It's all about the pictures
by
majordomo
·
· Score: 5, Interesting
I'm sitting right now one story down from the office of Ken Libbrecht, the guy who wrote the book (and the website). Ken told me that he was writing a book on the physics of snowflakes, and I asked him how he expected to get anyone to buy it. "Pictures," he replied, "lots of pretty pictures!"
Some of the best eary snow flake photograph are from Bentley (1930s). There's even a web site for the Bently snowflake museum.
http://snowflakebentley.com/
Take a break from the trolling, posting and hacking, and enjoy the photographs. They're quite beautiful.
Why they're symmetrical
by
RobotWisdom
·
· Score: 5, Interesting
Because each arm experiences the same conditions, the arms tend to look alike, producing large-scale, intricate, six-fold symmetric snow crystals.
This explanation is obviously handwaving-- the symmetry is perfect (or close to it) over scales of millions of molecules.
I've been arguing since 1980 or so that an ice crystal in freefall is not at absolute zero (obviously) so it must have internal vibrations. This is basically 'noise', but as it echoes thru the ice, it stops looking random and becomes symmetrical, like Chladni patterns on a vibrating plate or drumhead. (Or like the radiating circles from a drip of water into a circular pool, reconverging at an opposite point.) Because these symmetries are present from the first stage of growth, they maintain symmetrical growth.
I don't think the 104.5 degree angle between the hydrogens in water molecules is close enough to 120 to deliver perfect hexagonality-- it's probably due to the geometry of echoes in any disk, because hexagons can be inscribed in circles. (The spinning of the seed probably contributes to the flatness-- growing favors the outside edge of the bulge, otherwise it might be more spherical.)
Slashdot Mirror
I'm sitting right now one story down from the office of Ken Libbrecht, the guy who wrote the book (and the website). Ken told me that he was writing a book on the physics of snowflakes, and I asked him how he expected to get anyone to buy it. "Pictures," he replied, "lots of pretty pictures!"
Looks like he was right!
Some of the best eary snow flake photograph are
from Bentley (1930s). There's even a web site
for the Bently snowflake museum.
http://snowflakebentley.com/
Take a break from the trolling, posting and
hacking, and enjoy the photographs. They're
quite beautiful.
This explanation is obviously handwaving-- the symmetry is perfect (or close to it) over scales of millions of molecules.
I've been arguing since 1980 or so that an ice crystal in freefall is not at absolute zero (obviously) so it must have internal vibrations. This is basically 'noise', but as it echoes thru the ice, it stops looking random and becomes symmetrical, like Chladni patterns on a vibrating plate or drumhead. (Or like the radiating circles from a drip of water into a circular pool, reconverging at an opposite point.) Because these symmetries are present from the first stage of growth, they maintain symmetrical growth.
I don't think the 104.5 degree angle between the hydrogens in water molecules is close enough to 120 to deliver perfect hexagonality-- it's probably due to the geometry of echoes in any disk, because hexagons can be inscribed in circles. (The spinning of the seed probably contributes to the flatness-- growing favors the outside edge of the bulge, otherwise it might be more spherical.)