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  • Many of the inanimate objects around you probably seem perfectly still.

    在你身邊的許多無生命的物體似乎是完全靜止不動

  • But look deep into the atomic structure of any of them,

    但深入地以原子結構的角度來看它們

  • and you'll see a world in constant flux.

    那你將會看到一個不斷擾動的世界

  • Stretching,

    延展

  • contracting,

    收縮

  • springing,

    彈跳

  • jittering,

    抖動

  • drifting atoms everywhere.

    飄移的原子到處都是

  • And though that movement may seem chaotic, it's not random.

    看到這種種的移動你可能以為它們是亂動的,但它們並不是隨機在動的

  • Atoms that are bonded together,

    幾乎所有的物質都是藉由

  • and that describes almost all substances,

    原子的鍊結組合而成

  • move according to a set of principles.

    它們是遵照一套規則在移動的

  • For example, take molecules, atoms held together by covalent bonds.

    例如,拿分子來說,它們是原子們藉由共價鍵鍊結在一起

  • There are three basic ways molecules can move:

    分子有三種基本方式來移動:

  • rotation,

    旋轉

  • translation,

    平移

  • and vibration.

    和振動

  • Rotation and translation move a molecule in space

    旋轉和平移是在同一空間上讓一個分子移動

  • while its atoms stay the same distance apart.

    原子彼此間的距離不會改變

  • Vibration, on the other hand, changes those distances,

    振動,換句話說,就是改變原子之間的距離

  • actually altering the molecule's shape.

    事實上這還改變了分子的形狀

  • For any molecule, you can count up the number of different ways it can move.

    就任何分子來說,我們都可以將其所有不同的移動方式加總起來

  • That corresponds to its degrees of freedom,

    而這跟它們裡頭原子組成結構

  • which in the context of mechanics

    的自由度有關係

  • basically means the number of variables we need to take into account

    基本上意思就是我們要去解析整個系統

  • to understand the full system.

    需要考慮到的變因數目

  • Three-dimensional space is defined by x, y, and z axes.

    三度空間裡定義了x,y和z軸

  • Translation allows the molecule to move in the direction of any of them.

    換位就是分子能夠在任意一軸上移動

  • That's three degrees of freedom.

    這樣就有三個自由度了

  • It can also rotate around any of these three axes.

    它們也可以沿著這三個軸轉動

  • That's three more,

    這樣又有三個了

  • unless it's a linear molecule, like carbon dioxide.

    除非是像二氧化碳這樣形狀像是直線的分子

  • There, one of the rotations just spins the molecule around its own axis,

    你看,其轉動只是在相對應的軸上旋轉

  • which doesn't count because it doesn't change the position of the atoms.

    因為這並沒有改變原子在其軸上的位置,所以不能算是一個自由度

  • Vibration is where it gets a bit tricky.

    振動就有一點難懂了

  • Let's take a simple molecule, like hydrogen.

    我們就拿最簡單的氫分子來說

  • The length of the bond that holds the two atoms together is constantly changing

    兩個氫原子間鍊結的長度是一直在改變的

  • as if the atoms were connected by a spring.

    就好像兩原子間連結了一條彈簧一樣

  • That change in distance is tiny, less than a billionth of a meter.

    但這距離的改變是非常微小的,比一奈米還小

  • The more atoms and bonds a molecule has, the more vibrational modes.

    一個分子裡有越多原子鍊結在一起,那們就有越多的振動方式

  • For example, a water molecule has three atoms:

    例如,一個由三個原子組成的水分子:

  • one oxygen and two hydrogens, and two bonds.

    一個氧原子和兩個氫原子,和兩條鍊結

  • That gives it three modes of vibration:

    這讓水分子有三種振動方式

  • symmetric stretching,

    對稱的伸縮

  • asymmetric stretching,

    不對稱的伸縮

  • and bending.

    和彎曲

  • More complicated molecules have even fancier vibrational modes,

    更複雜的分子甚至有令人意想不到的振動方式

  • like rocking,

    像是搖動

  • wagging,

    擺動

  • and twisting.

    和扭轉

  • If you know how many atoms a molecule has, you can count its vibrational modes.

    如果你知道一個分子由多少原子組成,那麼你就可以數出它有多少振動方式

  • Start with the total degrees of freedom,

    先從總自由度開始算

  • which is three times the number of atoms in the molecule.

    算法是三乘上一個分子內的原子總數

  • That's because each atom can move in three different directions.

    這是因為每個原子都可以在三度空間中沿著三個軸向移動

  • Three of the total correspond to translation

    平移則共有三種方式

  • when all the atoms are going in the same direction.

    因為平移時所有原子都往同一方向移動

  • And three, or two for linear molecules, correspond to rotations.

    然後有三種,直線形狀的分子則有兩種,轉動方式

  • All the rest, 3N-6 or 3N-5 for linear molecules,

    所以其它,3乘上原子數目減去6,直線分子則是減去5,的移動數目

  • are vibrations.

    就是所有振動的方式了

  • So what's causing all this motion?

    所以,到底是甚麼原因造成這些運動呢?

  • Molecules move because they absorb energy from their surroundings,

    分子的運動是因為吸收了環境中的能量

  • mainly in the form of heat or electromagnetic radiation.

    主要是吸收了熱能或是電磁輻射

  • When this energy gets transferred to the molecules,

    當這些能量轉移到分子上

  • they vibrate,

    分子就會振動

  • rotate,

    轉動

  • or translate faster.

    或是快速平移

  • Faster motion increases the kinetic energy of the molecules and atoms.

    快速的運動使得分子和原子的動能增加

  • We define this as an increase in temperature and thermal energy.

    我們知道這會使得溫度和熱能上升

  • This is the phenomenon your microwave oven uses to heat your food.

    我們的微波爐就是利用這種現象來加熱食物

  • The oven emits microwave radiation, which is absorbed by the molecules,

    微波爐發出的微波輻射會被食物分子吸收

  • especially those of water.

    特別是水分子

  • They move around faster and faster,

    它們移動越來越快

  • bumping into each other and increasing the food's temperature and thermal energy.

    並且會撞在一起,這會讓食物的溫度和其熱能升高

  • The greenhouse effect is another example.

    溫室效應則是另一個例子

  • Some of the solar radiation that hits the Earth's surface

    有些太陽輻射照射到地球表面時

  • is reflected back to the atmosphere.

    會被反射回大氣層

  • Greenhouse gases, like water vapor and carbon dioxide absorb this radiation

    溫室氣體,像是水蒸氣和二氧化碳吸收了這些輻射之後

  • and speed up.

    就加速移動了起來

  • These hotter, faster-moving molecules emit infrared radiation in all directions,

    這些較熱,快速移動的分子會向不同方向發射出遠紅外線

  • including back to Earth, warming it.

    包含向著地球發射,這樣就造成暖化了

  • Does all this molecular motion ever stop?

    這些分子的運動有沒有可能停止呢?

  • You might think that would happen at absolute zero,

    你可能會認為在絕對零度下,這已是宇宙中的最低溫了

  • the coldest possible temperature.

    這些運動會停止

  • No one's ever managed to cool anything down that much,

    目前還沒有人有辦法讓溫度達到如此的低溫

  • but even if we could,

    但就算我們有辦法

  • molecules would still move due to a quantum mechanical principle

    分子仍會依量子動力學的規則來運動

  • called zero-point energy.

    稱為零點能量

  • In other words, everything has been moving since the universe's very first moments,

    換句話說,所有物體從宇宙初始就一直在運動

  • and will keep going long, long after we're gone.

    而且還會一直保持運動狀態,直到人類消失的未來

Many of the inanimate objects around you probably seem perfectly still.

在你身邊的許多無生命的物體似乎是完全靜止不動

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B2 中高級 中文 TED-Ed 分子 原子 自由度 運動 輻射

【TED-Ed】靜止物體的隱形運動--蘭-蒂沃尼。 (【TED-Ed】The invisible motion of still objects - Ran Tivony)

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