We are now living in a three-dimensional space, and some people add it to the timeline, called the four-dimensional world. Here we simply call the world we live in three-dimensional space.
In the universe, in addition to the three-dimensional space in which we are on earth, it is said that there are also high-dimensional spaces and low-dimensional spaces, high-dimensional spaces are four dimensions and above, and there are five-dimensional and six-dimensional and even more than a dozen dimensions; the low-dimensional world is a 0-dimensional one-dimensional two-dimensional world. These are all conjectures, and there is still no complete theory that can prove their real existence.
Then the world we see and everything that operates now is done according to the laws of the three-dimensional world. I can't explain what the high-dimensional world looks like, but the low-dimensional world can be described.
The general saying is that 0-dimensional space is a point, an infinitesimally small point, so there should be nothing; a one-dimensional world is a line, which has only length and no width and no height; the two-dimensional world is a plane, with length and width without height (thickness), if you do not consider thickness, like a piece of paper. Some of the shapes drawn on paper are like things that live in a two-dimensional world (I can only describe things because I really don't know what a two-dimensional world can have). It is more figurative to say that the shadow should be two-dimensional, because it really has no thickness.
As for the high dimension, some statements are also difficult to argue, such as four-dimensional space, some people say that there are countless three-dimensional spaces according to the timeline, which constitutes a four-dimensional space, and the three-dimensional space is only a time node of the four-dimensional space.
The idea of reducing dimensions and striking comes from Liu Cixin's science fiction novel "The Three-Body Problem", which involves a lot of advanced content in basic physics, and its principle is unproven.
Dimensionality reduction strike refers to the launch of a very small two-dimensional space fragment to a certain area of the three-dimensional universe (usually the area where the hostile civilization is located), the fragment is encapsulated with a force field, and after the force field evaporates, the two-dimensional space and the three-dimensional space will be in contact, which will make the three-dimensional space fall to the two-dimensional space, so that the entire space will fall to the two-dimensional, the fall process of this range will never stop, the speed of spread is the speed of light, and everything in this space will fall to the two-dimensional, thus achieving the effect of complete destruction.
Two-way foil is a typical dimensional strike (dimensionality reduction attack) weapon envisioned by Liu Cixin in his science fiction novel "The Three-Body Problem". Due to the exposure of the Earth's geographical coordinates between the universes, based on the principle that any exposed civilization under the law of the Dark Forest must be eliminated as soon as possible, and because it is impossible to ensure that conventional weapons can quickly and completely destroy humans in the solar system, a grassroots explorer of the Singer Civilization (a civilization much higher than human civilization) threw a two-way foil at it while passing through the solar system, resulting in the demise of the Earth civilization along with the entire solar system under the blow of the dimension.
Our universe is four-dimensional, it is composed of three dimensions of length, width and height and timeline, but we habitually call it three-dimensional, a playing card-sized two-way foil (without thickness) in contact with the three-dimensional universe, will make one dimension of the three-dimensional universe curl up indefinitely, thus forcing the three-dimensional universe and all its matter to collapse to the two-dimensional universe, and "melt" in the two-dimensional space as an absolute plane that only exists in length and width and is deprived of the concept of height. In a word, the universe is squashed, and everything in three dimensions will unfold in two dimensions, stars, planets, people, and so on. When the solar system is two-dimensionalized, it becomes a flat picture. What people, animals, nuclear weapons, spaceships, earth, sun, Mercury, Saturn, and so on, all became graphics in the picture, and what else can these figures do, space-time communication can not be imagined.
The famous physicist Hawking wrote in "A Brief History of Time": If there is a two-dimensional space, if there is life in it, such as two-dimensional animals, in order to pass each other, one must climb on top of the other. If a two-dimensional animal cannot completely digest it when it eats, it must spit out the residue from the same channel that swallows the food, because if there is a passage through the whole body, it divides the organism into two parts, and our two-dimensional organism disintegrates. Similarly, achieving any blood circulation in a two-dimensional organism is very difficult. According to this theory, the two-dimensional world cannot survive, and some people interpret Hawking's statement that no matter what creatures can't see things and can't eat, cars can't open doors and can't use power, people can't get on the car, and they can't give way to each other when they walk to the road. Someone also drew a lot of schematic diagrams to illustrate.
Although Hawking is a master of science, space-time communication does not agree with this statement. Because we can't be sure whether there is a two-dimensional space civilization in the end, if there is, we can't use the laws and civilization states of the three-dimensional world, or the living material to explain the civilization of the two-dimensional space, the two-dimensional civilization is certainly not the way we imagine the three-dimensional world, what biological cars eat and flowers, grasses, insects and fish and the like, their space has the laws and laws of that space, if they have intelligent civilization, they are certainly not the so-called creatures we think, and our brain holes will be opened and open again, and we may be able to peek into this secret , may never be able to solve this mystery. Hawking's statement is at best a description of the inability of organisms in three-dimensional space to survive in two-dimensional space.
General multidimensional space theory believes that dimensionality reduction strikes can only strike high-dimensional civilizations to attack low-dimensional civilizations, and low-dimensional civilizations cannot strike high-dimensional civilizations, because we cannot see their world, let alone understand the laws and operations of their world, but they can see and control us. Just like we can see two-dimensional objects, such as a painting, if the person on it is alive, we can control it at any time, draw a circle around him, he can't run, but we can lift him up and put him outside the circle.
Then the civilization of the four-dimensional space strikes us down, and we become people drawn on paper, and we cannot survive without waiting for others to draw a circle, and there is no doubt that they will die, and they do not know what kind of death it is, because Hawking has already demonstrated that creatures in the three-dimensional world cannot survive in the two-dimensional world. Such a blow is more terrifying than taking a fly and slapping it to death, because the dead fly still has some thickness, and the two-dimensional space has no thickness. So the horror of this blow is indescribable.
Of course, this horror only exists in the imagination at least for now, because this kind of dimensionality reduction strike is only an idea that exists in science fiction, there is no theoretical basis that can be confirmed, and whether the high-dimensional space is there, even if there is something that can control or affect the low-dimensional space, it is still an unknown, the science fiction movie Star Trek describes the father in the high-dimensional space, although he can see the daughter of the low-dimensional space, but it takes a lot of effort to affect her, and it is barely a hint. Therefore, this fear is just the fear of watching horror movies, which is just a stimulus, and you can breathe a sigh of relief.