Everyone different, or twinkle, twinkle little star



If there is one thing people in Montreal become familiar with quickly, it is snowflakes. We walk through snow, we shovel it, we ski on it, and it falls on our heads. We welcome snow’s arrival, and then welcome its departure.

The truism is that all snowflakes are different, and there are books cataloging their symmetrical complex shapes. The reason they are all different is interesting.

Snowflakes are a crystalline form of water, created by super-cooled water vapour, the gaseous form of water existing in clouds. When the snowflake forms it is in a reservoir of very appealing—if you are a snowflake—super-cooled vapour, and the snowflake grows rapidly in all directions chasing this vapour. The pointiness of the tips of the snowflake’s arms arises because it is almost literally reaching out towards the vapour. The six-sided pattern reflects the symmetry enforced by the three-sided shape of the water molecule in a way which is not complicated to understand, but I won’t explain here.

Why are they all different?  It is the same reason that stars twinkle. Stars twinkle because we are looking at them through the air. Our atmosphere fluctuates slightly, and these small fluctuations distort the light from stars. The variations in the atmosphere are normally too small to see, but stars are so small when viewed in the sky that the fluctuations can shift the image enough that they seem to twinkle. It is not stars that are twinkling; it is the atmosphere between us and the stars.

This twinkling of the atmosphere means that the super-cooled vapor in clouds “twinkles” hotter and colder on tiny distance scales as well. When a snowflake grows into a cold and tiny twinkle of atmosphere, it grows faster, likewise it grows slower in a warmer twinkle of atmosphere. The twinkles are about the same size as a snowflake. So all the arms of the snowflake which are pointed in different directions speed up, or slow down, together.

The perfectly symmetrical complex pattern of the snowflake then reflects the twinkling fluctuations of the atmosphere, and the difference between snowflakes reflects the different tiny atmospheric twinkles in different parts of a cloud as each snowflake forms and grows independently.

Perhaps to stretch a point a little too far, there is an interesting analogy here in terms of providing opportunities for McGill undergraduates, who make decisions that will set the course for the rest of their lives. One way to help our students make informed decisions is by opening the doors to different disciplines, and creating opportunities for students to take part in research.

Like the snowflakes—and here comes the point-stretching analogy—the background our students receive can be different, depending where their interests lead them, thereby making each McGill science graduate unique. 

Our Faculty’s undergraduate research initiative is described further here: http://www.mcgill.ca/science/ours/.

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