‘Tis the season to be merrily thinking about crystals!!
You may go out of your way to avoid the X-crystallographer and physicist at a Christmas party but they have the most interesting story to tell at Christmas time (at least in the Northern hemisphere!) – the story of a snowflake!!
The first scientific reference to snowflakes is from Johannes Kepler from Prague who recognised the 6-fold symmetry of a snowflake in 1611. By 1665, the latest invention of the microscope made it possible for Robert Hooke to sketch the image of a snow crystal. It wasn’t until 1885 that the first snowflake was photographed (Figure 1). Wilson Bentley later published over 2,400 of them in a book called Snow Crystals (a soft copy of which is still in print today -Dover Publications). Wilson made the observation that “every crystal was a masterpiece of design and no design was ever repeated. When a snowflake melted, that design was forever lost.”
Figure 1. The first photograph of a snowflake in 1885 by Wilson Bentley
The study of snowflakes led to the inception of crystallography. This field has been revolutionised by the finding that the diffraction patterns created when X-rays are passed through crystals, are directly related to the arrangement of atoms inside the crystal. 2014 has been the International year of Crystallography and follows the centenary celebration in 2013 when William Bragg and his son, Lawrence received their Nobel Prize on this very discovery.
How many types of snow crystals are there?
A Japanese nuclear physicist, Ukichiro Nakaya was the first person to perform a true systematic study of snow crystals in 1954. He grew his own crystals in the lab and described the crystal morphology under different conditions that gave an important clue to our modern understanding of snow crystal formation. He subdivided falling snow into 41 individual morphological types. We now have an International Commission on Snow and Ice that simplifies this to 7; plates, stellar crystals, columns, needles, spatial dendrites, capped columns and irregular forms. To these are added three additional types of frozen precipitation: graupel, ice pellets and hail.
The life of a snowflake
Snowflakes are not frozen raindrops (commonly known as sleet). Snow crystals form when water vapour condenses directly into ice that takes place in the clouds. The patterns emerge as the crystals grow and are dependent on two main properties of the environment: temperature and humidity. For example, plates and stars can grow around -2oC whereas columns and needles appear at -5oC (Figure 2).
Figure 2. Phases of snowflake growth, original designed by Kenneth Libbrecht, Caltech www.snowcrystals.com.
Will there be a white Christmas where you are? If so look out for the unique crystal structures and think about the impact of studying these has had, not only in understanding snow crystals but in helping many other fields of science such as drug discovery, agro-food, aeronautic, automobile, beauty care, computer, electro-mechanical and mining industries.
All the science aside, TTP Labtech would like to wish all its dedicated customers and supporters a Happy Christmas with a short snowflake video. >>Watch the snowflake video
Keep up to date with what’s going on at TTP Labtech and visit us at the SLAS conference 7-11th February, booth #1329.