The classic image of a snowflake can be traced back to home-schooled farmer Wilson “Snowflake” Bentley of Vermont. When he was 15, he started peering down his mother’s microscope. “Always, from the very beginning, it was snowflakes that fascinated me most,” he . Bentley eventually persuaded his parents to get a camera and hooked it up to the microscope. In 1885, after much trial and error, he finally managed to take a decent photograph of a snowflake. His hobby was to become a lifelong obsession, and he went on to take thousands of .

Bentley was the first to claim that no two snowflakes are alike. Yet while his images show great diversity in shapes, they are dominated by symmetrical, six-sided star-like beauties. This was in keeping with the Victorian ethos of divinely created perfection, and when Bentley’s photos appeared in magazines, they caught the public imagination.

Bentley’s star-like images have continued to shape the popular idea of a snowflake ever since, but do they really show the real thing? In 1892, . His images showed imperfect, irregular specimens. , and the argument went on for decades.

What is clear is that Bentley gave his white-on-white images a black background by around the outline of each snowflake. But did he sometimes scrape away asymmetries too? Hellmann claimed he had “mutilated the outlines”, and Bentley’s defence of his methods is not entirely reassuring. “A true scientist wishes above all to have his photographs as true to nature as possible, and if retouching will help in this respect, then it is fully justified.”

Bentley continued to create images in the same way and to defend his methods until he died from pneumonia, aged 66, in 1931. Since then, of course, we have learned much more about snowflakes. We now know they usually form when a super-cooled water droplet in a cloud freezes around a speck of dust to form a basic six-sided crystal. This crystal grows and becomes more complicated as it steals water vapour from the air and starts to fall.

At -2 °C, simple hexagons and star shapes form. Between -5 and -10 °C, it’s columns. Then below -15 °C, the six-siders appear again. What’s more, each tiny snow crystal experiences a gamut of temperatures and humidities as it falls, and often collides with other crystals. A snowflake can consist of a single crystal, or it can be many thousands of these crystals joined together. “Every snowflake that falls to earth has its own unique history,” says ice physicist John Hallett of the Desert Research Institute in Reno, Nevada.

“Every snowflake that falls to Earth has its own unique history”

The complexity of the snowflakes that reach the ground has been revealed by a high-speed camera designed by atmospheric scientist Tim Garrett of the University of Utah and his colleagues. It can snap shots at shutter speeds of up to 1/40,000 of a second – fast enough to capture snowflakes in mid-air (below).

Over the past two winters, has captured more than a million pictures of falling flakes at Utah’s Alta Ski Area in the Wasatch Range mountains. The aim is to improve weather forecasting but it is also revealing what “normal” snowflakes look like. “The complexity of nature almost seems to defy categorisation,” Garrett says. More often than not, his pictures reveal . “The chances of a snowflake falling without colliding with other snowflakes or water droplets is a near impossibility,” he says.

Some flakes, known as graupels, collect millions of tiny water droplets that freeze as they fall. They look like mini-snowballs and feel like ball bearings under your skis. Others are snow crystals that have bumped into other snow crystals to make the fluffy, air-packed aggregates that make Utah’s ski slopes so fantastic. Then there’s everything in-between.

But the camera does also occasionally capture snowflakes like those Bentley photographed. Perfect six-sided snowflakes do exist, says Bentley’s modern-day successor, Ken Libbrecht of the California Institute of Technology in Pasadena. They are, however, extremely rare and only form when conditions are perfect. “I have to go to great lengths to ignore the ugly stuff,” says Libbrecht, a physicist by trade and also a keen photographer of snowflakes.

His photos reveal , from spiky needles to stumpy hollow columns. Sometimes, if the conditions are right, he finds triangular crystals, 12-sided snowflakes or icy cufflinks – columns with hexagonal stars on either end. “I find the real gemstones,” he says.

For perfect six-siders, it needs to be around -15 °C, with low cloud and no wind. Caught in the halo of urban street lamps, symmetrical snow crystals twinkle as they fall to earth. So Libbrecht can sometimes be found staring skyward in the parking lots of Northern Ontario, trying to catch the ephemeral sparkles on a piece of card. He uses a tiny brush to transfer them under the microscope, but even after all this effort only 1 in 1000 are perfect six-siders.

Did Bentley also find these rare flakes? Or did he tidy up less than perfect ones? Libbrecht, for one, does not think that Bentley did anything dubious. “All he did was the old-school version of Photoshop,” he says. Others suspect Bentley did go further, but not to deceive. “Bentley produced the paragon,” says history of science researcher Latif Nasser of Harvard University. “He created images he believed were true to nature, whilst Hellman photographed snowflakes exactly as they were, warts and all.”

So, in keeping with the spirit of the season, it seems that Bentley and Hellmann were both right. If Bentley and Libbrecht’s snowflakes are the supermodels of the skies, then Hellmann and Garrett’s are the paparazzi-free jolie laides. Their beauty is unconventional and quirky, and perhaps it’s time we gave them their own photo shoot.

This article appeared in print under the headline “No great flakes”

STANDING at the entrance of a 74-acre dust bath full of diggers, trenches and men in hard hats, waiting for my guide, I realise I am the only woman on site. Wearing my thickest skin, I wonder what to expect.

The sun is shining and I am at Silverwoods, a building site in Worcestershire being transformed into a mixed development of houses, offices, shops and green spaces. There is even going to be a pub. I am here to meet graduate engineer Kirsty Burwood.

Burwood, who works for international engineering consultancy , has designed the drainage system, and she is on site to scrutinise progress. As one of the 5.4 million people working in the UK engineering sector, she is part of an industry that turns over more than £1 trillion per year and prides itself on innovation and problem solving – and yet is only 8.7 per cent female.

But the tide is beginning to change. Employers like Arup are finally starting to tackle the challenges that women in engineering face.

“Engineering is a white male bastion,” says sociologist from the University of California in Irvine. “Half the world is not involved in the way the world is designed.” Women are under-represented at every level, and are more likely to leave the profession than men.

Seron says . Female engineers can be put off early in their careers if they find themselves relegated to gender-stereotyped roles such as making coffee or taking notes. A recent found that of those who had started work in the sector and then left it, a fifth did so because they didn’t like the workplace climate or their boss.

Covert sexism

“It’s not overt sexism,” says study author at the University of Wisconsin, Milwaukee. “It’s more covert. Women are sometimes belittled or undermined.” Around 8 per cent left to spend time with their family, while 11 per cent left the sector because of working conditions, excessive travel, lack of advancement or low salary. Indeed, earlier this year a UK study found that when they start work with an engineering company.

So what is being done to redress the balance? My idea to boost the proportion of women in engineering by firing all the men is, apparently, not an option. Aside from anything else, diversity is in companies’ own interests: a balance of both sexes has been shown to improve productivity.

“Boosting the proportion of women in engineering by firing all the men is, apparently, not an option”

Employers can start by tackling stereotypes. Biases linking, say, women to fashion and the arts, and men to money-making and maths-related subjects, are common even among those who actively reject these stereotypes. I took an designed to highlight implicit biases only to find, alarmingly, that I have a “strong automatic association of females with family and males with career”.

Employers are finally starting to overcome those biases, through training. “A woman with kids might, for example, be overlooked for an international project because people presume she won’t want to travel, but she should have the same opportunity as anyone else,” says Arup director Kate Hall. Through carefully crafted workshops, leaders are encouraged to recognise, challenge and manage prejudices.

Catching up later with Burwood and her colleagues in their open-plan Arup-engineered office, I experience a culture of inclusion. Employees seem to feel valued. Opinions are listened to. “People on site are professional and respectful,” says Burwood. Inappropriate behaviour is challenged and new recruits are mentored. Ask employees what they value the most, and a flexible work schedule tops the bill. Perhaps that is why nine out of 10 mums return to the company after taking maternity leave.

As a result, Arup can now boast a workforce that is 30 per cent female – 22 per cent up on the industry average. Both Arup and engineering consultancy Atkins recently bagged themselves a place on list.

But even Arup admits it has a sticking point. As with the engineering sector as a whole, there are too few women in senior leadership roles. Mid-career, the mentoring and training fade away, leaving people to carve their own career paths. Women can become disillusioned about their prospects when there are so few female role models, so they either leave, or stay and struggle to get promoted (see “It’s time to stir up trouble“).

Hall believes that networking is the key to helping women move up the career ladder. She has set up a supportive, 600-strong networking initiative for Arup women (and men) to meet, mentor each other and network with industry partners. As a result, says Hall, Arup has progressed from having no women in board positions to having women on seven out of nine management boards.

“There is no one magic silver bullet to solve the women-in-engineering problem,” Hall says. “But there are lots of things that employers can do.” The final hurdle, perhaps, is to address the dearth of cultural references to engineering. “There are very few cultural role models in engineering to inform and motivate the next generation,” says Sophie Robinson, flight physics engineer at defence and aerospace company . Those that do exist – Howard from The Big Bang Theory, Tony Stark (aka Iron Man) and Bob the Builder – are made-up and male. So perhaps it is time for a new role model on the block. Move over Bob the Builder, make way for Emma the Engineer.

Glasses developed to help doctors spot veins more easily have a useful side effect – they enhance the ability to see reds and greens.

The , made by in Boise, Idaho, use filters to enhance perception of blood oxygen levels in vessels under the skin. But the filters happen to concentrate their effects around the wavelengths where red-green colour blind people are deficient. “We didn’t design them for colour blind people,” says , of 2AI Labs, “but we weren’t too surprised to find they help.”

, a red-green colour blind neuroscientist at the University of Sussex in Brighton, UK, experimented with the specs after Changizi asked for testers on Twitter. “They made my daughter’s lips and her red-orange jumper really stand out,” he said.

The spectacles helped Bor ace the Ishihara test, the standard test for red-green colour blindness, but he didn’t do so well on another test focusing on the entire colour spectrum.

Most cases of red-green colour blindness are genetic, so glasses like this correct rather than cure, and amplify reds and greens at the expense of discerning yellows and blues. “I couldn’t tell if the yellow light on my daughter’s baby monitor was on or off,” says Bor.

Changizi has suggested that and so help sense health and emotion. The glasses were developed to enhance this ability and different versions are currently being tested by doctors to help spot bruising, and by poker players to help detect the subdued blushes of bluffing opponents.