Who decides how long a second is? - John Kitching

2,474,411 views ・ 2021-01-19

TED-Ed


μ•„λž˜ μ˜λ¬Έμžλ§‰μ„ λ”λΈ”ν΄λ¦­ν•˜μ‹œλ©΄ μ˜μƒμ΄ μž¬μƒλ©λ‹ˆλ‹€.

λ²ˆμ—­: Yujin Son κ²€ν† : DK Kim
00:06
In 1967, researchers from around the world
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1967λ…„, μ „ μ„Έκ³„μ˜ μ—°κ΅¬μžλ“€μ΄
00:10
gathered to answer a long-running scientific questionβ€”
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였랜 μ‹œκ°„ κ³Όν•™κ³„μ—μ„œ 풀리지 μ•Šμ•˜λ˜ 문제의 닡을 λ‚΄κΈ° μœ„ν•΄ λͺ¨μ˜€μŠ΅λ‹ˆλ‹€.
00:14
just how long is a second?
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1초의 κΈΈμ΄λŠ” μ–Όλ§ˆλ‚˜ κΈ΄κ°€?
00:17
It might seem obvious at first.
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μ²˜μŒμ—λŠ” 무슨 λ‹Ήμ—°ν•œ κ±Έ 물어보냐고 λŠλ‚„μ§€λ„ λͺ¨λ¦…λ‹ˆλ‹€.
00:19
A second is the tick of a clock,
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1μ΄ˆλŠ” μ‹œκ³„μ˜ 초침이 ν•œ 번 λ˜‘λ”±μ΄λŠ” μ‹œκ°„μ΄λ©°,
00:21
the swing of a pendulum, the time it takes to count to one.
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μ‹œκ³„μΆ”κ°€ ν•œ 번 ν”λ“€λ¦¬λŠ” μ‹œκ°„μ΄λ©°, 1을 μ„ΈλŠ” 데에 κ±Έλ¦¬λŠ” μ‹œκ°„μ΄μ£ .
00:25
But how precise are those measurements?
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그런데 κ·Έ 츑정이 μ–Όλ§ˆλ‚˜ μ •ν™•ν• κΉŒμš”?
00:28
What is that length based on?
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κ·Έ κΈΈμ΄λŠ” 무엇이 기쀀이죠?
00:30
And how can we scientifically define this fundamental unit of time?
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이 기본적인 μ‹œκ°„ λ‹¨μœ„λ₯Ό μ–΄λ–»κ²Œ κ³Όν•™μ μœΌλ‘œ μ •μ˜ν•  수 μžˆμ„κΉŒμš”?
00:35
For most of human history, ancient civilizations
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거의 λͺ¨λ“  μ—­μ‚¬μ—μ„œ
κ³ λŒ€ λ¬Έλͺ…μ—μ„œλŠ” λ…νŠΉν•œ 달λ ₯으둜 μ‹œκ°„μ„ 재며
00:38
measured time with unique calendars
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00:41
that tracked the steady march of the night sky.
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λ°€ν•˜λŠ˜μ˜ κ·œμΉ™μ μΈ μ›€μ§μž„μ„ κ΄€μ°°ν•΄μ™”μŠ΅λ‹ˆλ‹€.
00:44
In fact, the second as we know it wasn’t introduced until the late 1500’s,
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사싀, μš°λ¦¬κ°€ μ•„λŠ” μ΄ˆλΌλŠ” κ°œλ…μ€
1500λ…„λŒ€ ν›„λ°˜μ—μ•Ό λ‚˜μ˜¨ 것이고,
00:51
when the Gregorian calendar began to spread across the globe
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그레고리λ ₯이 μ „ 세계에 νΌμ Έλ‚˜κ°”μ„ μ¦ˆμŒμž…λ‹ˆλ‹€.
00:54
alongside British colonialism.
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영ꡭ의 μ‹λ―Όμ£Όμ˜μ™€ ν•¨κ»˜μš”.
00:57
The Gregorian calendar defined a day as a single revolution of the Earth
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그레고리λ ₯은 ν•˜λ£¨λ₯Ό 지ꡬ가 ν•œ 번 νšŒμ „ν•˜λŠ” μ‹œκ°„μœΌλ‘œ μ •μ˜ν•©λ‹ˆλ‹€.
01:02
about its axis.
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지좕을 μ€‘μ‹¬μœΌλ‘œ 말이죠.
01:03
Each day could be divided into 24 hours, each hour into 60 minutes,
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ν•˜λ£¨λŠ” 24μ‹œκ°„μœΌλ‘œ λ‚˜λˆŒ 수 있고,
1μ‹œκ°„μ€ 60λΆ„μœΌλ‘œ,
01:09
and each minute into 60 seconds.
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1뢄은 60초둜 λ‚˜λˆŒ 수 μžˆμŠ΅λ‹ˆλ‹€.
01:12
However, when it was first defined,
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ν•˜μ§€λ§Œ μ΄ˆκ°€ 처음 μ •μ˜λ˜μ—ˆμ„ λ•Œ,
01:15
the second was more of a mathematical idea than a useful unit of time.
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μ΄ˆλŠ” μ‹œκ°„μ˜ μœ μš©ν•œ λ‹¨μœ„λΌκΈ°λ³΄λ‹€λŠ” μˆ˜ν•™μ μΈ κ°œλ…μ— κ°€κΉŒμ› μŠ΅λ‹ˆλ‹€.
01:20
Measuring days and hours was sufficient for most tasks in pastoral communities.
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농경 μ‚¬νšŒμ—μ„œ 일을 ν•  λ•Œμ—λŠ” μš”μΌκ³Ό λͺ‡ μ‹œμΈμ§€λ§Œ μ•Œλ©΄ λκ±°λ“ μš”.
01:26
It wasn’t until society became interconnected
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μ‚¬νšŒκ°€ μƒν˜Έ κ΄€κ³„μ μœΌλ‘œ λ³€ν•˜κ³  λΉ λ₯Έ 철도가 생기고 λ‚˜μ„œμ•Ό
01:29
through fast-moving railways that cities needed to agree on exact timekeeping.
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μ •ν™•ν•œ μ‹œκ°„ 츑정이 ν•„μš”ν•΄μ‘ŒμŠ΅λ‹ˆλ‹€.
01:34
By the 1950’s, numerous global systems required every second
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1950λ…„μ—λŠ” μ „ 세계 μˆ˜λ§Žμ€ μ‹œμŠ€ν…œλ“€μ΄
μ •λ°€ν•œ 초 λ‹¨μœ„κΉŒμ§€ μžˆμ–΄μ•Ό
01:39
to be perfectly accounted for, with as much precision as possible.
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κ°€λŠ₯ν•œ ν•œ μ •λ°€ν•˜κ²Œ μΈ‘μ •ν•  수 μžˆμ—ˆμŠ΅λ‹ˆλ‹€.
01:44
And what could be more precise than the atomic scale?
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μ›μž 규λͺ¨λ³΄λ‹€ μ •λ°€ν•œ 게 또 μžˆμ„κΉŒμš”?
01:49
As early as 1955, researchers began to develop atomic clocks,
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1955년에 이미 μ—°κ΅¬μžλ“€μ€ μ›μž μ‹œκ³„λ₯Ό κ°œλ°œν•˜κΈ° μ‹œμž‘ν–ˆκ³ ,
01:54
which relied on the unchanging laws of physics
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이듀은 λ¬Όλ¦¬ν•™μ˜ λΆˆλ³€ν•˜λŠ” 법칙을 μ‚¬μš©ν•΄μ„œ
01:57
to establish a new foundation for timekeeping.
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μ‹œκ°„ μΈ‘μ •μ˜ μƒˆλ‘œμš΄ 기초λ₯Ό λ§Œλ“€μ—ˆμŠ΅λ‹ˆλ‹€.
02:01
An atom consists of negatively charged electrons
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μ›μžλŠ” μŒμ „ν•˜λ₯Ό 띀 μ „μžλ“€μ΄
02:04
orbiting a positively charged nucleus at a consistent frequency.
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μ–‘μ „ν•˜λ₯Ό 띀 ν•΅μ˜ μ£Όμœ„λ₯Ό μΌμ •ν•œ 주기둜 돌고 μžˆμŠ΅λ‹ˆλ‹€.
02:09
The laws of quantum mechanics keep these electrons in place,
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μ–‘μž μ—­ν•™μ˜ 법칙은 이 μ „μžλ“€μ΄ μ œμžλ¦¬μ— λ¨Έλ¬ΌλŸ¬μžˆκ²Œλ” ν•˜μ§€λ§Œ
02:13
but if you expose an atom to an electromagnetic field
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μ›μžλ₯Ό μ „μžκΈ°μž₯에 λ…ΈμΆœμ‹œν‚€λ©΄,
02:17
such as light or radio waves,
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λΉ›μ΄λ‚˜ μ „νŒŒκ°™μ€ 것 λ§μž…λ‹ˆλ‹€,
02:19
you can slightly disturb an electron’s orientation.
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μ „μžμ˜ λ°©ν–₯을 살짝 λΉ„ν‹€ 수 μžˆμŠ΅λ‹ˆλ‹€.
02:24
And if you briefly tweak an electron at just the right frequency,
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λ§Œμ•½ μ λ‹Ήν•œ 주파수둜 μ „μžλ₯Ό 살짝 κ±΄λ“œλ¦¬λ©΄,
02:28
you can create a vibration that resembles a ticking pendulum.
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λ˜‘λ”±κ±°λ¦¬λŠ” μ§„μžμ™€ λΉ„μŠ·ν•œ 진동을 λ§Œλ“€μ–΄λ‚Ό 수 μžˆμŠ΅λ‹ˆλ‹€.
02:33
Unlike regular pendulums that quickly lose energy, electrons can tick for centuries.
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μ—λ„ˆμ§€λ₯Ό 빨리 μžƒλŠ” 보톡 μ§„μžμ™€ 달리,
μ „μžλŠ” λͺ‡λ°± 년이고 μ§„λ™ν•©λ‹ˆλ‹€.
02:39
To maintain consistency and make ticks easier to measure,
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일관성을 μœ μ§€ν•˜κ³  λ˜‘λ”±μž„μ„ 더 μ‰½κ²Œ μΈ‘μ •ν•˜κΈ° μœ„ν•΄,
02:43
researchers vaporize the atoms,
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μ—°κ΅¬μžλ“€μ€ μ›μžλ“€μ„ κΈ°ν™”μ‹œμΌœ
02:46
converting them to a less interactive and volatile state.
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μƒν˜Έμž‘μš©μ΄ 더 적고 더 μ•ˆμ •μ μΈ μƒνƒœλ‘œ λ°”κΏ‰λ‹ˆλ‹€.
02:51
But this process doesn’t slow down the atom’s remarkably fast ticking.
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κ·ΈλŸ°λ‹€κ³  ν•΄μ„œ μ›μžμ˜ 극히 λΉ λ₯Έ λ˜‘λ”±μž„μ˜ 속도가 λŠλ €μ§€μ§„ μ•ŠμŠ΅λ‹ˆλ‹€.
02:55
Some atoms can oscillate over nine billion times per second,
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μ–΄λ–€ μ›μžλ“€μ€ μ΄ˆλ‹Ή 90μ–΅ 번 이상 진동할 수 있고,
03:00
giving atomic clocks an unparalleled resolution for measuring time.
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μ›μž μ‹œκ³„κ°€ μ‹œκ°„μ„ μΈ‘μ •ν•˜λŠ” 데에 견쀄 데 μ—†λŠ” 정확도λ₯Ό μ œκ³΅ν•©λ‹ˆλ‹€.
03:05
And since every atom of a given elemental isotope is identical,
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νŠΉμ •ν•œ μ›μ†Œμ˜ λ™μœ„μ›μ†ŒλŠ” λͺ¨λ“  μ›μžκ°€ λ™μΌν•˜κΈ° λ•Œλ¬Έμ—,
03:10
two researchers using the same element and the same electromagnetic wave
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같은 μ›μ†Œμ™€ 같은 μ „μžνŒŒλ₯Ό μ‚¬μš©ν•˜κΈ°λ§Œ ν•œλ‹€λ©΄
03:14
should produce perfectly consistent clocks.
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μ™„λ²½νžˆ μΌκ΄€λœ μ‹œκ³„λ₯Ό μ œμž‘ν•  수 μžˆμ„ κ²ƒμž…λ‹ˆλ‹€.
03:18
But before timekeeping could go fully atomic,
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ν•˜μ§€λ§Œ μ‹œκ°„μ„ μ™„μ „νžˆ μ›μžλ‘œ μΈ‘μ •ν•˜κΈ° 전에
03:21
countries had to decide which atom would work best.
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ꡭ가듀은 μ–΄λŠ μ›μžκ°€ κ°€μž₯ 적합할지 κ²°μ •ν•΄μ•Ό ν–ˆμŠ΅λ‹ˆλ‹€.
03:25
This was the discussion in 1967,
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이 λ…Όμ˜λŠ” 1967λ…„,
03:28
at the Thirteenth General Conference of the International Committee
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제 13μ°¨ ꡭ제 λ„λŸ‰ν˜• μ΄νšŒμ—μ„œ
03:32
for Weights and Measures.
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μ΄λ£¨μ–΄μ‘ŒμŠ΅λ‹ˆλ‹€.
03:35
There are 118 elements on the periodic table,
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μ£ΌκΈ°μœ¨ν‘œμ—λŠ” μ›μ†Œκ°€ 118개 μžˆλŠ”λ°,
03:39
each with their own unique properties.
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각각의 μ›μ†ŒλŠ” κ³ μœ ν•œ μ„±μ§ˆμ΄ 있죠.
03:41
For this task, the researchers were looking for several things.
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이 문제λ₯Ό ν•΄κ²°ν•˜κΈ° μœ„ν•΄, μ—°κ΅¬μžλ“€μ€ μ—¬λŸ¬ 기쀀을 μ„Έμ› μŠ΅λ‹ˆλ‹€.
03:45
The element needed to have long-lived
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일단 이 μ›μ†ŒλŠ” 수λͺ…이 κΈΈκ³ 
03:47
and high frequency electron oscillation for precise, long-term timekeeping.
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고주파의 μ „μž 진동을 ν•΄μ•Ό
μ •ν™•ν•˜κ³  μž₯기적인 μ‹œκ°„ 츑정을 ν•  수 μžˆμŠ΅λ‹ˆλ‹€.
03:54
To easily track this oscillation,
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이 진동을 μ‰½κ²Œ μΈ‘μ •ν•˜κΈ° μœ„ν•΄μ„œλŠ”
03:56
it also needed to have a reliably measurable quantum spinβ€”
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μ•ˆμ •μ μœΌλ‘œ μΈ‘μ • κ°€λŠ₯ν•œ μ–‘μž μŠ€ν•€λ„ ν•„μš”ν•œλ°
04:00
meaning the orientation of the axis about which the electron rotatesβ€”
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μ΄λŠ” μ „μžκ°€ νšŒμ „ν•˜λŠ” μΆ•μ˜ λ°©ν–₯을 μ˜λ―Έν•©λ‹ˆλ‹€.
04:05
as well as a simple energy level structureβ€”
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그뿐 μ•„λ‹ˆλΌ λ‹¨μˆœν•œ μ—λ„ˆμ§€ μ€€μœ„ ꡬ쑰도 ν•„μš”ν•œλ°
04:08
meaning the active electrons are few and their state is simple to identify.
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ν™œμ„± μ „μžμ˜ μˆ˜κ°€ 적고 μ‹λ³„ν•˜κΈ° μ‰¬μš΄ μƒνƒœλΌλŠ” 뜻이죠.
04:14
Finally, it needed to be easy to vaporize.
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λ§ˆμ§€λ§‰μœΌλ‘œ, 이 μ›μ†ŒλŠ” κΈ°ν™”ν•˜κΈ° μ‰¬μ›Œμ•Ό ν•©λ‹ˆλ‹€.
04:18
The winning atom? Cesium-133.
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λ½‘νžŒ μ›μ†ŒλŠ” λ°”λ‘œ μ„ΈμŠ˜ 133μž…λ‹ˆλ‹€.
04:22
Cesium was already a popular element for atomic clock research,
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μ„ΈμŠ˜μ€ μ›μž μ‹œκ³„ 연ꡬ계에선 이미 자주 ν™œμš©ν•˜λŠ” μ›μ†Œμ˜€κ³ ,
04:26
and by 1968, some cesium clocks were even commercially available.
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1968λ…„μ—λŠ” μ„ΈμŠ˜μœΌλ‘œ λ§Œλ“  μ‹œκ³„κ°€ μ‹œμ€‘μ— λ‚˜μ˜€κΈ°κΉŒμ§€ ν–ˆμŠ΅λ‹ˆλ‹€.
04:31
All that was left was to determine how many ticks of a cesium atom
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이제 μ•Œμ•„λ‚΄μ•Ό ν•  것은
μ„ΈμŠ˜ μ›μžμ˜ λ˜‘λ”±μž„μ΄ λͺ‡ 번 μžˆμ–΄μ•Ό 1μ΄ˆκ°€ λ˜λŠλƒν•˜λŠ” κ²ƒμ΄μ—ˆμ£ .
04:35
were in a second.
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04:37
The conference used the most precise astronomical measurement
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μ΄νšŒμ—μ„œλŠ” κ°€μž₯ μ •λ°€ν•œ μ²œλ¬Έν•™μ  μΈ‘μ • 방법을 μ‚¬μš©ν–ˆμŠ΅λ‹ˆλ‹€.
04:40
of a second available at the timeβ€”
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κ·Έλ•Œ λ‹Ήμ‹œμ˜ 기술λ ₯을 κΈ°μ€€μœΌλ‘œμš”.
04:43
beginning with the number of days in a year and dividing down.
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1년에 μ†ν•œ λ‚ μ˜ μˆ˜λΆ€ν„° μ‹œμž‘ν•΄μ„œ μ„Έμ„Έν•˜κ²Œ λ‚˜λˆ κ°”μŠ΅λ‹ˆλ‹€.
04:47
When compared to the atom’s ticking rate,
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μ›μžμ˜ λ˜‘λ”±μ΄λŠ” 속도에 λΉ—λŒ€μ–΄,
04:50
the results formally defined one second
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κ³΅μ‹μ μœΌλ‘œ μ •μ˜λœ 1초의 κΈΈμ΄λŠ”
04:53
as exactly 9,192,631,770 ticks of a cesium-133 atom.
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μ„ΈμŠ˜ 133 μ›μžκ°€ μ •ν™•νžˆ
9,192,631,770번
λ˜‘λ”±μ΄λŠ” μ‹œκ°„μ΄μ—ˆμŠ΅λ‹ˆλ‹€.
05:06
Today, atomic clocks are used all over the Earthβ€” and beyond it.
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μ˜€λŠ˜λ‚  μ›μž μ‹œκ³„λŠ” 지ꡬ 상 λͺ¨λ“  κ³³, 그리고 μš°μ£Όμ—μ„œκΉŒμ§€ μ‚¬μš©λ˜κ³  있죠.
05:11
From radio signal transmitters to satellites
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무선 μ‹ ν˜Έ μ†‘μ‹ κΈ°μ—μ„œ μ‹œμž‘ν•˜μ—¬
05:14
for global positioning systems,
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GPS μΈκ³΅μœ„μ„±λ“€κΉŒμ§€,
05:16
these devices have been synchronized
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이 λͺ¨λ“  μž₯μΉ˜λ“€μ€ 동기화가 λ˜μ–΄
05:19
to help us maintain a globally consistent timeβ€”
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μ„Έκ³„μ μœΌλ‘œ λ™μΌν•œ μ‹œκ°„μ„ μœ μ§€ν•˜λ„λ‘ λ„μ™€μ€λ‹ˆλ‹€.
05:22
with precision that’s second to none.
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λ‘˜μ§Έκ°€λΌλ©΄ μ„œλŸ¬μšΈ λ§Œν•œ μ •λ°€λ„λ‘œ 말이죠.
이 μ›Ήμ‚¬μ΄νŠΈ 정보

이 μ‚¬μ΄νŠΈλŠ” μ˜μ–΄ ν•™μŠ΅μ— μœ μš©ν•œ YouTube λ™μ˜μƒμ„ μ†Œκ°œν•©λ‹ˆλ‹€. μ „ 세계 졜고의 μ„ μƒλ‹˜λ“€μ΄ κ°€λ₯΄μΉ˜λŠ” μ˜μ–΄ μˆ˜μ—…μ„ 보게 될 κ²ƒμž…λ‹ˆλ‹€. 각 λ™μ˜μƒ νŽ˜μ΄μ§€μ— ν‘œμ‹œλ˜λŠ” μ˜μ–΄ μžλ§‰μ„ 더블 ν΄λ¦­ν•˜λ©΄ κ·Έκ³³μ—μ„œ λ™μ˜μƒμ΄ μž¬μƒλ©λ‹ˆλ‹€. λΉ„λ””μ˜€ μž¬μƒμ— 맞좰 μžλ§‰μ΄ μŠ€ν¬λ‘€λ©λ‹ˆλ‹€. μ˜κ²¬μ΄λ‚˜ μš”μ²­μ΄ μžˆλŠ” 경우 이 문의 양식을 μ‚¬μš©ν•˜μ—¬ λ¬Έμ˜ν•˜μ‹­μ‹œμ˜€.

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