ROTATION OF EARTH AND SCIENCE BEHIND...

 THE EARTH IS ROTATING MUCH FASTER THAN EARLIER -  MATTER OF CONCERN OR JUST SCIENCE?

 

REF:HANS

 

It would not be summer without the long days. However, when it comes to the whole astronomical day, which is a single rotation of the Earth in which the hour hand revolves twice around a regular clock, some of this year's shortest will occur in July and August.

Last week saw the shortest days of the year thus far. According to data issued on July 11 by the US Naval Observatory and the International Earth Rotation and Reference Systems Service, rotation on July 9 was approximately 1.34 milliseconds shorter than 24 hours.

Not every day is equal.

This is not entirely abnormal. The Earth's rotations have been faster than usual recently. Over the last decade, the average day has decreased significantly, and in the last five years or so, the whole cycle has frequently been less than 24 hours long. Factors influencing the change include motions at the Earth's core, atmospheric fluctuations, and the Moon's position.

However, long-term patterns indicate that the days will not continue to shrink indefinitely. In fact, it is just the reverse. For millennia, days have grown longer. According to studies, a Tyrannosaurus rex that lived 70 million years ago had an average daily rotation of roughly 23 1/2 hours.

Researchers expect the lengthening trend to continue.

Tug of the Moon

 

Ref: Earth.com

The primary factor is energy lost due to tides. The Moon's gravitational attraction causes tidal shifts on Earth. Tidal currents heat the water, slowing the Earth's rotation and allowing the ocean to expand somewhat, releasing energy. The Moon moves away from Earth at a rate of approximately 4 centimeters every year. (Currently, the rate of retreat)

In other words, the Moon and Earth have a constant total angular momentum, which can be viewed as a single system measurement of their rotation. As the Moon's orbit expands and its angular momentum grows, Earth's angular momentum must decrease. That's why the days grow longer. However, short-term oscillations hinder this process, which takes billions of years.

Short-term oscillations hinder this process.

Centuries of evidence reveal that the rate of Earth's rotation has never been constant. There have been slow times, such as the early 1990s or 1970s, when the length of a day consistently exceeded 24 hours by more than 2 milliseconds. There have been speedier periods, such as the one we are currently experiencing.

Various forces both within and above the Earth drive these variations. These include the movement of materials across the planet, from the core to the mantle to the crust.

Recent research suggests that climate change could be a major cause of longer days. When ice melts into the sea, it moves water away from the poles and towards the equator. This causes the planet to become more oblate, which has the potential to slow down its spin.