These two days are on a business trip, so the update is affected, please understand.

………………

[Some references, please read selectively if you are interested, note that some theories are just conjectures, not scientific conclusions.] 】

The contradiction between the theory of relativity and the theory of quantum

Einstein's general theory of relativity is a theory about gravity. We have said earlier that gravitational attraction arises from the mutual attraction of the masses of objects, and the greater the mass of the object, the greater the gravitational force. But why does the mass of an object create a gravitational pull? Why is gravity so weak but working on a macroscopic scale? For example, the gravitational force between two people and two large rocks is almost zero, and only stars in the universe such as the sun, the earth, and the moon have obvious gravitational effects.

Einstein solved this puzzle and gave an unexpected but reasonable answer: space itself has a shape, when there is no matter or energy, space should be straight and smooth, when a massive object enters space, the straight space is bent and concave, which is like a very straight sheet on a sheet, when a bowling ball is put in, the sheet is dented, and the so-called gravitational force is caused by such a bending of space. The Earth orbits around the Sun because the Earth rolls into a "valley" in the curved space around the Sun, which is what we commonly call the gravitational pull of the Sun on the Earth. The reason why the gravitational force between two people, two large rocks, is almost non-existent, is that such a small mass makes the curvature of space almost zero. Therefore, the gravitational effect between ordinary objects is negligible.

Here, gravity becomes a beautiful geometric picture, gravity itself does not exist, it is only the obvious result of the geometric deformation of space. The nature of gravity is thus satisfactorily explained by the general theory of relativity.

However, the geometrical deformation of space cannot explain the other three forces, and the electromagnetic, strong, and weak forces do not seem to be able to achieve through the folds of space. Einstein had conceived that all matter was formed by spatial kinks and vibrations, in other words, that everything we see around us, from trees and clouds to stars in the sky, could be an illusion, some form of spatial folding. If this idea is correct, the other three forces must be the same as gravity, and they must be the inevitable result of the geometric deformation of space, so that the four forces are unified into the geometry of space bending, and different ways of bending space will create different forces. However, in the microcosm, space is not smooth at all, but there are countless particles that are violently and incessantly noisy, and the concept of smooth space geometry, the core principle of general relativity, is completely destroyed here.

The explanation of the other three forces requires quantum theory to complete. Quantum theory is the study of the behavior of elementary particles in the microscopic world, in which all matter in the universe is ultimately composed of hundreds of different elementary particles, whose trajectories are unpredictable and irregular, due to their masses being so small as they are close to zero. Here, the force is exchanged from the particles, the electromagnetic force is exchanged from photons, the weak force is exchanged from the weak gauge bosons, and the strong force is exchanged from gluons. For example, the interaction between two charged particles is actually the result of photons "haunting" back and forth between the two particles, and the two charged particles affect each other by exchanging small photons, a process that is a bit like two skaters passing the ball, and through passing, both of them are affected in their motion. The same is true for the interaction of the other two forces.

However, the gravitational attraction caused by the curvature of space cannot be obtained by the exchange of particles, and in the microscopic world, the particles themselves are not only small to almost non-existent, but always moving in a chaotic manner. Therefore, quantum theory cannot cover gravity.

The inability of general relativity and quantum theory to be unified, has become the core disaster of modern physics. It is hard for people to believe that at the micro and macro levels of the universe, there is not a unified and coherent whole, and that our understanding of the deepest part of the universe is actually spliced together by two separate theories. In order to reconcile the two theories, physicists have made a lot of attempts, and they have either revised the general theory of relativity or the quantum theory in one way or another. Although the courage of each effort is amazing, the results are one after another.

So, superstring theory came in.

How do particles become strings?

A litany of doubts has forced scientists to seriously consider: perhaps there is a deeper structure inside elementary particles that we have not yet understood. Since the 60s of the 20th century, with the tireless efforts of scientists, a new theory has gradually surfaced, which is the superstring theory. Superstring theory holds that inside every elementary particle, there is a thin line vibrating, just like the vibration of a violin string, so this thin line is figuratively called "string" by scientists.

Pluck a string on the guitar and you'll hear a note. Pluck another string and you will hear another different tone because different strings vibrate in different patterns. A musician can create a myriad of beautiful music by playing a six-string ensemble of a guitar and vibrating the strings at different frequencies. Just as the different vibration patterns of the strings play different musical sounds, the strings inside the particles also have different vibration patterns, except that the vibration of the strings does not produce any music, but produces individual particles. The properties of different particles are determined by the different vibrational behavior of the strings, the electrons are strings that vibrate one way, the upper quarks are strings that vibrate in another, and so on.

The correlation of strings with the mass of particles is easy to understand. The more violently the string vibrates, the greater the energy of the particles; The softer the vibration, the less energy the particles have. This is also a familiar phenomenon: when we pluck the strings hard, the vibrations will be violent; When you pluck it gently, the vibration will be gentle. According to Einstein's principle of mass and energy, energy and mass are like two sides of the same coin, different manifestations of the same thing: large energy means large mass, and small energy means small mass. As a result, particles that vibrate more violently are more massive, and conversely, particles that vibrate softly are less massive.

According to string theory, each elementary particle exhibits properties that result from the different vibrational modes of the strings within it. Every elementary particle is made up of a string, and all strings are absolutely identical. Different elementary particles are actually playing different "tones" on the same string. The universe is made up of countless such vibrating strings, like a great symphony.

In quantum theory, every particle also has the property of a wave, which is called wave-particle duality. Now we understand that the wave property of the particle is generated by the vibration of the string.

Previously, we imagined that all particles of matter were dot-like things with no spatial size. But now we understand that the dot particles are not actually physical dots, but contain pieces of smaller spatial structures, and the vibrations of such spatial structures seem to be dots at first glance, because we don't have more subtle detection technology yet.

Physicists have also discovered that there is a direct link between the vibrational mode of the string and the gravitational action of the particles. The same correlation exists between the vibrational mode of the string and the properties of other forces, and the electromagnetic, weak, and strong forces carried by a string are also entirely determined by its vibrational pattern.

How do strings move?

The string itself is simple, just a tiny line that can be closed into a circle (closed string) or opened like a hair (open string). A string can also be broken down into smaller strings, and it can also collide with other strings to form longer strings. For example, an open string can be split into two smaller open strings; It is also possible to form an open string and a closed string; A closed chord can be split into two smaller closed chords; Two strings colliding can create two new strings.

But when a string moves through space-time, it's not that simple. The motion of a string is so complex that three-dimensional space can no longer accommodate its trajectory, and there must be up to ten dimensions of space to satisfy its motion (ten-dimensional space is the result of mathematical equations). Just as human motion is so complex that it cannot be done in a two-dimensional plane, but must be done in three-dimensional space.

It may seem strange that the space inside the point particles is not three-dimensional, and there may be many dimensions, but when you think about it, the existence of high-dimensional space is completely reasonable. To see this, we can take an example of a water pipe. We know that the surface of a water pipe is two-dimensional, but when we look at it from a distance, it looks like a one-dimensional straight line. Why is that? It turns out that the two dimensions of the water pipe are very different, and the one dimension along the extension direction of the pipe is very long and easy to see; The circle that is easy to go around the tube is very short, "curled up", and it is not easy to find. You have to get close to the water pipe to see the dimension that circles around it.

This example illustrates a subtle but important feature of the spatial dimension: there are two kinds of spatial dimensions. It may be large and stretch far away, and it can be directly revealed; It can also be small, curled up, and hard to see. The water pipe is relatively thick, and it is easy to see the dimension around the pipe. If the tube is very thin—as thin as a strand of hair or a capillary—it's not so easy to see the curled Vico.

At the tiniest scale, scientists have proven that the spatial structure of our universe has both extended and convoluted dimensions. That is to say, our universe has large, easy-to-see dimensions like water pipes extending horizontally—the three dimensions that we normally experience—and dimensions that are condensed like the circles of water pipes in the horizontal—and these extra dimensions are tightly conjured up in tiny spaces that even our most sophisticated instruments simply cannot detect them.

How small might those invisible dimensions be? Our state-of-the-art instruments can detect structures in exaferions of a meter, and if those dimensions are convoluted smaller than that, we won't be able to see them. Scientists' calculations show that the dimensions of the condensation may be as small as Planck's length (i.e., 10-33 cm), which is far from being possible with current experiments.

Why do we need a multidimensional space?

After understanding that there are more dimensions in the space of the universe, and then looking back at how the theory of relativity and quantum theory contradict each other, it is easy for us to understand: these two theories cannot be unified in the daily three-dimensional space, their contradictions are inevitable, and they can only be unified in the high-dimensional space.

To better understand this, we can take an example of a three-dimensional world and a two-dimensional world. Let's start by assuming that there are beings living in two-dimensional planes that have only length and width in their worlds, and that they simply cannot understand the third dimension, the "high" dimension. Therefore, their perception of the three-dimensional world is limited to the projection of the three-dimensional object in the flat world, or the contact surface of the three-dimensional object and the flat world. When a three-dimensional object comes into contact with the flat world, the fragments of the three-dimensional object in the flat world, such as the four pillars of a table and the two pairs of shoe prints printed by people on the ground, make the plane life even more confused—what do these fragments that cannot be put together mean? They couldn't imagine how four disconnected imprints could form a complete table. How can there be a complete pair of shoes on the intermittent shoe prints? Moreover, there is a more complete person on the top of the shoe! Looking at the pieces in two dimensions, you can never put them together.

So one day, a resourceful flat being came up with a brilliant idea by chance. It declares that there is an "upward" third dimension beyond the flat world, and if you look "upward" along these fragments, the fragments are actually a complete whole! This is an astonishing insight, and most flat beings are baffled.

The encounter between relativity and quantum theory is very similar, in our three-dimensional space, they are like two disconnected pieces that can never be put together. But by lifting space "upward" and turning the universe into a ten-dimensional space, the two seemingly unrelated fragments of relativity and quantum theory will be astoundingly combined together to become two interdependent pillars of a more complete theoretical edifice! Although we cannot imagine and describe a multidimensional space in three-dimensional space, we can deduce its existence through complex mathematical equations.

How does multidimensional space crack?

In the very early days of the universe, within 10-43 seconds of its birth, it was only 10-33 centimeters in diameter, and it contained a wealth of ten-dimensional space, all of which were conjurified equally. In that space, the energy of the universe is extremely high, the temperature is extremely high, all four forces are integrated, and the theory of relativity and quantum theory can be reduced to one theory.

However, such a high-dimensional, high-energy, high-temperature space is extremely unstable, like a balloon with too much flatulence, so the big bang happens. Dimensions are dissolved, energy diverges, and temperature decreases. Three-dimensional space and one-dimensional time extend infinitely, gradually forming the universe that we can perceive today; The other six dimensions are still confined to Planck's scale (i.e., 10-33 centimeters).

When the universe is at an extremely high temperature of 1032K (which is 1026 times higher than the temperature of the sun we get), gravity separates from other grand unified forces, and gravity continues to extend as the universe expands. As the universe expands and cools further, the other three forces also begin to break down, and the strong interacting forces and the weak-electric forces are stripped apart.

When the universe is generated for 10-9 seconds, its temperature drops to 1015 K, at which point the weak-electric force breaks down to electromagnetic forces and weak interaction forces. At this temperature, all four forces have separated from each other, and the universe has become a "soup" of free quarks, leptons, and photons. Later, as the universe cools further, quarks combine into protons and neutrons. They eventually form the nucleus. 3 minutes after the creation of the universe, stable nuclei begin to form.

When the Big Bang took place 300,000 years later, the first atoms were invented. The temperature of the universe drops to 3000 K, and hydrogen atoms can be formed without breaking by collisions. At this point, the universe finally became transparent, and light could travel for several light-years without being absorbed.

Today, 100 to 20 billion years after the Big Bang, the universe is strikingly asymmetrical, with four forces that are strikingly different from each other. The original temperature of the fireball has now been cooled to 3K, which is close to absolute zero.

This is the history of the evolution of the universe, as the universe gradually cools, the forces will be unentangled with each other and gradually separated. First the gravitational force breaks out, then the strong interaction force, then the weak force, and finally only the electromagnetic force remains intact.

Cracks in space

Superstring theory also gives us an even more shocking result: our spatial structure is actually discrete, not continuous! In our daily experience, space and time are always infinitely inseparable, but the truth is that this could not be more true. Space and time have their own minimals: the minimum scale of space is 10-33 centimeters, and the minimum of time is 10-43 seconds. Because when the space is as small as 10-33 centimeters, time and space will merge into one, and the space dimension will be as high as 10 dimensions, in this case, even if the space can be divided, that is what we cannot understand at present.

In fact, quantum theory is the theory of "discrete quantities", and the word "quantum" means "a quantity" or "a discrete quantity".

As early as 1900, when quantum theory was first born, scientists discovered that in the world of tiny particles, energy is emitted one by one, not continuously. Just as the smallest unit of the renminbi is "cents", table tennis balls can only be bought one by one, not half and a half, these are all examples of the indivisibility of things in daily life.

Although scientists were already aware of the discontinuity of particle energy at that time, they did not know why it existed and were forced to accept it.

But now we all know that this is closely related to spatial discontinuity. It is precisely because space has the smallest, indivisible units that it affects the way elementary particles emit energy.

Now, our old theory based on the continuity of time and space must be abandoned, and on the Planck scale, the string is a segment, the open string is a line, and the closed string is a circle, and each string piece carries a piece of momentum and energy.

Space has a smallest, indivisible value, what is the result of this incredible phenomenon? It is easy for us to think that our macroscopic spatial structure is composed of the smallest spatial packages, and in the middle of these spatial packages, it is very likely that there are spatial cracks that we cannot detect! The idea of digging a hole in space in the so-called "wormhole theory" is really feasible theoretically, which is to find a crack between adjacent space packages, and then blast open this crack with unimaginably high energy, and a wormhole appears! It can be said that the tiny ten-dimensional space packets and the cracks between them exist in every corner of our space, and as long as we have enough energy, we can chisel a wormhole anywhere.

The Great Unified Universe

Today, we are deeply aware that all the complex phenomena in the vast universe can be traced back to the same source, and the large and small laws discovered by human beings can eventually be encompassed by a fundamental law. To understand this, let's take the development of life on Earth as an example: we humans can all trace different human races back to the same origin, and man, orangutans, apes can be traced back to the same ancestor, and so on, all mammals have the same ancestor, all animals and plants have the same ancestor, and finally, all life originates from the same cell – there is only one source of life.

The origins of all galaxies in the universe can also be traced back to the same source, the stars in the solar system all originated from the same nebula, all nebulae originated from the same molecule, and all the molecules evolved from those hundreds of elementary particles. In this way, following the flow of time all the way upwards, we finally come to the moment when the Big Bang began, where space, time, and matter all merge into one, and everything boils down to one point.

Starting from the same point, after more than 10 billion years of long years, the universe has evolved into a complex and changeable world, but no matter how ever-changing the world is, behind all phenomena, there is a fundamental law in operation, which is the source law at the beginning of the universe. This law is an all-encompassing law – the so-called "supreme principle of all things" is the case.

This theory of "the supreme reason of all things" is the superstring theory, which constructs the image of the ten-dimensional space at the beginning of the universe, and as the ten-dimensional space collapses, the superstring theory also splits into two theories, the theory of relativity and the quantum theory, and then, as the abundance of matter increases, they split into more theories.

Today, we continue to look upwards and finally paint a picture of the great unity of the universe - a ten-dimensional universe with extremely mysterious colors.