How does a cuttlefish move? ink souls

The logic of nature is the most accessible and most useful logic for children.

Konstantin Dmitrievich Ushinsky(03/03/1823–01/03/1871) - Russian teacher, founder of scientific pedagogy in Russia.

BIOPHYSICS: JET PROMOTION IN LIVING NATURE

I suggest readers of the green pages to look into the fascinating world of biophysics and get to know the main principles of jet propulsion in wildlife. Today's program: jellyfish cornerot- the largest jellyfish in the Black Sea, scallops, enterprising dragonfly larva, delicious squid with its unrivaled jet engine and wonderful illustrations by the Soviet biologist and animal painter Kondakov Nikolai Nikolaevich.

According to the principle of jet propulsion in wildlife, a number of animals move, for example, jellyfish, scallops, larvae of the rocker dragonfly, squid, octopus, cuttlefish ... Let's get to know some of them better ;-)

Jet way of moving jellyfish

Jellyfish are one of the most ancient and numerous predators on our planet! The body of a jellyfish is 98% water and is largely composed of watered connective tissue – mesoglea functioning like a skeleton. The basis of mesoglea is the protein collagen. The gelatinous and transparent body of a jellyfish is shaped like a bell or an umbrella (in diameter from a few millimeters up to 2.5 m). Most jellyfish move reactive way pushing water out of the cavity of the umbrella.

Jellyfish Cornerota(Rhizostomae), a detachment of coelenterates of the scyphoid class. Jellyfish ( up to 65 cm in diameter) are devoid of marginal tentacles. The edges of the mouth are elongated into oral lobes with numerous folds that grow together to form many secondary oral openings. Touching the mouth lobes can cause painful burns due to the action of stinging cells. About 80 species; They live mainly in tropical, less often in temperate seas. In Russia - 2 types: Rhizostoma pulmo common in black and Seas of Azov, Rhopilema asamushi found in the Sea of ​​Japan.

Jet escape sea scallop clams

Sea shellfish scallops, usually lying quietly at the bottom, when their main enemy approaches them - a delightfully slow, but extremely insidious predator - starfish- sharply squeeze the valves of their shell, pushing water out of it with force. Thus using jet propulsion principle, they float up and, continuing to open and close the shell, can swim a considerable distance. If, for some reason, the scallop does not have time to escape with its jet flight, the starfish clasps it with its hands, opens the shell and eats ...

Scallop(Pecten), a genus of marine invertebrates in the class of bivalves (Bivalvia). The scallop shell is rounded with a straight hinge edge. Its surface is covered with radial ribs diverging from the top. The shell valves are closed by one strong muscle. Pecten maximus, Flexopecten glaber live in the Black Sea; in the Sea of ​​Japan and the Sea of ​​Okhotsk - Mizuhopecten yessoensis ( up to 17 cm in diameter).

Rocker dragonfly jet pump

temperament dragonfly larvae, or ashny(Aeshna sp.) no less predatory than its winged relatives. For two, and sometimes four years, she lives in the underwater kingdom, crawls along the rocky bottom, tracking down small aquatic inhabitants, with pleasure including rather large-caliber tadpoles and fry in her diet. In moments of danger, the larva of the dragonfly-rocker takes off and jerks forward, driven by the work of a wonderful jet pump. Taking water into the hindgut and then abruptly throwing it out, the larva jumps forward, driven by the recoil force. Thus using jet propulsion principle, the larva of the rocker dragonfly hides from the threat pursuing it with confident jerks and jerks.

Reactive impulses of the nervous "freeway" of squids

In all the above cases (principles of the jet propulsion of jellyfish, scallops, larvae of the rocker dragonfly), pushes and jerks are separated from each other by significant intervals of time, therefore, a high speed of movement is not achieved. To increase the speed of movement, in other words, number of reactive impulses per unit time, needed increased nerve conduction that excite muscle contraction, serving a living jet engine. Such a large conductivity is possible with a large diameter of the nerve.

It is known that squid have the largest nerve fibers in the animal kingdom. On average, they reach 1 mm in diameter - 50 times larger than most mammals - and they conduct excitation at a speed 25 m/s. And a three-meter squid dosidicus(he lives off the coast of Chile) the thickness of the nerves is fantastically large - 18 mm. Nerves as thick as ropes! The signals of the brain - the causative agents of contractions - rush along the nervous "freeway" of the squid at the speed of a car - 90 km/h.

Thanks to squid, research on the vital activity of nerves has advanced rapidly since the early 20th century. "And who knows, writes the British naturalist Frank Lane, maybe there are now people who owe the squid that their nervous system is in a normal state ... "

The speed and maneuverability of the squid is also explained by the excellent hydrodynamic forms animal body, why squid and nicknamed "live torpedo".

squids(Teuthoidea), suborder cephalopods squad of ten-legged. The size is usually 0.25-0.5 m, but some species are the largest invertebrates(squids of the genus Architeuthis reach 18 m, including the length of the tentacles).
The body of squids is elongated, pointed at the back, torpedo-shaped, which determines the high speed of their movement as in water ( up to 70 km/h), and in the air (squids can jump out of the water to a height up to 7 m).

Squid jet engine

Jet propulsion, now used in torpedoes, aircraft, rockets and space projectiles, is also characteristic cephalopods - octopus, cuttlefish, squid. Of greatest interest to technicians and biophysicists is squid jet engine. Pay attention to how simply, with what minimal material consumption, nature solved this complex and still unsurpassed task ;-)

In essence, the squid has two fundamentally different engines ( rice. 1a). When moving slowly, it uses a large diamond-shaped fin, periodically bending in the form of a traveling wave along the body. The squid uses a jet engine to throw itself quickly.. The basis of this engine is the mantle - muscle. It surrounds the body of the mollusk from all sides, making up almost half of the volume of its body, and forms a kind of reservoir - mantle cavity - the "combustion chamber" of a living rocket into which water is periodically sucked. The mantle cavity contains gills and internal organs squid ( rice. 1b).

With a jet way of swimming the animal sucks water through the wide open mantle fissure into the mantle cavity from the boundary layer. The mantle gap is tightly “fastened” with special “button cufflinks” after the “combustion chamber” of a living engine is filled with sea water. The mantle gap is located near the middle of the squid body, where it has the greatest thickness. The force that causes the movement of the animal is created by ejecting a jet of water through a narrow funnel, which is located on the abdominal surface of the squid. This funnel, or siphon, - "nozzle" of a living jet engine.

The "nozzle" of the engine is equipped with a special valve and the muscles can turn it. By changing the installation angle of the funnel-nozzle ( rice. 1v), the squid swims equally well, both forward and backward (if it swims backward, the funnel extends along the body, and the valve is pressed against its wall and does not interfere with the water jet flowing from the mantle cavity; when the squid needs to move forward, the free end of the funnel somewhat elongates and bends in the vertical plane, its outlet is folded and the valve assumes a bent position). Jet thrusts and the suction of water into the mantle cavity follow one after another with imperceptible speed, and the squid rockets through the blue of the ocean like a rocket.

Squid and its jet engine - figure 1

1a) squid - live torpedo; 1b) squid jet engine; 1c) the position of the nozzle and its valve when the squid moves back and forth.

The animal spends fractions of a second on the intake of water and its expulsion. By sucking water into the mantle cavity in the aft part of the body during periods of slow inertial motion, the squid thereby sucks out the boundary layer, thus preventing flow separation during unsteady flow around. By increasing the portions of ejected water and increasing the contraction of the mantle, the squid easily increases the speed of movement.

The squid jet engine is very economical, so that it can reach the speed 70 km/h; some researchers believe that even 150 km/h!

Engineers have already created engine similar to squid jet engine: This water cannon operating with conventional gasoline or diesel engine. Why squid jet engine still attracts the attention of engineers and is the object of careful research by biophysicists? To work underwater it is convenient to have a device that works without access atmospheric air. The creative search of engineers is aimed at creating a design hydrojet engine, similar air-jet…

Based on great books:
"Biophysics at physics lessons" Cecilia Bunimovna Katz,
And "Primates of the Sea" Igor Ivanovich Akimushkina

Kondakov Nikolai Nikolaevich (1908–1999) – Soviet biologist, animal painter, candidate of biological sciences. His main contribution to biological science was his drawings of various representatives of the fauna. These illustrations have been included in many publications, such as Big Soviet Encyclopedia, Red Book of the USSR, in animal atlases and teaching aids.

Akimushkin Igor Ivanovich (01.05.1929–01.01.1993) – Soviet biologist, writer - popularizer of biology, author of popular science books about animal life. Laureate of the All-Union Society "Knowledge" award. Member of the Writers' Union of the USSR. The most famous publication of Igor Akimushkin is a six-volume book "Animal world".

The materials of this article will be useful to apply not only in physics lessons And biology but also in extracurricular activities.
Biophysical material is extremely beneficial for mobilizing the attention of students, for turning abstract formulations into something concrete and close, affecting not only the intellectual, but also the emotional sphere.

Literature:
§ Katz Ts.B. Biophysics at physics lessons

§ § Akimushkin I.I. Primates of the sea
Moscow: publishing house "Thought", 1974
§ Tarasov L.V. Physics in nature
Moscow: Enlightenment publishing house, 1988

Jet propulsion 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 the given organism with external bodies.

In order to understand what is at stake, it is best to turn to examples. in nature and technology are numerous. We will first talk about how animals use it, and then how it is applied in technology.

Jellyfish, dragonfly larvae, plankton and molluscs

Many, swimming in the sea, met jellyfish. In the Black Sea, at least, there are enough of them. However, not everyone thought that jellyfish move just with the help of jet propulsion. Dragonfly larvae, as well as some representatives of marine plankton, resort to the same method. 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, octopus. In particular, the scallop marine mollusk 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, revealing the topic: "Jet propulsion in everyday life, nature and technology."

How cuttlefish move

The cuttlefish is also very interesting in this respect. 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 lateral slit, the cuttlefish takes water into its gill cavity. Then she vigorously throws it out through the funnel. The cuttlefish directs the tube of the funnel back or sideways. In this case, the movement can be carried out in different directions.

The method that salpa uses

The method used by the salpa is also curious. This is the name of a marine animal that has a transparent body. The salpa, when moving, draws in water, using the anterior opening for this. Water is 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, the entire body of the animal contracts. Through the rear hole, water is pushed out. The animal moves forward due to the reaction of the outflowing jet.

Squid - "live torpedoes"

Perhaps the most interesting is the jet engine that the squid has. This animal is considered the most major representative invertebrates living at great depths of the ocean. In jet navigation, squids have reached real perfection. Even the body of these animals resembles a rocket with its external forms. Or rather, this rocket copies the squid, since it is he who owns the undisputed superiority in this matter. If you need to move slowly, the animal uses a large diamond-shaped fin for this, which bends from time to time. If you need a quick throw, a jet engine comes to the rescue.

On all sides, the body of the mollusk is surrounded by a mantle - muscle tissue. Almost half of the total volume of the animal's body falls on the volume of its cavity. The squid uses the mantle cavity to propel itself by sucking water into it. Then he abruptly ejects the accumulated jet of water through a narrow nozzle. As a result of this, he moves in jerks backwards at high speed. At the same time, the squid folds all of its 10 tentacles into a knot above its head in order to acquire a streamlined shape. The nozzle has a special valve, and the animal's muscles can turn it. Thus, the direction of movement changes.

Impressive squid movement speed

I must say that the squid engine is very economical. The speed that he is able to develop 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 called a "living torpedo" for a reason. He can turn to the right side, bending down, up, left or right tentacles folded in a bundle.

How the squid controls movement

Since the steering wheel is very large compared to the size of the animal itself, in order for the squid to easily avoid a collision with an obstacle, even moving with maximum speed only a slight movement of the steering wheel is sufficient. If you turn it sharply, the animal will immediately rush to reverse side. The squid bends back the end of the funnel and as a result of this it can slide head first. If he arches it to the right, he will be thrown to the left by a jet thrust. However, when it is necessary to swim quickly, the funnel is always located directly between the tentacles. The animal in this case rushes with its tail forward, like the run of a fast-walking crawfish, if it had the agility of a horse.

In the case when there is no need to hurry, cuttlefish and squid swim, while undulating their fins. Miniature waves run through them from front to back. Squids and cuttlefish glide gracefully. They only occasionally prod themselves with a jet of water that is ejected from under their mantle. Separate shocks that the mollusk receives during the eruption of jets of water are clearly visible at such moments.

flying squid

Some cephalopods can accelerate 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 flight speed of flying squids. It turns out that there are some. Stenoteuthis squid is the best pilot of all mollusks. English sailors call it the flying squid (flying squid). This animal, the photo of which is presented above, has small size, about the size of a herring. It chases fish so swiftly that it often jumps out of the water, darting over its surface like an arrow. 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 starts into the air, and then flies more than 50 meters above the waves. When flying, it is so high that flying squids often fall on the decks of ships. A height of 4-5 meters for them is by no means a record. Sometimes flying squids fly even higher.

Dr. Rhys, a British shellfish researcher, in his scientific article described a representative of these animals, whose body length was only 16 cm. However, at the same time, he was able to fly a fair distance through the air, after which he landed on the bridge of the yacht. And the height of this bridge was almost 7 meters!

There are times when a lot of flying squids fall on the ship at once. Trebius Niger, an ancient writer, once told a sad story about a ship that seemed to be unable to bear the weight of these marine animals and sank. Interestingly, squids are able to take off even without acceleration.

flying octopuses

Octopuses also have the ability to fly. Jean Verany, a French naturalist, watched as one of them accelerated in his aquarium and then suddenly jumped out of the water. The animal described an arc in the air of about 5 meters, and then flopped into the aquarium. The octopus, gaining the speed necessary for the jump, moved not only thanks to jet thrust. He also rowed with his tentacles. Octopuses are baggy, so they swim worse than squids, but in critical moments, these animals are able to give odds 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 even when using the special mode, the photos turned out to be blurry. This means that the throw lasted a matter of fractions of a second!

However, octopuses usually swim quite slowly. Scientist Joseph Signl, who studied the migration 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, backwards, since he swims backwards) by about 2-2.5 m.

"Squirting cucumber"

Jet propulsion 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 stem at the slightest touch. Then, from the hole formed as a result of this, a special sticky liquid is ejected with great force, in which the seeds are located. The cucumber itself flies in the opposite direction at a distance of up to 12 m.

Law of conservation of momentum

Be sure to tell about it, considering jet propulsion 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 some stones with you. If you throw them in a certain direction, the boat will move in the opposite direction. This law also operates in outer space. However, for this purpose they use

What other examples of jet propulsion in nature and technology can be noted? Very well the law of conservation of momentum is illustrated by 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 would be equal to the weight of the gun. In this case, they would fly apart at the same speed. Recoil happens because a reactive force is created, since there is a discarded mass. Thanks to this force, movement is ensured both in airless space and in air. The greater the speed and mass of the outflowing gases, the greater the recoil force felt by our shoulder. Accordingly, the reactive force is higher, the stronger the reaction of the gun.

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, mankind 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 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 wagon. Over this design, he constantly tossed a strong magnet. The wagon, attracted to him, rose higher and higher above the Earth. Eventually, she reached the moon. Another famous character, Baron Munchausen, climbed to the moon on a bean stalk.

Of course, at that time little was known about how the use of jet propulsion in nature and technology can make life easier. But the flight of fancy, of course, opened up new horizons.

On the way to an outstanding discovery

In China at the end of the 1st millennium A.D. e. invented jet propulsion that powered rockets. The latter were simply bamboo tubes filled with gunpowder. These rockets were launched for fun. The jet engine was used in one of the first car designs. This idea belonged to Newton.

N.I. also thought about how jet propulsion arises in nature and technology. Kibalchich. This is a Russian revolutionary, the author of the first project of a jet aircraft, which is designed for a person to fly on it. 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 the execution of a death sentence, he continued to study such interesting phenomenon, as a reactive motion in nature and in technology, which occurs when a part of an object is separated. As a result of these studies, he developed his project. Kibalchich wrote that this idea supported him in his position. He is ready to face his death calmly, 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). Back in the early 20th century, this great Russian scientist proposed the idea of ​​using rockets for space flight. His article on this subject 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 a variable mass. In his later writings, he presented a diagram of a rocket engine powered by liquid fuel. Tsiolkovsky, studying the use of jet propulsion in nature and technology, developed a multi-stage rocket design. He also owns the idea of ​​the possibility of creating entire space cities in near-Earth orbit. These are the discoveries the scientist came to while studying jet propulsion in nature and technology. Rockets, as shown by Tsiolkovsky, are the only vehicles that can overcome the Rocket, he defined as a mechanism that has a jet engine that uses the fuel and oxidizer located on it. This apparatus 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 motion of bodies in nature and technology, switched to practice. There was a large-scale task of realizing the long-standing dream of mankind. And a group of Soviet scientists, headed by academician S.P. Korolev, coped with it. She implemented the idea of ​​Tsiolkovsky. First artificial satellite our planet was launched in the USSR on October 4, 1957. Naturally, a rocket was used in this case.

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 on the satellite ship "Vostok" circled the entire Earth. The USSR was the first state whose rockets reached the Moon, flew around it and photographed the side invisible from the Earth. In addition, it was the Russians who first visited Venus. 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) studied 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 questions that are considered in it. And the achievements of this science are very, very significant.

How jet propulsion is used today in nature and technology

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 the body could use to interact in order to change the modulus and direction of its velocity. That is why only rockets can be used to fly in vacuum.

Today, jet propulsion is actively used in everyday life, nature and technology. It is no longer a mystery like it used to be. However, humanity should not stop there. New horizons lie ahead. I would like to believe that the jet propulsion in nature and technology, briefly described in the article, will inspire someone to new discoveries.

Cuttlefish (Sepia) belong to the class of cephalopods. About 30 belong to this group. modern species. Cuttlefish are the smallest of all cephalopods. In most species, the body length reaches 20 cm, and in small species- 1.8-2 cm. Only one species - wide-armed sepia - has a length of 150 cm along with "hands". Cuttlefish live mainly near the coast in shallow water in the tropical and subtropical seas of the Atlantic Ocean and the Mediterranean Sea.

Structure

The structure of the cuttlefish is in many ways similar to the structure of other cephalopods. Its body is represented by a skin-muscle bag (the so-called mantle) and has an elongated oval shape, slightly flattened and does not change in size (octopuses, for example, easily squeeze into narrow crevices). In cuttlefish, the head is fused to the body. On the head are large eyes with a complex structure and a slit-like pupil, and on its front part there is a kind of beak designed for crushing food. The beak is hidden between the tentacles.

Eight short tentacles-arms and two long grasping tentacles extend from the body of the mollusk, all of which are dotted with suckers. In a calm state, the "arms" of the cuttlefish are folded together and stretched forward, thus giving the body a streamlined appearance. Grasping tentacles are hidden in special pockets under the eyes and fly out from there only during the hunt. In males, one of the arms differs in its structure from the others and serves to fertilize females.

On the sides of the body of the cuttlefish are fins, elongated in the form of a border, which are a means of facilitating movement. The cuttlefish accelerates its movement in the water through several sudden movements. It draws water into a compression chamber, which compresses to expel water from a siphon under the head. The clam changes direction by turning the opening of this siphon. The cuttlefish differs from other cephalopods in the presence of an internal calcareous shell in the form of a wide plate that covers its entire back and protects the internal organs. The inner shell of a cuttlefish is built of aragonite. This substance forms the so-called "cuttlefish bone", which is responsible for the buoyancy of the mollusk. The cuttlefish regulates its buoyancy by the ratio of gas and liquid inside this bone, which is divided into small chambers.

The remaining internal organs in cuttlefish are arranged in the same way as in other representatives of cephalopods. This animal has three hearts: one heart for two gills and one heart for the rest of the body. Cuttlefish have blue-green blood, due to the pigment hemocyanin in it, saturated with copper-containing proteins that are capable of long time"conserve" oxygen, preventing the mollusk from suffocating at great depths. Also, cuttlefish have an ink sac that produces very a large number of ink compared to other cephalopods. The ink substance is brown and is called sepia. Having such a protective agent, the cuttlefish uses it directly for protection as a last resort.

The color of cuttlefish is very variable. In the structure of their skin there are three layers of chromatophores (coloring pigment cells): on the surface there is a light yellow layer, the middle one is an orange-yellow layer and a dark layer located under the two previous layers. The transition from one shade to another is adjustable nervous system and happens within a second. In terms of the variety of colors, the complexity of the pattern and the speed of its change, these animals are unmatched. Some types of cuttlefish can luminesce. Color change and luminescence are used by the mollusk for camouflage.

reproduction

Cuttlefish live alone, very rarely in small flocks, and lead a sedentary lifestyle. During the breeding season, they form large aggregations and may migrate. Usually cuttlefish swim at a short distance from the bottom, tracking down prey, when they see it, they freeze for a moment, and then overtake the victim with a swift movement. When cuttlefish are in danger, they lie down on the bottom, and with a wave of their fins they cover themselves with sand. By nature, these animals are very cautious and timid. Cuttlefish hunt during the daytime and feed on various fish, shrimps, crabs, mollusks, worms - almost all organisms that move and do not exceed their size. To increase the effectiveness of hunting, the mollusk blows a jet of water from the siphon into the sand and catches small living creatures washed by the jet. Cuttlefish swallow small animals whole, large ones are butchered with their beaks.

Cuttlefish have many enemies, as their low movement speed makes them vulnerable to predatory fish. These mollusks are eaten by dolphins, sharks and rays. Cuttlefish are sometimes called "chameleons of the sea" for their good color camouflage. environment. When hunting or fleeing predators, they rely more on their ability to disguise themselves than on their protective ink.

Cuttlefish are dioecious animals. They breed once in a lifetime. The male treats the female with quivering tenderness, swimming nearby, he strokes her with tentacles, while both flare up bright colors. The male brings sperm to the female with a modified tentacle, the eggs are fertilized already during laying. Eggs of cuttlefish are black in color and look like bunches of grapes; when laying, the females attach them to underwater vegetation. Some time after spawning, adults die. Juveniles are born fully formed, having an ink sac and an inner shell. Already from the first moments of life they can apply ink. Cuttlefish grow quickly, but do not live long - only 1-2 years.

Since ancient times, people have hunted cuttlefish because of their tasty meat, which is used in Mediterranean and Chinese cuisine. The crushed shell is part of a number of toothpastes. In the old days, cuttlefish ink was used for writing, and diluted to prepare a special paint for artists - sepia. Therefore, people owe countless masterpieces of painting and writing to cuttlefish.

It will be strange for you to hear that there are not a few living creatures for whom the imaginary "lifting oneself by the hair" is the usual way of moving them in the water.

Figure 10. Swimming movement of a cuttlefish.

The cuttlefish and, in general, most cephalopods move in water in this way: they take water into the gill cavity through the lateral slit and a special funnel in front of the body, and then vigorously throw out a stream of water through the said funnel; at the same time, they - according to the law of counteraction - receive a reverse push, sufficient to swim fairly quickly with the back side of the body forward. The cuttlefish can, however, direct the tube of the funnel sideways or backwards and, rapidly squeezing water out of it, move in any direction.

The movement of the jellyfish is also based on the same: by contraction of the muscles, it pushes water out from under its bell-shaped body, receiving a push in the opposite direction. Salps, dragonfly larvae and other aquatic animals use a similar technique when moving. And we still doubted whether it was possible to move like that!

To the stars on a rocket

What could be more tempting than to leave the globe and travel through the vast universe, fly from Earth to the Moon, from planet to planet? How many fantastic novels have been written on this subject! Who has not taken us on an imaginary journey through the heavenly bodies! Voltaire in Micromegas, Jules Verne in Journey to the Moon and Hector Servadacus, Wells in The First Men on the Moon and many of their imitators made the most interesting trips to the heavenly bodies - of course, in dreams.

Is there really no way to realize this old dream? Are all the witty projects depicted with such tempting plausibility in novels really unrealizable? 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.

Can you fly to the moon by plane? Of course not: airplanes and airships move only because they lean against the air, repel from it, and there is no air between the Earth and the Moon. In the world space, there is generally no sufficiently dense medium on which an "interplanetary airship" could rely. This means that it is necessary to invent such an apparatus 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 - with a rocket. Why not make a huge rocket, with a special room for people, food supplies, air tanks and everything else? Imagine that people in a rocket carry a large supply of combustible substances with them and can direct the outflow of explosive gases in any direction. You will get a real controllable celestial ship, on which you can sail in the ocean of world space, fly to the Moon, to 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 wanted to descend to some planet, they could, 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.

It will be strange for you to hear that there are not a few living creatures for whom the imaginary "lifting oneself by the hair" is the usual way of moving them in the water.

Figure 10. Swimming movement of a cuttlefish.

The cuttlefish and, in general, most cephalopods move in water in this way: they take water into the gill cavity through the lateral slit and a special funnel in front of the body, and then vigorously throw out a stream of water through the said funnel; at the same time, they - according to the law of counteraction - receive a reverse push, sufficient to swim fairly quickly with the back side of the body forward. The cuttlefish can, however, direct the tube of the funnel sideways or backwards and, rapidly squeezing water out of it, move in any direction.

The movement of the jellyfish is also based on the same: by contraction of the muscles, it pushes water out from under its bell-shaped body, receiving a push in the opposite direction. Salps, dragonfly larvae and other aquatic animals use a similar technique when moving. And we still doubted whether it was possible to move like that!

To the stars on a rocket

What could be more tempting than to leave the globe and travel through the vast universe, fly from Earth to the Moon, from planet to planet? How many fantastic novels have been written on this subject! Who has not taken us on an imaginary journey through the heavenly bodies! Voltaire in Micromegas, Jules Verne in Journey to the Moon and Hector Servadacus, Wells in The First Men on the Moon and many of their imitators made the most interesting trips to the heavenly bodies - of course, in dreams.

Is there really no way to realize this old dream? Are all the witty projects depicted with such tempting plausibility in novels really unrealizable? 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.

Can you fly to the moon by plane? Of course not: airplanes and airships move only because they lean against the air, repel from it, and there is no air between the Earth and the Moon. In the world space, there is generally no sufficiently dense medium on which an "interplanetary airship" could rely. This means that it is necessary to invent such an apparatus 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 - with a rocket. Why not make a huge rocket, with a special room for people, food supplies, air tanks and everything else? Imagine that people in a rocket carry a large supply of combustible substances with them, and they can direct the outflow of explosive gases in any direction. You will get a real controllable celestial ship, on which you can sail in the ocean of world space, fly to the Moon, to 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 wanted to descend to some planet, they could, 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. The project of an interplanetary airship arranged like a rocket.

Let us recall how recently aviation made its first timid conquests. And now - the planes are already flying high in the air, they fly over mountains, deserts, continents, oceans. Perhaps, "astronomy" will have the same magnificent flowering in two or three decades? Then a person will break the invisible chains that have chained him to his native planet for so long, and will rush into the boundless expanse of the universe.