In a world of booked calendars and packed schedules, it's hard to imagine life without them.

在這個訂滿日曆、排滿日程的世界裡，很難想象沒有日曆的生活。

But as it turns out, we've been keeping track of the hours long before the clock's invention.

但事實證明，早在時鐘發明之前，我們就已經開始記時了。

For millennia, people have used the stars to understand and organize the movement of time.

千百年來，人們利用星空來理解和組織時間的運動。

By far the most accessible timekeeper is our nearest star, the Sun.

到目前為止，最容易獲得的時間記錄器是我們最近的恆星，太陽。

As early as 3500 BCE, the Egyptians began building obelisks to divide their days into parts

早在公元前3500年，埃及人就開始建造方尖碑，將他們的日子抽成若干部分。

resembling the hours we know today.

類似於我們今天所知道的時間。

The moving shadows created by the Sun hitting the obelisk helped to divide morning from afternoon,

太陽打在方尖碑上產生的移動陰影有助於劃分上午和下午。

while the length of the noontime shadow showed the year's longest and shortest days.

而中午影子的長短則顯示了一年中最長和最短的日子。

This is the same principle behind sundials, which you may be more familiar with.

這也是大家比較熟悉的日晷背後的原理。

But watching shadows move across the Earth isn't the only way the sky can help us keep time.

但觀看影子在地球上移動並不是天空幫助我們保持時間的唯一方式。

Around the same time the Egyptians were building obelisks,

大約在同一時間，埃及人正在建造方尖碑。

a 366-day calendar structured on the movements of the Sun and the moon was being developed in China.

中國正在開發以太陽和月亮運動為結構的366天日曆。

But after a few centuries of use, astronomers began noticing that the calendar became inaccurate every 300 years or so.

但經過幾個世紀的使用，天文學家開始注意到，每隔300年左右，曆法就會變得不準確。

The reason? Well, the stars, including the Sun, aren't as “fixed” in the night sky as they appear to be.

原因是什麼？嗯，包括太陽在內的星星，在夜空中並不像它們看起來那樣 "固定"。

There's movement happening; something that we call precession.

有運動在發生，我們稱之為 "衰退 "的東西。

As the Earth's rotational axis slowly moves, the stars shift in our night sky.

隨著地球自轉軸的緩慢移動，我們的夜空中的星星也在移動。

About every 26,000 years or so, we get a new view of the stars.

大約每隔26000年左右，我們就能看到新的星空。

Today, most of us know that Polaris is the North Star.

今天，我們大多數人都知道北極星是北極星。

But years ago, Thuban—a star in the 'tail' of the constellation Draco—was the marker of the poles!

但在多年前，圖班--一顆位於德拉科星座 "尾巴 "的恆星--是兩極的標誌!

By the 5th century CE, Chinese scholars had figured out the whole precession problem and factored it into their calendar.

到了公元5世紀，中國學者已經弄清了整個先期問題，並將其納入曆法。

And roughly 500 years later, one of the greatest time-keeping achievements of ancient China was unveiled:

而大約500年後，中國古代最偉大的計時成就之一揭開了面紗。

a five-story astronomical clock tower.

一座五層的天文鐘樓。

This mechanical structure ran on a day and night time-keeping wheel that was powered by water!

這個機械結構是靠一個日夜不停的計時輪運行的，而這個計時輪是由水來驅動的!

Astronomical clocks displaying the relative position of the Sun, planets, and even astrological information

天文鐘，顯示太陽、行星的相對位置，甚至星象資訊

also became all the rage in medieval Europe.

在中世紀的歐洲也變得風靡一時。

Some of these clocks, like the Orloj in Prague, still run to this very day.

其中一些時鐘，如布拉格的Orloj，至今仍在運行。

But not all of us have fancy clocks nearby to go look at.

但並不是所有的人附近都有漂亮的時鐘可以去看。

Fortunately, using the stars to tell time is as simple as pointing a finger.

幸運的是，用星星來顯示時間，就像用手指點一下一樣簡單。

Simple being a relative term.

簡單是一個相對的名詞。

First, find the Big Dipper and the North Star.

首先，找到北斗七星和北極星。

Next, trace a line through those last two stars of the Dipper, called the Pointers, towards Polaris.

接下來，通過北斗七星的最後兩顆星，也就是所謂的指針，向北極星方向劃一條線。

Imagine that Polaris is the center of a 24-hour clock, with its hour hand passing up to the Pointers.

想象一下，北極星是24小時時鐘的中心，其時針向上傳遞給尖兵。

But instead of turning clockwise, its hour hand turns backwards.

但它的時針不是順時針轉動，而是向後轉動。

There's another pretty big catch: You can only read this clock directly from the sky on March 6!

還有一個非常大的問題。你只能在3月6日從天上直接讀到這個鍾！

On any other night of the year,

在一年中的任何其他夜晚。

take the reading off the "Dipper Clock" and subtract two times the number of months after March.

把 "北斗鍾 "上的讀數減去3月以後的月數的2倍。

This system works well, but definitely involves some math.

這個系統很好用，但肯定涉及到一些數學問題。

We've linked a handy reference down in the comments if you're curious to try it out on your own!

我們已經在評論中鏈接了一個方便的參考資料，如果你好奇的話，可以自己嘗試一下。

Once you get the hang of it, you'll be able to calculate the time on any given solar day!

一旦你掌握了訣竅，你就能計算出任何一個太陽日的時間了。

For those of us here on Earth wondering the time, thankfully the sky offers us a fair number of clocks to use.

對於我們這些在地球上想知道時間的人來說，值得慶幸的是，天空為我們提供了相當多的時鐘供我們使用。

But what if you're out in space amongst the stars, with no shadows to read and no ecliptic line to follow?

但如果你在太空中的星空中，沒有影子可讀，沒有黃道線可循，怎麼辦？

Well, that's where atomic clocks come in.

嗯，這就是原子鐘的作用。

They're used by GPS satellites to produce super precise signals

它們被GPS衛星用來產生超精確的信號。

and on the ISS to study the relationship between gravity and time.

並在國際空間站上研究重力與時間的關係。

But despite their extreme precision, these clocks aren't perfect;

但是，儘管它們的精度極高，但這些時鐘並不完美。

they require constant communication with the more accurate atomic clocks located here on Earth to stay calibrated.

它們需要不斷地與地球上更精確的原子鐘溝通，以保持校準。

This works fine for now, but as we continue to navigate deep space,

這暫時還行得通，但隨著我們繼續在深空航行。

we're going to need ultra-accurate clocks that can run on their own.

我們需要能夠獨立運行的超精確時鐘。

That's why NASA engineer Jill Seubert and her team are developing and testing the Deep Space Atomic Clock—

這就是為什麼NASA工程師Jill Seubert和她的團隊正在開發和測試深空原子鐘--。

a clock that's about as close to perfect as it gets.

一個接近完美的時鐘，因為它得到。

The reason that timekeeping is important for navigation is because we can figure out how far away spacecraft are

計時對導航很重要，因為我們可以計算出航天器的距離有多遠

by measuring the time it takes to send a signal from the ground station to the spacecraft.

通過測量從地面站向航天器發送信號所需的時間。

And if we collect those measurements over time,

而如果我們隨著時間的推移收集這些測量結果。

we can get tracking information that tells us what the trajectory of the spacecraft is,

我們可以得到跟蹤資訊，告訴我們航天器的軌跡是什麼。

or what its position and velocity is.

或它的位置和速度是什麼。

NASA's Deep Space Atomic Clock is a precise instrument for measuring how long it takes

美國宇航局的深空原子鐘是一個精確的儀器，用於測量它需要多長時間。

for a signal to travel from point A and B.

為信號從A點和B點傳來。

Using the frequencies of light emitted by atoms, it's been shown to lose just one second

利用原子發出的光的頻率，證明只損失一秒鐘的時間

every 10 million years during controlled tests on Earth.

在地球上進行的控制試驗中，每1000萬年。

That's up to 50 times more stable than the atomic clocks used onboard GPS satellites!

這比GPS衛星上使用的原子鐘穩定50倍!

Since 2019, the clock has been undergoing a series of tests up in space

2019年以來，時鐘在太空中進行了一系列測試。

to make sure everything is running just as accurately.

以確保一切都能準確無誤地運行。

Once confirmed, it will be instrumental in helping spacecraft navigate on their own,

一旦確認，它將在幫助航天器自主導航方面發揮重要作用。

without having to rely on directions sent from Earth.

而不必依靠地球發出的訓示。

Your computer can actually determine where the spacecraft is, predict where it's headed,

你的電腦其實可以確定航天器的位置，預測它的方向。

and determine if it needs to fire its thrusters to correct its course and get back on track.

並決定它是否需要發射推進器來修正航向，重回正軌。

From an ancient sundial used to gauge the length of a day to an atomic clock developed for deep space travel,

從古代用來測量一天長度的日晷到為深空旅行開發的原子鐘。

humanity continues to rely on the cosmos to make sense of the mysterious flow of time.

人類繼續依靠宇宙來理解時間的神祕流動。

But no matter the timekeeping tools we use, one thing is for sure:

但無論我們用什麼計時工具，有一點是肯定的。

the search to find our place in the universe is truly a story as old as time.

尋找我們在宇宙中的位置 是一個真正的故事，因為古老的時間。

I'm Sarafina Nance and this is Seeker Constellations.

我是薩拉菲娜-南斯，這裡是 "探索者星座"。

If there's another astronomy topic you'd like to see us to cover, let us know in the comments.

如果有其他的天文學主題，你想看到我們覆蓋，讓我們知道在評論。

Thanks for watching!

謝謝你的觀看!