The book "The Universe. The origin of life, the meaning of our existence and a huge space "

    imageThe famous physicist Sean Carroll, in his fascinating manner, explains the principles that underlie the scientific revolutions from Darwin to Einstein, and shows how the incredible scientific discoveries of the last century have changed our world.

    What is life and death, what is our place in this Universe, how does the world work on the quantum, cosmic and human levels, how are human values ​​associated with science. Fourteen billion years have passed since the Big Bang, the observable region of space is filled with several hundred billion galaxies, each galaxy on average contains one hundred billion stars. Man is a tiny, inconspicuous being. In comparison with the Universe, man is even smaller than an atom in comparison with the Earth.

    We are small, the universe is large. And we do not have instructions for her knowledge. Nevertheless, we have learned a lot about how things are arranged around.


    We decided to share a passage from the book:

    The matter of which we are


    Quantum field theory is an incredibly powerful scientific apparatus. If it were possible to imagine that the framework of any physical theory could be born of the union of Godzilla and Hulk, then it would be a question of quantum field theory.

    “Powerful” does not mean “dusting entire cities”. (Although quantum field theory is just that, because only it allows us to describe how one particle turns into another, and such a process is the most important aspect of nuclear reactions and, therefore, atomic weapons.) In the context of scientific theories, “powerful” actually means “strict “- According to a truly powerful theory, many things simply cannot happen. The force we are talking about here is an opportunity to start with the minimum number of packages and come to conclusions that are reliable and widely applicable. Quantum field theory does not demolish buildings that fall into its path; it destroys our speculations about which phenomena are possible in physical reality.
    Now we will make a very bold statement.

    Statement: The physical laws underlying everyday reality are completely known.

    Such a statement immediately causes considerable skepticism. It is impudent, self-satisfied, and it seems that it is quite possible to imagine in what respects our picture of the world can turn out to be depressingly incomplete. Such a statement painfully recalls numerous historical examples when one or another great thinker boasted that the road to exhaustive knowledge is nearing its end. Every time such statements turned out to be ridiculously premature.

    However, we argue that we do not know all the laws of physics, but only their limited set, sufficient to describe everything that happens in our daily life. Even such a formulation seems quite presumptuous. Surely there should be numerous opportunities to add new particles and interactions to the Basic Theory, which may be important for ordinary physics, and, for that matter, discover completely new phenomena that are completely beyond quantum field theory. Right?

    Not. The situation is now really different than anything that has ever been in the history of science. Not only do we have a successful theory, we also know how far this theory can spread before it can be doubted. Yes, just quantum field theory is so powerful.

    * * *

    Our bold statement is based on simple logic.

    1. Everything that we know indicates that quantum field theory is an adequate apparatus for describing the physics of everyday life.
    2. The laws of quantum field theory imply that no new particles, forces, or interactions that would be essential for our daily life can be discovered. We have already opened them all.

    Could quantum field theory fail anywhere? Of course. As good Bayesians, we have fully learned that it is better not to nullify the subjective probability even in the most extreme cases. In particular, quantum field theory may not be able to fully describe human behavior, since physics may not be suitable for this. A miraculous intervention can occur or some initial non-physical phenomenon affecting the properties of physical matter. No scientific progress will ever completely eliminate this possibility. But we can show that physics as such is absolutely sufficient to describe everything that we see.

    SpecialEinstein's theory of relativity (in contrast to the general theory of relativity) unites space and time into one whole and postulates that the speed of light is the absolute limit of speed in the Universe. Suppose we want to formulate a theory that simultaneously encompasses these three ideas:

    1) quantum mechanics,
    2) special theory of relativity,
    3) significantly distant regions of space operate independently of each other.

    Nobel laureate Steven Weinberg argues that any theory that meets these requirements will resemble quantum field theory at (relatively) large distances and at low energies — say, more than a proton. Regardless of what happens at the finite, most fundamental and exhaustive level of nature, the world that is accessible to human observation will be well described by quantum field theory.
    Consequently, if we want to describe the everyday world of low energies around us, strictly adhering to physical laws, then we must act in the context of quantum field theory.

    * * *

    Let's recognize that quantum field theory works in everyday conditions, and ask ourselves why there can no longer exist undiscovered particles that would have any influence on the world around us.

    First, you need to make sure that there can be no real material particles that would be worn around and penetrate our body, in any way affecting the behavior of particles already known to us. Then you need to make sure that there are no virtual particles or new interactions in the world, which with a certain probability could influence the particles that we observe. In quantum field theory, virtual particles are called such particles that appear at lightning speed and just as quickly disappear, forming quantum fluctuations and affecting real particles, but themselves remain completely invisible. We will look at this problem in the next chapter, but for now let's focus on real particles.

    We know that in physics there are no new particles and fields that would play an important role in everyday life; This is due to the key property of quantum field theory, the so-called cross-symmetry . This amazing phenomenon helps to ensure that some species of particles do not exist, otherwise we would have found them. In principle, cross-symmetry is as follows: if one field can interact with another (for example, dissipate upon contact with it), then the second field under suitable conditions can generate particles of the first. It can be said that at the level of quantum field theory, this principle is analogous to the law “for every action is a counteraction”.

    Consider a new particle X, which, as we can assume, causes subtle, but important effects in the everyday world - for example, it allows you to bend spoons by thought or is a source of consciousness as such. In such a case, particle X must directly or indirectly interact with ordinary particles, for example, quarks and electrons. If this does not happen, then in no way can it affect the world that we are directly observing.

    The interactions between particles in quantum field theory are visualized with the help of pretty pictures called Feynman diagrams.. Suppose that particle X bounces off an electron, while exchanging some new particle Y with it. From left to right, the diagram shows the following: X appears and the electron exchanges particle Y and flies away on its own roads.

    image

    The diagram does not depict what might happen: the diagram corresponds to a number indicating how strong this interaction is - in this case, with what probability X will bounce off the electron. According to cross symmetry, each such phenomenon corresponds to a different process of the same force, which can be represented by turning the diagram 90 degrees, and in all lines whose direction has changed, replace the particle with an antiparticle. An example of the result of cross-symmetry is shown in the following figure.

    image

    In field theory, each particle has its own antiparticle, which has an opposite electric charge. The antiparticle of an electron is called a “positron”; it has a positive charge. According to cross-symmetry, the first phenomenon, the rebound of particle X from an electron, implies that there is a similar phenomenon, in which an electron annihilates with a positron and as a result our particle X is generated, as well as its antiparticle.

    And that's what happened in the end. We experimented with collisions of electrons and positrons, set up such experiments often and carefully. From 1989 to 2000, the Large Electron-Positron Collider (the predecessor of the modern Large Hadron Collider) was used for this purpose in an underground laboratory near Geneva. In the course of these experiments, electrons and positrons collided at inconceivable energies, and physicists closely followed everything that arose as a result. At the same time, they wholeheartedly hoped to find new particles; the discovery of new particles, especially unexpected ones, is the most exciting side of this field of physics. But they did not meet anything new. Only known particles from the Basic Theory, which appeared in huge quantities.

    * * *

    The same was done for the collisions of protons with antiprotons, tried and various other combinations. The verdict is unequivocal: we have discovered all the elementary particles that only allow us to detect our most cutting-edge technology. Cross symmetry leaves no doubt that if some more particles interacting with ordinary matter would have eluded us enough to affect ordinary matter, then such particles would have to arise easily in experiments. But nothing happens.

    Probably, we still have to find new elementary particles. They just do not affect the everyday world. The fact that we have not yet found such particles in itself tells us a great deal about what properties they should have; this is the power of quantum field theory. Any particle that we have not yet found should have one of the following characteristics:

    1) it must interact so weakly with ordinary matter that such particles almost never form, or
    2) it can be extremely massive, therefore it can be formed only in collisions such high energies that are so far unattainable even in our best accelerators, or
    3) it can be extremely short-lived, so much so that, once formed, it immediately disintegrates into other particles.

    If any of the particles that we did not detect existed for quite a long time and interacted with ordinary matter so strongly that it could affect the physical phenomena of the surrounding world, then we would have already received it in experiments.

    It is believed that another kind of particles that are not yet open can exist, and it is from these particles that dark matter consists. Astronomers who study the movements of stars and galaxies, as well as the large-scale structure of the Universe, have seen that most of the matter is “dark”, that is, it consists of some new particles that are not related to the Basic Theory. Dark matter particles must be durable enough, otherwise they would have disintegrated long ago. But they cannot interact strongly enough with ordinary matter, since otherwise they would have been discovered long ago in one of many experiments designed to discover dark matter — physicists are conducting such experiments right nowadays. Whatever dark matter is, it definitely does not make the weather here on Earth — it has nothing to do with biology, nor with consciousness, nor with human life.

    * * *

    There is an obvious flaw in this analysis. There is a particle that, in our opinion, should exist, but which so far has not been found: it is a graviton. It is light and stable enough to arise, but gravity is such a weak interaction that all the gravitons that we could get in the particle accelerator will be immediately absorbed by many other particles formed there. However, gravity affects our daily lives.

    The main reason gravity is so important is this. This is a long-range force that accumulates: the more we have a substance that exerts a gravitational effect, the stronger this effect. (Such a pattern may not be observed, for example, for electromagnetism, since positive and negative charges are zeroed out, and gravity always only increases.) So, although there is no hope of synthesizing or fixing a separate graviton when two particles collide, the total gravitational effect of the entire Earth gives a significant force of force.

    Perhaps some other force “uses” this loophole: when considering only a few particles, it may be insignificant, but suddenly it accumulates, if you gather together quite a lot of matter? Physicists have been searching for such a “fifth interaction” for many years. Have not found anything yet.

    The search for new interactions is greatly simplified due to the fact that ordinary objects consist of only three types of particles: protons, neutrons and electrons. Another feature of quantum field theory is that it does not allow "turning on" and "turning off" the effects of individual particles; the corresponding fields go nowhere. It is possible to generate macroscopic forces by correctly combining positive and negative charges, for example, in an electromagnet, but particle fields are always present. So, you need to look for interactions between particles of these three types. Physicists are doing just that: they put immaculately accurate experiments in which bodies of different composition first approach each other, and then are again removed; while looking for any hint of any influence unrelated to the known forces of nature.

    The results obtained as of 2015 are shown schematically in the following figure. Any possible interactions between two given types of particles have two numerical parameters: the strength of this interaction and the distance at which it is felt. (Gravity and electromagnetism are "long-range" forces, stretching virtually infinite distances; the zone of influence of weak and strong nuclear interactions is very small - less than the size of an atom.) It is easier to measure strong and at the same time long-range forces. We have already excluded the existence of such undiscovered interactions.

    image

    Thus, if the range of the new force is more than one tenth of a centimeter - which would be a necessary condition if it allowed the spoon to bend or was the mechanism that allows Saturn to influence you at the time of your birth - then it would be much weaker than gravity . At first glance it seems “not so weak”, but do not forget that the force of gravity is vanishingly small. Whenever you jump up, the tiny electromagnetic forces of your body allow you to briefly overcome the total gravity of the entire Earth. Such weak interaction, like gravity, is a force of one billion billion billion billion billion of electromagnetism. Even weaker interactions should be completely neglected in everyday conditions.

    Here, in everyday reality, in the world of people, houses, and machines, we have fully cataloged all the particles, forces, and interactions that can have a noticeable effect on anything. This is a colossal intellectual achievement that the human race can rightly be proud of.

    »More information about the book is available on the publisher's website.

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