodies and materials constantly forming. The expansion of the universe is not difficult to observe. Through astronomical telescopes, we can easily observe that the galaxies in the deep universe are constantly away from us. The farther away the galaxies are, the faster they are away from us. Therefore, we have the setting of observable universe.
The constant expansion of the universe also tells us such a truth: there may be space outside the universe, so what will be outside the universe? I believe many friends know that an important prerequisite for a balloon to expand is that there should be enough space for it to expand. If the balloon is fixed in a limited space, then the balloon can not expand indefinitely, at most it can only expand to the size of the fixed space.
The universe has been 13.8 billion years since its birth, and its expansion has been going on. If there is no space outside the universe, how can it expand? Therefore, more and more scientists believe that there is space outside the universe, but we are not clear about what is going on outside the universe. Some scientists speculate that the universe may be pluralistic.
Outside our universe is a more vast mother universe, in which there are countless kinds of universes, and our universe is just one of them. The universe is expanding rapidly, so there are observable universe and unobservable universe. What is observable universe?
I believe many friends know that the observable cosmic range of mankind is about 92 billion light-years. How did this range come about? In fact, it is defined according to the speed of light. We all know that the speed of light is the fastest speed in the universe. Only photon plasma can achieve it. A mass object can only infinitely approach the speed of light. This is the answer that relativity tells us.
There was nothing in the universe before the big bang, no matter, no radiation. It wasn’t until 13.8 billion years ago that the big bang at the singularity produced vacuum energy, which pushed the universe outward. According to the research of scientists, at the moment of the big bang, the expansion speed of the universe far exceeded the speed of light, thus forming a very large space in a very short time.
The universe has been expanding ever since its birth, or even in the future, and the expansion speed of the universe is far faster than the speed of light. After the universe experienced the reheating stage, the big bang began, and experienced a series of high-energy collisions between particles, which also created all the basic particles we know or don’t know today.
380000 years after the big bang, with the expansion and cooling of the universe, neutral atoms were formed. At this time, there are no stars, galaxies, etc. these luminous material structures are formed between 50 million and 100 million years after the birth of the universe. Therefore, when the star forming photons rush towards us, the universe has expanded to infinity.
Light from galaxies closer to us can reach Earth in a short time, while it takes longer for galaxies farther away. But there is a limit to the speed of light. If the universe is not expanding, the photons that are far away from us will come to the earth one day. However, the universe is constantly expanding, and due to the existence of dark energy, the universe began to accelerate expansion 4.5 billion years after its birth, which exceeded the speed of light.
This means that those galaxies whose light has not reached the earth will never reach the earth. Those that have reached the earth will be visible to us, but they have expanded to 46 billion light-years. This is our observable universe. Those galaxies whose light has not reached the earth are beyond the observable universe.
Whether the observable universe or the unobservable universe belongs to our universe, and there may be more vast space outside the universe, otherwise the expansion of the universe should have stopped long ago. If there is space outside the universe, it must also be an extraordinary space. More scientists guess that it is a multiverse.
Before human beings entered the era of science and technology, the ancients also believed that our earth was the whole universe, a vast space. But when we enter the era of science and technology, and out of the earth, we wake up: the original space outside the earth is more vast and mysterious, our earth is just one of countless planets.
In the same way, the current scientific and technological strength of human beings is still very weak, and they have no ability to observe the edge of the universe, let alone go out of the universe. If in the future, human technology has reached a higher level, we can jump into space and reach the edge of the universe at will. Then it is possible to really see the world beyond the universe, just like human beings standing in the atmosphere of tens of thousands of meters. Although they are still on the earth, we can already see space.
When human beings have the ability to go to the edge of the universe, the tip of the iceberg outside the universe may appear in front of us. When human science and technology develop to a higher level, we may be able to go out of the universe and explore the world outside the universe. At that time, perhaps we will also sigh: the original human existence of the universe is just a dust in the mother universe.