Millions of snowflakes fall from the sky this winter. That’s trillions of billions of them, now mostly gone as spring approaches.
Few people look closely at each one.
Kenneth G. Libbrecht, professor of physics at the California Institute of Technology, has spent a quarter of a century trying to figure out how such a simple substance – water – can freeze into myriad shapes. .
“How do snowflakes form?” Dr Libbrecht said during an online talk on February 23 hosted by the Bruce Museum in Greenwich, Conn. “And how do these structures come out – and as I mean, literally in thin air?”
One of the people fascinated by Dr. Libbrecht’s research and photography of snowflakes is Nathan P. Myhrvold, a former chief technology officer at Microsoft, who has pursued projects in a myriad of sciences, including ancient biology, cooking and astronomy.
Dr. Myhrvold, a passionate photographer, first met Dr. Libbrecht more than a decade ago, and in the spring of 2018 he decided he wanted to photograph the complex frozen crystals himself. He recalls thinking, “Oh, we’re going to throw something together, and we’ll be ready for winter.”
But, like many of his projects, things are not as simple as Dr. Myhrvold’s plans.
“It’s actually more complicated than I thought,” said Dr. Myhrvold. “So it took 18 months to build the damn thing.”
The “damn thing” is a camera system for capturing snowflakes. He wants to use the best digital sensors, those that capture a million pixels. “The snow is very, very fragile,” he said. “It’s super complicated. So you want high resolution ”.
But that type of sensor has a much larger area than the image normally produced by a microscope lens, the result of decisions made nearly a century ago by microscope manufacturers. .
That means he needs to find a way to stretch the microscope image to fill the sensor.
During his tinkering, “I came up with a custom optical path that would actually allow it to work,” he said.
Then there is housing for optics. That is usually made of metal, but the metal expands when warm and contracts when cold. Moving the device from a warm indoors to a cold balcony where he will collect snowflakes “will ruin the entire microscope,” said Dr. Myhrvold, making it impossible to practice. middle okay.
Instead of metal, he used carbon fiber, which did not expand or contract significantly.
Dr. Myhrvold also found a special LED light, produced by a company in Japan for industrial use, will emit 1/1000 beams of light equivalent to that of a conventional camera flash. This minimizes the heat released from the flash, which can slightly melt the snowflakes.
To see something under a microscope, a specimen is usually placed on a slide. But glass holds heat. That also melts the snowflakes. So he switched from glass to sapphire, a more easily cooled material.
By February 2020, he is ready. But where to find the best snowflakes to photograph? At first, he thought he could go to a ski resort town – perhaps Aspen or Vail in Colorado or Whistler in British Columbia.
But these places are not cold enough.
Dr Myhrvold said: “The powder snow that a skier might love to slide through, is in fact pretty much powder. “There isn’t a lot of beauty in those things.”
Indeed, snowflakes that fall on most people most of the time are rarely what people think of them as snowflakes.
Water is a simple molecule consisting of two hydrogen atoms and one oxygen atom. When the temperature drops below 32 degrees Fahrenheit, molecules start to stick together – that is, they freeze.
A snowflake is born in a cloud when a drop of water freezes into a small ice crystal. The shape of the water molecules causes them to stack in hexagons. That is why the prototype snowflake has six arms.
The crystal then grows, absorbing water vapor from the air and other droplets evaporating nearby to replenish the steam. “It may take 100,000 drops of evaporated water to make a snow crystal,” Dr Libbrecht said.
But how the crystal grows depends on temperature and humidity. In the 1930s, a Japanese physicist, Ukichiro Nakaya, was the first to grow artificial snowflakes in his lab, and by changing the conditions he was able to catalog the types of artificial snowflakes. in most conditions.
When the temperature is just below freezing, the snowflakes are usually simple hexagons. At around 20 degrees Fahrenheit, common shapes are hexagonal columns. Temperatures from 15 degrees to -5 degrees F often form beautiful, classic snowflakes.
At these temperatures, the points of the hexagon develop into branches. These branches then lay out other branches and smaller hexagonal plates. Slight changes in temperature and humidity affect growth patterns, and conditions constantly change as snowflakes fall to the ground.
Dr. Libbrecht said: “Because it has a complicated path through the clouds, it has a complex shape. “They all follow different paths, and so each one looks a little bit different, depending on the one.”
So in order to find beautiful snowflakes, Dr. Myhrvold went north, much further north. He and a few assistants shipped thousands of pounds of equipment to Fairbanks, Alaska; Yellowknife, the largest community in the Northwest Territory of Canada; and Timmins, Ontario, about 150 miles north of Lake Huron.
A month later, the coronavirus pandemic disrupted their efforts. But Dr. Myhrvold was able to capture what he calls the highest resolution ever images of snowflakes.
That claim has left others in the snowflake world, including Don Komarechka, a Canadian photographer who has a lower tech approach to the decision. He uses a store bought digital camera with a high capacity macro lens. He doesn’t even use a tripod – he just held the camera while snowflakes lay on the black glove his grandmother gave him.
“Extremely simple,” said Mr. Komarechka. “It is very accessible to anyone with any camera.”
“I think it’s a little over-engineered,” he said of the custom-built system by Dr. Myhrvold.
Mr. Komarechka also takes a different approach to illumination, using light reflected off a snowflake, while Dr. Myhrvold’s image records the passing light. “You can see the surface texture, and sometimes the beautiful rainbow colors in the center of a snowflake,” said Mr. Komarechka.
The rainbow effect is similar to what you see in a soap film, but the colors “usually show up much more clearly than what you would see in a soap film or anything else,” he says. “It was an almost illusionary color, almost like a tie-dyed T-shirt.”
To contradict Dr. Myhrvold’s claims, Mr. Komarechka took a photo that he thinks is of even higher resolution. Dr. Myhrvold responded with a lengthy rebuttal explaining why his image was, however, more detailed.
In practical terms, Dr. Myhrvold’s image is sharper when printed on paper in enlarged sizes. They are available to buy in sizes up to 2 meters x 1.5 meters.
“In that narrow sense, yes, that’s what Nathan is claiming, and he’s not wrong,” said Dr. Komarechka.