Is there a margin to the universe? What kind of space is the universe?

The universe has no boundaries.

The universe is infinite, because the universe refers to the sum of all material space and time, and time is infinite.

The word "universe" probably originated from the famous ancient philosopher Mozi (about 468-376 BC). He used "universe" to refer to the east, west, south, and north, and the space in all directions, and "Zhou" to refer to the time of the past and the present. Past, present, or future; Is it a recognized, or an unrecognized......In short, everything is everything.

From a philosophical point of view. It is believed that the universe has no beginning and no end, and that it is boundless. However, we are not going to go deep into this esoteric concept, and we will leave it to philosophers to study.

We might as well zoom out a little and talk about the universe that can be understood and observed using the science and technology available to us, which people call "our universe" or "total galaxy".

According to the latest observations, the farthest galaxy that has been observed from us is 13 billion light-years. That is, if a beam of light is emitted from the galaxy at a speed of 300,000 kilometers per second, it will take 13 billion years to reach Earth. This distance of 13 billion light-years is the extent of the universe as we know it today.

To be clear, the extent of the universe as we know it today, or size, is a spherical space centered on the Earth and radiated by a distance of 13 billion light-years. Of course, the Earth is not really the center of the universe, and the universe is not necessarily a sphere, but we can only understand this extent due to our current observation capabilities.

In this spherical space with a radius of 13 billion light-years, about 125 billion galaxies have been discovered and observed, and each galaxy has hundreds to trillions of stars like the Sun. So with a simple math problem, it's not hard to see how many stars there are in the universe that we've observed. In such a vast universe, the earth is really like a drop in the ocean, so small that it is insignificant.

If according to the big ** theory (this is the view recognized by most scientists), the universe is the product of the big **, so it should be limited, but it has been constantly expanding, and we don't know when it stops, whether it can stop or what happens after it stops.

As for the "boundary" of the universe, I think there is, and the "outside" of the universe should also exist, but it is limited by the level of human knowledge and understanding, and we cannot imagine and explain these contents. Let me give you a small example to illustrate this problem:

A small fish lives in the center of the Pacific Ocean, its life can not leave the center of the Pacific Ocean, in its "eyes", the surrounding sea water is its "universe", it can only "know" to this extent, it can only think that its "universe" is boundless and infinite, if a fish tells it that the outside is very big, the border between the front and back and left and right is the land, the fish will definitely "laugh" at its ignorance, but in fact, if someone fishes out the fish and puts it on the seashore, Only then can this fish know that the "cosmic space" in which it lives is really boundary, and at the same time, it can also see what is outside its "universe".

We human beings are like the "little fish" mentioned above, because we are limited by knowledge and technology (in the final analysis, it is the degree of development of the brain), we cannot find the "edge" of this space of life, so we think that the universe is infinite, if which day, which year, which one? If. If we really reach the "edge" of the universe like a small fish to the seaside, we will find that the universe is really finite, and then we can realize what is outside the universe, otherwise, human beings will never think that the "outside" is "incredible" because they cannot find the edge of the universe!

Perhaps, before the death of the earth, human beings will not be able to reach the "edge" of the universe, because there is nothing that we humans can put on the edge of the universe like catching a small fish and putting it on the seashore, but we cannot say that the "edge" does not exist because we can't reach it, nor can we say that there is nothing outside the "edge" because we can't see the "edge". The so-called "universe is infinite" can only be understood to mean that the level of knowledge relative to human beings is infinite, and it is certainly finite in substance.

A little humble opinion, welcome to discuss.

The universe is boundary.

None of the matter has a relative gravitational pull, so the planets don't fly back.

Of course, this is just human speculation.

No, it's an ever-expanding space, subject to gravity.

The development of science and technology is changing with each passing day, and human beings cannot learn how far science and technology will develop in the future, because people have the ability to create, so human beings can only reproduce on the earth as a weak species, and can gradually enter the universe to explore space, so they believe in their own creativityWhat we can't do now, we will definitely be able to do in the future, and the future that we don't know now can be clear.

The concept of time exists in the universe. After the singularity of the universe is large, it is expanding all the time and the expansion rate is very fast, and there are a large number of galaxies in the universe that will form different spaces, and it is almost impossible for human beings to reach the boundary of the universe.

According to Einstein's theory of relativity, the universe is generated by the big **, there is no boundary, human beings have not flown out of the solar system so far, and it is impossible to reach the boundary of the universe now, and there is no boundary in the universe, how to reach the boundary.

There is also the concept of space in the universe, the universe is made up of space, and human beings cannot reach the edge of the universe, because the edge of the universe has been expanding faster than the speed of light and has no end.

In three-dimensional space, the universe has no boundaries.

The famous astrophysicist Stephen Hawking once said that the universe is finite but boundless, just like our earth, we all know that the earth is finite, but we can never find its boundaries, at least from the perspective of three-dimensional space.

And if we can find a way to enter the four-dimensional space-time, we may be able to break through the universe and reach the world outside the universe. Some people now think that the outside of the universe is actually a multidimensional space, but it is difficult for us to enter it. Just as a flat-slipped person who exists in a two-dimensional world cannot travel to our three-dimensional space under normal circumstances, it is difficult for us in three-dimensional space to travel to a four-dimensional or more space, unless the universe provides us with convenience and opens the door of time and space.

I guess the world outside our universe is like a world outside of a balloon. We are now comfortable inside the balloon, and as long as we can find a way to break through the balloon skin, then we will be able to travel freely between the universe and the world outside the universe. And I think that method should be able to allow us to travel between different dimensional spaces.