Name: 雪花是如何形成的？ (How Do Snowflakes Form?)
Uploaded: 2021-01-14T08:03:01.000Z
Duration: 2 min 40 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

Chemistry is in everything, including snow.

Crystallography allows us to study the arrangement of atoms

Though they all pretty much start the same, once they begin crystallizing,

it's true that no two snow flakes are alike.

And the number of possible shapes is staggering.

A snowflake starts as a dust grain floating in a cloud. Water vapor in the

air sticks to the dust grain and the resulting droplet turns directly into ice.

Crystal faces appear on the frozen droplet.

Then, a prism forms with six faces and a top and bottom.

A cavity forms in each prism face because ice grows fastest near the edges.

Faster growth on the corners causes six branches to sprout.

The lines in each branch are due to ridges and grooves on the surface.

These six branches form the corners of a hexagon, which occurs because the water

molecules chemically bond into a hexagonal network.

When the temperature cools to -13 degrees C (9F), new

At -14 degrees (6F), side branches sprout on each branch.

Suddenly, the crystal encounters a quick blast of warmer air followed by cooler

The crystal gradually warms, making the tips long and narrow.

The crystal encounters into even warmer air, which slows

Finally, this unique and delicate structure falls to the earth along

Over the years, crystallographers have been classifying snow crystals into

different categories based on their arrangement of atoms

(column, plane, aggregation, rimmed, germs, irregular, other).

In the 1930s, there were 21 different classifications of snowflake could be in,

but by 2013 that number has soared to 121 categories.

To see the snow crystals at the molecular level, scientists send a beam of

The X-rays bounce off all the atoms in the snowflake and head in all

different directions, sort of like light off all the sides of a disco ball.

By seeing where these beams end up, we can figure out what arrangement

the snowflake's atoms are in, and therefore what it looks like at the atomic level.

Who's to say what new snowflake categories crystallographers will find in 2016.

But one thing's for certain, the ever-changing environment means that snowflakes

can have a mind-boggling array of shapes.

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雪花是如何形成的？ (How Do Snowflakes Form?)

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