Chapter 1: Introduction to Earth's Rotation

The year 2020, marked by the onset of the coronavirus pandemic, has finally come to a close. For many, it felt like an endless stretch of time, yet it concluded surprisingly quickly. In fact, during this year, Earth recorded its fastest rotational speeds, with 28 days being the shortest since 1960.

Before delving deeper, it's important to understand that our planet rotates around its axis, giving rise to sunrises and sunsets as it orbits the Sun. If you're curious about the mechanics behind this rotation, you can check out the article titled “Why Does the Earth Rotate?”. Remember, it's completely normal to have gaps in our knowledge; every day presents a new opportunity for learning and growth.

But should we be concerned about these changes?

Section 1.1: Understanding Earth's Rotation Variability

There's no immediate cause for alarm. Earth's rotation can fluctuate slightly due to various factors, including atmospheric pressure, wind patterns, the movements of the inner core, ocean currents, and the gravitational pull from other celestial bodies in the solar system.

These variations, although minuscule and often unnoticeable in our daily lives, can affect highly precise measurement systems, such as atomic clocks. How do we determine if Earth's rotation is speeding up?

The International Earth Rotation and Reference Systems Service (IERS) conducts official measurements of day length. The variations in the Earth's rotational vector, both relative to the planet and in inertial space, result from gravitational torques exerted by the Moon, Sun, and other planets, as well as from mass displacements within the planet itself.

Subsection 1.1.1: The Role of Satellite Geodesy

The IERS utilizes satellite geodesy to monitor changes in the Earth's gravity field, which reflect its shape and the redistribution of mass within the planet. These programs have also noted shifts in the Earth's center of mass relative to the crust, enabling the study of global phenomena such as mass changes in the atmosphere and oceans.

Chapter 2: The Record-Breaking Days of 2020

In 2020, the Earth experienced an unprecedented acceleration in its rotation, breaking the record for the shortest days a remarkable 28 times. The shortest day was recorded on July 5th, when Earth completed a rotation 1.0516 milliseconds quicker than the average 86,400 seconds.

Will the trend continue into 2021?

Scientists predict that the average day in 2021 will be 0.05 milliseconds shorter than 86,400 seconds, resulting in an estimated accumulation of a 19-millisecond lag by the year’s end for atomic clocks, which have been tracking day lengths since the 1960s.

What solutions might exist for this situation?

While we currently add leap seconds when the Earth slows, could we potentially subtract a leap second if the Earth speeds up? Although it's premature to conclude, the likelihood of needing to subtract a second rather than add one seems plausible, given the noticeable increase in Earth's rotational speed.

Senior research scientist Peter Whibberley from the National Physics Laboratory in the UK remarked, “International discussions regarding the future of leap seconds are ongoing, and the possibility of a negative leap second may lead to the discontinuation of leap seconds altogether,” as reported to The Telegraph.

Some experts have proposed that, instead of relying on leap seconds, we might let atomic and astronomical time diverge until a larger adjustment, such as a leap hour, can be implemented. This is especially relevant as leap seconds pose challenges for various sectors, including data logging and telecommunications.

References:

• “Earth is whipping around quicker than it has in a half-century” by Stephanie Pappas.
• “Earth Is in a Hurry in 2020” by Graham Jones.
• “The Earth is spinning faster now than at any time in the past half-century” by Sarah Knapton.

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