Context:
A recent study highlighted that due to factors like climate change and geological shifts, Earth’s changing rotation may prompt clocks to skip a second, potentially necessitating a “negative leap second” around 2029.
Relevance:
Facts for Prelims
Dimensions of the Article:
- Understanding Leap Second
- Exploring Negative Leap Second
Understanding Leap Second
Purpose of Leap Second:
- Introduced to address the Earth’s long-term slowdown in rotation due to constant melting and refreezing of ice caps.
- Added occasionally to Coordinated Universal Time (UTC) to align global clocks with Earth’s decreasing rotation speed.
History and Implementation:
- The system of leap seconds was established in the early 1970s, with 27 positive leap seconds added to date.
- UTC is based on a time scale from over 300 precise Atomic clocks worldwide, which remain accurate within one second over millions of years.
Comparison with Astronomical Time:
- Universal Time (UT1) represents Earth’s rotation on its axis and determines a day’s length.
- Earth’s rotation is inconsistent due to factors like moon’s gravitational forces and resulting ocean tides, causing UT1 to drift from UTC.
- A leap second is added to UTC when the discrepancy between UTC and UT1 approaches 0.9 seconds, ensuring synchronization.
Timing of Leap Second Addition:
- Leap seconds are typically inserted on either June 30 or December 31.
Exploring Negative Leap Second
Definition:
- A negative leap second subtracts a second from clocks to maintain synchronization with Earth’s rotation.
Historical Context:
- No negative leap seconds have been introduced to date, primarily because the Earth’s rotation has generally been slowing down over recent decades.
Monitoring and Decision-making:
- The International Earth Rotation and Reference Systems Service (IERS) oversees Earth’s rotation monitoring and determines leap second adjustments.
Consideration of Negative Leap Second:
- Due to Earth’s recent faster spin, timekeepers have considered introducing negative leap seconds, which would subtract seconds from clocks to align with Earth’s rotation.
-Source: Indian Express
