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Two Snowflakes May Be Alike After All
An anonymous reader writes "LiveScience is reporting that it may be possible for two snowflakes to be alike after all. For anyone who studies probability, this seems reasonable, given that the article mentions that 10^24 snowflakes fall in any given year. The article contains links to fascinating snowflake pictures. From the article: 'A typical snow crystal weighs roughly one millionth of a gram. This means a cubic foot of snow can contain roughly one billion crystals ... "It is probably safe to say that the possible number of snow crystal shapes exceeds the estimated number of atoms in the known universe," Nelson said. Still, while "no two snowflakes are alike" might hold true for larger snowflakes, Nelson figures it might ring false for smaller crystals that sometimes fall before they have a chance to fully develop. "How likely is it that two snowflakes are alike? Very likely if we define alike to mean that we would have trouble distinguishing them under a microscope and if we include the crystals that hardly develop beyond the prism stage--that is, the smallest snow crystals," Nelson said.'"
Nancy Knight, 1988
3 95.htm
"The old saw that no two snow crystals are identical was disproved in 1988, when National Center for Atmospheric Research scientist Nancy Knight found two that apparently were. The twin crystals were found by accident when Knight was examining samples collected at 6 kilometers (20,000 feet) over Wisconsin for a cloud-climatology study. Thick, hollow, and columnar, the crystals seem to have been Siamese twins that grew attached to each other. No satisfying explanation has yet been found." -
http://www.proquestk12.com/curr/snow/snow395/snow
From snowflake chemistry
There are shills on slashdot. Apparently, I'm one of them.
See Cecil Adams at the straightdope http://www.straightdope.com/classics/a3_392.html
Freshly-fallen snow is roughly 1/10 to 1/5 as dense as liquid water, so one cubic foot of snow weighs about 6250 to 12500 grams. At one million crystals per gram, that's -- guess what -- about 0.625 to 1.25 billion crystals per cubic foot.
Who made one cubic foot equal to 1000 grams?
Mother nature. Air is part of her recipe for snow.
rj
The National Centre for Atmospheric Research (NCAR) has a pic of the identical (attached) snowflakes on their kid's page.
They look more like nanopumps than snowflakes to me!
There are shills on slashdot. Apparently, I'm one of them.
However, is our starting number of 15 reasonable? The standard snowflake crystals are all formed at temperatures just below freezing under fairly normal conditions. The rate at which the water cools will have a major impact, as will any airborne particles around which the snow crystals can condense. (Particles may cause a break in the symmetry or may force the ice to contain patterns that simply aren't possible when only hexagonal ice crystals are present.) There again, anything dissolved in the water will change the chemistry as well. As not everything freezes at the same temperature, it is entirely possible for snowflakes to acquire bubbles and other oddities where something has remained liquid even as the water froze.
Then, there are the exotic states of frozen H2O which are not considered "ice", per se. Water that has frozen under really strange pressures or at extreme rates will not form regular ice crystals, but form other solid states instead. Slashdot has covered a few of these in the past. Is it possible to have a snowflake form from such states? Maybe. Then you add a whole new set of possibilities to the mix, although it would be unlikely that you could get a mixture of regular ice and these exotic states. (Not impossible, though. If the higher-level clouds chucked down snow in the exotic states, which then got added to by regular snowflake crystals, then you could indeed have a mixture. Not sure this could happen on Earth, but there may be planets where this is common.)
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
(37065N-89115)(46^(N-4))+(2N-1)(2(^N-1)) in fact, and that is just for N number of bricks in a tower N-1 bricks tall. I think they predict the final value to be around 100^n
Check the math here if you want.
According to a book that i'm reading "It ain't necessarily so ...bro" by Dr Karl Kruszelnicki (Ignoble award winner, Radio host on Triple J (Australia)).
"In 1988 the scientist Nancy Knight (at the National Center for Atmospheric research in Boulder, Colorado) was studying cirrus clouds. During a snow storm in Wisconsin her research plane collected snowflakes on a chilled glass slide coated with sticky oil. Two of the snowflakes where identical (atleast under a microscope, atleast)." page 148