The 2,400-year search for the atom - Theresa Doud

話說 2400 年來的原子研究歷史 - Theresa Doud

譯者: 瑞文Eleven 林Lim 審譯者: Helen Chang

What do an ancient Greek philosopher

古希臘哲學家、

and a 19th century Quaker

19世紀的貴格會成員，

have in common with Nobel Prize-winning scientists?

與諾貝爾獎科學家的共同點是甚麼？

Although they are separated over 2,400 years of history,

儘管他們相隔超過2400年，

each of them contributed to answering the eternal question:

他們的貢獻都為了這個永恆的問題：

what is stuff made of?

物質是由甚麼所組成的？

It was around 440 BCE that Democritus first proposed

德謨克利特在公元前440年首次提出：

that everything in the world was made up of tiny particles

這世界上的一切都由微小粒子所組成，

surrounded by empty space.

粒子的四周都是空的。

And he even speculated that they vary in size and shape

他甚至推測粒子依它們組成的物質不同，

depending on the substance they compose.

而有不同的大小與形狀。

He called these particles "atomos," Greek for indivisible.

他稱這些粒子為「atomos」-- 希臘語中的「不可分割」之意。

His ideas were opposed by the more popular philosophers of his day.

他的觀點不被當時 較受歡迎的哲學家接受，

Aristotle, for instance, disagreed completely,

例如亞里士多德就完全不同意，

stating instead that matter was made of four elements:

他認為物質是由四個要素組成：

earth, wind, water and fire,

土、風、水、火，

and most later scientists followed suit.

其後大多數科學家紛紛遵從。

Atoms would remain all but forgotten until 1808,

原子觀念被所有人遺忘，直至1808年，

when a Quaker teacher named John Dalton sought to challenge Aristotelian theory.

一個名為約翰‧道耳頓的貴格會老師， 他試圖挑戰亞里士多德的理論。

Whereas Democritus's atomism had been purely theoretical,

不同於德謨克利特的原子論是純粹的理論，

Dalton showed that common substances always broke down into the same elements

道爾頓展現同種物質都可被分解成

in the same proportions.

相同的比例的數種元素。

He concluded that the various compounds

他的結論是不同的化合物

were combinations of atoms of different elements,

是由不同原子的元素所組合

each of a particular size and mass

每種元素的原子都有 特定的大小與質量，

that could neither be created nor destroyed.

而且原子既不能被創造、也不能被消滅。

Though he received many honors for his work,

雖然他的研究得到許多讚譽，

as a Quaker, Dalton lived modestly until the end of his days.

作為貴格會員，道爾頓 一生一直保持謙虛低調。

Atomic theory was now accepted by the scientific community,

現在原子論被科學界接受了，

but the next major advancement

但接下來的重大進展，

would not come until nearly a century later

卻直至近一個世紀之後才發生：

with the physicist J.J. Thompson's 1897 discovery of the electron.

1897年物理學家J•J湯木生發現電子。

In what we might call the chocolate chip cookie model of the atom,

在我們可以稱之為巧克力餅乾模型原子，

he showed atoms as uniformly packed spheres of positive matter

湯木生的原子是負電荷的電子，

filled with negatively charged electrons.

均勻分布在球狀正電雲中。

Thompson won a Nobel Prize in 1906 for his electron discovery,

湯木生因發現電子 而榮獲1906年諾貝爾物理獎。

but his model of the atom didn't stick around long.

但他的原子模型沒有維持很久，

This was because he happened to have some pretty smart students,

這是因為他有一些非常聰明的學生，

including a certain Ernest Rutherford,

而歐尼斯特•拉塞福必列名其中，

who would become known as the father of the nuclear age.

他被稱為原子核物理學之父。

While studying the effects of X-rays on gases,

當研究X射線對氣體的影響時，

Rutherford decided to investigate atoms more closely

拉塞福決定更進一步研究原子，

by shooting small, positively charged alpha particles at a sheet of gold foil.

他用帶正電荷的α粒子轟擊金箔。

Under Thompson's model,

在湯木生的原子模式中，

the atom's thinly dispersed positive charge

原子中均勻分布的正電荷

would not be enough to deflect the particles in any one place.

並不足以使α粒子發生偏轉。

The effect would have been like a bunch of tennis balls

結果應像是以一堆網球

punching through a thin paper screen.

射向一張薄薄的紙屏。

But while most of the particles did pass through,

結果是：雖然大多數的顆粒都穿過金箔，

some bounced right back,

但是一些被反彈回來，

suggesting that the foil was more like a thick net with a very large mesh.

表示所金箔片更像有大網眼的厚網，

Rutherford concluded that atoms consisted largely of empty space

拉塞福的結論是原子中除了幾個電子外，

with just a few electrons,

大部分空的，

while most of the mass was concentrated in the center,

大部分的質量集中在中央，

which he termed the nucleus.

他稱之為原子核。

The alpha particles passed through the gaps

多數α粒子由原子中空部位通過，

but bounced back from the dense, positively charged nucleus.

但撞到帶正電荷原子核的就被散射開。

But the atomic theory wasn't complete just yet.

但原子論尚未完備，

In 1913, another of Thompson's students by the name of Niels Bohr

1913年，湯木生的另一個學生尼爾斯•波耳

expanded on Rutherford's nuclear model.

對拉塞福的核模型進行擴展修正。

Drawing on earlier work by Max Planck and Albert Einstein

他延續早期馬克斯•普朗克和 愛因斯坦的研究成果，

he stipulated that electrons orbit the nucleus

他提出：電子繞核的軌道

at fixed energies and distances,

有固定的半徑與能量，

able to jump from one level to another, but not to exist in the space between.

電子能夠從一層跳到另一個， 但不能存在於各層間的空間。

Bohr's planetary model took center stage,

玻爾的行星模型成為主流的學說，

but soon, it too encountered some complications.

但很快，它也遇到了一些困難。

Experiments had shown that rather than simply being discrete particles,

實驗已經證明， 電子不僅僅是一顆顆的粒子，

electrons simultaneously behaved like waves,

同時也會表現出波的特性，

not being confined to a particular point in space.

並非局限於空間中的特定位置。

And in formulating his famous uncertainty principle,

因此海森堡並提出了 著名測不準(不確定性)原理，

Werner Heisenberg showed it was impossible to determine

表示當測量一個電子時，

both the exact position and speed of electrons

不可能同時確定

as they moved around an atom.

電子的確切位置與速度

The idea that electrons cannot be pinpointed

電子不能被精確定位，

but exist within a range of possible locations

但存在於可能位置的範圍內，

gave rise to the current quantum model of the atom,

此觀念啟發了現今原子的量子模型，

a fascinating theory with a whole new set of complexities

那是一套迷人的理論， 具有全新的複雜性，

whose implications have yet to be fully grasped.

然而其意涵尚未被完全掌握。

Even though our understanding of atoms keeps changing,

雖然我們對原子的理解不斷的進化，

the basic fact of atoms remains,

但原子的存在為基本事實，

so let's celebrate the triumph of atomic theory

讓我們放煙火慶祝原子學說的勝利！

with some fireworks.

As electrons circling an atom shift between energy levels,

電子在環繞原子能階之間轉移時，

they absorb or release energy in the form of specific wavelengths of light,

它們以特定波長的光釋放或吸收能量，

導致所有我們看到奇妙的色光。

resulting in all the marvelous colors we see.

我們可以想像德謨克利特 從什麼地方看著煙火，

And we can imagine Democritus watching from somewhere,

satisfied that over two millennia later,

心滿意足於經過了兩千多年，

he turned out to have been right all along.

他的學說一直都是正確的。