Thought experiment examples. Gravitational waves. Gravitational collapse of a binary system

But despite the well-developed sense of smell in dogs and outstanding ability to distinguish between smells, not all of them are equally well perceived by the dog. How to develop a sense of smell in a dog? We will try to give a detailed answer in this article.

For example, a dog perfectly distinguishes the smell of butyric acid contained in rancid butter. In order for a person to feel this smell, at least 7 billion molecules in 1 cm2 of air are needed, and for a dog - only 9 thousand molecules.

Worse perceived acetic acid. But the smell of flowers is easily recognized by the dog, moreover, it gives her pleasure. However, dog breeders are most interested in the ability of dogs to smell people. Studies have shown that it is possible to artificially simulate the smell of a person. It contains fatty acids: butyric, acetic, propionic and others.

What affects a dog's sense of smell and the spread of a scent?

Long-term experience confirms the data of scientific research: a person leaves behind a trace that is clearly visible to a dog. But its quality is not always the same. The composition and concentration of chemicals on the surface of the skin is different for each person. In order to properly train a dog, its owner must first understand what, in fact, is a smell.

In fact, it is similar to any fluid substance. We know from physics that any body at a temperature above absolute zero evaporates molecules into the external environment. The rate of evaporation depends on the temperature. The higher the temperature, the greater the intensity. The evaporation process is the emission of molecules and their dispersion in space.

In the end, these molecules settle on the ground and various objects. It is they who form the smell: chemical elements irritate various parts of the dog's nasal mucosa. It has been proven that dogs equally well perceive substances that give both acidic and alkaline reactions. The quality of the smell is due to a number of factors.

The temperature of the surface of the earth and various objects depends on the intensity of sunlight. Under the action of sunlight, moisture evaporates from the surface of the earth. The persistence of the smell depends on the intensity of evaporation. This is especially noticeable during the day. The sun's rays cause active evaporation of molecules from various sources - be it an object or a trace of a person.

With strong evaporation, the molecules quickly disperse in the air, sometimes rising to a considerable height. This leads to a rapid odor reduction. At night, all smells are much more stable. The cooled surface of the earth at this time evaporates much less particles. There is a condensation of water vapor contained in the air, which falls in the form of dew and, as it were, preserves odors. Therefore, at night, the trail remains fresh much longer than during the day.

Atmospheric pressure also affects the distribution of odors. If it decreases, the intensity of evaporation increases - which means that the smell becomes more easily perceptible to the dog. With high humidity and wind, the dog will easily take the trail. Humidity is perhaps the most important factor. The ideal weather for hunting down criminals should be considered drizzling rain and fog, in which the humidity of the air reaches its maximum. But a downpour is undesirable: although it provides high humidity, it washes away traces. Particles of smell are simply absorbed along with water into the ground.

The wind can both help and interfere with the instinct of dogs - depending on the direction and speed. On the one hand, it contributes to the rarefaction and dispersion of molecules, reducing the smell, on the other hand, it increases the intensity of evaporation from the surface of the earth and objects. In this case, however, the trace quickly loses its freshness. That is all that can be said about the important factors that a dog owner must take into account if he is going to train him outdoors.

The smell of a person is due to the metabolism in all his organs and tissues. The products of this exchange are various secretions: sweat, fat, liquids, gases, particles of dead skin. All this makes up, so to speak, the general outline of a person's smell, which further breaks down into specific shades: breath, sweat, skin breath and "local" smells - from the armpits, head, palms, legs, genitals.

In addition, the dog also smells the environment in which a person lives and works - for example, furniture or tools - not to mention cosmetics.

The most common way dogs develop a sense of smell and sense of smell is to train them to recognize human tracks. Therefore, it is necessary to remember all the components that form their smell.

In addition to the individual smell of a particular person, the trace contains accompanying odors that occur when people move in various environments: in a field, meadow, forest, city, etc. These odors arise from the violation of the structure of the soil when walking, damage to plants, destruction of microorganisms. Accompanying odors cannot be ignored in any way: they are often so strong that they drown out the individual smell of a person.

If you want your pet to follow the trail well, start developing dog's sense needed as soon as possible. Caring for, systematically prepare him for future "professional" activities. Try to make him use his flair as often as possible even in games. Hide your favorite food (for example, meat) or a toy in thick grass and encourage their search in every possible way. Hide yourself, for example, behind a tree or a bush, so that the puppy has to find you by smell. Teach your puppy to the "Seek!" command. It is important, however, not to overdo it or go too far, or your puppy will lose his taste for play.

An almost adult dog should be taught to recognize specific tracks - when it becomes possible to choose a suitable motivation. For some dogs, this is a treat, for others it is a favorite toy, sometimes both. For others, it is the owner himself, and then you have to work with an assistant. One dog is not like another, and therefore it is the first steps that are most important. The choice of motivation becomes a decisive factor: in case of a mistake, a long chain of failures awaits you.

Technique for the development of flair, scent in dogs

Just in case, we recall the most important rule of any: a gradual transition from simple to complex. A dog is a predator, and therefore a nocturnal animal. Its activity increases at dusk and before dawn. Therefore, it is better to choose morning or evening hours for training. Take care of a convenient place: it can be a meadow or a sparse undergrowth. Don't forget about climate conditions. The easiest way to encourage a dog to search for tracks is to scatter pieces of food on the ground. Finely chopped lean meat or boiled beef liver is good.

We recommend liver not because dogs usually prefer it to meat, but because it crumbles more easily. When laying a trail, a good orientation to the terrain is necessary. When it comes to your own footprint, this rule is doubly important. Mark the beginning of the trail with a peg, twig or large stone. Never use your clothes or personal items for this! Establish in which direction the wind is blowing, and with this in mind, mark a suitable landmark. The wind should blow from the side or in the back.

The first track is never laid against the wind!

A so-called “step” is made next to the peg. A surface area of ​​approximately 3/4 m is carefully trampled down, and pieces of meat are scattered over it. Just don't kick too hard or you'll damage the soil. All this is necessary so that the dog at first thoroughly "tasted" the smell and could easily search for it further.

Then, at a normal pace, head towards a pre-selected landmark, leaving a piece of meat in each track (or even between them). The length of the first track should not exceed 10-15 m. At the end of the track, put a piece of paper or cloth, on which leave larger pieces of meat. The dog at this time should be tied nearby so that it can observe all your actions. If the bait is food, the dog must be hungry.

Accustom your dog to a collar in advance, which he will wear only when working with the trail. A long leash will get in the way. Even at first, the dog must independently determine the direction of the track. Therefore, bring it to the trail by all means from the side, and not from the beginning to the end. Naturally, during the first training sessions, the dog will collect and eat the pieces of meat that lead him on the trail.

Your task is to lead it and encourage it to search. Make sure that your dog does not run back and forth on the trail and is not distracted. Use the commands "Search!" and "Next!" During the work of the dog on the “step”, do not rush it. In general, all such training should be carried out calmly and with concentration. Shouting and trying to fit the dog will not lead to anything good. At the end of the trail, allow the dog to take his time to finish the meat, praise him and play with him.

One single track, even if repeated by a dog three times a week, is not training. At each lesson, there should be at least a few short chains of footprints. If you want to achieve serious success, work with your dog every day or at least every other day. Gradually reduce the surface of the "step" and the amount of scattered meat; increase the intervals between lying pieces.

In the future, leave the meat only at the end of the trail, wrapped in paper or a rag. Over time, remove the meat altogether, put some object at the end of the trail, but from your own hands. At first, short and straight, lengthen the trace, make turns and loops. Further, the turns should become more and more steep, from obtuse angles at the bends of the track, go to sharp ones. Leave more and more items on the trail, reduce the degree of its freshness.

Start changing the type of terrain and the appearance of the trail. Pay special attention to the transition from one area to another. It must be rehearsed separately, as different areas of the area have their own smells, which will create serious difficulties for an inexperienced dog. Therefore, when changing places, increase the smell by stomping your foot several times with each step.

Another important point is the work of the dog on turns and breaks in the track. Beginning dog breeders often use awkward handling to train their dog to ignore curves. Over time, the dog will not repeat them, not because of the inconvenience of a short leash, but out of habit. It is much better to make the dog's work easier by careful application of traces and special stomping on turns, but then make sure that she repeats all the breaks in the track to the end.

It is absolutely unacceptable to mark turns with sticks and other objects. The dog will focus on them, and not on the exact passage of the track. Of course, on turns, in no case should you pull the leash, pull or push the dog. The dog will quickly get used to such treatment and stop working on its own.

If the dog ignores turns, which happens quite often, it is necessary to lay a fresh track, reducing its length, simplifying the general contour and increasing both the smell at the breaks and their number. Working with a short leash, as a rule, is the weak point of the dog breeder. The length of the leash should not exceed 7-10 m, and it must be handled in such a way that in no case does it hamper the movements of the dog. When the dog follows the trail, the leash should sag a little or be slightly pulled over the dog's back. He should not interfere with the trainer either.

Fingering with his hands, he reduces the length of the leash, or vice versa increases it, allowing the leash to slip between his fingers. You can obediently follow the dog only after making sure that it really took the trail. The length of the leash regulates the distance between you and her. Accompanying the dog, you can not follow the trail, but one step away from him on the leeward side. You can only follow the dog at a walk. You do not need to run, this will affect the accuracy of the track.

Particular care is needed when turning if the leader is extended. Under no circumstances should the dog be entangled in it. Raise the leash higher if your dog has to go back a little to check the trail. If the dog's behavior shows that he missed the trail at the turn, repeat the search command and dial on the leash when the dog turns back. At the same time, take a few steps yourself in order to return to the place where the trail was still clear. In this way, you will make it easier for the dog to correct and train him to return immediately if he loses the track.

You should not lay tracks of the same length and configuration with the same arrangement of objects. The dog in this case works with less interest. Gradually change the length and degree of freshness of the trail, do not forget about changing terrain. Each dog will be glad to see the increased variety of tracks, which will manifest itself in his increased attention.

If experiments with your own footprint show good results, it will not be difficult for you to move on to recognizing someone else's footprints. It is better to ask for the first such trail to be laid by a person who is well known to the dog: someone from relatives or friends at home. Then it is interesting to try to work with the trace of a complete stranger. The dog takes a particular track, guided by the innate ability to differentiate odors. Our task is to help her develop this ability. Training helps a lot in recognizing not only traces, but also objects. While you are training your dog on your own trail, teach him to distinguish your items from any other. When she masters this exercise, move on to recognizing other people's things. Here, too, it is necessary to go from simple to complex. The lesson plan might look like this:

• recognition of a thing belonging to you among objects of the same unfamiliar smell;
• recognition of your thing among objects that have two different unfamiliar smells;
• recognition of your thing among objects, each of which has its own smell unfamiliar to the dog.

All items that the dog works with must be made of the same material and have the same accompanying smells: it can be a choice of one shoe, a hat, a dress from several shoes, dresses and hats. The purpose of these experiments is to develop in every possible way the dog's ability to differentiate odors, which is so necessary for it when working with someone else's trace. From such experiments, one can then move on to recognizing people by the smell of things belonging to them.

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What are some of the most impressive thought experiments you've come across?

Why aliens don't contact us

There is a worm on the road, and you pass by it. Does the worm know that you are intelligent? The worm has no idea about the concept of intelligence because you are much more intelligent than he is. So, the worm has no idea that something intelligent passed him by. This makes one wonder if we might have the notion that some super-beings are also "passing" by us. Maybe they are not interested in us because we are too stupid for them to even think about a possible dialogue? You don't walk past a worm thinking, "I wonder what he's thinking about?" This may be one of the best explanations why aliens have not yet made contact with us. If they are watching us, then they could come to the conclusion that there are no signs of intelligent life on Earth.

How "traces" of you and me travel the universe

Any object that has mass has a gravitational field. Thus, at the time of the birth of a child, its gravitational field becomes independent and begins to spread through space at the speed of light in the form of a constantly growing sphere.

The strength of our gravitational field weakens with distance, but never reaches zero. So, waves propagating in infinity already 8.3 minutes after our birth touched the surface of the Sun. 5.5 hours later they reached Pluto.

After 1 year, our gravitational field expands to a sphere with a diameter of 11.8 trillion miles. After 4 years with a small field slips on the surface of our closest known star - Proxima Centauri. By age thirty, our gravitational field has expanded 300 trillion miles around us in space.

Still feeling small? What makes it really uncomfortable is that when we die, our gravitational field will continue to exist forever, spreading endlessly through the universe, passing through the Andromeda galaxy after millions of years and beyond.

Pieces of everyone we've ever known, living or dead, are sweeping through the depths of space right now. The gravitational fields of our most distant ancestors and everything that ever existed are rushing through the universe, ever diminishing but never truly disappearing.

What does traveling back in time look like?

What is it like to experience time travel back? At first it seems that you will just watch everything as if in a rewind, but if you think about it, it will feel completely different.

At every single moment in time, let's call it T=0, we process information encoded in our brain that reflects memories from the past, moments: T=-1, T=-2, T=-3, etc., as well as much more fuzzy expectations and visualizations of the future: T=1, 2, 3, etc.

Usually from the moment T=0 we follow to T=1. At this time, physical processes create in memory a record of the moment T=0, which rises in a long series of moments from the past.

Now let's assume that instead we follow back to T=-1. Do we have memories of T=0? No. They are not, because we went back in time to the moment when the Universe existed at T=-1, and at that moment we had memories of T=-2 and only expectations of T=0. And if we go back to T=-2, then at that moment we will have memories of T=-3 and expectations of T=-1.

Thus, no matter how far back we go, at any given moment in time, we will still remember the previous one and imagine the next one. There is no moment at which we could see how the egg is assembled into a whole instead of how it is broken. Feels like it will be the same as moving forward.

And now we come to the realization that we cannot move back. If every moment of moving backward feels exactly the same as the moment of moving forward, then what can that mean? Are we moving forward at all?

The solid earth below us is a myth

On a clear night, lie down in your backyard and gaze up at the stars.

At first, you will feel the familiar comfort of resting on stable ground, looking up at the stars twinkling in the sky. But just think that we are not really "here" and the stars are not really "there". It's all an illusion. In reality, we "stuck" to the surface of the sphere, which is thrown in space from side to side with great speed. You don't just look at a static starry sky, you see the vastness of space almost as if you were in the cockpit of a giant spaceship.

What does traveling to a parallel universe look like?

Imagine that you are a black square on a white sheet of paper. Welcome to Flatland. You can move absolutely freely here, but only in two dimensions. There is simply no third and there is no up and down.
But do three-dimensional objects exist here? Yes, they are. But Flatlanders like you will never see them. You can only see the plane of the 3D object.

Now imagine that on the other side of a sheet of paper you find your own kind. Can you get to the other side to say hello to your neighbor? Because there is a plane between you and him, and it seems incredible that you can penetrate to the other side, moreover, it is impossible to make a hole, because the third dimension does not exist.

But still, there is a possibility. If the sheet were a Möbius strip, then, for example, an ant would crawl along the entire length of this sheet and return to its starting point, passing along both sides of it, but not crossing its edges.

That is, for this Flatland needs a bend. But is it allowed? Wouldn't Flatland thus become a three-dimensional space? Yes and no. The Möbius strip is three-dimensional, but like the ants on it, the inhabitants of Flatland are limited to two dimensions of a sheet of paper.

As humans, we are similar to Flatlanders in that we are limited to three dimensions and cannot travel in the fourth at will.

Imagine a Mobius strip made from our universe in 3D space, which also has a curve that gives access to a parallel universe. Just like the inhabitants of Flatland, we can get to know the inhabitants of the "other side of our three-dimensional universe", that is, from a parallel universe. We can discover a universe that is drastically different from ours.

But where is this bend? And, in general, does it exist? What are the consequences of the existence of this Möbius strip? Is it possible that superbeings with access to 4th dimensions created this bend just for fun, just like we can glue the Mobius strip for ants? These are just a few of the many questions...

What is it like to be blind

I'm half blind, meaning I can't see anything with my left eye. This means I can't see anything at all. All this simply does not exist. Most people don't understand what it means to see nothing. And when they ask this question, I usually answer like this.

Raise your hand in front of your face. Look at her. Can you see what your hand looks like right now? Keep thinking about your hand. Now take your hand off your head. How does your hand look now? No way. The hand you saw in front of you is now out of your peripheral vision and is simply not there. Now imagine that your peripheral vision on the left side is reduced, and you see only half of the field of view. That's just how I see it.

American educator, entrepreneur, and former hedge fund analyst Sal Khan proposed a surprising and inspiring thought experiment during his 2012 MIT graduation speech.

“Imagine yourself in 50 years. You have recently turned 70, your career is nearing its end. You are sitting on the couch having just watched President Kardashian's holographic address.

You begin to remember your life, reflect on all the most important moments. Think about success in your career, about whether you were able to provide for your family. But then you think about what you regret, about all the things you wish you had done a little differently. I guess there will be moments like this.

Imagine that the moment you think about it, a genie appears out of nowhere and says, “I overheard your regrets. They are really weighty. But since you're a good person, I'm willing to give you a second chance if you want." You say, "Of course," and the genie snaps his fingers.

Suddenly you will be where you are today. Feeling your toned, healthy 20-year-old body, you begin to understand that this actually happened. You really have a chance to do it all over again to build a career and strong relationships.”

Scientists often face a situation where it is very difficult or even simply impossible to test a particular theory experimentally. For example, when it comes to movement at near-light speeds or physics in the vicinity of black holes. Then thought experiments come to the rescue. We invite you to participate in some of them.

Thought experiments are sequences of logical inferences whose purpose is to emphasize some property of a theory, formulate a reasonable counterexample, or prove some fact. In general, any proof in one form or another is a thought experiment. The main beauty of mental exercises is that they do not require any equipment and often no special knowledge (as, for example, when processing the results of the LHC experiments). So get comfortable, we're getting started.

Shroedinger `s cat

Perhaps the most famous thought experiment is the cat experiment, proposed by Erwin Schrödinger over 80 years ago. Let's start with the context of the experiment. At that moment, quantum mechanics was just beginning its victorious march, and its unusual laws seemed unnatural. One such law is that quantum particles can exist in a superposition of two states: for example, they can "rotate" clockwise and counterclockwise at the same time.

Experiment. Imagine a sealed box (large enough) containing a cat, enough air, a Geiger counter, and a radioactive isotope with a known half-life. As soon as the Geiger counter detects the decay of an atom, a special mechanism breaks the ampoule with poisonous gas and the cat dies. After the half-life, the isotope decayed with a 50 percent probability and remained intact with exactly the same probability. This means that the cat is either alive or dead - as if being in a superposition of states.

Interpretation. Schrodinger wanted to show the unnaturalness of the superposition, bringing it to the point of absurdity - such a large system as a whole cat cannot be both alive and dead. It is worth noting that from the point of view of quantum mechanics, the moment when the Geiger counter is triggered by the decay of the nucleus, a measurement occurs - an interaction with a classical macroscopic object. As a result, the superposition should break up.

Interestingly, physicists are already conducting experiments similar to introducing a cat into a superposition. But instead of a cat, they use other large objects by the standards of the microworld - for example, molecules.

Twin paradox

This thought experiment is often cited as a critique of Einstein's special theory of relativity. It is based on the fact that when moving at near-light speeds, the flow of time in the frame of reference associated with the moving object slows down.

Experiment. Imagine a distant future where there are rockets that can travel at close to the speed of light. There are two twin brothers on Earth, one of them is a traveler and the other is a homebody. Suppose a traveling brother boarded one of these rockets and made a journey on it, after which he returned. For him, at that moment, when he was flying at near-light speed relative to the Earth, time passed more slowly than for his homebody brother. So when he returns to Earth, he will be younger than his brother. On the other hand, his brother himself was moving at near-light speed relative to the rocket - which means that the position of both brothers is in some sense equivalent, and when they meet, they must again be of the same age.

Interpretation. In reality, the traveler brother and the stay-at-home brother are not equivalent, so, as the thought experiment suggests, the traveler will be younger. Interestingly, this effect is also observed in real experiments: short-lived particles traveling at near-light speed seem to "live" longer due to time dilation in their frame of reference. If we try to extend this result to photons, it turns out that they do live in stopped time.

Einstein lift

There are several concepts of mass in physics. For example, there is a gravitational mass - this is a measure of how a body enters into a gravitational interaction. It is she who presses us into the sofa, armchair, subway seat or floor. There is an inertial mass - it determines how we behave in an accelerating coordinate system (it makes us deviate back in a subway train starting from a station). As you can see, the equality of these masses is not an obvious statement.

The basis of the general theory of relativity is the principle of equivalence - the indistinguishability of gravitational forces from the pseudoforces of inertia. One way to demonstrate this is the following experiment.

Experiment. Imagine that you are in a soundproof, hermetically sealed elevator car with enough oxygen and everything you need. But at the same time, you can be anywhere in the universe. The situation is complicated by the fact that the cabin can move, developing a constant acceleration. You feel yourself being slightly pulled towards the cabin floor. Can you tell if this is due to the fact that the cabin is, for example, on the Moon, or because the cabin is moving with an acceleration of 1/6 of the acceleration of free fall?

Interpretation. According to Einstein, no, you can't. Therefore, for other processes and phenomena there is no difference between uniformly accelerated motion in the elevator and in the field of gravitational force. With some reservations, it follows from this that the gravitational field can be replaced by an accelerating frame of reference.

Today, no one doubts the existence and materiality of gravitational waves - a year ago, the LIGO and VIRGO collaborations caught the long-awaited signal from the collision of black holes. However, at the beginning of the 20th century, after the first publication of Einstein's paper on space-time distortion waves, they were treated with skepticism. In particular, even Einstein himself at some point doubted their realism - they could turn out to be a mathematical abstraction devoid of physical meaning. To illustrate their realism, Richard Feynman (anonymously) proposed the following thought experiment.

Experiment. To begin with, a gravitational wave is a wave of change in the metrics of space. In other words, it changes the distance between objects. Imagine a cane along which balls can move with very little friction. Let the cane be located perpendicular to the direction of motion of the gravitational wave. Then, when the wave reaches the reed, the distance between the balls first decreases and then increases, while the reed remains motionless. This means that they slide and release heat into the space.

Interpretation. This means that the gravitational wave carries energy and is quite real. It can be assumed that the stick contracts and stretches along with the balls, compensating for relative motion, but, like Feynman himself, it is restrained by electrostatic forces acting between atoms.

Demon Laplace

The next pair of experiments is "demonic". Let's start with the less known, but no less beautiful Demon Laplace, which allows (or not) to know the future of the Universe.

Experiment. Imagine that somewhere there is a huge, very powerful computer. So powerful that it can, taking as a starting point the state of all the particles of the Universe, calculate how these states will develop (evolve). In other words, this computer can predict the future. To make it even more interesting, let's imagine that the computer predicts the future faster than it comes - say, in a minute it can describe the state of all the atoms in the universe, which they will reach two minutes after the start of the calculation.

Suppose we started the calculation at 00:00, waited for its end (at 00:01) - now we have a prediction for 00:02. Let's start the second calculation, which will end at 00:02 and predict the future at 00:03. Now pay attention to the fact that the computer itself is also part of our fictional universe. This means that at 00:01 he knows his state at 00:02 - he knows the result of calculating the state of the Universe at 00:03. Therefore, by repeating the same technique, it can be shown that the machine knows the future of the Universe at 00:04 and so on - ad infinitum.

Interpretation. Obviously, the speed of calculation, which is realized in a material device, cannot be infinite - therefore, it is impossible to predict the future with the help of a computer. But it is worth noting a few important points. First, the experiment forbids the material demon of Laplace - consisting of atoms. Secondly, it should be noted that the Laplace demon is possible under conditions when the lifetime of the Universe is fundamentally limited.

Maxwell's Demon

And finally, Maxwell's Demon is a classic experiment from the course of thermodynamics. It was introduced by James Maxwell to illustrate a way to violate the second law of thermodynamics (the one that forbids perpetual motion in one of its formulations).

Experiment. Imagine a medium-sized airtight vessel, divided inside by a partition into two parts. There is a small door or hatch in the partition. Next to her sits a reasonable microscopic creature - actually Maxwell's demon.

Let us fill the vessel with gas at a certain temperature - for definiteness, with oxygen at room temperature. It is important to remember that temperature is a number that reflects the average speed of movement of gas molecules in a vessel. For example, for oxygen in our experiment, this speed is 500 meters per second. But there are molecules in the gas that move faster and slower than this mark.

The task of the demon is to monitor the speed of particles flying up to the door in the partition. If a particle flying from the left half of the vessel has a speed of more than 500 meters per second, the demon will let it through by opening the door. If less, the particle will not fall into the right half. Conversely, if a particle from the right half of the tank has a speed of less than 500 meters per second, the demon will let it through to the left half.

After waiting long enough, we will find that the average speed of the molecules in the right half of the vessel has increased, while in the left it has dropped, which means that the temperature in the right half has also increased. We can use this excess heat, for example, to run a heat engine. At the same time, we did not need external energy to sort the atoms - Maxwell's demon did all the work.

Interpretation. The main consequence of the work of the demon is a decrease in the total entropy of the system. That is, after the separation of atoms into hot and cold, the measure of the chaotic state of the gas in the vessel decreases. The second law of thermodynamics strictly forbids this for closed systems.

But in reality, Maxwell's demon experiment turns out to be less paradoxical if the demon itself is included in the description of the system. He spends work on opening and closing the shutter, and also, and this is important, on measuring the velocities of atoms. All this compensates for the decrease in the entropy of the gas. Note that there are experiments to create analogues of Maxwell's demons.

Particularly noteworthy is the "Brownian ratchet" - although it does not itself divide molecules into warm and cold, it uses the chaotic Brownian movement to do work. The ratchet consists of blades and a gear that can rotate only in one direction (it is limited by a special clamp). The blade must rotate randomly, and it will succeed in making a full revolution only if its intended direction of rotation coincides with the permitted rotation of the gear. However, Richard Feynman analyzed the device in detail and explained why it didn't work - the average particle impact in the chamber would reset to zero.

Vladimir Korolev

This thought experiment was born in a dispute between the philosophers John Locke and William Molyneux.

Imagine a person blind from birth who knows how a ball differs from a cube by touch. If he suddenly regains his sight, will he be able to visually distinguish these objects? Can not. As long as the tactile perception is not connected with the visual, he will not know where the ball is and where the cube is.

The experiment shows that up to a certain point we do not have any knowledge about the world, even those that seem to us "natural" and innate.

Infinite monkey theorem

We believe that Shakespeare, Tolstoy, Mozart are geniuses, because their creations are unique and perfect. And if you were told that their works could not appear?

Probability theory states that everything that can happen will definitely happen in infinity. If you put an infinite number of monkeys at typewriters and give them an infinite amount of time, then someday one of them will repeat one of Shakespeare's plays word for word.

Everything that can happen, must happen - what place is there for personal talent and achievements?

ball collision

We know that morning will give way to night, that glass breaks with a strong blow, and an apple falling from a tree will fly down. But what gives rise to this conviction in us? Real connections between things or our belief in this reality?

Philosopher David Hume showed that our belief in causal relationships between things is nothing more than a belief that is generated by our previous experience.

We are convinced that the evening will follow the day, only because always until this moment the evening followed the day. We cannot be absolutely certain.

Imagine two billiard balls. One hits the other, and we believe that the first ball is the cause of the movement of the second. However, we can imagine that the second ball will remain in place after colliding with the first. Nothing prevents us from doing this. This means that the movement of the second ball does not logically follow from the movement of the first ball, and the cause-and-effect relationship is based solely on our previous experience (previously we pushed the balls many times and saw the result).

Donor lottery

Philosopher John Harris proposed to imagine a world that differs from ours in two ways. First, it considers that letting a person die is the same as killing him. Secondly, organ transplant operations in it are always performed successfully. What follows from this? In such a society, donation will become an ethical norm, because one donor can save many people. Then a lottery is held in it, which randomly determines the person who will have to sacrifice himself in order to prevent several sick people from dying.

One death instead of many - from the point of view of logic, this is a justified sacrifice. However, in our world it sounds blasphemous. The experiment helps to understand that our ethics is not built on a rational basis.

Philosophical zombie

Philosopher David Chalmers in 1996 in one of his reports puzzled the world with the concept of "philosophical zombie". This is an imaginary being that is identical to a person in everything. It gets up in the morning to the sound of an alarm clock, goes to work, smiles at friends. His stomach, heart, brain work in the same way as in humans. But at the same time, he does not have one component - the internal experiences of what is happening. Falling and injuring his knee, the zombie will scream like a human, but he will not feel pain. It has no consciousness. The zombie acts like a computer.

If human consciousness is the result of biochemical reactions in the brain, then how will a person differ from such a zombie? If a zombie and a human are physically the same, then what is consciousness? In other words, is there something in a person that is not conditioned by material interactions?

Brain in a flask

This experiment was proposed by the philosopher Hilary Putnam.

Our perception is arranged as follows: the sense organs perceive data from the outside and convert it into an electrical signal that is sent to the brain and decoded by it. Imagine the following situation: we take the brain, place it in a special life-sustaining solution, and send electrical signals through electrodes in exactly the same way as the sense organs would do.

What would such a brain experience? The same thing as the brain in the cranium: it would seem to him that he is a person, he would “see” and “hear” something, would think about something.

The experiment shows that we do not have sufficient grounds to assert that our experience is the ultimate reality.

It is quite possible that we are all in a flask, and around us is something like a virtual space.

Chinese room

How is a computer different from a person? Is it possible to imagine a future in which machines replace people in all areas of activity? A thought experiment by philosopher John Searle makes it clear that it is not.

Imagine a person locked in a room. He does not know the Chinese language. There is a slot in the room through which a person receives questions written in Chinese. He cannot answer them himself, he cannot even read them. However, there are instructions in the room for converting one character to another. That is, it says that if you see such and such a combination of hieroglyphs on paper, then you should answer with such and such a hieroglyph.

Thus, thanks to the instructions for converting characters, a person will be able to answer questions in Chinese without understanding either the meaning of the questions or their own answers. This is the principle of artificial intelligence.

Curtain of ignorance

Philosopher John Rawls proposed to imagine a group of people who have to create a kind of society: laws, government structures, social order. These people have neither citizenship, nor gender, nor any experience - that is, when designing a society, they cannot proceed from their own interests. They do not know what role will fall to everyone in the new society. What kind of society will they build as a result, from what theoretical premises will they proceed?

It is unlikely that they would have turned out to be at least one of the societies that exist today. The experiment shows that all social organizations in practice act in one way or another in the interests of certain groups of people.