It will be strange for you to hear that there are quite a few living creatures for which the imaginary “lifting of oneself by the hair” is their usual way of moving in water.
Figure 10. Swimming movement of cuttlefish.
Cuttlefish and, in general, most cephalopods move in water in this way: they take water into the gill cavity through a side slit and a special funnel in front of the body, and then energetically throw out a stream of water through the said funnel; at the same time, according to the law of reaction, they receive a reverse push sufficient to swim quite quickly with the back side of the body forward. The cuttlefish can, however, direct the funnel tube sideways or backwards and, rapidly squeezing water out of it, move in any direction.
The movement of the jellyfish is based on the same thing: by contracting its muscles, it pushes water out from under its bell-shaped body, receiving a push in the opposite direction. A similar technique is used when moving by salps, dragonfly larvae and other aquatic animals. And we still doubted whether it was possible to move like that!
To the stars on a rocket
What could be more tempting than leaving the globe and traveling across the vast universe, flying from Earth to the Moon, from planet to planet? How many science fiction novels have been written on this topic! Who hasn’t taken us on an imaginary journey through the heavenly bodies! Voltaire in Micromegas, Jules Verne in A Trip to the Moon and Hector Servadac, Wells in The First Men on the Moon and many of their imitators made the most interesting journeys to the heavenly bodies - of course, in their dreams.
Is there really no way to make this long-standing dream come true? Are all the ingenious projects depicted with such tempting verisimilitude in novels really impossible? In the future we will talk more about fantastic projects of interplanetary travel; Now let’s get acquainted with the real project of such flights, first proposed by our compatriot K. E. Tsiolkovsky.
Is it possible to fly to the moon by plane? Of course not: airplanes and airships move only because they rely on the air, are pushed away from it, and there is no air between the Earth and the Moon. In global space, there is generally no sufficiently dense medium on which an “interplanetary airship” could rely. This means that we need to come up with a device that would be able to move and be controlled without relying on anything.
We are already familiar with a similar projectile in the form of a toy - a rocket. Why not build a huge rocket, with a special room for people, food supplies, air tanks and everything else? Imagine that people in a rocket are carrying with them a large supply of flammable substances; they can direct the outflow of explosive gases in any direction. You will receive a real controllable celestial ship on which you can sail in the ocean of cosmic space, fly to the Moon, to the planets... Passengers will be able, by controlling explosions, to increase the speed of this interplanetary airship with the necessary gradualness so that the increase in speed is harmless to them. If they want to descend to some planet, they can, by turning their ship, gradually reduce the speed of the projectile and thereby weaken the fall. Finally, passengers will be able to return to Earth in the same way.
Figure 11. Project of an interplanetary airship, designed like a rocket.
Let us remember how recently aviation made its first timid gains. And now the planes are already flying high in the air, flying over mountains, deserts, continents, and oceans. Maybe “astronavigation” will have the same magnificent blossoming in two or three decades? Then man will break the invisible chains that have chained him to his native planet for so long and rush into the boundless expanse of the universe.
It will be strange for you to hear that there are quite a few living creatures for which the imaginary “lifting of oneself by the hair” is their usual way of moving in water.
Figure 10. Swimming movement of cuttlefish.
Cuttlefish and, in general, most cephalopods move in water in this way: they take water into the gill cavity through a side slit and a special funnel in front of the body, and then energetically throw out a stream of water through the said funnel; at the same time, according to the law of reaction, they receive a reverse push sufficient to swim quite quickly with the back side of the body forward. The cuttlefish can, however, direct the funnel tube sideways or backwards and, rapidly squeezing water out of it, move in any direction.
The movement of the jellyfish is based on the same thing: by contracting its muscles, it pushes water out from under its bell-shaped body, receiving a push in the opposite direction. A similar technique is used when moving by salps, dragonfly larvae and other aquatic animals. And we still doubted whether it was possible to move like that!
To the stars on a rocket
What could be more tempting than leaving the globe and traveling across the vast universe, flying from Earth to the Moon, from planet to planet? How many science fiction novels have been written on this topic! Who hasn’t taken us on an imaginary journey through the heavenly bodies! Voltaire in Micromegas, Jules Verne in A Trip to the Moon and Hector Servadac, Wells in The First Men on the Moon and many of their imitators made the most interesting journeys to the heavenly bodies - of course, in their dreams.
Is there really no way to make this long-standing dream come true? Are all the ingenious projects depicted with such tempting verisimilitude in novels really impossible? In the future we will talk more about fantastic projects of interplanetary travel; Now let’s get acquainted with the real project of such flights, first proposed by our compatriot K. E. Tsiolkovsky.
Is it possible to fly to the moon by plane? Of course not: airplanes and airships move only because they rely on the air, are pushed away from it, and there is no air between the Earth and the Moon. In global space, there is generally no sufficiently dense medium on which an “interplanetary airship” could rely. This means that we need to come up with a device that would be able to move and be controlled without relying on anything.
We are already familiar with a similar projectile in the form of a toy - a rocket. Why not build a huge rocket, with a special room for people, food supplies, air tanks and everything else? Imagine that people in a rocket are carrying with them a large supply of flammable substances; they can direct the outflow of explosive gases in any direction. You will receive a real controllable celestial ship on which you can sail in the ocean of cosmic space, fly to the Moon, to the planets... Passengers will be able, by controlling explosions, to increase the speed of this interplanetary airship with the necessary gradualness so that the increase in speed is harmless to them. If they want to descend to some planet, they can, by turning their ship, gradually reduce the speed of the projectile and thereby weaken the fall. Finally, passengers will be able to return to Earth in the same way.
Figure 11. Project of an interplanetary airship, designed like a rocket.
Let us remember how recently aviation made its first timid gains. And now the planes are already flying high in the air, flying over mountains, deserts, continents, and oceans. Maybe “astronavigation” will have the same magnificent blossoming in two or three decades? Then man will break the invisible chains that have chained him to his native planet for so long and rush into the boundless expanse of the universe.
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From the editor
The proposed edition of “Entertaining Physics” basically repeats the previous ones. Ya. I. Perelman worked on the book for many years, improving the text and supplementing it, and finally
Cheapest way to travel
The witty French writer of the 17th century, Cyrano de Bergerac, in his satirical “History of the States on the Moon” (1652), talks, among other things, about what allegedly happened to
Letter from an airplane
Imagine that you are in an airplane flying quickly over the ground. Below are familiar places. Now you will fly over the house where your friend lives. “It would be nice to send him a greeting
Bombing
After what has been said, it becomes clear how difficult the task of a military pilot who is tasked with dropping a bomb on a certain place is: he has to take into account the speed of the aircraft,
Non-stop railway
When you are standing on a stationary station platform and a courier train rushes past it, jumping into the carriage while it is moving is, of course, tricky. But imagine that the platform is below you
Moving sidewalks
Another device, hitherto used only at exhibitions, is based on the principle of the relativity of motion: the so-called “moving sidewalks.” For the first time they were carried out
Difficult Law
None of the three fundamental laws of mechanics probably causes as much confusion as the famous “Newton's third law” - the law of action and reaction. Everyone knows him, they can
Why did Svyatogor the hero die?
Do you remember the folk epic about Svyatogor the hero, who decided to raise the Earth? Archimedes, according to legend, was also ready to accomplish the same feat and demanded a fulcrum for
Is it possible to move without support?
When walking, we push off with our feet from the ground or floor; You cannot walk on a very smooth floor or on ice from which your foot cannot push off. The locomotive pushes away when moving
Why does a rocket take off?
Even among people who have studied physics, it often happens to hear a completely wrong explanation for the flight of a rocket: it flies because its gases formed during combustion
The swan, crayfish and pike problem
The story of how “a swan, a crayfish and a pike began to carry a load of luggage” is known to everyone. But hardly anyone tried to consider this fable from a mechanical point of view. The result is obtained in
Contrary to Krylov
We have just seen that Krylov’s everyday rule: “when there is no agreement among the comrades, things will not go well for them” is not always applicable in mechanics. Forces can be directed in more than one direction
Is it easy to break eggshells?
Among the philosophical questions over which the thoughtful Kifa Mokievich from “Dead Souls” racked his wise head was the following problem: “Well, what if an elephant was born in an egg, because
Sailing against the wind
It is difficult to imagine how sailing ships can go “against the wind” - or, as sailors say, go “close-hauled”. True, a sailor will tell you that sailing directly against the wind
Could Archimedes lift the Earth?
“Give me a foothold and I will lift the Earth!” – this exclamation is attributed by legend to Archimedes, the brilliant mechanic of antiquity who discovered the laws of the lever.
Jules Vernov's strongman and Euler's formula
Do you remember Jules Verne’s strongman-athlete Matifa? “Magnificent head, proportional to gigantic height; chest like a blacksmith's bellows; legs are like good logs, arms are like us
What determines the strength of the knots?
In everyday life, without even knowing it, we often take advantage of the benefits that Euler’s formula indicates to us. What is a knot if not a string wound around a roller, whose role in this
If there was no friction
You see how friction manifests itself in various and sometimes unexpected ways in the environment around us. Friction takes part, and a very significant one at that, where we don’t even think about it.
Self-balancing stick
Place a smooth stick on the index fingers of your outstretched hands, as shown in Fig. 24. Now move your fingers towards each other until they come together tightly. Strange thing! Oka
Why doesn't the spinning top fall?
Of the thousands of people who played with a top as children, not many will be able to answer this question correctly. How, in fact, can one explain the fact that a spinning top placed vertically
The art of jugglers
Many amazing tricks of the varied juggling program are also based on the property of rotating bodies to maintain the direction of the axis of rotation. Let me quote an excerpt from the fascinating
New solution to the Columbus problem
Columbus solved his famous problem of how to place an egg too simply: he broke its shell. This decision is, in essence, incorrect: having broken the egg shell, Columbus changed
Destroyed" gravity
“Water does not pour out from a vessel that rotates, nor does it pour out even when the vessel is turned upside down, because rotation interferes with this,” wrote Aristotle two thousand years ago.
You as Galileo
For lovers of strong sensations, sometimes a very peculiar entertainment is arranged - the so-called “devil's swing”. There was such a swing in Leningrad. I didn't have to
My argument is with you
It will not be as easy for you to prove that you are right as you may think. Imagine that you actually find yourself on a “damn swing” and want to convince your neighbors that they are
The end of our argument
Now let me advise you on how to win this argument. You need to take spring scales with you to the “damn swing”, put a weight, for example 1 kg, on its cup, and watch
In the "enchanted" ball
One entrepreneur in America arranged for the entertainment of the public a very funny and instructive carousel in the form of a spherical rotating room. The people inside her experience such a need
Liquid telescope
The best shape for the mirror of a reflecting telescope is parabolic, i.e. exactly the shape that the surface of a liquid in a rotating vessel naturally takes. Body constructors
Mathematics in the circus
I know that rows of “soulless” formulas scare off some physics lovers. But by refusing to get acquainted with the mathematical side of phenomena, such enemies of mathematics deprive themselves of the pleasure
Lack of weight
Some joker once announced that he knew a way to overweight customers without deception. The secret is to buy goods in equatorial countries and sell them closer
Is the force of gravity strong?
“If we had not observed the fall of bodies every minute, it would have been the most amazing phenomenon for us,” wrote the famous French astronomer Arago. Habit does what attraction does
Steel rope from the Earth to the Sun
Imagine that the powerful attraction of the Sun for some reason actually disappeared and the Earth faces the sad fate of forever retiring into the cold and dark deserts of the universe.
Is it possible to escape gravity?
Now we were fantasizing about what would happen if the mutual attraction between the Sun and the Earth disappeared: freed from the invisible chains of gravity, the Earth would rush off into the endless
How Wells' heroes flew to the moon
The novelist interestingly describes the very moment the interplanetary carriage sets off. A thin layer of “kevorite” covering the outer surface of the projectile makes it seem completely invisible.
Half an hour on the moon
Let's see how the heroes of Wells' story felt when they found themselves in a world where the force of gravity is weaker, less than on Earth. These are the curious pages of the novel “The First People of
Shooting on the Moon
The following episode, taken from the story “On the Moon” by the outstanding Soviet inventor K. E. Tsiolkovsky, will help us understand the conditions of movement under the influence of gravity. Atmos on Earth
In a bottomless well
Very little is known yet about what is happening in the deep interior of our planet. Some believe that under the solid crust, hundreds of kilometers thick, a fiery liquid mass begins;
Fairytale road
At one time, a brochure with a strange title appeared in St. Petersburg: “The scooter underground railway between St. Petersburg and Moscow. Fantasy novel still in t
How are tunnels dug?
Take a look at fig. 47, showing three methods of tunneling, and tell me which one is dug horizontally?
Journey in a Cannonball
At the end of our conversations about the laws of motion and the force of gravity, we will analyze
Newton's mountain
Let's give the floor to the brilliant Newton, who discovered the law of universal gravitation. In his “Mathematical principles of physics” he writes (we present this place for the sake of easier understanding in free
Fantastic gun
And so the members of the Cannon Club cast a giant cannon, a quarter of a kilometer long, vertically dug into the ground. A huge projectile is made accordingly, which inside represents
Heavy hat
The most dangerous moment for our travelers would be those few hundredths of a second during which the cabin-projectile moves in the cannon channel. After all, during this
How to relieve shaking?
The mechanics give an indication of how the fatal rapidity of the increase in speed could be weakened. This can be achieved by lengthening the gun barrel many times. Udley
For math friends
Among the readers of this book, there will no doubt be those who would like to check the calculations mentioned above for themselves. We present these calculations here. They are only approximately correct.
The sea you can't drown in
Such a sea exists in a country known to mankind since ancient times. This is the famous Dead Sea of Palestine. Its waters are unusually salty, so much so that it cannot live in them.
How does an icebreaker work?
While taking a bath, do not miss the opportunity to do the following experiment. Before leaving the bathtub, open the bathtub outlet while still lying on the bottom of the bathtub. As it becomes more prominent
Where are the sunken ships?
It is a common belief, even among sailors, that ships sunk in the ocean do not reach the seabed, but hang motionless at some depth, where the water is “appropriately compacted.”
How the dreams of Jules Verne and Wells came true
Real submarines of our time have in some respects not only caught up with the fantastic Nautilus of Jules Werp, but even surpassed it. True, the speed of current submarines
How was Sadko raised?
In the vast expanse of the ocean, thousands of large and small ships perish every year, especially in wartime. The most valuable and accessible of the sunken ships began to be recovered from the bottom of the sea. Co
Eternal" water engine
Among the many “perpetual motion” projects, there were many that were based on the floating of bodies in water. A high tower 20 m high is filled with water. At the top and bottom of the tower
Who coined the words "gas" and "atmosphere"?
The word "gas" is one of the words coined by scientists, along with such words as "thermometer", "electricity", "galvanometer", "telephone" and, above all, "atmosphere". Of all the
Seems like a simple task
The samovar, which holds 30 glasses, is full of water. You place the glass under its tap and, with a watch in your hands, watch the second hand to see how long it takes for the glass to fill to the brim. Dopu
Pool problem
From what has been said, it is one step to the notorious pool problems, without which not a single arithmetic and algebraic problem book can do. Everyone remembers the classically boring, scholastic
Amazing vessel
Is it possible to construct a vessel from which water would flow out in a uniform stream all the time, without slowing down its flow, despite the fact that the liquid level decreases? After that,
Luggage from thin air
In the middle of the 17th century, residents of the city of Rogensburg and the sovereign princes of Germany, led by the emperor, who gathered there, witnessed an amazing sight: 16 horses at full speed.
New experiences
Chapter XXIII of this book is devoted to the experience that interests us. We give its literal translation. “An experiment proving that air pressure connects the two hemispheres so firmly that they cannot be separated
New Heron fountains
The usual form of the fountain attributed to the ancient mechanician Heron is probably known to my readers. Let me remind you here of its structure before proceeding to a description of the latest modifications
Deceptive Vessels
In the old days - in the 17th and 18th centuries - nobles amused themselves with the following instructive toy: they made a mug (or jug), in the upper part of which there were large patterned cutouts (p
How much does water weigh in an overturned glass?
“Of course, it doesn’t weigh anything: the water doesn’t hold in such a glass, it spills out,” you say. – What if it doesn’t pour out? – I’ll ask. – What then? In fact, it is possible
Why are ships attracted?
In the fall of 1912, the following incident occurred with the ocean-going steamer Olympic, then one of the greatest ships in the world. "Olympic" sailed in the open sea, and almost parallel to it, on the race
Bernoulli's principle and its consequences
The principle, first stated by Daniel Bernoulli in 1726, states that in a stream of water or air, the pressure is high if the speed is low, and the pressure is low if the speed is high. There are known
Purpose of the fish bladder
The following is usually said and written about the role played by the swim bladder of fish - it would seem quite plausible. In order to emerge from the depths to the surface from
Waves and vortices
Many of the everyday physical phenomena cannot be explained based on the elementary laws of physics. Even such a frequently observed phenomenon as rough seas on a windy day is not
Journey into the bowels of the Earth
Not a single person has ever descended deeper into the Earth than 3.3 km - and yet the radius of the globe is 6400 km. There is still a very long way to go to the center of the Earth. Still inventive
Fantasy and mathematics
This is how the novelist narrates; but this will turn out to be the case if we check the facts mentioned in this passage. We will not have to go down into the bowels of the Earth for this; for a small excursion to
In a deep mine
Who has moved closest to the center of the Earth - not in the fantasy of a novelist, but in reality? Of course, miners. We already know (see Chapter IV) that the deepest mine in the world is about
High with stratospheric balloons
In previous articles, we mentally traveled into the bowels of the earth, and the formula for the dependence of air pressure on depth helped us. Let us now dare to rise up and, using that
Why is it colder when there is wind?
Everyone knows, of course, that in calm weather frost is much easier to bear than in windy weather. But not everyone clearly understands the reason for this phenomenon. Greater cold is felt when there is wind
Hot breath of the desert
“This means that the wind should bring coolness even on a hot day,” the reader may say after reading the previous article. - Why, then, do travelers talk about hot breath?
Is the veil warm?
Here is another problem from the physics of everyday life. Women claim that the veil provides warmth and that without it, the face feels cold. When looking at the light fabric of the veil, often with rather large cells, men
Cooling jugs
If you have never seen such jugs, then you have probably heard or read about them. These vessels made of unfired clay have the curious feature that the water poured into them
Glacier without ice
The design of a cooling cabinet for storing food, a kind of “glacier” without ice, is based on evaporative cooling. The design of such a cooler is quite simple: it is a box made of
How much heat can we tolerate?
Man is much more tolerant of heat than is usually thought: he is able to withstand temperatures in southern countries that are noticeably higher than what we in the temperate zone consider barely
Thermometer or barometer?
There is a well-known joke about a naive man who did not dare to take a bath for the following unusual reason:
What is lamp glass used for?
Few people know how long lamp glass has come before reaching its modern form. For a long series of millennia, people have used flames for lighting, not
Why doesn't the flame go out on its own?
If you think carefully about the combustion process, the question involuntarily arises: why doesn’t the flame go out by itself? After all, combustion products are carbon dioxide and water vapor - substances
Breakfast in a weightless kitchen
“My friends, we haven’t had breakfast yet,” Michel Ardant announced to his companions on the interplanetary journey. - From the fact that we lost our weight in a cannon shell, it does not follow at all
Why does water extinguish fire?
They don’t always know how to answer such a simple question correctly, and the reader, we hope, will not complain about us if we briefly explain what this effect of water on water actually consists of.
How do you extinguish fire with fire?
You have probably heard that the best, and sometimes the only, means of fighting a forest or steppe fire is to set fire to the forest or steppe from the opposite side. A new flame is coming
Is it possible to boil water with boiling water?
Take a small bottle (jar or vial), pour water into it and place it in a pan with clean water standing on the fire so that the bottle does not touch the bottom of your pan; to you in
Can you boil water with snow?
“If boiling water is unsuitable for this purpose, then what can we say about snow!” - another reader will answer. Don’t rush to answer, but rather do the experiment with at least the same glass bottle,
Is boiling water always hot?
The gallant orderly Ben-Zouf, whom the reader, no doubt, met through Jules Verne’s novel Hector Servadac, was firmly convinced that boiling water is always and everywhere equally hot.
Hot Ice
Now we were talking about cool boiling water. There is an even more amazing thing: hot ice. We are accustomed to thinking that water in a solid state cannot exist at temperatures above 0°
Cold from coal
Producing not heat from coal, but, on the contrary, cold is not something unrealistic: it is carried out every day in so-called “dry ice” factories. Coal is burned here in
Magnetism. Electricity
"Loving Stone"
Compass problem
We are accustomed to thinking that the compass needle always faces one end to the north and the other to the south. Therefore, the following question will seem completely absurd to us: where on the globe is magnesium
Lines of magnetic forces
A curious picture is depicted in Fig. 91, reproduced from a photograph: from a hand placed on the poles of an electromagnet, bunches of “large nails stick out upward, like coarse hair. Herself
How is steel magnetized?
To answer this question, which is often asked by readers, it is necessary to explain, first of all, how a magnet differs from a non-magnetic bar of steel. Each atom of iron contained in
Gigantic electromagnets
In metallurgical plants you can see electromagnetic lifting cranes carrying huge loads. Such cranes provide invaluable services when lifting and moving iron masses.
Magnetic tricks
Magicians sometimes use the power of electromagnets; It’s easy to imagine what spectacular tricks they perform with the help of this invisible force. Dari, author of the famous book “Electricity”
Magnet in agriculture
Even more curious is the useful service that a magnet provides in agriculture, helping the farmer to clear the seeds of cultivated plants from weed seeds. Weeds have fleecy
Magnetic flying machine
At the beginning of this book, I referred to the entertaining essay of the French writer Cyrano de Bergerac, “History of the States on the Moon and the Sun.” It, by the way, describes a curious le
Electromagnetic transport
In the railway, which was proposed to be organized by prof. B.P. Weinberg, the cars will be completely weightless; their weight is destroyed by electromagnetic attraction. You won't be surprised, therefore, if
The battle of the Martians with the earth multipliers
The naturalist of ancient Rome, Pliny, conveys a story that was widespread in his time about a magnetic rock somewhere in India, near the seashore, which attracted with extraordinary force
Clocks and magnetism
When reading the previous passage, the question naturally arises: is it possible to protect yourself from the action of magnetic forces, to hide from them behind some barrier impenetrable to them?
Magnetic "perpetual" motion machine
In the history of attempts to invent a “perpetual” motion machine, the magnet played an important role. Unsuccessful inventors tried in different ways to use a magnet to create a mechanism,
Museum task
In the practice of museum work, the need often arises to read ancient scrolls that are so dilapidated that they break and tear with the most careful attempt to separate one layer of the manuscript from
Another imaginary perpetual motion machine
Recently, the idea of connecting a dynamo with an electric motor has gained great popularity among seekers of perpetual motion. Every year I receive almost half a dozen of these
Almost perpetual motion machine
For a mathematician, the expression “almost eternal” does not present anything tempting. Motion can be either eternal or non-eternal; “almost eternal” means, in essence, non-eternal. But
Birds on wires
Everyone knows how dangerous it is for a person to touch the electrical wires of a tram or high-voltage network when they are live. Such a touch is fatal to humans and
By the light of lightning
Have you ever seen a busy city street during a thunderstorm with brief flashes of lightning? You, of course, noticed one strange feature: the street, just
How much does lightning cost?
In that distant era, when lightning was attributed to the “gods,” such a question would have sounded blasphemous. But these days, when electrical energy has become a commodity that is measured and
Thunderstorm shower in the room
It is very easy to make a small fountain at home from a rubber tube, one end of which is immersed in a bucket placed on a raised surface, or placed on a water tap. Output hole
Five times shot
One of the curiosities of photographic art are photographs in which the photographed person is depicted in five different rotations. In Fig. 105, made from a similar photograph, can be
Solar Motors and Heaters
The idea of using the energy of the sun's rays to heat the engine boiler is very tempting. Let's do a simple calculation. The energy received every minute from the Sun by each square
Dream of an invisibility hat
Hoary antiquity has left us a legend about a wonderful hat that makes everyone who puts it on invisible. Pushkin, who revived the legends of deep antiquity in “Ruslan and Lyudmila,” gave a cla
Invisible Man
In the novel The Invisible Man, the English writer Wells seeks to convince his readers that the possibility of becoming invisible is quite feasible. His hero (the author of the novel presented
The Power of the Unseen
The author of the novel “The Invisible Man” with extraordinary wit and consistency proves that a person, having become transparent and invisible, thereby acquires
Transparent drugs
Are the physical arguments that form the basis of this science fiction novel correct? Undoubtedly. Any transparent object in a transparent medium becomes invisible even when
Can the invisible see?
If Wells had asked himself this question before writing the novel, the amazing story of The Invisible Woman would never have been written... Indeed, at this point the whole and
Protective coloring
But there is another way to solve the “invisibility cap” problem. It consists of painting objects with an appropriate color, making them invisible to the eye. I constantly resort to him
Protective color
People have adopted from inventive nature this useful art of making their body invisible, blending into the surrounding background. The motley colors of the brilliant uniforms of former times, etc.
Human eye underwater
Imagine that you are given the opportunity to remain under water for as long as you like and that you keep your eyes open. Could you see there? It would seem that since the water is clear
How do divers see?
Many will probably ask: how can divers working in their spacesuits see anything under water if our eyes in water almost do not refract light rays? After all, the diver
Glass lentils underwater
Have you tried this simple experiment: immerse a biconvex (“magnifying”) glass in water and examine the immersed objects through it? Try it, you will be amazed
Inexperienced bathers
Inexperienced bathers are often exposed to great danger only because they forget about one curious consequence of the law of refraction of light: they do not know that refraction is like
Invisible pin
Stick a pin into a flat cork circle and place it pin side down on the surface of the water in the bowl. If the cork is not too wide, then no matter how you tilt your head, you will not be able to
The world from under water
Many people do not even suspect how extraordinary the world would seem if we began to look at it from under water: it must appear to the observer changed and distorted almost literally.
Colors in the deep waters
American biologist Bieb vividly describes the change in light shades under water. “We plunged into the water in the bathysphere, and the sudden transition from the golden-yellow world to the green
The blind spot of our eye
If they tell you that there is an area in your field of vision that you cannot see at all, although it is right in front of you, you, of course, will not believe it. Is it possible that we
How big does the Moon appear to us?
By the way, about the apparent size of the Moon. If you ask your friends what size the Moon seems to them, you will get a wide variety of answers. Most would say that the Moon
Apparent sizes of luminaries
If, while maintaining the angular dimensions, we wanted to depict the constellation Ursa Major on paper, we would get the figure shown in Fig. 126. Looking at her from a better distance
Why does a microscope magnify?
“Because it changes the path of rays in a certain way, described in physics textbooks,” is what you most often hear in response to this question. But this answer states
Visual self-deceptions
We often talk about “optical deception”, “hearing deception”, but these expressions are incorrect. There are no deceptions of feelings. The philosopher Kant aptly said about this: “Feelings do not deceive us, not according to
Illusion useful for tailors
If you want to apply the visual illusion just described to larger figures that cannot be immediately captured by the eye, then your expectations will not be justified. Everybody knows,
That more?
Which ellipse in Fig. 131 is larger: the lower one or the inner upper one? It's hard to get rid of the thought that the bottom one is larger than the top one. Meanwhile, both are equal, and only the presence of the outer, bordering
The power of imagination
Most optical illusions, as already indicated, depend on the fact that we not only look, but also unconsciously reason. “We look not with our eyes, but with our brains,” say physicists
Another visual illusion
We are not able to explain all visual illusions. Often it is impossible to guess what kind of conclusions are made unconsciously in our brain and determine this or that visual deception
What is this?
When looking at Fig. 142 you can hardly immediately guess what it depicts, “Just a black mesh, nothing more,” you say. But place the book vertically on the table, step back 3 steps -
Extraordinary wheels
Have you ever watched the spokes of the wheels of a fast-moving cart or car through the cracks of a fence or, better yet, on a movie screen? You probably noticed a strange phenomenon;
Microscope of time" in technology
The first book of Entertaining Physics describes a “time magnifying glass” based on the use of a movie camera. Here we will talk about another way to achieve a similar effect, based on
Nipkow disk
A remarkable technical application of optical illusion was the so-called “Nipkow disk,” which was used in the first television installations. In Fig. 146 you see a solid circle,
Why is the hare sideways?
Man is one of the few creatures whose eyes are adapted to simultaneously viewing some object: the field of vision of the right eye only slightly differs from the right eye.
Why are all cats gray in the dark?
A physicist would say: “in the dark all cats are black,” because in the absence of lighting no objects are visible at all. But the saying does not mean complete darkness, but darkness in everyday life.
Sound and radio waves
Sound travels about a million times slower than light; and since the speed of radio waves coincides with the speed of propagation of light vibrations, sound is a million times slower
Sound and bullet
When the passengers of the Jules Verne projectile flew to the moon, they were puzzled by the fact that they did not hear the sound of the colossal cannon firing from its mouth. It could be otherwise
Imaginary explosion
The competition in speed between a flying body and the sound it produces sometimes forces us to unwittingly make erroneous conclusions, sometimes completely inconsistent with the true picture of the phenomenon.
Slowest conversation
If you think, however, that the true speed of sound in air - a third of a kilometer per second - is always fast enough, then change your mind now. Imagine what me
The fastest way
There was, however, a time when even this method of transmitting news would have been considered very fast. A hundred years ago no one dreamed of an electric telegraph and telephone, and the transmission of news
Drum telegraph
The transmission of news through sound signals is still common among the primitive inhabitants of Africa, Central America and Polynesia. Primitive tribes use it for this
Sound clouds and air echoes
Sound can be reflected not only from solid obstacles, but also from such delicate formations as clouds. Moreover, even completely transparent air can, under certain conditions, reflect
Silent sounds
There are people who do not hear such sharp sounds as the singing of a cricket or the squeak of a bat. These people are not deaf; – their hearing organs are in good working order, and yet they do not hear very high pitches
Ultrasounds at the service of technology
The physics and technology of our days have the means to create “silent sounds” of a much higher frequency than those that we have just talked about: the number of vibrations can reach in these “sounds”
Voices of Lilliputians and Gulliver
In the Soviet film “The New Gulliver,” the Lilliputians speak in high voices, corresponding to the small size of their larynx, and the giant, Petya, speaks in a low voice. During the shooting they spoke for lil
For whom is the daily newspaper published twice a day?
Now we will tackle a task that, at first glance, has nothing to do with sound or physics. Nevertheless, I ask you to pay attention to it: it will help you understand more easily.
Locomotive whistle problem
If you have a developed ear for music, you have probably noticed how the pitch (not volume, but tone, pitch) of a locomotive whistle changes when an oncoming train rushes past.
Doppler phenomenon
The phenomenon that we have just described was discovered by the physicist Doppler and has forever remained associated with the name of this scientist. It is observed not only for sound, but also for light phenomena
The story of one fine
When Doppler first (in 1842) came to the idea that the mutual approach or distance of the observer and the source of sound or light should be accompanied by a change in the length of the perceived sounds
At the speed of sound
What would you hear if you moved away from a playing orchestra at the speed of sound? A man traveling from Leningrad on a postal train sees newsboys at all stations alone and
Cuttlefish do not move as fast as their squid relatives, although they are armed with a jet funnel. They usually swim using fins, but can also use jet propulsion. The fins can act separately, which gives the cuttlefish amazing maneuverability when moving - it can even move sideways. If the cuttlefish moves only in a reactive manner, then it presses its fins to its belly. Often cuttlefish gather in small schools, moving rhythmically and in concert, while simultaneously changing body color. The spectacle is very mesmerizing.
Slide 15 from the presentation "Cephalopods". The size of the archive with the presentation is 719 KB.Biology 7th grade
summary of other presentations"Bird Facts" - Nervous System. Digestive system. Bird eggs. Bird class. External building. Interesting Facts. A little about birds. Evolution of birds. Variety of birds. Reproductive system. The meaning of birds in nature. Birds in human life. Circulatory system. Excretory system.
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Jet motion in nature and technology is a very common phenomenon. In nature, it occurs when one part of the body separates at a certain speed from some other part. In this case, the reactive force appears without the interaction of this organism with external bodies.
In order to understand what we are talking about, it is best to look at examples. in nature and technology are numerous. We will first talk about how animals use it, and then how it is used in technology.
Jellyfish, dragonfly larvae, plankton and mollusks
Many people, while swimming in the sea, came across jellyfish. In the Black Sea, in any case, there are plenty of them. However, not everyone realized that jellyfish move using jet propulsion. The same method is used by dragonfly larvae, as well as some representatives of marine plankton. The efficiency of invertebrate marine animals that use it is often much higher than that of technical inventions.
Many mollusks move in a way that interests us. Examples include cuttlefish, squid, and octopus. In particular, the scallop clam is able to move forward using a jet of water that is ejected from the shell when its valves are sharply compressed.
And these are just a few examples from the life of the animal world that can be cited to expand on the topic: “Jet propulsion in everyday life, nature and technology.”
How does a cuttlefish move?
The cuttlefish is also very interesting in this regard. Like many cephalopods, it moves in water using the following mechanism. Through a special funnel located in front of the body, as well as through a side slit, the cuttlefish takes water into its gill cavity. Then she vigorously throws it through the funnel. The cuttlefish directs the funnel tube back or to the side. The movement can be carried out in different directions.
The method that the salpa uses
The method that the salpa uses is also curious. This is the name of a sea animal that has a transparent body. When moving, the salpa draws in water using the front opening. The water ends up in a wide cavity, and gills are located diagonally inside it. The hole closes when the salpa takes a large sip of water. Its transverse and longitudinal muscles contract, compressing the entire body of the animal. Water is pushed out through the rear hole. The animal moves forward due to the reaction of the flowing jet.
Squids - "living torpedoes"
The greatest interest is, perhaps, the jet engine that the squid has. This animal is considered the largest representative of invertebrates, living at great ocean depths. In jet navigation, squids have achieved real perfection. Even the body of these animals resembles a rocket in its external shape. Or rather, this rocket copies the squid, since it is the squid that has the undisputed primacy in this matter. If it needs to move slowly, the animal uses a large diamond-shaped fin for this, which bends from time to time. If a quick throw is needed, a jet engine comes to the rescue.
The mollusk's body is surrounded on all sides by a mantle - muscle tissue. Almost half of the total volume of the animal’s body is the volume of its cavity. The squid uses the mantle cavity to move by sucking water inside it. Then he sharply throws out the collected stream of water through a narrow nozzle. As a result of this, it pushes backwards at high speed. At the same time, the squid folds all 10 tentacles into a knot above its head in order to acquire a streamlined shape. The nozzle contains a special valve, and the animal's muscles can turn it. Thus, the direction of movement changes.
Impressive squid speed
It must be said that the squid engine is very economical. The speed it is capable of reaching can reach 60-70 km/h. Some researchers even believe that it can reach up to 150 km/h. As you can see, the squid is not called the “living torpedo” for nothing. It can turn in the desired direction, bending its tentacles folded in a bundle down, up, left or right.
How does a squid control movement?
Since the steering wheel is very large compared to the size of the animal itself, only a slight movement of the steering wheel is sufficient for the squid to easily avoid a collision with an obstacle, even moving at maximum speed. If you turn it sharply, the animal will immediately rush in the opposite direction. The squid bends the end of the funnel back and, as a result, can slide head first. If he bends it to the right, he will be thrown to the left by the jet thrust. However, when it is necessary to swim quickly, the funnel is always located directly between the tentacles. In this case, the animal rushes tail first, like the running of a fast-moving crayfish if it had the agility of a racer.
When there is no need to rush, cuttlefish and squid swim, undulating with their fins. Miniature waves run across them from front to back. Squid and cuttlefish glide gracefully. They only push themselves from time to time with a stream of water that shoots out from under their mantle. The individual shocks that the mollusk receives during the eruption of jets of water are clearly visible at such moments.
Flying squid
Some cephalopods are capable of accelerating up to 55 km/h. It seems that no one has made direct measurements, but we can give such a figure based on the range and speed of flying squids. It turns out that there are such people. The Stenoteuthis squid is the best pilot of all mollusks. English sailors call it a flying squid (flying squid). This animal, the photo of which is presented above, is small in size, about the size of a herring. It chases fish so quickly that it often jumps out of the water, skimming like an arrow over its surface. He also uses this trick when he is in danger from predators - mackerel and tuna. Having developed maximum jet thrust in the water, the squid launches into the air and then flies more than 50 meters above the waves. When it flies, it is so high that frequent flying squids end up on the decks of ships. A height of 4-5 meters is by no means a record for them. Sometimes flying squids fly even higher.
Dr. Rees, a mollusk researcher from Great Britain, in his scientific article described a representative of these animals, whose body length was only 16 cm. However, he was able to fly a fair distance through the air, after which he landed on the bridge of a yacht. And the height of this bridge was almost 7 meters!
There are times when a ship is attacked by many flying squids at once. Trebius Niger, an ancient writer, once told a sad story about a ship that seemed unable to withstand the weight of these sea animals and sank. Interestingly, squids are able to take off even without acceleration.
Flying octopuses
Octopuses also have the ability to fly. Jean Verani, a French naturalist, watched one of them speed up in his aquarium and then suddenly jump out of the water. The animal described an arc of about 5 meters in the air and then plopped down into the aquarium. The octopus, gaining the speed necessary for the jump, moved not only thanks to jet thrust. It also paddled with its tentacles. Octopuses are baggy, so they swim worse than squids, but at critical moments these animals can give a head start to the best sprinters. California Aquarium workers wanted to take a photo of an octopus attacking a crab. However, the octopus, rushing at its prey, developed such a speed that the photographs, even when using a special mode, turned out to be blurred. This means that the throw lasted only a fraction of a second!
However, octopuses usually swim quite slowly. Scientist Joseph Seinl, who studied the migrations of octopuses, found that the octopus, whose size is 0.5 m, swims at an average speed of about 15 km/h. Each jet of water that he throws out of the funnel moves him forward (more precisely, backward, since he swims backwards) by about 2-2.5 m.
"Squirting cucumber"
Reactive movement in nature and technology can be considered using examples from the plant world to illustrate it. One of the most famous is the ripened fruits of the so-called They bounce off the stalk at the slightest touch. Then, from the resulting hole, a special sticky liquid containing the seeds is ejected with great force. The cucumber itself flies in the opposite direction at a distance of up to 12 m.
Law of conservation of momentum
You should definitely talk about it when considering jet motion in nature and technology. Knowledge allows us to change, in particular, our own speed of movement if we are in open space. For example, you are sitting in a boat and you have several stones with you. If you throw them in a certain direction, the boat will move in the opposite direction. This law also applies in outer space. However, for this purpose they use
What other examples of jet propulsion can be noted in nature and technology? The law of conservation of momentum is illustrated very well using the example of a gun.
As you know, a shot from it is always accompanied by recoil. Let's say the weight of the bullet was equal to the weight of the gun. In this case, they would fly apart at the same speed. Recoil occurs because a reactive force is created, since there is a thrown mass. Thanks to this force, movement is ensured both in airless space and in the air. The greater the speed and mass of the flowing gases, the greater the recoil force that our shoulder feels. Accordingly, the stronger the reaction of the gun, the higher the reaction force.
Dreams of flying into space
Jet propulsion in nature and technology has been a source of new ideas for scientists for many years. For many centuries, humanity has dreamed of flying into space. The use of jet propulsion in nature and technology, it must be assumed, has by no means exhausted itself.
And it all started with a dream. Science fiction writers several centuries ago offered us various means of how to achieve this desired goal. In the 17th century, Cyrano de Bergerac, a French writer, created a story about a flight to the moon. His hero reached the Earth's satellite using an iron cart. He constantly threw a strong magnet over this structure. The cart, being attracted to him, rose higher and higher above the Earth. Eventually she reached the moon. Another famous character, Baron Munchausen, climbed to the moon using a bean stalk.
Of course, at that time little was known about how the use of jet propulsion in nature and technology could make life easier. But the flight of fancy certainly opened up new horizons.
On the way to an outstanding discovery
In China at the end of the 1st millennium AD. e. invented jet propulsion to power rockets. The latter were simply bamboo tubes that were filled with gunpowder. These rockets were launched for fun. The jet engine was used in one of the first automobile designs. This idea belonged to Newton.
N.I. also thought about how jet motion arises in nature and technology. Kibalchich. This is a Russian revolutionary, the author of the first project of a jet aircraft, which is intended for human flight. The revolutionary, unfortunately, was executed on April 3, 1881. Kibalchich was accused of participating in the assassination attempt on Alexander II. Already in prison, while awaiting execution of the death sentence, he continued to study such an interesting phenomenon as jet motion in nature and technology, which occurs when part of an object is separated. As a result of these researches, he developed his project. Kibalchich wrote that this idea supports him in his position. He is ready to calmly face his death, knowing that such an important discovery will not die with him.
Implementation of the idea of space flight
The manifestation of jet propulsion in nature and technology continued to be studied by K. E. Tsiolkovsky (his photo is presented above). At the beginning of the 20th century, this great Russian scientist proposed the idea of using rockets for space flights. His article on this issue appeared in 1903. It presented a mathematical equation that became the most important for astronautics. It is known in our time as the “Tsiolkovsky formula”. This equation described the motion of a body having variable mass. In his further works, he presented a diagram of a rocket engine running on liquid fuel. Tsiolkovsky, studying the use of jet propulsion in nature and technology, developed a multi-stage rocket design. He also came up with the idea of the possibility of creating entire space cities in low-Earth orbit. These are the discoveries the scientist came to while studying jet propulsion in nature and technology. Rockets, as Tsiolkovsky showed, are the only devices that can overcome a rocket. He defined it as a mechanism with a jet engine that uses the fuel and oxidizer located on it. This device transforms the chemical energy of the fuel, which becomes the kinetic energy of the gas jet. The rocket itself begins to move in the opposite direction.
Finally, scientists, having studied the reactive movement of bodies in nature and technology, moved on to practice. A large-scale task lay ahead to realize the long-standing dream of humanity. And a group of Soviet scientists, led by Academician S.P. Korolev, coped with it. She realized Tsiolkovsky's idea. The first artificial satellite of our planet was launched in the USSR on October 4, 1957. Naturally, a rocket was used.
Yu. A. Gagarin (pictured above) was the man who had the honor of being the first to fly in outer space. This important event for the world took place on April 12, 1961. Gagarin flew around the entire globe on the Vostok satellite. The USSR was the first state whose rockets reached the Moon, flew around it and photographed the side invisible from Earth. In addition, it was the Russians who visited Venus for the first time. They brought scientific instruments to the surface of this planet. American astronaut Neil Armstrong is the first person to walk on the surface of the Moon. He landed on it on July 20, 1969. In 1986, Vega 1 and Vega 2 (ships belonging to the USSR) explored at close range Halley's Comet, which approaches the Sun only once every 76 years. Space exploration continues...
As you can see, physics is a very important and useful science. Jet propulsion in nature and technology is just one of the interesting issues that are discussed in it. And the achievements of this science are very, very significant.
How jet propulsion is used in nature and technology these days
In physics, particularly important discoveries have been made in the last few centuries. While nature remains virtually unchanged, technology is developing at a rapid pace. Nowadays, the principle of jet propulsion is widely used not only by various animals and plants, but also in astronautics and aviation. In outer space there is no medium that a body could use to interact in order to change the magnitude and direction of its speed. That is why only rockets can be used to fly in airless space.
Today, jet propulsion is actively used in everyday life, nature and technology. It is no longer a mystery as it used to be. However, humanity should not stop there. New horizons are ahead. I would like to believe that the jet movement in nature and technology, briefly described in the article, will inspire someone to make new discoveries.
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