What is the universe made of? - Dennis Wildfogel

宇宙由甚麼組成？ - 丹尼斯．萬弗喬

譯者: Toby Wong 審譯者: Becky Ma

All the material objects around you

你身邊一切事物

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.

Molecules frequently break apart

分子不斷分裂

and then form new molecules.

然後又組成新分子

On the other hand,

另一方面

virtually all the atoms you come in to contact with

你一生中所接觸到的原子

through the course of your life,

the ones in the ground beneath you,

大地、空氣、食物

the air you breath, the food you eat,

those that make up every living thing, including you,

組成你和一切生物的原子

have existed for billions of years

已存在數以億年

and were created in places very unlike our planet.

發源地與地球非常不同

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

以下說的就是原子如何誔生

It all started 14 billion years ago

一切源於一百四十億年前

with an event we call The Big Bang,

發生了宇宙大爆炸

which resulted in a universe consisting of gas alone.

產生了只有氣體的宇宙

There were no stars and no planets.

無恆星亦無行星

The gas was made up only of atoms

氣體只由原子組成

belonging to the simplest elements.

那些原子屬於最簡單的元素

It was about 75 percent hydrogen

當中75%為氫

and almost all the rest was helium.

其餘多為氦

No elements like carbon, oxygen or nitrogen existed.

仍未有碳、氧或氮等元素

No iron, silver or gold.

亦無鐵、銀或金

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

氣體密度有些地方稍高

Due to gravity, those places attracted even more gas,

因萬有引力而吸引更多氣體

which further strengthened the pull of gravity,

引力因而更強

which then drew more gas in, and so on.

再吸引更多氣體,循環不息

Eventually, large dense gas balls formed,

最後形成大氣團

shrinking under their own gravity

氣團因自身引力而萎縮

and consequently heating up on the inside.

結果內部發熱

At some point, the core of such a ball

氣團核心熱到若干程度

gets hot enough that nuclear fusion occurs.

就發生核融合

Hydrogen atoms smash together to form helium,

氫原子融合為氦

accompanied by a great release of energy,

同時釋放巨大能量

strong enough to counteract the shrinking force of the gravity.

大得可對抗向內拉扯的引力

When the energy pushing out from the fusion reactions

融合所生向外推的能量

matches the gravity pulling all the gas inwards,

足以對抗向內拉扯的引力時

an equilibrium occurs.

就會達平衡狀態

From this a star is born.

恆星就自此而生

Over its lifetime,

巨大恆星一生之中

the fusion reactions in the core of a massive star

核心的融合反應不只產生氦

will produce not only helium,

but also carbon, oxygen, nitrogen

亦產生週期表中各元素

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

自碳、氧、氮至鐵止

But eventually, the core's fuel runs out,

但核心最終將耗盡燃料

leaving it to collapse completely.

完全崩潰

That causes an unbelievably powerful explosion

崩潰造成巨大爆炸

we call a supernova.

這爆炸稱為超新星爆發

Now there are two things to note

對超新星如何產生元素

about how supernovas create elements.

有兩點須注意

First, this explosion releases so much energy

一, 爆炸釋放巨大能源

that fusion goes wild

使融合能力變強

forming elements with atoms even heavier than iron

產生較鐵更重的原子

like silver, gold and uranium.

如銀、金及鈾

Second, all the elements that had been accumulating

二,聚於恆星核心的所有元素

in the core of the star,

like carbon, oxygen, nitrogen, iron,

如碳、氧、氮、鐵

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

和超新星爆炸所產生的所有元素

are ejected in to interstellar space

均被排進星際空間

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

與空間已有的氣體混合

History then repeats itself.

然後前事重演

Gas clouds, now containing many elements

氣團現在含多種元素

besides the original hydrogen and helium,

不單只有氫和氦

have higher density areas

密度較高區域

that attract more matter, and so on.

吸引更多物質,如此類推

As before, new stars result.

如前所述,產生新星

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

太陽就在五十億年前如此產生

That means that the gas it arose from

即是說,產生太陽旳氣團

had itself been enriched with many elements

自宇宙開始,超新星爆發時

from supernova explosions since the universe began.

吸收過多種元素

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

所以現在太陽所有元素俱備

It's still mostly hydrogen at 71 percent,

但氫仍佔71%

with most of the rest being helium at 27 percent.

其餘27%為氦

But bear in mind

但請緊記

that while the first stars were made up

首批恆星產生時

of hydrogen and helium alone,

只有氫和氦

the remaining elements in the periodic table

週期表中其餘元素

make up two percent of the sun.

只佔太陽2%

And what about Earth?

地球又如何?

Planets form as an incidental process to star formation

行星是恆星產生過程的副產品

out of the same gas cloud as the star itself.

來自同一氣體

Small planets like ours don't have enough gravity

地球等小行星

to hold on to much hydrogen or helium gas

引力不足以捉緊氫或氦氣

since both of those are very light.

因氫、氦均極輕

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

雖然碳、氮、氧等元素

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

在產生地球的氣團中只佔2%

these heavier elements form the bulk of our planet

這些較重的元素組成地球大部份

and everything on it.

也組成地球各種物體一大部份

Think about this:

試想想:

with the exception of hydrogen and some helium,

除氫和氦外

the ground you walk on,

你腳下大地

the air you breath, you,

所吸空氣,還有你

everything is made of atoms

當中的原子均來自恆星

that were created inside stars.

When scientists first worked this out

二十世紀前半

over the first half of the 20th Century,

科學家有此發現時

the famous astronomer Harlow Shapley commented,

著名太空人沙普利曾說

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

｢人與石為兄弟,與雲為表親｣