are composed of submicroscopic units

都是由極微細的單位組成

we call molecules.

這些單位稱為分子

And molecules in turn are composed

而分子則由一粒一粒原子組成

of individual atoms.

分子不斷分裂

Molecules frequently break apart

然後又組成新分子

and then form new molecules.

另一方面

On the other hand,

你一生中所接觸到的原子

virtually all the atoms you come in to contact with

大地、空氣、食物

through the course of your life,

組成你和一切生物的原子

the ones in the ground beneath you,

已存在數以億年

the air you breath, the food you eat,

發源地與地球非常不同

those that make up every living thing, including you,

以下說的就是原子如何誔生

have existed for billions of years

一切源於一百四十億年前

and were created in places very unlike our planet.

發生了宇宙大爆炸

How those atoms came about is what I want to share with you.

產生了只有氣體的宇宙

It all started 14 billion years ago

無恆星亦無行星

with an event we call The Big Bang,

氣體只由原子組成

which resulted in a universe consisting of gas alone.

那些原子屬於最簡單的元素

There were no stars and no planets.

當中75%為氫

The gas was made up only of atoms

其餘多為氦

belonging to the simplest elements.

仍未有碳、氧或氮等元素

It was about 75 percent hydrogen

亦無鐵、銀或金

and almost all the rest was helium.

氣體密度有些地方稍高

No elements like carbon, oxygen or nitrogen existed.

因萬有引力而吸引更多氣體

No iron, silver or gold.

引力因而更強

In some places, the density of this gas was slightly higher than in others.

再吸引更多氣體,循環不息

Due to gravity, those places attracted even more gas,

最後形成大氣團

which further strengthened the pull of gravity,

氣團因自身引力而萎縮

which then drew more gas in, and so on.

結果內部發熱

Eventually, large dense gas balls formed,

氣團核心熱到若干程度

shrinking under their own gravity

就發生核融合

and consequently heating up on the inside.

氫原子融合為氦

At some point, the core of such a ball

同時釋放巨大能量

gets hot enough that nuclear fusion occurs.

大得可對抗向內拉扯的引力

Hydrogen atoms smash together to form helium,

融合所生向外推的能量

accompanied by a great release of energy,

足以對抗向內拉扯的引力時

strong enough to counteract the shrinking force of the gravity.

就會達平衡狀態

When the energy pushing out from the fusion reactions

恆星就自此而生

matches the gravity pulling all the gas inwards,

巨大恆星一生之中

an equilibrium occurs.

核心的融合反應不只產生氦

From this a star is born.

亦產生週期表中各元素

Over its lifetime,

自碳、氧、氮至鐵止

the fusion reactions in the core of a massive star

但核心最終將耗盡燃料

will produce not only helium,

完全崩潰

but also carbon, oxygen, nitrogen

崩潰造成巨大爆炸

and all the other elements in the periodic table up to iron.

這爆炸稱為超新星爆發

But eventually, the core's fuel runs out,

對超新星如何產生元素

leaving it to collapse completely.

有兩點須注意

That causes an unbelievably powerful explosion

一, 爆炸釋放巨大能源

we call a supernova.

使融合能力變強

Now there are two things to note

產生較鐵更重的原子

about how supernovas create elements.

如銀、金及鈾

First, this explosion releases so much energy

二,聚於恆星核心的所有元素

that fusion goes wild

如碳、氧、氮、鐵

forming elements with atoms even heavier than iron

和超新星爆炸所產生的所有元素

like silver, gold and uranium.

均被排進星際空間

Second, all the elements that had been accumulating

與空間已有的氣體混合

in the core of the star,

然後前事重演

like carbon, oxygen, nitrogen, iron,

氣團現在含多種元素

as well as all of those formed in the supernova explosion,

不單只有氫和氦

are ejected in to interstellar space

密度較高區域

where they mix with the gas that's already there.

吸引更多物質,如此類推

History then repeats itself.

如前所述,產生新星

Gas clouds, now containing many elements

太陽就在五十億年前如此產生

besides the original hydrogen and helium,

即是說,產生太陽旳氣團

have higher density areas

自宇宙開始,超新星爆發時

that attract more matter, and so on.

吸收過多種元素

As before, new stars result.

所以現在太陽所有元素俱備

Our sun was born this way about 5 billion years ago.

但氫仍佔71%

That means that the gas it arose from

其餘27%為氦

had itself been enriched with many elements

但請緊記

from supernova explosions since the universe began.

首批恆星產生時

So that's how the sun wound up with all the elements.

只有氫和氦

It's still mostly hydrogen at 71 percent,

週期表中其餘元素

with most of the rest being helium at 27 percent.

只佔太陽2%

But bear in mind

地球又如何?

that while the first stars were made up

行星是恆星產生過程的副產品

of hydrogen and helium alone,

來自同一氣體

the remaining elements in the periodic table

地球等小行星

make up two percent of the sun.

引力不足以捉緊氫或氦氣

And what about Earth?

因氫、氦均極輕

Planets form as an incidental process to star formation

雖然碳、氮、氧等元素

out of the same gas cloud as the star itself.

在產生地球的氣團中只佔2%

Small planets like ours don't have enough gravity

這些較重的元素組成地球大部份

to hold on to much hydrogen or helium gas

也組成地球各種物體一大部份

since both of those are very light.

試想想:

So, even though carbon, nitrogen, oxygen and so on

除氫和氦外

made up only two percent of the gas cloud from which Earth was formed,

你腳下大地

these heavier elements form the bulk of our planet

所吸空氣,還有你

and everything on it.

當中的原子均來自恆星

Think about this:

二十世紀前半

with the exception of hydrogen and some helium,

科學家有此發現時

the ground you walk on,

著名太空人沙普利曾說

the air you breath, you,

｢人與石為兄弟,與雲為表親｣

everything is made of atoms

that were created inside stars.

When scientists first worked this out

over the first half of the 20th Century,

the famous astronomer Harlow Shapley commented,

"We are brothers of the boulders, cousins of the clouds."