When we think of the universe, we will think of the "world beyond the earth", and the world we call it refers to the blue planet under our feet, the civilization of mankind, the history of mankind, and everything about mankind on this azure rocky planet. However, a mountain is more high, and beyond the world is a more vast and boundless and magnificent "world".
The "universe" is the limit of the human "world", it is the sum of time and space, in other words, the universe is "everything", because human physical laws and scientific theories are only valid in the universe, and everything outside the universe cannot be reasonably described. Human beings can only make the most reasonable explanation for this universe to a limited extent and as much as possible.
The age of the universe is 13.82 billion years, a "relatively" more accurate number, the existing theory is that in the endless nothingness of 13.82 billion years ago, a "singularity" exploded, the universe was born in this big bang, and experienced a short "inflation" phase, that is, in a very short period of time the volume of the universe underwent a huge change, and then the universe continued to expand, and constantly cooled, the first light and matter began to appear, with the birth of the first star, The universe gradually evolved into what it is today.
This is the "Big Bang Model of the Universe", a once unrecognized model of the universe, which Einstein did not approve of at first, until Hubble proved that other celestial bodies in the universe are moving away from us, that is, evidence that the universe is expanding, and Einstein is willing to believe that our universe is constantly expanding, and the reason for the expansion is that the universe was born from a "Big Bang".
The Big Bang theory raises deeper questions, such as, what was before the Big Bang? Does time and space exist? Is there an end to the universe, and what is outside the universe?
Traditional theories believe that the universe is infinitely large and eternal, so there is no need to consider these problems, and after the emergence of the big bang theory, these problems need to be considered by humans one by one, because since the universe has a "starting point", it is likely that there will be an "end point" in the future.
So is there an "end" in the universe?
Before thinking about this question, we need to determine from what model of the universe to discuss, in the "steady state" model of the universe we do not need to discuss this question, because in this model of the universe the universe is infinitely large and always constant, if you talk about our universe from the "Big Bang universe model", you may be able to get an answer.
In the process of cosmological development, many cosmic models were born, no universe model is completely correct, even the most recognized "Big Bang universe model" now has many theoretical loopholes, in fact, not only a variety of cosmic models, human physics theory is not so perfect, there is a contradiction between relativity and quantum mechanics is incompatible, our theory can not describe the interior of the black hole, because the physical theory inside the black hole will fail, And our laws of physics can only describe everything within the Planck scale, beyond which our theories will also fail.
In the "Big Bang Universe Model", the universe has the concept of "size", because in the beginning the universe did not exist, there was only an infinitely small and infinitely large "singularity", this singularity was born after the explosion of the universe, that is to say, the universe underwent a "from scratch" process, in this process the size of the universe continues to grow, until it becomes today, the current size of the universe is already impossible for human beings to determine.
The universe is like an expanding balloon, standing on the surface of the balloon, even if we do not move, we will be because of the expansion of the balloon itself, we can not feel it, because everything in the solar system is attracted by the gravitational pull of the sun, with the sun in the center of the milky way in motion, so in the milky way is not felt the universe is expanding, rising to the cosmic scale such as the Milky Way, you can find that other galaxies in the universe are gradually moving away from us, The farther away the galaxy is, the faster it is moving away.
Nearby galaxies are moving away from the Milky Way, with the exception of the Andromeda galaxy, which is moving closer to the Andromeda galaxy and may have an "epic" collision in the future. The expansion of the universe also has a consequence, that is, the light emitted by stars at a certain distance can never be earth, because the speed of expansion of the universe exceeds the speed of light at a certain point in time, so the light emitted by stars will not keep up with the speed of cosmic expansion after moving for a period of time, and "lost" in the universe.
02
The shape of the universe
If you want to figure out where the end of the universe is, you also need to know the "geometry" of the universe, the entities in the universe have an external shape, this shape can be a fixed geometry, or it can be an amorphous state such as fluids or gases.
According to the existing theory, there may be many kinds of geometric shapes of the external manifestations of our universe, because in the Big Bang universe model, the beginning and beginning of the existence of the universe, then it proves that the universe exists an exact size, but with the current ability of human beings can not observe, since the size of the universe is limited, there must be a so-called "end", to figure out the shape of the universe, can help us think about where the "end" of the universe is.
There are many speculations about the shape of the universe, for example, the most traditional view is that the universe is a closed spherical space, Einstein believes that the shape of the universe is a closed spherical space, and this spherical space is "finite and boundless", he believes that there is no "boundary" in the universe, just like we travel around the world on Earth, go in one direction, and eventually return to the starting point.
Another view is that the shape of the universe may be "absolutely flat", and scientists believe that observing the movement of light in the universe can deduce the specific structure of the universe:
Astronomers have found that light travels in straight lines throughout the observable universe's 90 billion light-years, which means that the shape of our universe may be an "absolutely flat" plane, or it may be that the universe is too big to observe the subtle changes that occur as light moves.
No matter what the shape of the universe is, we cannot find the "end" of the universe, because the universe itself is not static, and the three possible guesses actually point to the answer of "the end of the universe, but this end is constantly moving."
Unless the universe stops expanding, we can't find the "end" of the universe, because every second the universe is expanding, and we in the universe can't find the end of the universe, and perhaps only by leaving the universe and standing outside the universe can we see the whole picture of the universe.
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