and she might reply, "Well, that's just a theory."

她可能會跟你說 『那不就是個理論而已嘛』

But a conversation about an established scientific law

但是聊到一個確立的科學定律

rarely ends with, "Well, that's just a law."

很少有這樣回應 『那不就是個定律而已嘛』

Why is that?

為什麼呢？

What is the difference between a theory and a law,

理論與定律之間有何差別

and is one better?

其中一個有比另一個好嗎？

Scientific laws and theories have different jobs to do.

科學定律和理論有不同的作用

A scientific law predicts the results of certain initial conditions.

科學定律預測 某些初始狀態最後會有的結果

It might predict your unborn child's possible hair colors,

它可以預測腹中胎兒可能的髮色

or how far a baseball travels when launched at a certain angle.

或以某個角度投擲棒球可投多遠

In contrast, a theory tries to provide the most logical explanation

相反地，理論嘗試 提供最合理的解釋

about why things happen as they do.

來闡述事情發生的原因

A theory might invoke dominant and recessive genes

理論可能利用顯性和隱性基因

to explain how brown-haired parents ended up with a red-headed child,

去解釋為什麼褐髮父母 會生出紅髮孩子

or use gravity to shed light on the parabolic trajectory of a baseball.

或利用重力去解釋 棒球的拋物線軌跡

In simplest terms,

最簡單地說

a law predicts what happens while a theory proposes why.

定律預測『事件的結果』 而理論提出『發生的原因』

A theory will never grow up into a law,

理論永遠不可能成為定律

though the development of one often triggers progress on the other.

儘管如此，任一方的發展 常能激發另一方的進步

In the 17th century, Johannes Kepler theorized cosmic musical harmonies

在十七世紀，約翰尼斯·克卜勒 提出天體音樂和諧論

to explain the nature of planetary orbits.

以解釋行星軌道的自然現象

He developed three brilliant laws of planetary motion

他制訂三條卓越的行星運動定律

while he was studying decades of precise astronomical data

前後花了數十年 埋首於精確的天文學數據

in an effort to find support for his theory.

以找出支持他理論的證據

While his three laws are still in use today,

雖然他的三大定律至今仍在使用

gravity replaced his theory of harmonics to explain the planets' motions.

但重力已經取代了他的和諧理論 來解釋行星的運動

How did Kepler get part of it wrong?

克卜勒為什麼會犯下 這個錯誤呢？

Well, we weren't handed a universal instruction manual.

嗯！沒有人給我們 一本宇宙的使用手冊啊！

Instead, we continually propose, challenge, revise, or even replace

科學的想法一直在進展， 我們會不斷地提出挑戰、修正

our scientific ideas as a work in progress.

甚至取代原來的觀念

Laws usually resist change

定律通常是難以改變的

since they wouldn't have been adopted if they didn't fit the data,

因為當初如果不能符合數據 就根本不會被採用

though we occasionally revise laws in the face of new unexpected information.

雖然我們偶爾會 意外發現新資訊而修正定律

A theory's acceptance, however, is often gladiatorial.

反觀理論的接納， 常常需要激烈的爭辯

Multiple theories may compete to supply the best explanation

許多理論會互相競爭 以提供最合理的說明

of a new scientific discovery.

來解釋科學新發現

Upon further research,

經進一步的研究後

scientists tend to favor the theory that can explain most of the data,

科學家會傾向支持 可以解釋大部分數據的理論

though there may still be gaps in our understanding.

即使它與我們的理解仍有落差

Scientists also like when a new theory successfully predicts

科學家也喜歡 新的理論能成功地預測

previously unobserved phenomena,

先前未被留意的現象

like when Dmitri Mendeleev's theory about the periodic table

就像迪米特里．門得列夫的 元素週期表理論

predicted several undiscovered elements.

能預測許多尚未被發現的元素

The term scientific theory covers a broad swath.

科學理論這個名詞 涵蓋的範圍很廣

Some theories are new ideas with little experimental evidence

有些理論是只有極少 實驗證據的新想法

that scientists eye with suspicion,

常招到科學家的質疑

or even ridicule.

甚至當成笑柄

Other theories,

其他的理論

like those involving the Big Bang, evolution, and climate change,

像大爆炸、演化論和氣候變遷論

have endured years of experimental confirmation

經歷多年實驗的驗證

before earning acceptance by the majority of the scientific community.

最終才獲得大多數科學界的接納

You would need to learn more about a specific explanation

你需要先深入了解某個詳盡解釋

before you'd know how well scientists perceive it.

才能知道科學家對它的認知程度

The word theory alone doesn't tell you.

單靠字面上的解說 並不能達到此目的

In full disclosure,

不隱瞞地說

the scientific community has bet on the wrong horse before:

科學界曾經下錯賭注，諸如

alchemy,

煉金術

the geocentric model,

地心說

spontaneous generation,

自然發生說

and the interstellar aether

還有宇宙「以太」理論

are just a few of many theories discarded in favor of better ones.

是其中幾個 被更好的理論淘汰的學說

But even incorrect theories have their value.

然而不正確的理論 也是有其價值的

Discredited alchemy was the birthplace of modern chemistry,

名譽掃地的煉金術 孕育了現代化學

and medicine made great strides

而醫學的大幅進步是

long before we understood the roles of bacteria and viruses.

早在我們瞭解 細菌和病毒的角色之前

That said, better theories often lead to exciting new discoveries

不過，更好的理論 常會促成令人振奮的新發現

that were unimaginable under the old way of thinking.

用老舊的思考模式是無法想像的

Nor should we assume all of our current scientific theories

我們也不應認定 現今所有的科學理論

will stand the test of time.

都經得起時間的考驗

A single unexpected result is enough to challenge the status quo.

只要一個出乎意料之外的結果 就足以動搖它的地位了

However, vulnerability to some potentially better explanation

然而，現行的科學理論 雖然可能有更好的解釋方式

doesn't weaken a current scientific theory.

但不會減弱它的價值

Instead, it shields science from becoming unchallenged dogma.

反而可以避免科學 變成不能挑戰的教條

A good scientific law is a finely-tuned machine,

一個好的科學定律 好比一個精確的機器

accomplishing its task brilliantly

出色地完成其任務

but ignorant of why it works as well as it does.

但是只知其然而不知其所以然

A good scientific theory is a bruised, but unbowed, fighter

一個好的科學理論好比 一個傷痕累累不屈不撓的拳擊手

who risks defeat if unable to overpower or adapt to the next challenger.

如果不能擊敗或適應下一個對手 就會有被擊敗的風險

Though different,

雖然不一樣

science needs both laws and theories to understand the whole picture.

科學是需要定律與理論兩者 以瞭解完整的真相

So next time someone comments that it's just a theory,

所以下次有人說 『這只是個理論而已嘛！』

challenge them to go nine rounds with the champ

挑戰他們去跟冠軍比上九個回合

and see if they can do any better.

看他們能不能做得更好