Comments by K.H. n. O. V. Mosina.
Why elementary ice crystals are hexagonal is easy to understand by analyzing the structure of crystalline water - ice.
In a water molecule, two electron pairs form polar covalent bonds between hydrogen and oxygen atoms, and the remaining two electron pairs remain free and are called unshared.
Rice. Water molecule
Because the oxygen atom has more electrons (chemists say the oxygen atom is more electronegative) than the hydrogen atom, the electrons of the two hydrogen atoms shift towards the more electronegative oxygen atom, causing the two positive charge hydrogen atoms are compensated by the negative charge of the oxygen atom equal in magnitude to two hydrogen atoms. Therefore, the electron cloud has a non-uniform density. There is a deficiency near hydrogen nuclei electron density, and on opposite side molecules, near the oxygen nucleus, there is an excess of electron density. This results in the water molecule being a small dipole containing positive and negative charges at the poles. It is this structure that determines the polarity of the water molecule. If we connect the epicenters of positive and negative charges it will turn out voluminous geometric figure- regular tetrahedron.
The unit cell of water is tetrahedra containing five H2O molecules connected to each other by hydrogen bonds. Moreover, each of the water molecules in simple tetrahedra retains the ability to form hydrogen bonds. Due to their simple tetrahedrons, they can be united by vertices, edges or faces, forming a variety of spatial structures.
Rice. IN crystal structure ice, each water molecule participates in 4 hydrogen bonds, forming a tetrahedron
Thus, the structure of water is associated with the so-called Platonic solids (tetrahedron, dodecahedron), the shape of which is related to the golden ratio. The water molecule also has the shape of a Platonic solid (tetrahedron).
And of all the variety of structures in nature, the basic one is the hexagonal (six-sided) structure, when six water molecules (tetrahedra) are combined into a ring. This type of structure is typical for ice, snow and melt water.
A snowflake is a complex symmetrical structure consisting of ice crystals collected together. There are many options for “assembly” - so far it has not been possible to find two identical ones among the snowflakes. Research conducted in Libbrecht's laboratory confirms this fact - crystal structures can be grown artificially or observed in nature. There is even a classification of snowflakes, but despite general laws constructions, snowflakes will still be slightly different from each other even in the case of relatively simple structures.
Rice. 1. Crystal structure of ice
So why are snowflakes hexagonal? In the crystal structure of ice, each water molecule participates in 4 hydrogen bonds directed to the vertices of the tetrahedron at strictly defined angles equal to 109°28" (while in ice structures I, Ic, VII And VIII this tetrahedron is correct). In the center of this tetrahedron there is an oxygen atom, at two vertices there is a hydrogen atom, the electrons of which are involved in the formation covalent bond with oxygen. The two remaining vertices are occupied by pairs of oxygen valence electrons, which do not participate in the formation of intramolecular bonds. Now it becomes clear why the ice crystal is hexagonal.
The main feature that determines the shape of a crystal is the connection between water molecules, similar to the connection of links in a chain. Moreover, due to different ratio heat and moisture, the crystals, which in principle should be the same, take on different shapes. Colliding with supercooled small droplets on its way, the snowflake simplifies its shape while maintaining symmetry.
But why do elongated snowflakes sometimes form? A snowflake is a single crystal of ice, an analogue of a hexagonal crystal, but one that grew quickly under non-equilibrium conditions. Under some conditions, ice hexagons grow intensively along their axis, and then elongated snowflakes are formed - columnar snowflakes, needle snowflakes. Under other conditions, hexagons grow predominantly in directions perpendicular to their axis, and then snowflakes are formed in the form of hexagonal plates or hexagonal stars.
For more information about snowflakes and the processes of their formation, read the article by Sergei Apresov “White Magic”:
K. x. n. O. V. Mosin
WHY ARE SNOWFLAKES HEXAGONAL?
To understand why snowflakes look so beautiful, we need to consider the life history of one snow crystal.
Ice snowflakes in the cloud are formed at -15 degrees due to the transition of water vapor into solid state. The basis for the formation of snowflakes are fine particles dust or microscopic pieces of ice that serve as a nucleus for water molecules to condense on them. The crystallization nucleus is where the formation of snowflakes begins.
More and more water molecules join the growing snowflake in certain places, giving it a distinct hexagonal shape. The key to the structure of solid water lies in the structure of its molecule, which can be simplified to imagine in the form of a tetrahedron - a pyramid with triangular base in which only angles of 60° and 120° are possible. In the center there is oxygen, in two vertices there is hydrogen, or more precisely, a proton, the electrons of which are involved in the formation of a covalent bond with oxygen. The two remaining vertices are occupied by pairs of oxygen valence electrons, which do not participate in the formation of intramolecular bonds, which is why they are called lone.
A snowflake is a single crystal of ice, a variation on the theme of a hexagonal crystal, but one that grew quickly under non-equilibrium conditions. Under some conditions, ice hexagons grow intensively along their axis, and then elongated snowflakes are formed - columnar snowflakes, needle snowflakes. Under other conditions, hexagons grow predominantly in directions perpendicular to their axis, and then snowflakes are formed in the form of hexagonal plates or hexagonal stars.
A drop of water can freeze to a falling snowflake, resulting in the formation of snowflakes of irregular shape. The common belief that snowflakes necessarily have the shape of hexagonal stars is erroneous. The shapes of snowflakes turn out to be very diverse.
Astronomer Johannes Kepler wrote a whole treatise “On Hexagonal Snowflakes” in 1611. In 1665, Robert Hooke used a microscope to see and publish many drawings of snowflakes of various shapes. The first successful photograph of a snowflake under a microscope was taken in 1885 by American farmer Wilson Bentley. The most famous followers of the Bentley cause are Ukihiro Nakaya and American physicist Kenneth Libbrecht. Nakaya was the first to suggest that the size and shape of snowflakes depend on air temperature and moisture content, and brilliantly confirmed this hypothesis experimentally by growing ice crystals of different shapes in the laboratory. And Libbrecht, at Caltech, is still busy growing snowflakes all day long. The scientist, together with photographer Patricia Rasmussen, are planning to publish a book that will include the most photogenic snowflakes, some of which can already be seen on his website SnowCrystals.com.
There is another mystery inherent in the structure of a snowflake. In it, order and chaos coexist together. Depending on the conditions of receipt solid must be either in a crystalline (when the atoms are ordered) or in an amorphous (when the atoms form a random network) state. Snowflakes have a hexagonal lattice in which oxygen atoms are arranged in an orderly manner, forming regular hexagons, and the hydrogen atoms are arranged randomly. However, the relationship between the structure crystal lattice and the shape of a snowflake, which more molecule water ten million times, is not obvious: if water molecules were attached to the crystal in a random order, the shape of the snowflake would be irregular. It's all about the orientation of molecules in the lattice and the location of free hydrogen bonds, which promotes the formation of smooth edges.
Water vapor molecules with more likely fill voids rather than stick to smooth edges, because voids contain more free hydrogen bonds. As a result, snowflakes take the shape of regular hexagonal prisms with smooth edges. Such prisms fall from the sky, with relatively low air humidity in a wide variety of temperature conditions.
Sooner or later, irregularities appear on the edges. Each tubercle attracts additional molecules and begins to grow. A snowflake travels through the air for a long time, and the chances of meeting new water molecules near the protruding tubercle are slightly higher than at the faces. This is how rays grow on a snowflake very quickly. One thick ray grows from each face, since molecules do not tolerate emptiness. Branches grow from the tubercles formed on this ray. During the journey of a tiny snowflake, all its faces are in the same conditions, which serves as a prerequisite for the growth of identical rays on all six faces. In ideal laboratory conditions, all six directions of the snowflake grow symmetrically and with similar configurations. In the atmosphere most of Snowflakes are irregular crystals; only some of the six branches can be symmetrical.
Nowadays, the study of snowflakes has become a science. Back in 1555, the Swiss explorer Mangus made sketches of the shapes of snowflakes. In 1955, Russian scientist A. Zamorsky divided snowflakes into 9 classes and 48 species. These are plates, needles, stars, hedgehogs, columns, fluffs, cufflinks, prisms, group ones. International Commission on snow and ice took quite a lot in 1951 simple classification ice crystals: plates, star crystals, columns or columns, needles, spatial dendrites, columns with tips and irregular shapes. And three more types of icy precipitation: fine snow pellets, ice pellets and hail.
In 1932, nuclear physicist Ukihiro Nakaya, a professor at Hokkaido University, began growing artificial snow crystals, which made it possible to compile the first classification of snowflakes and identify the dependence of the size and shape of these formations on temperature and air humidity. In the city of Kaga, located on west bank Honshu Island, there is a Museum of Snow and Ice founded by Ukihiro Nakaya, which now bears his name, symbolically built in the form of three hexagons. The museum houses a machine for making snowflakes. Nakaya identified 41 individual morphological types among snowflakes, and meteorologists S. Magano and Xu Li in 1966 described 80 types of crystals.
Under certain conditions, in the absence of wind, falling snowflakes can adhere to each other, forming huge snow flakes. In the spring of 1944, flakes measuring up to 10 centimeters in diameter, similar to whirling saucers, fell in Moscow. And in Siberia, snow flakes with a diameter of up to 30 centimeters were observed. The largest snowflake was recorded in 1887 in Montana, America. Its diameter was 38 cm, and its thickness was 20 cm. This phenomenon requires complete calmness, because the longer the snowflakes travel, the more they collide and adhere to each other. Therefore, at low temperatures and strong wind snowflakes collide in the air, crumble and fall to the ground in the form of fragments - “diamond dust”. The likelihood of seeing large snowflakes increases significantly near bodies of water: evaporation from lakes and reservoirs is an excellent building material.
The ice that forms a snowflake is transparent, but when there are a lot of them, sunlight, reflected and scattered on numerous faces, gives us the impression of a white opaque mass - we call it snow. The snowflake is white because water absorbs the red and infrared parts very well light spectrum. Frozen water largely retains the properties of liquid water. Sunlight, passing through a layer of snow or ice, loses red and yellow rays, which are scattered and absorbed in it, and the light that passes through is bluish-green, blue or bright blue - depending on how thick the layer was in the path of the light .
DATA about snowflakes
Snowflakes form a snow cover that reflects up to 90% into space sunlight.
In one cubic meter There are 350 million snowflakes in the snow, and throughout the entire Earth - 10 to the 24th power.
The weight of the snowflake itself is only about a milligram, rarely 2…3. However, by the end of winter the mass of snow cover northern hemisphere planet reaches 13,500 billion tons.
Snow is not only white. In arctic and mountainous regions, pink or even red snow is common. This is due to algae living between the crystals. But there are cases when snow fell from the sky already colored. So, on Christmas Day 1969, black snow fell in Sweden. Most likely, this is soot absorbed from the atmosphere and industrial pollution. In 1955, phosphorescent green snow fell near Dana, California, killing several people and causing severe harm to those who tried it on their tongues. Arose different versions this phenomenon, even atomic tests in Nevada. However, they were all rejected and the origin of green snow remained a mystery.
Kenneth Libbrecht: snow under a microscopeThe popularity of the American Kenneth Libbrecht all over the world was brought by winter, or rather by such a necessary attribute as snow. The epigraph to his work is the words of Henry David Thoreau: “The air in which they arise is filled with creative genius. It’s unlikely that I would have admired it more, even if real stars had fallen on my coat.” Can you guess what we're talking about? Right. About snowflakes! Kenneth Libbrecht was born in 1958 in Fargo, North Dakota. And he is not a photographer, as it might seem at first glance, but a scientist. Kenneth is a professor of physics at California Institute of Technology. At the beginning of his career, our hero was interested in astronomy, but his latest research is devoted to studying the qualities of ice crystals, and especially the structure of snowflakes. Just as an addition to professional studies Kenneth published several popular books, illustrated with photographs of the most various forms and sizes. Most snowflakes have six-sided symmetry, although there are specimens with three and twelve sides. But it is impossible to see a crystal with four, five or eight sides, Kenneth assures us. The most ideally shaped snowflakes, according to the author, can be found when there is light snowfall and a light wind blowing, and the weather is especially cold. The popularity of Kenneth's work is also evidenced by the fact that four of his photographs were selected Postal service USA as the design for the 2006 winter holiday stamps. The total circulation of stamps was about three billion copies. “Every snowfall is an adventure for a photographer because they all bring different crystals,” says Kenneth Libbrecht. - And it’s true - two identical snowflakes No". Well, if this is so, then we can say two things with confidence: the author is provided with work for life, and his creations can be viewed endlessly. Photographer Yaroslav Gnatyuk - HIV virus model - visualscience.ru/illustrations/modelling/gripp-H1N1-interactive/ |
If you have ever noticed that they have different shapes. It is believed that there are about 350 million snowflakes in one cubic meter of snow! They are all hexagonal and have crystal-like structures, but each has its own unique shape. For years, scientists have been trying to understand where this shape comes from, what influences this symmetry, and why it is different for everyone. Every tiny piece of information received reveals another amazing secret, enclosed in a snowflake.
The variety and ideality of the hexagonal structure of snowflakes is a manifestation of the wisdom and creativity of God as the Creator. The formation of snowflakes is another manifestation of God's limitless ingenuity. These thin, small snowflakes look like stars or the head of a needle with many fragile tips. The shape of the snowflakes in the pictures is truly amazing. For many years this structure has been a subject of interest to people. Since 1945, research has been carried out to determine the cause of the formation of geometric shapes from microscopic ice crystals. One snowflake consists of more than 200 ice crystals. Snowflakes are made up of water molecules that have taken on intricate shapes. Snow, nature's most architectural wonder, takes shape when water vapor freezes as it passes through a cloud. It goes like this.
When entering clouds, water molecules, chaotically scattered in water vapor, begin to lose their chaotic movement due to an increase in temperature. After some time, the water molecules slow down, begin to cluster and harden. At the same time, they are ordered and have the shape of hexagonal figures, which are often similar friends on a friend. At first, each snowflake consists of one geometrically hexagonal water molecule. Then other similar molecules join it.
According to the researchers' theories, the main factor determining the shape of a snowflake is that these hexagonal water molecules are connected to each other like links in a chain. In addition, crystal particles that should normally look the same become various shapes depending on temperature and humidity level. (Roger Davey, David Stanley, “All about ice,” New Scientist, September 6, 1993.)
And yet, why do all snowflakes have hexagonal symmetry and why are they all different from each other? Why are their contours angular and not smooth? Scientists are still trying to find answers to these questions. But one thing is clear: only God, the One Creator, possessing enormous power, could provide the diversity of thousands of billions of snowflakes.
One of the most amazing phenomena nature are unique and always hexagonal snowflakes, which, like small butterflies, swirl in the air, covering the ground with a continuous layer snow-white snow. What precision does nature observe when creating only hexagonal snowflakes, but what is the secret of such a structure of snowflakes? In addition, each snowflake is unique in its shape.
To understand why snowflakes are hexagonal, you need to consider that snowflakes are frozen droplets of water. Snowflakes are formed not from rain, but from water vapor. To clarify this fact at one time, many millions of dollars were spent. And here White color The appearance of snowflakes is due to the fact that snowflakes are small ice crystals of a special shape, so light reflects off them and makes them snow-white. When freezing, all the molecules in an ice droplet line up in a special way, as a result of which a specific geometric figure is formed, which is a crystal. The water molecule, as the science of chemistry tells us, consists of two hydrogen atoms and one oxygen atom. When frozen, such a composition is arranged into a triangle or hexagon. Each such crystal is very small and invisible without special equipment. Such mini crystals move in the air due to air currents that make upward and downward movements. During this movement, they group together around a particle of dust or a drop of water. Gradually this formation grows, collecting hundreds of crystals together. After a while, such a cluster becomes quite heavy and falls to the ground. This is how snow falls. The size of falling snowflakes can be very diverse, sometimes reaching three centimeters in diameter. The size of a snowflake is determined by the air temperature at which it was formed. The lower the temperature, the smaller the size of the snowflake.
Exists unique phenomenon- colorful snowfall. Snowflakes can be red, blue, green and even black. This is very simply explained, and it is these colors that are given to snowflakes by fungi or dust in the air.
In addition, snowflakes have many more secrets. Few people know that these small natural wonders are 95% air. That is why they have low density and descend to the ground so slowly, as if floating. One snowflake weighs no more than 2-3 milligrams, but this applies only to the largest representatives of this species. Usually the weight of snowflakes does not exceed a milligram. The largest snowflakes that humanity has ever seen fell in Moscow in 1944, when one snowflake was the size of a human palm.
Why are snowflakes hexagonal?
Snowflake is one of the most beautiful creatures nature. We would have to work hard to create a shape comparable in beauty to that of a snowflake. When it snows, millions of snowflakes fall to the ground, and no two of them are alike.
Snow, as you already know, is just frozen water. Why is snow white then if it is frozen water? It should be colorless. Snow is white because the planes of the snowflake, which are ice crystals, reflect light, which is why the snow appears white.
When water freezes, crystals form. This means that the molecules are arranged in a special order, forming geometric shape, which is what we call a “crystal”.
It so happens that a water molecule consists of three particles - two hydrogen atoms and one oxygen atom. Therefore, upon crystallization, it can form a three- or hexagonal figure.
Water turning into snow is a form of water vapor in the atmosphere. When freezing, the water crystals are so small that they are not visible. When snow forms, these crystals move up and down with air currents in the atmosphere.
During such movements, they group around the smallest particles of dust or droplets of water. Such a group of crystals becomes larger and larger; several hundred such crystals can gather around one such core.
This group becomes large, heavy and falls to the ground. We call it a "snowflake". Some snowflakes reach three centimeters in diameter. The size of snowflakes depends on temperature. The lower the temperature, the fewer snowflakes.
Did you know that in some parts of the planet colored snow fell: blue, green, red and even black? This is due to the presence of a certain fungus or dust in the air where snowflakes form.
Why do all snowflakes have one very strange feature they are all hexagonal in shape. Famous Johann Kepler, the astronomer who discovered the laws." planetary movements. And he approaches a simple “snow” question like a real scientist and devotes it to treatise"About hexagonal snowflakes." In search of the “active principle,” Kepler examines and compares the shapes of honeycombs and pomegranate seeds, sections of plant stems and flower shapes. It would seem that these objects of research are not related to winter snow, but the scientist sees the harmony of the surrounding world in the interconnection of all its elements. Moreover, he discovers the connection of these forms with the “divine proportion” (the proportion of the “Golden Section”) and with Fibonacci numbers. Let's continue Let's continue!?
Snowflake Bentley Wilson A. Bentley, an amazing self-taught farmer from Vermont (USA), nicknamed “Snowflake Man”. In 1885, when he was 20 years old, after numerous unsuccessful attempts Wilson finally took the first photograph of the snowflake that had so amazed him, attaching a large folding camera to the microscope. From that moment on, Wilson Bentley did not let go of the camera. For 46 years, Bentley collected a unique collection of photographs of snowflakes. By the end of Bentley's life, the collection numbered more than 5,000 pieces. Surprisingly, not a single snowflake shape is repeated. There are snowflakes that are similar, but none are absolutely identical!
In the Eskimo language there are more than 20 words for snow. The Yakut language has about 70. They have 50 different words to represent the colors of snow. The Eskimos have 28 words for snow. And in the Eskimo language there are 14 definitions of snow. The Eskimos have 150 words for snow. He is their whole life. Therefore, spring snow is called differently than winter snow.
Snow forms when water in the atmosphere as vapor freezes. The vapor freezes, producing clean, transparent crystals. The movement of air causes these crystals to fly up and down. Snow is white because snowflakes are crystals that reflect the entire spectrum of light that we see. Further
In Siberia, snow flakes reached 30 centimeters in diameter. Such giants can only fall out when there is complete calm. At low temperatures and strong winds, snowflakes collide in the air, crumble and fall to the ground in the form of debris. At a frost of 40 degrees, nascent ice crystals fall out in the form of “diamond dust.” In Yakutia, in clear frosty weather, thin ice needles fall out.
The hexagonal shape of snowflakes explained molecular structure water, but the question of why snowflakes are flat has not yet been answered. Some snowflakes reach three centimeters in diameter. The size of snowflakes depends on temperature. The lower the temperature, the fewer snowflakes. In some parts of the planet, colored snow fell: blue, green, red and even black? This is due to the presence of a certain fungus or dust in the air where snowflakes form.
