I ve read a lot of posts saying that the universe is a four dimensional space, finite and boundless?

The universe is indeed a closed, finite four-dimensional space. In fact, the landlord does not take into account the dimension of time, you are the ant living in the second dimension, you can't see the three-dimensional, and you look at the universe from the three-dimensional mind, if you imagine from the four-dimensional, after you move, time changes, maybe you are not in this three-dimensional, it is equivalent to flying from the plane, flying from the ground, in fact, you have left the two-dimensional space of the ground, but you still feel that you are still in this two-dimensional space, so you think that he is boundless. By the way, you walk along the surface of the earth, it seems that you are still in the same two dimensions, right?

You can understand it this way, what you see is a three-dimensional, after you move, what you see is still like this, but it is not the previous three-dimensional, but the future three-dimensional, assuming that there are countless three-dimensional dimensions, then it constitutes a four-dimensional universe. So, the universe is boundless, but it really only has these three dimensions, so it's finite. It's not like a three-dimensional cube, it's finite to you, but it's infinite to the two-dimensional person, because there's a lot of two-dimensional.

As long as you reduce the dimensionality, by analogy, you can understand.

So it's finite and boundless.

It's true that you can go back to square one in any direction, but the time to go back is definitely not very short.

If you go back to square one in the universe for billions of light-years, then it's already finite for humanity.

And again, the so-called four-dimensional space is actually very simple, we are in a three-dimensional world, and the characters in the computer game you play are people in the binary world, so it's easy to understand, you can enter any time and any place in the game, and you can enter any time and any place in the game, which is equivalent to you entering a parallel world......

Well, you can refer to the relevant plot of ever17 for details, I hope it helps you.

A bit of a problem upstairs.

The example of ants is not intended to illustrate how big the universe is, but to illustrate the concept of "finite and boundless".

As you said, an ant can walk the entire sphere back to the point of origin, or even walk through every point on the sphere (i.e., the sphere is finite), but it cannot find the boundary of the sphere (that is, it is boundless). This "can't find the boundary" is not because the ant doesn't run enough (it can run all over the sphere), but because it is confined to the sphere (two-dimensional space), and only the higher dimensions (such as us in three-dimensional space) can see where the boundary of the sphere is.

In the same way, if our universe is "finite and boundless", then we can go through every point of the universe in three-dimensional space (let's say we can do this) and we will not be able to find out where the boundaries are.

A lot of people say that the 4th dimension is time, but it depends on how you understand the 4th dimension.

It can also be difficult for an ant to understand how it fell from the ceiling to the ground.

The universe is 4 dimensions, and you can't go back to Earth if you start from Earth. When you set off at the speed of light for a week in the universe, you will find that the universe no longer exists, haha.

Those statements were just for the little class. You come to different conclusions depending on the angle you stand. Can't stand on Earth.

To look at the universe, you have to stand in the universe and look at it.

The universe is an 11-dimensional space.

The universe is physically defined as all space and time (collectively referred to as space-time) and their connotations, including all forms of energy, such as electromagnetic radiation, ordinary matter, dark matter, dark energy, etc., of which ordinary matter includes planets, satellites, stars, galaxies, galaxy clusters, and intergalactic matter. The universe also includes physical laws that affect matter and energy, such as conservation laws, classical mechanics, relativity, etc.

Physical. Of the four fundamental interactions, gravity dominates the astronomical scale. Gravitational effects are cumulative, in contrast, the effects of positive and negative charges tend to cancel each other out, making the electromagnetic force relatively insignificant on astronomical scales.

The other two interactions, weak and strong nuclear forces, decline very quickly with distance, and their effects are mainly confined to the subatomic scale.

It seems that there is more matter in the universe than antimatter, an asymmetry that may be related to CP destruction. This imbalance between matter and antimatter is partly responsible for the existence of all matter at the moment, because if the same amount of matter and antimatter were produced in the Great **, there would be an interaction that completely annihilated each other, leaving only photons.

The universe also does not seem to have either net momentum nor angular momentum, and if the universe is finite, it follows the accepted laws of physics. These laws are Gauss's law and non-divergence pressure energy momentum pseudotensor.

The universe is 11 dimensions.

According to the M theory (a type of superstring theory) proposed in the 90s, the universe is 11 dimensions and is made up of vibrating planes. For Albert Einstein, the universe is only 4 dimensions (3 dimensions of space and 1 dimension of time), and modern physics believes that there are 7 dimensions of space that we cannot see.

How do scientists explain the difference between the dimensions we already know and those that may exist but are not? They made an analogy: an ant walks on a piece of paper, and it can only walk right or left, forward or backward.

Neither high nor low means to it, which means that the third dimension of space exists, but it is not recognized by ants. In the same way, our world is made up of 4 dimensions (3 spatial dimensions, 1 temporal dimension), but we are not aware of all the other dimensions.

According to physicists, there should also be 7 dimensions. Although there are so many dimensions, these dimensions are invisible, they are wrapped up in each other and are called compressed dimensions. To clarify this view, let's take the example of the ant in our imagination.

We can imagine rolling up the piece of paper on which the ant walks until it forms a cylindrical shape. If an ant walks along the wall of paper, it will eventually return to the starting point, which is an example of a compressed dimension. The above phenomenon also occurs if you can walk along the famous Mebius, of course, it is 3 dimensions, but if you walk along it, you will always return to the starting point.

The Mebius belt is compressed from the perspective of dimensions, according to physics, it has three dimensions, but whoever walks on it can only recognize one dimension of people. It's a bit like the guy on the left: up or down, but never to the end.

If the ant does not walk along the curved wall of the paper tube, it will never return to its original starting point. This is the example of 2 dimensions (or the kind of dimension that we perceive), and if we follow it all the way, it is impossible to return to the original starting point.

So far, scientists have discovered a total of 5 dimensions in space, which has been announced so far.

Whether the universe is a multidimensional space is still uncertain. What people can feel is a three-dimensional space, which is a time axis added to the structure of the space compared to the three axes of length, width and height of ordinary three-dimensional space, and this time axis is an imaginary value axis. There are now 11 dimensions of space as we know.

Now scientists believe that the entire universe is 11 dimensions, but human understanding can only understand 3 dimensions. The world we see with our own eyes Three-dimensional space is the space where the position of a point is determined by three coordinates. The objectively existing real space is three-dimensional space, with three measures: length, width, and height.

The concept of multi-dimensional space introduced in mathematics, physics and other disciplines is a scientific abstraction based on three-dimensional space. Moreover, modern physics believes that there are 7 dimensions that we cannot see.

The first three dimensions are the position, which exists in space;

The fourth dimension is velocity, which exists in time;

The fifth and sixth dimensions are velocity pointing, which exists in the (velocity) time direction;

The seventh and eighth dimensions are state directions, which exist in the spatial direction corresponding to their shapes;

The ninth dimension is the state corner, which exists in the roll corresponding to its shape;

The tenth dimension is the spin rate, which exists in the rolling time;

The eleventh and twelfth dimensions are the spin equatorial axis pointing and exist in the rolling (velocity) time direction;

The thirteenth is the spin equatorial axis pointing drift rate, which exists in the temporal direction of rolling change (acceleration rate);

The 15th and 5th dimensions are the direction of the spin equatorial axis pointing to the equatorial plane of the drift velocity, which exists in the time direction of rolling change (acceleration).

The sixteenth dimension is the acceleration rate (or force intensity), and the seventeenth and eighteenth dimensions are the acceleration (or force) direction, which is still a purely geometrical dimension, belonging to the category of multivariate geometry, that is, dimensionality, such a dimension is not only related to position (representing the position of a geometric point in space).

In the actual world of physical nature, the situation is much more complicated: the object of mental consciousness (logarithmic dimension) under investigation can be integrated into the world to form a perspective; It is also impossible to be completely free of size, and therefore possible to move in the magnification (exponential dimension) of the world: to form a zoom and zoom of the world; Even all systems can be particle-based, motion-based 、......Therefore, the dimensions of physics can also include temperature, density, velocity, 、......And so on and so forth.

Refer to the new multi-angle definition of multi-dimensional space, high-dimensional space, and 18-dimensional space for them.

Counting that the three-dimensional universe is composed of 11 dimensions, the mainstream string theory is proposed, and based on this, please take a look at the string theory or M theory, pure hand play, watchtower!

String theory holds that the universe is 11 dimensions, and although there are still many contradictions between string theory and quantum mechanics, it is still the most reliable one for other theories.

"Universe" is space, "Universe" is time, and according to this literal meaning, it is four-dimensional.

"Universe" is space, "Universe" is time, and according to this literal meaning, it is four-dimensional. Spatial three-dimensional plus temporal one-dimensional.

The universe is a five-dimensional space of the solar system, the Milky Way, and the cosmic celestial element (the largest atomic nucleus).

Boundless! The universe is infinite, and it can be said that galaxies are infinite, which means that there are no specific numbers of planets.