The heavenly designs of snowflakes

133

Dr Irengbam Mohendra Singh
The whole world is a nuclear family. We are all built of atoms. Now we know where we came from and who we are. So are the snowflakes. Everything has an architecture, based on physical laws of nature. Creativity thrives in the strangest places as that of snowflakes, somewhere in Heaven.

As a little boy, I vaguely remember my two older sisters putting out a bowl of water outside, at night in mid-winter, hoping that the hoarfrost ie small particles of ice formed at the edges of the front thatched roof of our house, would fall into it to form a big lump of ice in the morning. Occasionally they succeeded. Imphal had never a snowfall.

A snowfall is exciting. I first saw it in the cinema hall in Imphal, as news of “the first snowfall in Shimla” just after the war in 1946, with boys and girls skating on a patch. I’ve experienced snowflakes and heavy snow falls in Darjeeling and Nainital. The snow-capped Trishul of Kanchenjunga turning orange with the early morning Sun that I saw from our hostel at St Joseph’s, North Point, Darjeeling, has always been endearing. So was the snow-peaked Mount Kilimanjaro in the “Snows of Kilimanjaro”, staring Gregory Peck, Susan Hayward, and Ava Gardner in Bombay in 1952.

Here, in the UK in winter, there were heavy snowfalls. Now, they are much less with the global warming. I’ve seen many snowflakes that look like hand-knitted cotton coaster squares. They didn’t last very long and I never thought anything about them until, Prof Brian Cox from Manchester University, explained on a BBC TV program about the hexagonal ie six-pointed symmetry of snowflakes.

Snowflakes are feathery ice crystals that are never whole solid like ice. It’s an open framework with strict hexagonal symmetry. And no two snowflakes are similar. There are a seemingly endless variety of shapes, such as trees, needles and prisms. These make it notoriously difficult for scientists to model them on a computer. That was why they couldn’t quite theorise how they are so shaped for so many years. No one had any good answer. It’s like why no two human beings are alike. Darwin though, had an answer for living things as he wrote in his ‘On the Origin of Species’. He rocked the world with his reflection on ‘natural selection for survival’, producing different ‘phenotypes’ ie the observable physical characteristics of an organism.

The study of snowflakes began with Johannes Kepler, a German astronomer and mathematician, born at university town of Regensburg, Germany. He is best known for his empirical laws of planetary motions published in 1610, that they move in elliptical orbits around the Sun. His laws laid the foundations upon which Issac Newton built his Law of Universal Gravitation, published in 1687.

Shortly after his publication, Kepler was walking across the Charles Bridge in Prague (a famous old cobble-stoned bridge with its rows of statutes, a tourist spot, you can’t miss it) during Christmas in late 1610, when a snowflake landed on his coat. The elegant structure delighted him. He studied them and wrote an essay, On the Six-cornered Snowflakes in 1611. But he couldn’t explain how the snowflakes are so highly structured.

In his essay, Kepler thought, after looking at the snowflake that, it would be a perfect Christmas gift since it came down from heaven and looked like a star. He asked himself why do snowflakes, before they become entangled with other snowflakes, always fall with six corners, not with five or seven corners? He surmised, perhaps it is, because hexagon is one of the three shapes along with the triangle and the square that fill up a plane without leaving spaces.

It wasn’t until a 15-year-old boy from Jericho, Vermont, US, began spending winter months, at his farm, studying them with a battered microscope, and later in 1885, began experimenting with a camera taking first ever photographs of snowflakes. His name was Wilson Bentley. He became well-known as Wilson “Snowflake” Bentley, after 45 years of collecting over 5,000 images and dedicated his life to methodically observing and documenting raindrops, snowfalls and mists that he had seen.

In May 1898, Bentley conjointly wrote an article with George Henry Perkins, Professor of Natural
History at the University of Vermont, in which he argued that from the evidence he collected “no two snowflakes were ever alike, and every crystal was a masterpiece of design and one design was ever repeated”. He further wrote: “their uniqueness is part of their fascination and romance, yet there is undoubtedly something similar about them; they share ‘six-ness.”
How these exquisite regular and ordered snowflakes formed from apparently formless water was the question that haunted many a man of genius. Brian Cox says it was because of a lack of knowledge of atomic theory of chemistry and a chunk of modern physics. Now any physicist would understand that snowflakes acquire such beautifully sophisticated designs because of the laws of nature.

Physicist Ken Libbrecht of the Californian Institute of Technology, who also studied snowflakes since childhood in North Dakota, US, has built a machine to make snowflakes in the laboratory to study the changing shapes of ice crystals. He says that despite the new advances in modelling snowflake growth, the fundamental mystery about snowflakes, how they form in the first place, is still far from solved. To understand how they grow, “we have to marry mathematics with physics, and that’s not been done, partly because we don’t know the right physics,” he adds.

Brian Cox explains with a flourish. An atom consists of a nucleus made up of protons and neutrons held together by one of the four fundamental forces of Nature ie strong nuclear force, and with electrons orbiting around it, held in position by another force, electromagnetism.

The water molecule (H2O) consists of two hydrogen atoms bonded to a single oxygen atom but not in a linear structure. The two hydrogen atoms are displaced at an angle of 104.5 degrees. The reason for this is the presence of two extra pairs of electrons that sit on the opposite side of the oxygen atom because of atomic physics and quantum mechanics. This gives water molecule its distinctive shape, and its many unusual properties.

The water molecule is electrically neutral, but the uneven distribution of electrons means that it has a negative and positive end, and so water molecules like to stick together. This opens up a world of complexity. This happens to an extent in liquid water, resulting in large and complex structures. The effect is more dramatic when temperatures drop and water freezes to form ice. There are seventeen known forms of ice. Here on Earth, there is generally just one kind of ice in Antarctica, the same as the ice in your freezer.
Brian Cox says the complex theory of ice is a consequence of the laws of quantum theory that describe a wide range of natural phenomena of all sizes, from the structure of atoms and molecules to the nuclear reactions in the Sun. They also describe the action of real world devices such as transistors and lasers and, more recently, exotic pieces of technology, such as quantum computers.

According to Brian Cox, the concept of symmetry is central to modern physics, but the asymmetric structure of the water molecule is a consequence of the way that electrons fit around the nucleus of an oxygen atom. It’s because there are four available outer slots and several electrons to fill them that an asymmetric molecular structure results when two hydrogen atoms approach the oxygen atom, and that structure emerges spontaneously.
In a simplified version, Miriam Rossi, professor of chemistry at Vassar College, New York, explains. Snowflakes are symmetrical because they reflect the internal order of the water molecules as they arrange themselves in the solid state ie crystallisation or the growth of snowflakes from its liquid water. In the solid state, such as ice and snow, water molecules forms weak bonds (called hydrogen bonds) to one another.
These ordered arrangements result in the basic symmetrical, hexagonal shape of the snowflake. In reality, there are many types of snowflakes that no two types of flakes are alike. They are because each snowflake is a separate crystal that is subject to specific atmospheric conditions, notably temperature and humidity under which it is formed.
During crystallisation, the water molecules align themselves to maximise attractive forces and minimise repulsive ones. As a result, water molecules arrange themselves in predetermined spaces in order to maintain the pattern of symmetry. In this way the different arms of snowflakes are formed.

Explained slightly differently. When water freezes its molecules tend to settle in the lowest-energy state. This requires some form of symmetry. When water molecules are floating freely in vapour in the sky, they begin to arrange themselves into a crystalline solid when the temperature drops below freezing. Then the two hydrogen atoms of the water molecule tend to attract neighbouring water molecules. When the thermal motion (temperature) is low enough, the water molecules link together to form a solid and open framework that has a strict hexagonal symmetry of the snowflake. But the flake might branch off in a different direction. In the end, we get all kinds of forms, shapes and sizes of snowflakes.

(The writer is based in the UK. Email; irengbammsingh@gmail.uk. Website: www. drimsingh.co.uk)

Source: The Sangai Express

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