Quantum physics cat. John Gribbin - In Search of Schrödinger's Cat. Quantum physics and reality. Schrödinger's theory: description

Surely you have heard more than once that there is such a phenomenon as “Schrödinger’s Cat”. But if you are not a physicist, then most likely you have only a vague idea of what kind of cat this is and why it is needed.

« Shroedinger `s cat“- this is the name of the famous thought experiment of the famous Austrian theoretical physicist Erwin Schrödinger, who is also a Nobel Prize laureate. With the help of this fictitious experiment, the scientist wanted to show the incompleteness of quantum mechanics in the transition from subatomic systems to macroscopic systems.

This article is an attempt to explain in simple words the essence of Schrödinger’s theory about the cat and quantum mechanics, so that it is accessible to a person who does not have a higher technical education. The article will also present various interpretations of the experiment, including those from the TV series “The Big Bang Theory.”

Description of the experiment

Erwin Schrödinger's original article was published in 1935. In it, the experiment was described using or even personifying:

You can also construct cases in which there is quite a burlesque. Let some cat be locked in a steel chamber with the following diabolical machine (which should be regardless of the cat's intervention): inside a Geiger counter there is a tiny amount of radioactive substance, so small that only one atom can decay in an hour, but with the same probability may not disintegrate; if this happens, the reading tube is discharged and the relay is activated, releasing the hammer, which breaks the flask with hydrocyanic acid.

If we leave this entire system to itself for an hour, then we can say that the cat will be alive after this time, as long as the atom does not disintegrate. The very first disintegration of the atom would poison the cat. The psi-function of the system as a whole will express this by mixing or smearing a living and a dead cat (pardon the expression) in equal parts. What is typical in such cases is that uncertainty originally limited to the atomic world is transformed into macroscopic uncertainty, which can be eliminated by direct observation. This prevents us from naively accepting the “blur model” as reflecting reality. This in itself does not mean anything unclear or contradictory. There's a difference between a blurry or out-of-focus photo and a photo of clouds or fog.

In other words:

There is a box and a cat. The box contains a mechanism containing a radioactive atomic nucleus and a container of poisonous gas. The experimental parameters were selected so that the probability of nuclear decay in 1 hour is 50%. If the nucleus disintegrates, a container of gas opens and the cat dies. If the nucleus does not decay, the cat remains alive and well.
We close the cat in a box, wait an hour and ask the question: is the cat alive or dead?
Quantum mechanics seems to tell us that the atomic nucleus (and therefore the cat) is in all possible states simultaneously (see quantum superposition). Before we open the box, the cat-core system is in the state “the nucleus has decayed, the cat is dead” with a probability of 50% and in the state “the nucleus has not decayed, the cat is alive” with a probability of 50%. It turns out that the cat sitting in the box is both alive and dead at the same time.
According to the modern Copenhagen interpretation, the cat is alive/dead without any intermediate states. And the choice of the decay state of the nucleus occurs not at the moment of opening the box, but even when the nucleus enters the detector. Because the reduction of the wave function of the “cat-detector-nucleus” system is not associated with the human observer of the box, but is associated with the detector-observer of the nucleus.

Explanation in simple words

According to quantum mechanics, if the nucleus of an atom is not observed, then its state is described by a mixture of two states - a decayed nucleus and an undecayed nucleus, therefore, a cat sitting in a box and personifying the nucleus of an atom is both alive and dead at the same time. If the box is opened, then the experimenter can see only one specific state - “the nucleus has decayed, the cat is dead” or “the nucleus has not decayed, the cat is alive.”

The essence in human language: Schrödinger's experiment showed that, from the point of view of quantum mechanics, the cat is both alive and dead, which cannot be. Therefore, quantum mechanics has significant flaws.

The question is: when does a system cease to exist as a mixture of two states and choose one specific one? The purpose of the experiment is to show that quantum mechanics is incomplete without some rules that indicate under what conditions the wave function collapses, and the cat either becomes dead or remains alive, but ceases to be a mixture of both. Since it is clear that a cat must be either alive or dead (there is no state intermediate between life and death), this will be similar for the atomic nucleus. It must be either decayed or undecayed (Wikipedia).

Video from The Big Bang Theory

Another more recent interpretation of Schrödinger's thought experiment is a story that Big Bang Theory character Sheldon Cooper told his less educated neighbor Penny. The point of Sheldon's story is that the concept of Schrödinger's cat can be applied to human relationships. In order to understand what is happening between a man and a woman, what kind of relationship is between them: good or bad, you just need to open the box. Until then, the relationship is both good and bad.

Below is a video clip of this Big Bang Theory exchange between Sheldon and Penia.

Did the cat remain alive as a result of the experiment?

For those who didn’t read the article carefully, but are still worried about the cat, good news: don’t worry, according to our data, as a result of a thought experiment by a crazy Austrian physicist

NO CAT WAS HURT

There was a kind of “secondary” quality. He himself rarely dealt with a specific scientific problem. His favorite genre of work was response to someone else's scientific research, development of this work, or criticism of it. Despite the fact that Schrödinger himself was an individualist by nature, he always needed someone else’s thought, support for further work. Despite this peculiar approach, Schrödinger managed to make many discoveries.

Biographical information

Schrödinger's theory is now known not only to students of physics and mathematics departments. It will be of interest to anyone who is interested in popular science. This theory was created by the famous physicist E. Schrödinger, who went down in history as one of the creators of quantum mechanics. The scientist was born on August 12, 1887 in the family of the owner of an oilcloth factory. The future scientist, famous throughout the world for his riddle, was fond of botany and drawing as a child. His first mentor was his father. In 1906, Schrödinger began his studies at the University of Vienna, during which he began to admire physics. When the First World War came, the scientist went to serve as an artilleryman. In his free time, he studied the theories of Albert Einstein.

By the beginning of 1927, a dramatic situation had developed in science. E. Schrödinger believed that the basis of the theory of quantum processes should be the idea of wave continuity. Heisenberg, on the contrary, believed that the foundation for this field of knowledge should be the concept of discreteness of waves, as well as the idea of quantum leaps. Niels Bohr did not accept either position.

Advances in science

For his creation of the concept of wave mechanics, Schrödinger received the Nobel Prize in 1933. However, brought up in the traditions of classical physics, the scientist could not think in other categories and did not consider quantum mechanics a full-fledged branch of knowledge. He could not be satisfied with the dual behavior of particles, and he tried to reduce it exclusively to wave behavior. In his discussion with N. Bohr, Schrödinger put it this way: “If we plan to preserve these quantum leaps in science, then I generally regret that I connected my life with atomic physics.”

Further work of the researcher

Moreover, Schrödinger was not only one of the creators of modern quantum mechanics. It was he who was the scientist who introduced the term “objectivity of description” into scientific use. This is the ability of scientific theories to describe reality without the participation of an observer. His further research was devoted to the theory of relativity, thermodynamic processes, and nonlinear Born electrodynamics. Scientists have also made several attempts to create a unified field theory. In addition, E. Schrödinger spoke six languages.

The most famous riddle

Schrödinger's theory, in which that same cat appears, grew out of the scientist's criticism of quantum theory. One of its main postulates states that while the system is not being observed, it is in a state of superposition. Namely, in two or more states that exclude each other’s existence. The state of superposition in science has the following definition: this is the ability of a quantum, which can also be an electron, photon, or, for example, the nucleus of an atom, to simultaneously be in two states or even at two points in space at a moment when no one is observing it.

Objects in different worlds

It is very difficult for an ordinary person to understand such a definition. After all, every object of the material world can be either at one point in space or at another. This phenomenon can be illustrated as follows. The observer takes two boxes and puts a tennis ball in one of them. It will be clear that it is in one box and not in the other. But if you put an electron in one of the containers, then the following statement will be true: this particle is simultaneously in two boxes, no matter how paradoxical it may seem. In the same way, an electron in an atom is not located at a strictly defined point at one time or another. It rotates around the core, located at all points of the orbit simultaneously. In science, this phenomenon is called an “electron cloud.”

What did the scientist want to prove?

Thus, the behavior of small and large objects is implemented according to completely different rules. In the quantum world there are some laws, and in the macroworld - completely different ones. However, there is no concept that would explain the transition from the world of material objects familiar to people to the microworld. Schrödinger's theory was created in order to demonstrate the inadequacy of research in the field of physics. The scientist wanted to show that there is a science whose goal is to describe small objects, and there is a field of knowledge that studies ordinary objects. Largely thanks to the work of the scientist, physics was divided into two areas: quantum and classical.

Schrödinger's theory: description

The scientist described his famous thought experiment in 1935. In carrying it out, Schrödinger relied on the principle of superposition. Schrödinger emphasized that as long as we do not observe the photon, it can be either a particle or a wave; both red and green; both round and square. This principle of uncertainty, which directly follows from the concept of quantum dualism, was used by Schrödinger in his famous riddle about the cat. The meaning of the experiment in brief is as follows:

A cat is placed in a closed box, as well as a container containing hydrocyanic acid and a radioactive substance.
The nucleus can disintegrate within an hour. The probability of this is 50%.
If an atomic nucleus decays, it will be recorded by a Geiger counter. The mechanism will work, and the box of poison will be broken. The cat will die.
If decay does not occur, then Schrödinger's cat will be alive.

According to this theory, until the cat is observed, it is simultaneously in two states (dead and alive), just like the nucleus of an atom (decayed or not decayed). Of course, this is only possible according to the laws of the quantum world. In the macrocosm, a cat cannot be both alive and dead at the same time.

The Observer's Paradox

To understand the essence of Schrödinger's theory, it is also necessary to understand the observer's paradox. Its meaning is that objects of the microworld can be in two states simultaneously only when they are not observed. For example, the so-called “Experiment with 2 slits and an observer” is known in science. The scientists directed a beam of electrons onto an opaque plate in which two vertical slits were made. On the screen behind the plate, the electrons painted a wave pattern. In other words, they left black and white stripes. When the researchers wanted to observe how electrons flew through the slits, the particles displayed only two vertical stripes on the screen. They behaved like particles, not like waves.

Copenhagen explanation

The modern explanation of Schrödinger's theory is called the Copenhagen one. Based on the observer's paradox, it sounds like this: as long as no one observes the nucleus of an atom in the system, it is simultaneously in two states - decayed and undecayed. However, the statement that a cat is alive and dead at the same time is extremely erroneous. After all, in the macrocosm the same phenomena are never observed as in the microcosm.

Therefore, we are not talking about the “cat-nucleus” system, but about the fact that the Geiger counter and the atomic nucleus are interconnected. The kernel can choose one state or another at the moment when measurements are made. However, this choice does not take place at the moment when the experimenter opens the box with Schrödinger's cat. In fact, the opening of the box takes place in the macrocosm. In other words, in a system that is very far from the atomic world. Therefore, the nucleus selects its state precisely at the moment when it hits the Geiger counter detector. Thus, Erwin Schrödinger did not describe the system fully enough in his thought experiment.

General conclusions

Thus, it is not entirely correct to connect the macrosystem with the microscopic world. In the macrocosm, quantum laws lose their force. The nucleus of an atom can be in two states simultaneously only in the microcosm. The same cannot be said about the cat, since it is an object of the macrocosm. Therefore, only at first glance does it seem that the cat passes from a superposition to one of the states at the moment the box is opened. In reality, its fate is determined at the moment when the atomic nucleus interacts with the detector. The conclusion can be drawn as follows: the state of the system in Erwin Schrödinger’s riddle has nothing to do with the person. It depends not on the experimenter, but on the detector - the object that “observes” the nucleus.

Continuation of the concept

Schrödinger's theory is described in simple words as follows: while the observer is not looking at the system, it can be in two states simultaneously. However, another scientist, Eugene Wigner, went further and decided to bring Schrödinger’s concept to the point of complete absurdity. “Excuse me!” said Wigner, “What if his colleague is standing next to the experimenter watching the cat?” The partner does not know what exactly the experimenter himself saw at the moment when he opened the box with the cat. Schrödinger's cat emerges from superposition. However, not for a fellow observer. Only at the moment when the fate of the cat becomes known to the latter can the animal be finally called alive or dead. In addition, billions of people live on planet Earth. And the final verdict can be made only when the result of the experiment becomes the property of all living beings. Of course, you can tell all people the fate of the cat and Schrödinger’s theory briefly, but this is a very long and labor-intensive process.

The principles of quantum dualism in physics were never refuted by Schrödinger's thought experiment. In a sense, every being can be said to be neither alive nor dead (in superposition) as long as there is at least one person not observing it.

Don't look for "eastern mysticism", spoon bending or extrasensory perception here. Seek the true story of quantum mechanics, the truth of which is more amazing than any fiction. This is science: it does not need outfits from another philosophy, because it itself is full of beauties, mysteries and surprises. This book attempts to answer the specific question: “What is reality?” And the answer (or answers) may surprise you. You may not believe it. But you will understand how modern science looks at the world.

Nothing is real

The cat in the title is a mythical creature, but Schrödinger really existed. Erwin Schrödinger was an Austrian scientist who, in the mid-1920s, played a major role in creating the equations of a branch of science now called quantum mechanics. However, to say that quantum mechanics is just a branch of science is hardly true, because it underlies all modern science. Its equations describe the behavior of very small objects - the size of atoms and smaller - and represent the only thing description of the world of the smallest particles. Without these equations, physicists would not be able to design working nuclear power plants (or bombs), create lasers, or explain how the temperature of the Sun does not decrease. Without quantum mechanics, chemistry would still be in the Dark Ages and molecular biology would not have appeared at all: there would be no knowledge of DNA, no genetic engineering, nothing.

Quantum theory is the greatest achievement of science, much more significant and much more applicable in a direct, practical sense than the theory of relativity. And yet she makes some strange predictions. The world of quantum mechanics is indeed so unusual that even Albert Einstein found it incomprehensible and refused to accept all the consequences of the theory derived by Schrödinger and his colleagues. Like many other scientists, Einstein decided that it was more convenient to believe that the equations of quantum mechanics were just a kind of mathematical trick that accidentally provided a reasonable explanation for the behavior of atomic and subatomic particles, but they contained a deeper truth that better relates to our ordinary sense of reality. After all, quantum mechanics states that there is no reality and we cannot say anything about the behavior of things when we do not observe them. Schrödinger's mythical cat was intended to clarify the differences between the quantum and ordinary worlds.

In the world of quantum mechanics, the laws of physics familiar to us from the ordinary world cease to work. Instead, events are governed by probabilities. A radioactive atom, for example, may decay and, say, release an electron, or it may not. You can conduct an experiment by imagining that there is exactly a fifty percent probability that one of the atoms of a bunch of radioactive substance will decay at a certain moment and the detector will register this decay if it occurs. Schrödinger, as upset by the conclusions of quantum theory as Einstein, tried to demonstrate their absurdity by imagining such an experiment taking place in a closed room or box containing a live cat and a bottle of poison, and if decay occurs, the container with the poison breaks and the cat dies. In the ordinary world, the probability of a cat's death is fifty percent, and without looking into the box, we can safely say only one thing: the cat inside is either alive or dead. But this is where the strangeness of the quantum world reveals itself. According to the theory none Of the two possibilities that exist for the radioactive substance, and therefore the cat, it does not seem realistic unless there is observation of what is happening. Atomic decay did not happen and did not happen, the cat did not die and did not die, until we look into the box to find out what happened. Theorists who accept a pure version of quantum mechanics argue that the cat exists in some indeterminate state, being neither alive nor dead, until an observer looks into the box and sees how the situation has turned out. Nothing is real unless observation is made.

This idea was hated by Einstein, as well as many others. “God doesn’t play dice,” he said, referring to the theory that the world is determined by the totality of the results of an essentially random “selection” of possibilities at the quantum level. As for the unreality of the state of Schrödinger's cat, Einstein did not take it into account, suggesting that there must be some deep “mechanism” that determines the truly fundamental reality of things. For many years he tried to develop experiments that would help show this deep reality at work, but he died before it became possible to conduct such an experiment. Perhaps it was for the best that he did not live to see the result of the chain of reasoning he had set in motion.

In the summer of 1982, a group of scientists from the University of Paris-Sud, led by Alain Aspé, completed a series of experiments designed to reveal the underlying reality that defines the unreal quantum world. This deep reality - the fundamental mechanism - was given the name “hidden parameters”. The essence of the experiment was to observe the behavior of two photons, or particles of light, flying in opposite directions from a source. The experiment is described in full in Chapter Ten, but overall it can be considered a reality check. Two photons from the same source can be detected by two detectors, which measure a property called polarization. According to quantum theory, this property does not exist until it is measured. According to the idea of "hidden parameters", every photon has a "real" polarization from the moment of its creation. Because two photons are emitted simultaneously, their polarization values depend on each other, but the nature of the dependence that is actually measured differs according to the two views of reality.

The results of this important experiment are clear. The dependence predicted by the theory of hidden parameters was not discovered, but the dependence predicted by quantum mechanics was. Moreover, as quantum theory predicted, measurements made on one photon had an immediate effect on the nature of the other photon. Some interaction inextricably linked the photons, although they scattered in different directions at the speed of light, and the theory of relativity states that no signal can be transmitted faster than light. Experiments have proven that there is no deep reality in the world. “Reality” in the ordinary sense is not suitable for thinking about the behavior of the fundamental particles that make up the Universe, and these particles at the same time seem to be inextricably linked together into some indivisible whole, where each knows what happens to the others.

The search for Schrödinger's cat is the search for quantum reality. From this short review it may seem that this search was not crowned with success, since in the quantum world reality in the usual sense of the word does not exist. But the story doesn't end there, and the search for Schrödinger's cat may lead us to a new understanding of reality that transcends—and at the same time includes—the conventional interpretation of quantum mechanics. However, the search will take a long time, and you need to start with a scientist who, perhaps, would be more frightened than Einstein if he had a chance to find out the answers we have now given to the questions that tormented him. Studying the nature of light three centuries ago, Isaac Newton probably had no idea that he had already set foot on the path leading to Schrödinger’s cat.

Part one

Anyone who is not shocked by quantum theory has not understood it.

Niels Bohr 1885-1962

Chapter first

Isaac Newton invented physics, and the rest of science rests on it. While Newton certainly built on the work of others, it was his publication of the three laws of motion and the theory of gravity over three centuries ago that set science on the path that eventually led to space exploration, lasers, atomic energy, genetic engineering, the understanding of chemistry, and everything else. . For two centuries, Newtonian physics (what is now called "classical physics") ruled the world of science. Revolutionary new ideas advanced twentieth-century physics well beyond Newton, but without those two centuries of scientific growth, these ideas might never have appeared. This book is not the history of science: it talks about the new physics - quantum, and not about those classical ideas. However, even in Newton's work three hundred years ago, there are already signs that change is inevitable: they are contained not in his works on the movement of planets and their orbits, but in his studies of the nature of light.

John Gribbin

In search of Schrödinger's cat. Quantum physics and reality

I don't like all this, and I regret that I was involved in this at all.

Erwin Schrödinger 1887-1961

Nothing is real.

John Lennon 1940-1980

IN SEARCH OF SCHRÖDINGER'S CAT

Quantum Physics and Reality

Translation from English by Z. A. Mamedyarova, E. A. Fomenko

Acknowledgments

My acquaintance with quantum theory took place more than twenty years ago, back in school, when I discovered that the theory of the shell structure of the atom magically explained the entire periodic system of elements and almost all of the chemistry with which I had struggled in many boring lessons. I immediately began to dig further, resorting to library books said to be "too complex" for my limited scientific training, and immediately noticed the beautiful simplicity of the explanation of the atomic spectrum from the perspective of quantum theory and discovered for the first time that the best in science is simultaneously beautiful and simple, and this is a fact that too many teachers - accidentally or on purpose - hide from their students. I felt just like the hero of the novel “The Search” by C. P. Snow (although I read it much later), who discovered the same thing:

I noticed how mixed up random facts suddenly fell into place... “But this is the truth,” I said to myself. - This is wonderful. And this is the truth." (Edition A, 1963, p. 27.)

It was partly because of this insight that I decided to study physics at university. In due course, my ambitions were realized, and I became a student at the University of Sussex in Brighton. But there, the simplicity and beauty of the deep ideas were eclipsed by the variety of details and mathematical methods for solving specific problems using the equations of quantum mechanics. The application of these ideas to the world of modern physics gave, perhaps, about the same idea of \u200b\u200bdeep beauty and truth that piloting gives Boeing 747 about hang gliding. Although the power of the original insight remained the most significant influence on my career, for a long time I ignored the quantum world and discovered other delights of science.

The embers of that early interest were reignited by a combination of factors. In the late 1970s and early 1980s, books and articles began to appear that tried, with varying degrees of success, to explain the strange quantum world to non-scientific audiences. Some of the so-called “popular texts” were so monstrously far from the truth that I could not even imagine that there would be a reader who would understand the truth and beauty of science by studying them, and therefore wanted to tell it like it is. At the same time, information emerged about a long series of scientific experiments that proved the reality of some of the strangest aspects of quantum theory, and this information forced me to go back to the libraries and refresh my understanding of these amazing things. And finally, one Christmas, the BBC invited me to appear on a radio program as a sort of scientific opponent to Malcolm Muggeridge, who had just announced his conversion to Catholicism and was the chief guest for the festive season. After this great man had made his point, emphasizing the mystery of Christianity, he turned to me and said, “But here is someone who knows all the answers—or claims to know them all.” Time was limited, and I tried to give a decent response, pointing out that science does not claim to have all the answers, and it is religion, not science, that relies entirely on boundless faith and the belief that the truth is known. “I don’t believe in anything,” I said and began to explain my position, but at that moment the program came to an end. Throughout the Christmas holidays, friends and acquaintances reminded me of these words, and I spent hours repeating that my lack of unlimited faith in anything did not prevent me from living a normal life, using the completely reasonable working hypothesis that the sun was unlikely to disappear overnight .

All this helped me sort out my own thoughts about the nature of science during long discussions about the basic reality - or unreality - of the quantum world, and it was enough to convince me that I could write the book you now hold in your hands. While working on it, I tested many of the more subtle arguments during my regular appearances on the British Forces Broadcasting Corporation's science radio program, hosted by Tommy Vance. Tom's inquisitive questions quickly revealed the imperfections in my presentation, and with their help I was able to organize my ideas in a better way. The main source of reference material I used in writing the book was the University of Sussex library, which contains perhaps one of the best collections of books on quantum theory in the world, and more rare materials were selected for me by Mandy Caplin from the magazine New Scientist, who persistently sent me teletype messages while Christina Sutton corrected my misconceptions about particle physics and field theory. My wife not only provided me with invaluable assistance in reviewing the literature and organizing the material, but also softened many of the rough edges. I am also grateful to Professor Rudolf Pearls for explaining to me in detail some of the intricacies of the clock-in-a-box experiment and the Einstein-Podolsky-Rosen paradox.

All that is good about this book is due to: "difficult" chemistry texts, the names of which I no longer remember, which I discovered in the Kent County Library at the age of sixteen; woe to the “popularizers” of quantum ideas who convinced me that I could describe them better; Malcolm Muggeridge and the BBC; University of Sussex Library; Tommy Vance and BFBS; Mandy Caplin and Christina Sutton and especially Min. Any complaints regarding those shortcomings that still remain in this book should, of course, be addressed to me.

John Gribbin

July 1983

Introduction

If you were to add up all the books and articles on the theory of relativity written for ordinary people, the stack would probably reach the moon. “Everyone knows” that Einstein’s theory of relativity is the greatest scientific achievement of the 20th century, and everyone is wrong. However, if you add up all the books and articles on quantum theory written for ordinary people, they will easily fit on my desk. This does not mean that quantum theory has not been heard outside the walls of academies. Quantum mechanics even became popular in certain sectors: with its help they tried to explain telepathy and bending spoons, and they drew inspiration from it for many science fiction stories. In popular mythology, quantum mechanics is associated - if at all - with the occult and extrasensory perception, that is, a strange, esoteric branch of science that no one understands and for which no one can find practical application.

This book is written in opposition to this perception of what is essentially the most fundamental and important area of scientific knowledge. This book owes its origin to several circumstances that arose in the summer of 1982. First, I just finished reading a book on the theory of relativity called The Curvatures of Space and decided it was time to take on the task of demystifying the other great branch of twentieth-century science. Secondly, at that time I was increasingly irritated by the incorrect ideas that existed under the name of quantum theory among people far from science. Fridtjof Capra's excellent book The Tao of Physics gave rise to many imitators who understood neither physics nor the Tao but felt that money could be made by linking Western science with Eastern philosophy. And finally, in August 1982, news came from Paris that a group of scientists had successfully carried out a crucial experiment that confirmed - for those who still doubted - the accuracy of the quantum mechanical view of the universe.

Nothing is real

If you are interested in an article on a topic from quantum physics, then there is a high probability that you love the TV series “The Big Bang Theory”. So, Sheldon Cooper came up with a fresh interpretation Schrödinger's thought experiment(You will find a video with this fragment at the end of the article). But to understand Sheldon's dialogue with his neighbor Penny, let's first turn to the classical interpretation. So, Schrödinger's Cat in simple words.

In this article we will look at:

Brief historical background
Description of the experiment with Schrödinger's Cat
The solution to the Schrödinger's Cat paradox

Immediately good news. During the experiment Schrödinger's cat was not harmed. Because physicist Erwin Schrödinger, one of the creators of quantum mechanics, only conducted a thought experiment.

Before diving into the description of the experiment, let's make a mini excursion into history.

At the beginning of the last century, scientists managed to look into the microworld. Despite the external similarity of the “atom-electron” model with the “Sun-Earth” model, it turned out that the familiar Newtonian laws of classical physics do not work in the microcosm. Therefore, a new science appeared - quantum physics and its component - quantum mechanics. All microscopic objects of the microworld were called quanta.

Attention! One of the postulates of quantum mechanics is “superposition”. It will be useful to us to understand the essence of Schrödinger's experiment.

“Superposition” is the ability of a quantum (it can be an electron, a photon, the nucleus of an atom) to be not in one, but in several states at the same time or to be in several points of space at the same time, if no one is watching him

This is difficult for us to understand, because in our world an object can only have one state, for example, being either alive or dead. And it can only be in one specific place in space. You can read about “superposition” and the stunning results of quantum physics experiments In this article.

Here is a simple illustration of the difference between the behavior of micro and macro objects. Place a ball in one of the 2 boxes. Because the ball is an object of our macro world, you will say with confidence: “The ball lies in only one of the boxes, while the second one is empty.” If instead of a ball you take an electron, then the statement that it is simultaneously in 2 boxes will be true. This is how the laws of the microworld work. Example: The electron in reality does not rotate around the nucleus of the atom, but is located at all points of the sphere around the nucleus simultaneously. In physics and chemistry, this phenomenon is called the “electron cloud”.

Summary. We realized that the behavior of a very small object and a large object are subject to different laws. The laws of quantum physics and the laws of classical physics, respectively.

But there is no science that would describe the transition from the macroworld to the microworld. So, Erwin Schrödinger described his thought experiment precisely in order to demonstrate the incompleteness of the general theory of physics. He wanted Schrödinger's paradox to show that there is a science to describe large objects (classical physics) and a science to describe micro objects (quantum physics). But there is not enough science to describe the transition from quantum systems to macrosystems.

Description of the experiment with Schrödinger's Cat

Erwin Schrödinger described a thought experiment with a cat in 1935. The original version of the experiment description is presented on Wikipedia ( Schrödinger's cat Wikipedia).

Here is a version of the description of the Schrödinger's Cat experiment in simple words:

A cat was placed in a closed steel box.
The Schrödinger Box contains a device with a radioactive nucleus and poisonous gas placed in a container.
The nucleus may decay within 1 hour or not. Probability of decay – 50%.
If the nucleus decays, the Geiger counter will record this. The relay will operate and the hammer will break the gas container. Schrödinger's cat will die.
If not, then Schrödinger’s cat will be alive.

According to the law of “superposition” of quantum mechanics, at a time when we are not observing the system, the nucleus of an atom (and therefore the cat) is in 2 states simultaneously. The nucleus is in a decayed/undecayed state. And the cat is in a state of being alive/dead at the same time.

But we know for sure that if the “Schrödinger box” is opened, then the cat can only be in one of the states:

if the nucleus does not decay, our cat is alive
if the nucleus decays, the cat is dead

The paradox of the experiment is that according to quantum physics: before opening the box, the cat is both alive and dead at the same time, but according to the laws of physics of our world, this is impossible. Cat can be in one specific state - being alive or being dead. There is no mixed state “the cat is alive/dead” at the same time.

Before you get the answer, watch this wonderful video illustration of the paradox of the Schrödinger's cat experiment (less than 2 minutes):

The solution to the Schrödinger's Cat paradox - the Copenhagen interpretation

Now the solution. Pay attention to the special mystery of quantum mechanics - observer paradox. An object of the microworld (in our case, the core) is in several states simultaneously only while we are not observing the system.

For example, the famous experiment with 2 slits and an observer. When a beam of electrons was directed onto an opaque plate with 2 vertical slits, the electrons painted a “wave pattern” on the screen behind the plate—vertical alternating dark and light stripes. But when the experimenters wanted to “see” how electrons fly through the slits and installed an “observer” on the side of the screen, the electrons drew not a “wave pattern” on the screen, but 2 vertical stripes. Those. behaved not like waves, but like particles.

It seems that quantum particles themselves decide what state they should take at the moment they are “measured.”

Based on this, the modern Copenhagen explanation (interpretation) of the “Schrödinger’s Cat” phenomenon sounds like this:

While no one is observing the “cat-core” system, the nucleus is in a decayed/undecayed state at the same time. But it is a mistake to say that the cat is alive/dead at the same time. Why? Yes, because quantum phenomena are not observed in macrosystems. It would be more correct to talk not about the “cat-core” system, but about the “core-detector (Geiger counter)” system.

The nucleus selects one of the states (decayed/undecayed) at the moment of observation (or measurement). But this choice does not occur at the moment when the experimenter opens the box (the opening of the box occurs in the macroworld, very far from the world of the nucleus). The nucleus selects its state at the moment it hits the detector. The fact is that the system is not described enough in the experiment.

Thus, the Copenhagen interpretation of the Schrödinger's Cat paradox denies that until the moment the box was opened, Schrödinger's Cat was in a state of superposition - it was in the state of a living/dead cat at the same time. A cat in the macrocosm can and does exist in only one state.

Summary. Schrödinger did not fully describe the experiment. It is not correct (more precisely, it is impossible to connect) macroscopic and quantum systems. Quantum laws do not apply in our macrosystems. In this experiment, it is not “cat-core” that interacts, but “cat-detector-core”. The cat is from the macrocosm, and the “detector-core” system is from the microcosm. And only in its quantum world can a nucleus be in two states at the same time. This occurs before the nucleus is measured or interacts with the detector. But a cat in its macrocosm can and does exist in only one state. That's why, It’s only at first glance that it seems that the cat’s “alive or dead” state is determined at the moment the box is opened. In fact, its fate is determined at the moment the detector interacts with the nucleus.

Final summary. The state of the “detector-nucleus-cat” system is NOT associated with the person – the observer of the box, but with the detector – the observer of the nucleus.

Phew. My brain almost started boiling! But how nice it is to understand the solution to the paradox yourself! As in the old student joke about the teacher: “While I was telling it, I understood it!”

Sheldon's interpretation of Schrödinger's Cat paradox

Now you can sit back and listen to Sheldon's latest interpretation of Schrödinger's thought experiment. The essence of his interpretation is that it can be applied in relationships between people. To understand whether a relationship between a man and a woman is good or bad, you need to open the box (go on a date). And before that they were both good and bad at the same time.

Well, how do you like this “cute experiment”? Nowadays, Schrödinger would get a lot of punishment from animal rights activists for such brutal thought experiments with a cat. Or maybe it wasn’t a cat, but Schrödinger’s Cat?! Poor girl, she suffered enough from this Schrödinger (((

See you in the next publications!

I wish everyone a good day and a pleasant evening!

P.S. Share your thoughts in the comments. And ask questions.

P.S. Subscribe to the blog - the subscription form is located under the article.