I’m not a religious person, but I thought this snowflake might be symbolic for many people. I saved it for Christmas Eve for that reason, but I’ll explain scientifically how these “crossed needles” form. View large!
“Bullet rosette” type snowflakes like the one posted yesterday form in a similar way, but this is the “needle” variety. Needle crystals grow at slightly warmer temperature, only about 2 degrees below the freezing point of water. They form into elongated columns that grow much more rapidly, but they can also begin their lives around a common object with multiple nucleation sites.
Each crystal needs a nucleus to begin its growth. You can see a few new crystals forming from nucleation sites on top of the already-formed needed as well, two are easy to see where the needles cross. These could have been started from the impact of a super-cooled water droplet freezing on impact, giving rise to a new starting point. The same kind of origin is likely true for the initial needles that make up this snowflake.
Imagine a tiny pellet of ice, as if a small droplet of water has simply frozen solid. It wouldn’t be a crystal itself, but might have some irregular surface features for which water vapour could begin attaching itself to. This erratic start can cause crystals to begin forming at multiple points along the tiny ice pellet, growing independently of one another.
So, why the cross? Each crystal has the best chance of success if it grows into an open area where there is more water vapour to fuel further growth. The best-case scenario is seen when these crystals grow perpendicular to each-other, allowing for the maximum amount of space between the columns so that they do not inhibit the growth of one another. Other angles might be possible but by far the most common is this variety, as it has the greatest chance for outward growth.
This is similar to twelve-sided snowflakes, which are basically just two 6-sided crystals stuck together. They grow best when they’ve randomly stuck together in a 30-degree rotation, allowing each branch to have equal spacing on either side. Without equal spacing, twelve-sided snowflakes wouldn’t form and neither would crossed needles like this.
Needle-type crystals are very difficult to photograph because of the warm temperatures in which they form. The temperature in the clouds is often cooler than the temperature on the ground, and so close to the freezing point in the sky means they often begin melting before even hitting the ground. On rare occasions the ground temperature is equal or cooler than the environment where the crystal formed, and you have an opportunity to observe and photograph them before they disappear. There have only been two or three scenarios where I’ve been able to get solid needle images.
To understand how snowflakes form, and how to photograph them using the same techniques I use for all my snowflake photographs, pick up a copy of Sky Crystals: https://skycrystals.ca/book/
- it’s the best guide to photographing these beauties
, and winter in North America is about to hit us in a few days! Temperatures are dropping, so get ready!
To see the fruits of my labour over five years and 2500 hours with the subject in a single image, check out “The Snowflake”
- nothing like this has ever been done before. It’s worth a look! Merry Christmas!