Libbrecht began his research by growing synthetic snowflakes in his lab, where they can be created and studied under well-controlled conditions. Over several years, Libbrecht developed some specialized techniques for capturing images of snow crystals. In 2001, he also began photographing natural snowflakes. Precision microphotography was necessary for this work.
"A few years ago, I mounted my microscope in a suitcase, so I now can take it out into the field," he said. "Sometimes I arrange trips to visit colleagues in the frozen north, and other times I arrange extended ski vacations with my family.The most difficult part of his work nowadays, he said, is getting the complex-looking instrument through airport security. Libbrecht's camera rig is essentially a microscope with a camera attached. The entire apparatus was built on campus and designed specifically for snowflake photography.
"When photographing in the field, I first let the crystals fall onto a piece of cardboard," said Libbrecht. "Then I find one I like, pick it up using a small paintbrush and place it on a microscope slide. I then put it under the microscope, adjust the focus and lighting and take the shot. You need to search through a lot of snowflakes to find the most beautiful specimens."
Libbrecht said observing natural snowflakes in the field is an important part of his research and nicely complements his laboratory work.
"I've learned a great deal about crystal growth by studying ice and have gotten many insights from looking at natural crystals. Nature provides a wonderful variety of snow crystal types to look at, and the crystals that fall great distances are larger than what we can easily grow in the lab," he said. So where does one find really nice snowflakes? Libbrecht said some snowy places are better than others. The snowflakes chosen for the stamps were photographed in Fairbanks, Alaska, in the Upper Peninsula of Michigan, and in Libbrecht's favorite spot: Cochrane, in Northern Ontario. "Northern Ontario provides some really excellent specimens to photograph," said Libbrecht. "The temperature is cold, but not too cold, and the weather brings light snow frequently.
"Fairbanks sometimes offers some unusual crystal types, because it's so cold. Warmer climates, for example, in New York State and the vicinity, tend to produce less spectacular crystals." As for the nitty-gritty of snowflake research, probably the question Libbrecht is asked the most is whether the old story about no two snowflakes being exactly alike is really true. "The answer is basically yes, because there is such an incredibly large number of possible ways to make a complex snowflake," he said."In many cases, there are very clear differences between snow crystals, but of course there are many similar crystals as well. In the lab we often produce very simple, hexagonal crystals, and these all look very similar."
Falling from thousands of feet, these intricate ice crystals commonly begin as a piece of dust tumbling through the clouds. Gathering water molecules, they blossom into crystal forms in endlessly different patterns because of the constantly changing conditions of the atmosphere.
Libbrecht can grow many different snowflake forms at will in his lab, but says there are still many subtle mysteries in crystal growth that are of interest to physicists who are trying to understand and control the formation of various materials. A real-world application of research on crystals is the growth of semiconductors for electronic gadgets. These semiconductors are made possible in part by painstakingly controlling how certain substances condense into solid structures.
When he's not studying snowflakes, Libbrech is also involved in the Laser Interferometer Gravitational-Wave Observatory (LIGO), an NSF-funded project that seeks to confirm the existence of gravitational waves from exotic cosmic sources such as colliding black holes.
In LIGO, Libbrecht has a lot of professional company; in fact, the field was essentially founded by Albert Einstein, who first predicted the existence of gravitational waves as a consequence of general relativity. Kip Thorne and Ron Drever at Caltech, along with Rai Weiss at MIT, were instrumental in initiating the LIGO project in the 1980s.
But in snowflake research, Libbrecht is pretty much a one-man show. He said something about the exclusivity appeals to him.
"It suits some of my hermit-like tendencies," Libbrecht said. "As Daniel Boone once said, if you can smell the smoke of another person's fire, then it's time to move on. My research on snow crystal growth is the one thing I do that simply wouldn't get done otherwise."
For more information about the Holiday Snowflakes collection, visit: www.usps.com/communications/news/stamps/2005/sr05_054.htm