

What's Wrong With This Snowflake? - DrJokepu
http://www.npr.org/templates/story/story.php?storyId=121827582
I have found the article on The Old New Thing: http://blogs.msdn.com/oldnewthing/archive/2010/01/04/9943210.aspx
======
slapshot
Writing letters about the fact that artistic snowflakes aren't the same as
"real" snowflakes is like writing to complain that the symbol of a heart for
"I love you <3 " looks nothing like the human heart.

While scientifically correct, he's also a little pedantic.

~~~
dangoldin
I think the fact that the error was in a scientific magazine warrants the
letter.

~~~
DougBTX
Also, it trumps pedantic by being funny.

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nitrogen
I was hoping this story would be about actual snowflakes discovered with
unusual structures.

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stcredzero
Okay, so the crystals tend to follow a 6-sided geometry. Why are snowflakes
_symmetrical_? Why does one arm have to fall into the _exact_ same
configuration as the opposite one? Why not have 6 different arms, all
following the same 6-sided geometry? What mechanism communicates between the
arms to achieve 6-sided symmetry?

~~~
jerf
Well, they don't have to:
[http://www.its.caltech.edu/~atomic/snowcrystals/class/class....](http://www.its.caltech.edu/~atomic/snowcrystals/class/class.htm)

Given that different conditions produce different crystals (see for instance
the description for the "capped columns"), my best guess is simply that each
of the 6 sides experienced all-but-identical growth conditions, and thus the
correct question is rather why would they be _different_?

Someone else mentioned 12- and 3-siders, and trying to Google up those images
is how I got to that site in the first place. See:
[http://www.its.caltech.edu/~atomic/snowcrystals/unusual/unus...](http://www.its.caltech.edu/~atomic/snowcrystals/unusual/unusual.htm)
(Note you have to "-paper" in the Google search, or you'll just be hammered
with instructions for paper snowflakes of varying degrees of scientific
inauthenticity.)

Edit: Ah, the site addresses that:
[http://www.its.caltech.edu/~atomic/snowcrystals/faqs/faqs.ht...](http://www.its.caltech.edu/~atomic/snowcrystals/faqs/faqs.htm)

"While [a snowflake] grows, the crystal is blown to and fro inside the clouds,
so the temperature it sees changes randomly with time. But the crystal growth
depends strongly on temperature (as is seen in the morphology diagram). Thus
the six arms of the snow crystal each change their growth with time. And
because all six arms see the same conditions at the same times, they all grow
about the same way. The end result is a complex, branched structure that is
also six-fold symmetric. And note also that since snow crystals all follow
slightly different paths through the clouds, individual crystals all tend to
look different."

And see also the next question, "What synchronizes the growth of the six
arms?". I'm hitting the limit of what I feel comfortable just copying and
pasting into HN.

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hga
Source code here: <http://psoup.math.wisc.edu/Snowfakes.htm> (roughly in the
middle of the page).

~~~
icefox
Just one of the many lovely gem's in the source:

    
    
       for (i=1;i<nr;i++)
          for (j=1;((j<=i)&&(i+j<=nr-1));j++){
              b[i][j]=0.0; 
       }
    

When you see the following line you know you are in for a treat (best part i1
and j1 are not even used in one of the functions where it is declared).

int i,j,i1,j1,iup,no;

~~~
icefox
Hmm I guess I was being to obtuse from the downvotes. Having not found the
code from the article I was very interested in checking it out when the link
was posted here. Sadly the code is written in such as way that makes it
extremely difficult to easily learn anything from. Reading the code is often
the best way to understand how a program/problem runs. I went to the source to
answer the following questions: How is the snowflake generated? What factors
need to be taken into account? Looking at the code if you want to figure
anything you would have to put a lot of time and effort into it. Badly named
variables and function names are just one of the problems. Take for example
'initialize()', what does it initialize? Is it only initializing snow flake
code, only X11 code, both or just a dumping ground function? What about the
check() function? What does it check? and chi()? There is a shape12, but not a
shape6 or shape3 function, why not? What does parupdate do? What about
norminf()? None of this answers the original questions. How do I simulate
growing a snowflake?

If the code was written in a sane way you would be able to skim through it in
two minutes and have a good overview of how a snowflake is made. Given that it
would probably take a good hour at least to understand it and I am only so-so
interested in learning I wont bother. This is especially sad given that this
is coming out of edu where I would presume that part of the purpose is to
teach how a snowflake is grown.

~~~
jey
That's true for ordinary programs, but this is math, not software. Glancing at
the code in this case is kind of like glancing through some program's object
code or disassembly and trying to understand how it works: theoretically
possible in principle, but not really doable in practice. In math the proper
analogue to "glancing at the code" is "skimming the paper", which is here:
<http://psoup.math.wisc.edu/papers/h2l.pdf>

~~~
icefox
If this was generated from some math formulas or from some other code (such as
a fortran translator as another comment hinted), but if this was the code that
was created by the author I stand by my original statement.

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pcm
I'm ashamed to say that I'm guilty of misrepresenting snowflakes.

I wrote an iPhone app last year that allowed you to create virtual paper
snowflakes, and I didn't realize until later that all the flakes it created
were "abominations" that had 8, 10, or 12 sides.

I was a little surprised by the amount of feedback I received explaining to me
exactly what was wrong with the snowflakes in my app. Unfortunately, I haven't
gotten around to fixing this egregious error just yet ;) .

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rbanffy
Well... It's not water ice... 8 sides, symmetrical four-by-four at a 45 degree
angle, no stems and only borders...

I won't say it's impossible to naturally form it, but I am certain it wouldn't
involve clouds of water vapor. Perhaps around proteins or some biological
process...

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andreyf
Also, real stars are enormous balls of plasma and gas, and look nothing like
☆. I've been waiting about 19 years for an explanation from anyone what the
two have in common, and still have gotten none. Maybe I should write a letter
to Nature...

~~~
potatolicious
A picture of a bright light taken by a camera lens with a non-circular
aperture will generate stars like that. In this case, the 5-pointed star is
from a pentagonal aperture.

It's entirely likely this symbol came from _pictures_ of stars, as opposed to
real ones.

~~~
andreyf
Wow, cool! Thanks! :)

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city41
We can relate though, like the now infamous CSI line "I will create a GUI
interface in Visual Basic, see if I can track an IP address"

Surely that makes you cringe at least a little bit :)

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DannoHung
Is this a serious complaint or is this someone having a bit of fun?

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vinhboy
learned something new today. thanks.

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lucifer
<http://www.bluffton.edu/~gundyj/TreasonOfImagesShadow.jpg>

