Children's shoes who have seen "The Three-Body Problem" must have been impressed by one of the weapons inside- the two-way foil, a weapon that almost destroyed the entire human race.
To introduce a paragraph to children's shoes that have not seen "The Three-Body Problem":
The two-way foil is bound by a special force field in an inactive state and looks like a completely harmless two-dimensional film. However, when the two-way foil reaches the target space, the binding force field will disappear, and the weapon will be irreversibly launched, infinitely curling up one dimension in the three-dimensional space that is exposed, causing the three-dimensional space to collapse, become a two-dimensional plane space and continue to expand. The process of two-dimensionalization is like a huge bubble of endless expansion, all the three-dimensional matter involved in it inevitably becomes two-dimensional, loses a lot of physical properties and disintegrates after losing the concept of thickness, leaving no optical features (because two-dimensional objects have no thickness, so light will directly penetrate two-dimensional objects without any reflection, and the complete two-dimensional objects thus become completely transparent to the point of being impossible to witness) but mass two-dimensional plane remains.
In the book, the basic components of all the material (including space) swallowed up by the two-way foil are no longer the composition of the three-dimensional state, so any object that enters it will be destroyed. Of course, in the humanities "The Collapse of the Second Fleet of the Three-Body Problem", it is described that human miniature black holes still maintain a three-dimensional state in the two-dimensional world.
Okay, let's get down to business.
The dimensions we usually understand are often based on the category of space-time, which is a system composed of direction and time. But the two-dimensional world we are talking about here is not a two-dimensional space-time composed of one dimension plus time dimensions, but a two-dimensional space—a space composed of only one plane.
I personally think that two-dimensional space exists, but we can't perceive it unless it can actually fall.
To better help understand the two-dimensional world, use 3ds max to do a simulation:
Blue Stick and Green Stick are good friends who live in a two-dimensional universe.
One day, they suddenly encountered an indescribable change!
They don't know they're just ascending.
Of course, there can be no digestive tract like ours in two-dimensional space, because the digestive tract will divide the "two-dimensional creature" from the middle into two halves.
The following experiment has little relevance to the problem:
Here is a diagram of a knot:
Although we see three-dimensional resolution, this is a two-dimensional picture because it provides a visual clue to help our brain reconstruct a three-dimensional field of view. Each of our eyes sees two-dimensional information, and then the brain reprocesses the two pieces of information to create a three-dimensional scene, but this scene is in our minds and not on our retina!
So why is that? Do a visual experiment:
Comparing these two pictures, the difference is in the areas marked with different colors to add a dimension to us, so that the brain has the feeling of one more dimension!
We know
1D to 2D looks like this:
2D to 3D goes like this:
So what about 3D to 4D?
This thing is called Tesseract(four-dimensional cube), and there is no GIF here, only a set of graphs:
Going back to the beginning, we can't understand the two-dimensional reasons:
Our entry from three-dimensional to two-dimensional will inevitably lead to the "transformation" of some information (this part of the information is not lost, but can not be displayed in 2D), then it is unknown whether the harm caused to human beings by such changes in information (such as the law of inverse square ratio, etc.) exists.
Some of the content is excerpted from Zhihu
https://www.zhihu.com/question/38924966