full transcript
#### From the Ted Talk by John Kitching: Who decides how long a second is?

## Unscramble the Blue Letters

For most of human history, ancient civilizations meesarud time with uqunie calendars that tkeacrd the stdeay march of the night sky. In fact, the second as we know it wasn’t introduced until the late 1500’s, when the Gregorian calendar began to spread across the globe alongside British coslolnaiim. The Gregorian calendar defined a day as a single revolution of the Earth about its axis. Each day could be divdied into 24 hours, each hour into 60 minutes, and each minute into 60 seconds. However, when it was first denefid, the second was more of a mathematical idea than a useful unit of time. Measuring days and huros was sufficient for most tsaks in pastoral communities. It wasn’t until society became interconnected through fast-moving railways that cities needed to agree on exact timekeeping. By the 1950’s, numerous global systems riqeured every second to be perfectly accounted for, with as much precision as possible. And what could be more precise than the atomic scale?
## Open Cloze

For most of human history, ancient civilizations **________** time with **______** calendars that **_______** the **______** march of the night sky. In fact, the second as we know it wasn’t introduced until the late 1500’s, when the Gregorian calendar began to spread across the globe alongside British **___________**. The Gregorian calendar defined a day as a single revolution of the Earth about its axis. Each day could be **_______** into 24 hours, each hour into 60 minutes, and each minute into 60 seconds. However, when it was first **_______**, the second was more of a mathematical idea than a useful unit of time. Measuring days and **_____** was sufficient for most **_____** in pastoral communities. It wasn’t until society became interconnected through fast-moving railways that cities needed to agree on exact timekeeping. By the 1950’s, numerous global systems **________** every second to be perfectly accounted for, with as much precision as possible. And what could be more precise than the atomic scale?
## Solution

- measured
- defined
- tracked
- unique
- colonialism
- divided
- hours
- tasks
- steady
- required

## Original Text

For most of human history, ancient civilizations measured time with unique calendars that tracked the steady march of the night sky. In fact, the second as we know it wasn’t introduced until the late 1500’s, when the Gregorian calendar began to spread across the globe alongside British colonialism. The Gregorian calendar defined a day as a single revolution of the Earth about its axis. Each day could be divided into 24 hours, each hour into 60 minutes, and each minute into 60 seconds. However, when it was first defined, the second was more of a mathematical idea than a useful unit of time. Measuring days and hours was sufficient for most tasks in pastoral communities. It wasn’t until society became interconnected through fast-moving railways that cities needed to agree on exact timekeeping. By the 1950’s, numerous global systems required every second to be perfectly accounted for, with as much precision as possible. And what could be more precise than the atomic scale?
## Frequently Occurring Word Combinations

### ngrams of length 2

collocation |
frequency |

gregorian calendar |
2 |

atomic clocks |
2 |

## Important Words

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