Parallel cosmology is just one of the views, and is currently in the speculation stage and has not been confirmed.

However, the world view setting of this book is parallel universe theory.

Regarding the understanding of four-dimensional space, the thinking space you know should be a wrong understanding.

Four-dimensional space and four-dimensional space-time are two completely different concepts, so most popular science analysis on four-dimensional space on the Internet is wrong. Why? I will say it.

Then first we need to understand the concept of "dimensionality". In mathematics and physics, "dimensionality" is also two different concepts.

The "dimension" in mathematics refers to the number of independent parameters, such as x, y, and z can be dimensions, so in mathematics, it is possible to say that any dimension space can be used. The four-dimensional space in mathematics refers to the standard Euclidean space, and the fourth dimension should have the same properties as x, y, and z.

But in physics, dimensions refer to the independent number of space-time coordinates. Four-dimensional space-time is also called Minkowsky space-time. This person is Einstein's teacher. He first re-expressed the theory of Einstein and Lorentz in 3+1 dimensions, that is, three-dimensional space plus one-dimensional time.

Einstein did not agree with this view at the beginning, but later he realized the importance of this expression when he studied general relativity.

Then, based on these theories, two theories about spatial dimensions have been derived.

The first is Euclidean space. He believes that time and space should be independent, and the time dimension should not be considered when considering space. The specific way to describe four-dimensional space is the famous Mobius ring, Klein bottle and so on.

The second type is to believe that time and space are inseparable. We live in three-dimensional space, while time is one-dimensional. Based on this theory, scientists believe that time can also be represented by multiple coordinate axes, and time and space are recombined and arranged to form multi-dimensional space. This is the origin of parallel cosmology.

Let’s talk about four-dimensional space first. Usually, we call one dimension a line, two dimension a plane, and three dimension a three-dimensional thing. In fact, there is an error here. Why is a line a straight line? Can’t a curve? Two dimension a plane? Can’t a curve?

The answer is of course OK.

Because the coordinate system we know is artificially stipulated that x, y, and z are straight lines.

Therefore, if the curve is not one-dimensional, it is obviously looking at one-dimensional with a three-dimensional eye.

If a one-dimensional creature can only move forward or backward, not to left or right, up and down, then it lives in a one-dimensional world.

But fortunately, people can still imagine curves, straight lines, curved surfaces, and planes, but can they imagine a four-dimensional space?

The answer is, it's impossible!

Humans can't do it at all, and the reason is very straightforward, because we have never seen it before. When it comes to this, someone may be about to squirt. Don't rush to squirt, let's talk about it later.

We can deduce according to this theory that a low-dimensional space rotates and then folds in half will result in a high-latitude space.

Then, if you rotate a straight line and then fold it in half, you will get a circle, that is, a plane, and you will get a two-dimensional space; then imagine if you rotate a plane and then fold it in half, you will get a Mobius ring.

So imagine what it would be to rotate a three-dimensional space and then fold it in half?

Do you know what this is?

Then use the second theory to try it out. Low-dimensional space is a projection of high-latitude space, or the cross-section may be easy to understand.

One dimension, that is, a straight line cuts a knife, its cross section is a point, right?

Two-dimensional, a plane, cut a knife, its cross section should be a line, right?

Three-dimensional, such as a cube, cut a knife, and from its side it should be a plane, right?

Then the question is, Shenma Dongdong took a knife and saw from its side that its cross section is a cube?

On the side is a cube????

Obviously, it is against common sense to be a cross section or a cube itself.

So humans don’t know or imagine what the four-dimensional space is. There is another important thing that cannot be imagined, that is, the picture seen by the human eye is strictly just one side of the three objects, so the three-dimensional objects we know should be two-dimensional.

For example, you imagine a cube, and think about this cube in your mind, turning, turning, stop, okay, at this time you will find that what you always see is only one side of this cube, which is determined by our perspective.

If you have a pair of three-dimensional eyes, you can see six faces of the cube at the same time, or all faces of other three-dimensional objects at the same time.

For example, if you have three-dimensional eyes, even if the cards are covered when poking mahjong, you should know what all the cards are.

Some people like to use ants as an example, saying that ants are two-dimensional creatures, but the reason is that ants only live on one plane and have no concept of height.

I can only say that ants are helpless, ants can only say that I have a saying that I don’t know whether to say it or not. Labor and capital are obviously creatures in the same dimension as you, so I have to let me down one dimension. Some ants can still fly, and the new queen of ant flew out to establish a new kingdom. You should know this?

Let’s take a step back, no matter how small ant is, it is still height. One millimeter, one micrometer, and one nanometer is also height. So, if you and I say it three times, everything, everything, and all objects you and me see are three-dimensional objects.

Then there is the theory of four-dimensional space-time. This is more interesting, provided that time is the fourth dimension.

If we express space in a coordinate system, then there are three axes x, y, and z, and time currently only has the x-axis. Assuming that time also has the y-axis, what does this y-axis mean?

Based on this theory, the y-axis of time is defined as "possibility".

Then, every line parallel to the x-axis will be a time possibility, in which you may be a scientist, philosopher, professional player, brick mover, etc.

One word must have been thought of - parallel universe.

Therefore, this is the origin of parallel cosmology. According to this theory, the highest universe should be 10-dimensional. The 10-dimensional universe will contain all and all possibilities. Of course, what is said here is in the stage of assumptions and speculation and has not been proven. The truth still needs to be explained by scientists.

The worldview of this book adopts parallel universe theory, or multiverse, multiverse. Anyway, the vocabulary is different, but they all have the same meaning.
Chapter completed!