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All the material objects around you
你身邊一切事物
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are composed of submicroscopic units
都是由極微細的單位組成
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we call molecules.
這些單位稱為分子
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And molecules in turn are composed
而分子則由一粒一粒原子組成
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of individual atoms.
分子不斷分裂
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Molecules frequently break apart
然後又組成新分子
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and then form new molecules.
另一方面
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On the other hand,
你一生中所接觸到的原子
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virtually all the atoms you come in to contact with
大地、空氣、食物
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through the course of your life,
組成你和一切生物的原子
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the ones in the ground beneath you,
已存在數以億年
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the air you breath, the food you eat,
發源地與地球非常不同
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those that make up every living thing, including you,
以下說的就是原子如何誔生
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have existed for billions of years
一切源於一百四十億年前
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and were created in places very unlike our planet.
發生了宇宙大爆炸
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How those atoms came about is what I want to share with you.
產生了只有氣體的宇宙
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It all started 14 billion years ago
無恆星亦無行星
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with an event we call The Big Bang,
氣體只由原子組成
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which resulted in a universe consisting of gas alone.
那些原子屬於最簡單的元素
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There were no stars and no planets.
當中75%為氫
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The gas was made up only of atoms
其餘多為氦
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belonging to the simplest elements.
仍未有碳、氧或氮等元素
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It was about 75 percent hydrogen
亦無鐵、銀或金
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and almost all the rest was helium.
氣體密度有些地方稍高
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No elements like carbon, oxygen or nitrogen existed.
因萬有引力而吸引更多氣體
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No iron, silver or gold.
引力因而更強
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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
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Due to gravity, those places attracted even more gas,
最後形成大氣團
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which further strengthened the pull of gravity,
氣團因自身引力而萎縮
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which then drew more gas in, and so on.
結果內部發熱
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Eventually, large dense gas balls formed,
氣團核心熱到若干程度
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shrinking under their own gravity
就發生核融合
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and consequently heating up on the inside.
氫原子融合為氦
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At some point, the core of such a ball
同時釋放巨大能量
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gets hot enough that nuclear fusion occurs.
大得可對抗向內拉扯的引力
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Hydrogen atoms smash together to form helium,
融合所生向外推的能量
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accompanied by a great release of energy,
足以對抗向內拉扯的引力時
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strong enough to counteract the shrinking force of the gravity.
就會達平衡狀態
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When the energy pushing out from the fusion reactions
恆星就自此而生
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matches the gravity pulling all the gas inwards,
巨大恆星一生之中
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an equilibrium occurs.
核心的融合反應不只產生氦
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From this a star is born.
亦產生週期表中各元素
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Over its lifetime,
自碳、氧、氮至鐵止
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the fusion reactions in the core of a massive star
但核心最終將耗盡燃料
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will produce not only helium,
完全崩潰
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but also carbon, oxygen, nitrogen
崩潰造成巨大爆炸
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and all the other elements in the periodic table up to iron.
這爆炸稱為超新星爆發
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But eventually, the core's fuel runs out,
對超新星如何產生元素
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leaving it to collapse completely.
有兩點須注意
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That causes an unbelievably powerful explosion
一, 爆炸釋放巨大能源
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we call a supernova.
使融合能力變強
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Now there are two things to note
產生較鐵更重的原子
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about how supernovas create elements.
如銀、金及鈾
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First, this explosion releases so much energy
二,聚於恆星核心的所有元素
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that fusion goes wild
如碳、氧、氮、鐵
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forming elements with atoms even heavier than iron
和超新星爆炸所產生的所有元素
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like silver, gold and uranium.
均被排進星際空間
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Second, all the elements that had been accumulating
與空間已有的氣體混合
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in the core of the star,
然後前事重演
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like carbon, oxygen, nitrogen, iron,
氣團現在含多種元素
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as well as all of those formed in the supernova explosion,
不單只有氫和氦
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are ejected in to interstellar space
密度較高區域
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where they mix with the gas that's already there.
吸引更多物質,如此類推
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History then repeats itself.
如前所述,產生新星
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Gas clouds, now containing many elements
太陽就在五十億年前如此產生
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besides the original hydrogen and helium,
即是說,產生太陽旳氣團
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have higher density areas
自宇宙開始,超新星爆發時
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that attract more matter, and so on.
吸收過多種元素
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As before, new stars result.
所以現在太陽所有元素俱備
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Our sun was born this way about 5 billion years ago.
但氫仍佔71%
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That means that the gas it arose from
其餘27%為氦
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had itself been enriched with many elements
但請緊記
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from supernova explosions since the universe began.
首批恆星產生時
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So that's how the sun wound up with all the elements.
只有氫和氦
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It's still mostly hydrogen at 71 percent,
週期表中其餘元素
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with most of the rest being helium at 27 percent.
只佔太陽2%
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But bear in mind
地球又如何?
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that while the first stars were made up
行星是恆星產生過程的副產品
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of hydrogen and helium alone,
來自同一氣體
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the remaining elements in the periodic table
地球等小行星
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make up two percent of the sun.
引力不足以捉緊氫或氦氣
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And what about Earth?
因氫、氦均極輕
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Planets form as an incidental process to star formation
雖然碳、氮、氧等元素
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out of the same gas cloud as the star itself.
在產生地球的氣團中只佔2%
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Small planets like ours don't have enough gravity
這些較重的元素組成地球大部份
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to hold on to much hydrogen or helium gas
也組成地球各種物體一大部份
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since both of those are very light.
試想想:
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So, even though carbon, nitrogen, oxygen and so on
除氫和氦外
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made up only two percent of the gas cloud from which Earth was formed,
你腳下大地
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these heavier elements form the bulk of our planet
所吸空氣,還有你
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and everything on it.
當中的原子均來自恆星
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Think about this:
二十世紀前半
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with the exception of hydrogen and some helium,
科學家有此發現時
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the ground you walk on,
著名太空人沙普利曾說
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the air you breath, you,
「人與石為兄弟,與雲為表親」
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everything is made of atoms
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that were created inside stars.
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When scientists first worked this out
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over the first half of the 20th Century,
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the famous astronomer Harlow Shapley commented,
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"We are brothers of the boulders, cousins of the clouds."