Is it true that all snowflakes are different?
If we could create snowflakes in a cloud, we could control the weather, With this ambitious plan in mind, science is working to find out exactly how these fluffy fragments of ice form from moisture in the air. The weathermen have been able to increase rainfall about ten per cent by cloud seeding. But better control of rain and snowfall must wait until we have a more complete understanding of how ice fragments are formed in the clouds.
The secrets of the snowflake are being pried out in the laboratory. In the process, the frothy white doily has taught us some ,surprising facts. Water, of course, freezes at 0 degrees Centigrade and at this temperature we expect liquid water to become solid ice. Usually it does and on this basis we would expect vapor and moisture in the air also to become ice at 0 degrees. But this is not so and a whole new set of rules must b e explored. A snowflake is a lacy arrangement of ice crystals and pockets of air. The tiny crystals may be no bigger than molecules and they come in different shapes. At three degrees below freezing, the moisture in the air tends to form flat, six sided plates of ice. In air two degrees colder, the moisture tends to form Jagged needles of ice. The tiny ice crystals formed at minus eight degrees are hollow, six sided columns. In very dry air, the temperatures for forming ice crystals must, it seems, be much lower. In a low hanging snow cloud there are turbulent masses of cool and warmer air, moist and drier air. Hence, we get a wide variety of assorted crystals flying around.
When the temperature goes more than 12 degrees below freezing, numbers of ice crystals may team up to form flakes. They form around a solid fragment called a nucleus which may be a particle of dust or ice. This process is more likely to happen when there are many dusty particles of such minerals as silica and mica in the cloud.
Though they are of different shapes, all the ice crystals are hexagonal. For this reason, they tend to form a six sided design when they assemble themselves into a snowflake. But the different factors in forming each snowflake are endless. Its building blocks are different shapes. It forms while being wafted from cold to cool, moist to dry regions of the cloud. It assembles several hundred crystals, These chance variations in the building of each snowflake make identical twins almost impossible. It is not likely that two identical snowflakes could form in a nation wide blizzard.
The growth of a snowflake, like the formation of the ice crystals, also seems to vary with temperature. At any rate, in the laboratory, it has been found that a perfect, six sided snowflake cannot be hurried. It must grow very slowly in gradually cooling air. When the temperature takes a sudden drop, the flakes form faster and are lop sided.