Four ways to understand the Earth's age - Joshua M. Sneideman

你能看懂的地球年龄的计量 - 约书亚 M.斯雷德曼

翻译人员: Zhi Yin Wang 校对人员: Zhiting Chen

How old is the Earth?

地球的年龄有多大？

Well, by counting the number of isotopes

通过对岩石样品中

in a sample of rock

正经历着放射衰变的

that's undergone radioactive decay,

同位素的计数

geologists have estimated the Earth's birthday,

地质学家们已经估算出了地球的生日

when it first formed from a solar nebula,

当它从太阳星云中诞生的时候

to be 4.6 billion years ago.

大约是在46亿年之前

But just how long is that really?

但是那到底是多久呢？

Here's some analogies

这里有几个类比

that might help you understand.

应该会帮助我们理解

For example, let's imagine the entire history of Earth

例如，让我们把地球的整个历史

until the present day

一直到现在

as a single calendar year.

想象成一个日历年

On January 1st, the Earth begins to form.

在1月1号的时候，地球诞生了

By March 3rd, there's the first evidence

到了3月3号，开始有证据证明

of single-celled bacteria.

单细胞细菌的出现

Life remains amazingly unicellular until November 11th

直到10月11号，生物仍惊人地保持着单细胞的状态

when the first multicellular organisms,

第一种多细胞生物

known as the Ediacaran fauna, come along.

又被称为埃迪卡拉动物群，出现于

Shortly thereafter, on November 16th at 6:08 p.m.

不久之后的11月16号下午6点08分

is the Cambrian Explosion of life,

这就是寒武纪生命大爆发

a major milestone,

一个重要的里程碑

when all of the modern phyla started to appear.

现代生物门类开始出现的时刻

On December 10th at 1:26 p.m.,

12月10号下午1点26分

the dinosaurs first evolve

恐龙首先发展起来

but are wiped out by an asteroid

但却仅仅在两周以后

just two weeks later.

被一个小行星彻底抹去

On December 31st, the mighty Roman empire

在12月31号，强势的罗马帝国

rises and falls in just under four seconds.

崛起又衰落仅仅用了4秒钟

And Columbus sets sail

哥伦布扬帆起航于

for what he thinks is India

为了他认为的印度

at three seconds to midnight.

子夜的三秒钟之前

If you try to write the history of the Earth

如果你想要把地球的历史写下来

using just one page per year,

一页纸便是一年

your book would be 145 miles thick,

你这本书将会有145英里（约233公里）那么厚

more than half the distance

超过了一半的

to the international space station.

我们同国际空间站之间的距离

The story of the 3.2 million year-old

320万岁的

Australopithecine fossil known as Lucy

南方古猿化石露西的故事

would be found on the 144th mile,

将在第144英里上被找到

just over 500 feet from the end of the book.

仅仅还有500英尺（1英尺约等于0.3米）便到了书的结尾

The United States of America's Declaration of Independence

美国的独立宣言

would be signed in the last half-inch.

签署于最后的半英寸

Or if we compared geologic time

如果我们将地质年代

to a woman stretching her arms

同一个女士的伸展的双臂长度作比较

to a span of six feet,

大约6英尺的范围

the simple act of filing her nails

一个简单的修理指甲

would wipe away all of recorded human history.

便会抹去整个的人类历史

Finally, let's imagine the history of the Earth as your life:

最后，让我们把地球的历史想象成你的一生

from the moment you're born

从你出生的时刻

to your first day of high school.

到你进入高中的第一天

Your first word,

你说的第一个词

first time sitting up,

第一次坐起来

and first time walking

第一次行走

would all take place while life on Earth

统统发生于地球上的生物界

was comprised of single-celled organisms.

是由单细胞生物构成的时候

In fact, the first multicellular organism

事实上，第一个多细胞生物

wouldn't evolve until you were 12 years old

直到你12岁的时候才出现

and starting 7th grade,

也就是你开始7年级的时候

right around the time

这刚好是

your science teacher is telling the class

你的科学老师在课堂上

how fossils are formed.

告诉你化石是怎么形成的时候

The dinosaurs don't appear

恐龙直到

until three months into 8th grade

你8年级上了三个月的时候才出现

and are soon wiped out right around spring break.

但很快，在你春假的时候又消失了

Three days before 9th grade begins,

9年级开始的三天前

when you realize summer is over

当你发现夏天已经结束

and you need new school supplies,

你又需要新的学习用具的时候

Lucy, the Australopithecine, is walking around Africa.

露西，南方猿人，正在非洲散步

As you finish breakfast

当你吃完早餐

and head outside to catch your bus

出门追赶公交车

44 minutes before school,

还有44分钟就要上课的时候

the Neanderthals are going extinct throughout Europe.

尼安德特人将从整个欧洲消失

The most recent glacial period

最近的一次冰河时期

ends as your bus drops you off

结束于你从公交车上下来

16 minutes before class.

上课前16分钟的时候

Columbus sets sail 50 seconds before class

哥伦布于上课的50秒前起航

as you're still trying to find the right classroom.

正当你在寻找正确的教室的时候

The Declaration of Independence is signed

独立宣言签署与

28 seconds later

28秒钟之后

as you look for an empty seat.

这时你正在寻找空座位

And you were born 1.3 seconds before the bell rings.

然后你出生于上课铃响1.3秒之前

So, you see, the Earth is extremely,

所以，你看，地球真的是极其

unbelievably old

不可思议的高龄

compared to us humans

跟我们人类比起来

with a fossil record

化石记录

hiding incredible stories to tell us about the past

隐藏了太多关于过去的惊人故事

and possibly the future as well.

还可能包括将来的

But in the short time we've been here,

但在我们存在的这短短的时间内

we've learned so much

我们了解了如此之多

and will surely learn more

当然在未来的几十年到几个世纪

over the next decades and centuries,

我们一定会了解更多

near moments in geological time.

仅仅在这地质年代中的片刻