# How can the universe have multiple dimensions?

BEIJING, Feb. 27 (Xinhua) — According tomedia reports, many scientists hope to use string theory to explain everything in the universe. String theory holds that all the forces in the universe, all the particles, all the constants, and all the objects are under the same physical structure, and that everything we see is the product of countless tiny, constantly vibrating “strings”. Theorists have been studying string theory since the 1960s. They soon realized that if string theory was to be established, there must be more than four dimensions in the universe that we are accustomed to. This may sound crazy, but there is some basis for it.

Dimension Disaster

In string theory, rings made of vibrating strings are represented by a variety of particles (e.g. electrons, quarks, neutrinos, etc.) and carriers of natural forces (photons, gluons, glitrils, etc.). This is achieved by the vibration of the string. These strings are extremely small and look like a point to us, but each string vibrates in a variety of modes, just as a guitar string can pop up multiple notes.

Scientists believe that each pattern of vibration is related to a specific class of particles. So all strings that vibrate in one mode may appear as electrons, and all strings that vibrate in another mode are like photons… and so on. From the point of view of string theory, the particle collision we see is actually a lot of stringfusion and re-splitting process.

But for this theory to be true, it is not enough that there are only four dimensions in the universe, because normal space-time does not provide enough vibrational “space” for strings, making them unable to express themselves as all the particles in the world. In other words, these strings not only twist, but also “super-dimensional” twists.

The current string theory requires a total of 10 dimensions, in addition to a bolder set of string theory (called M theory), a total of 11 dimensions. But looking at the universe, we can only see three spatial dimensions and one time dimension. If there were more than four dimensions in the universe, we must have noticed it.

The question comes, on the one hand, string theory requires that there are many dimensions in the universe, on the other hand, we can only experience four dimensions in the universe, how can these two contradictions achieve harmony and unity?

Curl and compression

The concept of string theory may seem extreme, but fortunately in history there are predecessors that can be traced back.

In 1919, shortly after Einstein had just published General Relativity, the mathematician and physicist Theodor Kaluza studied the equations of general relativity out of pure interest. And when he added the fifth dimension to the equation, something interesting happened — in fact, nothing happened, and the relativistic equation was not affected by the dimension.

But Kaluza made some changes to the fifth dimension, making it curl up around itself and becoming “cylindrical”. Coupled with this new requirement, Karuza made a new discovery: in addition to the general relativity equations under the four common dimensions, he also derived the expression equations of electromagnetic forces. In this way, it seems possible to achieve greater unity in physics by increasing the number of dimensions in the universe.

In hindsight, this idea is a little overblown. But decades later, a physicist named Oskar Klein tried to interpret Karuza’s theory from the perspective of quantum mechanics. He found that if there was a fifth latitude, and the dimension was somewhat related to electromagnetic forces, the dimension would have to curl up (consistent with Karuza’s original idea), but at a much smaller scale, at 10-35 meters.

Numerous flow forms of string theory

If this (or these) extra dimensions are really small, they cannot be noticed, and even high-energy experiments cannot detect their existence directly. And if these dimensions are curled, every time we move in four-dimensional space, it’s the equivalent of turning hundreds of billions of circles around these extra dimensions.

The string theory of the string is in these dimensions.

Using further mathematics, scientists found that the other six spatial dimensions required for string theory had to be curled into a specific type of shape, the so-called Calabi-Yau manifolds. But string theory allows for far more than one stream, but as many as 102 million. Thus, if the six dimensions were to curl up as they pleased, they would be “all-encompassing”.

There are many ways to curl these extra dimensions, and each configuration affects how the chords inside the dimension vibrate. Since the way strings vibrate determines their performance in the macro world, each flow shape produces a unique universe, each with its own set of physical laws.

Therefore, only one flow shape creates the world we live in. But which one is it?

Unfortunately, string theory can’t tell us the answer for the time being. The trouble is that the problem of string theory has not been completely solved. We have only a varied approach to the truth, hoping to uncover the truth. But for now, we don’t know how correct our conclusions are. From specific flow shapes, to specific string vibrations, to the physical laws of the universe, we lack the mathematical techniques to solve this long list of problems.

In response, string theorists have come up with the concept of “landscape”, a multiverse consisting of a universe derived from various streams. On this “topographic map”, our universe is just one of many small dots.

And the same is true of the current state of string theory, which is unknowing. (Leaf)