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Author Topic: Snowflakes
ScholasticSpastic
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Icon 1 posted January 27, 2007 16:20      Profile for ScholasticSpastic     Send New Private Message       Edit/Delete Post   Reply With Quote 
Okay, so I understand that the structure of snowflakes is a result of the crystaline-lattice structure of H20 molecules locked into hydrogen-bond-induced 3-D hexagonal shapes. That part I get. I feel that it adequately explains the shape of the body of the flake and the fact of its symmetry. So, someone please tell me, by what mechanisms are the arms of the snowflake all symmetrical? Once the flake has split into six different tangents, I would expect each arm to find its own symmetry based upon the structure of the parent crystal at the core. There are always an infinite number of possible shapes for the arm of a snowflake to form, so how come all six arms are the same shape? How is it that the center of the snowflake dictates the branchings of its arms?

This is doubtless a much bigger question than I think it is. Then again, the sky-is-blue question is deceptively easy to answer once a kid understands how rainbows work.

That's symmetri for Freja42

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"As in repeating a well-known song, so in instincts, one action follows another by a sort of rhythm; if a person be interrupted in a song, or in repeating anything by rote, he is generally forced to go back to recover the habitual train of thought..." (Darwin, The Origin of Species)

Posts: 540 | From: Vernal, UT | Registered: Jan 2007  |  IP: Logged
Stibbons
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Icon 1 posted January 28, 2007 00:45      Profile for Stibbons   Author's Homepage     Send New Private Message       Edit/Delete Post   Reply With Quote 
Without much time to delve into papers, the next best thing wikipedia states that:

quote:
There are, broadly, two possible explanations for the symmetry of snowflakes. Firstly, there could be communication or information transfer between the arms, such that growth in each arm affects the growth in each other arm. Surface tension or phonons are among the ways that such communication could occur. The other explanation, which appears to be the prevalent view, is that the arms of a snowflake grow independently in an environment that is believed to be rapidly varying in temperature, humidity and other atmospheric conditions. This environment is believed to be relatively spatially homogeneous on the scale of a single flake, leading to the arms growing to a high level of visual similarity by responding in identical ways to identical conditions, much in the same way that unrelated trees respond to environmental changes by growing near-identical sets of tree rings. The difference in the environment in scales larger than a snowflake leads to the observed lack of correlation between the shapes of different snowflakes.
Perhaps I might look at this more tonight when I get some free time...
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TheMoMan
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Icon 1 posted January 28, 2007 07:42      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
ScholasticSpastic____________________Thoughts from an old storm chaser. What goes on in the cloud, there will be some updrafts, molecular sized water floating around attaching them selves to other water molocules. Remember water is polar so it will want to fit into the snowflake where it is most balanced, or maybe the snow flake turns because it is out of balance, until it becomes balanced. Eventually it will become big and heavy enough to fall out of the cloud, now what happens on its journey to the ground? If it goes through warm air melting and refreezing may occure, I am going to search the weather channel and see if they have lessons on snow, sleet, and hail you have caused an old man to start studing again.


Hey I have found this link

http://www.sciencetheatre.org/ask_st/100897.html

Now to find out about sleet and hail.

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Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.


Benjamin Franklin,

Posts: 5848 | From: Just South of the Huron National Forest, in the water shed of the Rifle River | Registered: Sep 2002  |  IP: Logged
ScholasticSpastic
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Icon 1 posted January 28, 2007 11:55      Profile for ScholasticSpastic     Send New Private Message       Edit/Delete Post   Reply With Quote 
That's a good link and I'm forced to redefine my question. Replace references to "snowflake" with the words "snow crystal" in prior posts. This is a crystalization question.

Note that terrestrial crystals are not symmetrical. I am not just referring to the absence of symmetry that results from interference by the substrate on which the crystal grows and impurities in the solution from which the crystal is growing (termination and rutilation, respectively). I understand that a greater degree of symmetry is possible in snow crystals because the only crystalization substrate is located within the crystal and so it cannot interfere overmuch with the shape of the resultant crystal (perhaps another question arrises: do you think the conformation of the seed-particle has any influence on the final crystal?) I also agree that the relatively small size of a crystal creates a more locally homogeneous environment for each arm of the crystal (and again, I'm interested primarily in the arms as I can model the symmetry of the core structure pretty accuratly). I also feel that it is worthy of note that the majority of snowflakes are not symmetrical and we merely fixate on the symmetrical ones because we're more visually stimulated by them.

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It's just that the degree of symmetry present in unconnected arms of the crystal seems absolutely uncanny. Understand that the spikes and cleavages in the structure result more from imperfections in the lattice than from the unit-structure of the lattice in this case. It boggles my mind that each arm could be so uniformly imperfect because I don't understand (the things grow from the center outward and information cannot flow both ways) how there could be any way for the crystal to carry information about the imperfections in its arms to the adjoining arms.

This may seem trivial, but I remember hearing about a group of scientists who discovered a new and lucrative manufacturing technique discussing the formation of coffee rings on a table-top. That taught me just how important mundane questions can be.

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"As in repeating a well-known song, so in instincts, one action follows another by a sort of rhythm; if a person be interrupted in a song, or in repeating anything by rote, he is generally forced to go back to recover the habitual train of thought..." (Darwin, The Origin of Species)

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TheMoMan
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Icon 1 posted January 28, 2007 14:09      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
ScholasticSpastic__________________Please remember that some of this was learned over forty years ago, when the theorys were much different. Because water is polar, it acts some what like a magnet and is affected by magnets when forming an ice crystal, just like salts in wet solutions are affected by the water molecules when they crystalise. I believe that much of the uniformaty is caused by trying to keep the magnetic fields even as the ice crystal forms. So the water molicules are being acted upon by their own polar qualitites, the North and South poles and gravity,

Maybe the very presence of the polar qualities is the communication method? How the H$#l do they end up looking like they do. The seed being a dust particle, it seems to me that the shape would not be as uniform as it is. Are we sure that there is dirt or dust in there, have we melted sufficient quantities to find the dirt?

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Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.


Benjamin Franklin,

Posts: 5848 | From: Just South of the Huron National Forest, in the water shed of the Rifle River | Registered: Sep 2002  |  IP: Logged
ScholasticSpastic
Highlie
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Icon 1 posted January 28, 2007 14:28      Profile for ScholasticSpastic     Send New Private Message       Edit/Delete Post   Reply With Quote 
Caltech has the answer and I was right, it is as simple as a blue sky!

http://www.its.caltech.edu/~atomic/snowcrystals/

It would seem that there is NO communication involved. Ice crystalizes in different shapes at different temperatures and levels of atmospheric saturation with H2O. As the snow crystal travels up and down through the cloud it encounters differing levels of water supersaturation and temperature. These effects are homogeneous for the crystals due to their small size. Dendrites (slender branches) form at some temperature and saturation levels while platelike, branching, and ridged growth patterns occur at other temperature and saturation levels. The branches grow the same forms because they are experiencing the same conditions. Be sure to check out the custom snowflake section of the webpage and enjoy the snow crystals that were designed by controlling water saturation and atmospheric temperature in a laboratory setting.

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"As in repeating a well-known song, so in instincts, one action follows another by a sort of rhythm; if a person be interrupted in a song, or in repeating anything by rote, he is generally forced to go back to recover the habitual train of thought..." (Darwin, The Origin of Species)

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Serenak

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Icon 1 posted January 28, 2007 14:58      Profile for Serenak     Send New Private Message       Edit/Delete Post   Reply With Quote 
All waaaaay over my head, but very interesting none the less, and the designer flakes part was amazingly interesting

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Posts: 1937 | From: Suffolk England | Registered: Sep 2004  |  IP: Logged
ScholasticSpastic
Highlie
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Icon 1 posted January 28, 2007 15:09      Profile for ScholasticSpastic     Send New Private Message       Edit/Delete Post   Reply With Quote 
Want to talk about over your head? The picture I used to illustrate my question is from the Caltech website. What that means is that I had access to the answer while I was asking the question and I was too blind to realize it (I didn't even notice it was a Caltech site, I just thought it was a page from some demented snowflake fan). I feel absolutely ... [crazy] ... I don't even know how I feel about that. I wouldn't even admit it but for the fact that it would have been even more embarassing if someone else had pointed out the origin of the picture. Also, embarassment, when funny, is a good thing. [Wink]

It looks like Stibbons had it pretty much right from Wikipedia.

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"As in repeating a well-known song, so in instincts, one action follows another by a sort of rhythm; if a person be interrupted in a song, or in repeating anything by rote, he is generally forced to go back to recover the habitual train of thought..." (Darwin, The Origin of Species)

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Stibbons
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Icon 1 posted January 29, 2007 00:18      Profile for Stibbons   Author's Homepage     Send New Private Message       Edit/Delete Post   Reply With Quote 
quote:
Originally posted by ScholasticSpastic:
It looks like Stibbons had it pretty much right from Wikipedia.

And who said wikipedia was full of errors and inaccuracies... [Smile]
Posts: 1143 | From: UK | Registered: Dec 2003  |  IP: Logged
ScholasticSpastic
Highlie
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Icon 1 posted January 29, 2007 11:36      Profile for ScholasticSpastic     Send New Private Message       Edit/Delete Post   Reply With Quote 
Stibbons, Wikipedia is full of errors and inaccuracies.

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"As in repeating a well-known song, so in instincts, one action follows another by a sort of rhythm; if a person be interrupted in a song, or in repeating anything by rote, he is generally forced to go back to recover the habitual train of thought..." (Darwin, The Origin of Species)

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Alan!
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Icon 12 posted January 29, 2007 19:47      Profile for Alan!     Send New Private Message       Edit/Delete Post   Reply With Quote 
It was you!

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Alan!

Two rabbis, a priest, and an awkward silence after there's no intelligible punch line to this joke, walk into a bar.

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ScholasticSpastic
Highlie
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Icon 1 posted January 30, 2007 09:19      Profile for ScholasticSpastic     Send New Private Message       Edit/Delete Post   Reply With Quote 
Nah, I'm just jumpin' on the bandwagon. (me likes bands, 'specially the ones with wagons!)

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"As in repeating a well-known song, so in instincts, one action follows another by a sort of rhythm; if a person be interrupted in a song, or in repeating anything by rote, he is generally forced to go back to recover the habitual train of thought..." (Darwin, The Origin of Species)

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alfrin
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Icon 1 posted January 30, 2007 09:30      Profile for alfrin     Send New Private Message       Edit/Delete Post   Reply With Quote 
quote:
Originally posted by ScholasticSpastic:
Nah, I'm just jumpin' on the bandwagon. (me likes bands, 'specially the ones with wagons!)

Just so long there be the rest of my band on it, I'd hate to have to be on my own wagon [Wink]

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Art is Resistance / Resistance is Art

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GrumpySteen

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Icon 1 posted January 30, 2007 09:43      Profile for GrumpySteen     Send New Private Message       Edit/Delete Post   Reply With Quote 
ScholasticSpastic wrote:
Nah, I'm just jumpin' on the bandwagon. (me likes bands, 'specially the ones with wagons!)

I'm not sure if they have a wagon, but I recommend the Extra Action Marching Band...

*whistles innocently*

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Worst. Celibate. Ever.

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garlicguy

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Icon 1 posted January 30, 2007 11:41      Profile for garlicguy   Author's Homepage     Send New Private Message       Edit/Delete Post   Reply With Quote 
I'd also like to jump on the bandwagon. Let me check the tires first...
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I don't know what I was thinking... it seemed like a good idea at the time.

Posts: 3752 | From: Pluto, no matter what you call it, is still my home. | Registered: Dec 2004  |  IP: Logged


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