Earth’s day was a constant 19.5 hours for over a billion years after the Big Bang
Have you ever wondered why our day, the time it takes for the Earth to complete one full rotation on its axis, is 24 hours long? The answer lies in the gradual slowing down of Earth's rotation over billions of years, primarily influenced by the tidal pull of the moon. In the early stages of Earth's history, when the moon was much closer than it is today, a day lasted only four hours. However, ongoing research has revealed that Earth's spin is slowing down at a rate of 1.35 seconds every 100,000 years.
However, a recent study conducted by a team of astrophysicists from the University of Toronto has unveiled an intriguing twist to this narrative. Their research indicates that, for over a billion years, an atmospheric tide generated by the sun counteracted the moon's influence, resulting in a steady 19.5-hour day.
This pause in the gradual slowing of Earth's rotation has had a profound impact on the length of our day as we know it today. Without this pause, our days on Earth would currently stretch over 60 hours.
The battle between the moon and the sun's tidal forces has played a significant role in shaping Earth's rotation. Since the moon's formation around 4.5 billion years ago, its gravitational pull has been gradually slowing down Earth's rotation. The moon's gravitational force creates tidal bulges on opposite sides of the planet, causing the ebb and flow of high and low tides. The friction between these tides and the ocean floor acts as a brake, gradually decelerating Earth's rotation.
On the other hand, the sun contributes to Earth's rotation in a different manner. Sunlight generates an atmospheric tide that creates bulges in the atmosphere, similar to how the moon influences ocean tides. However, unlike the moon, the sun's gravity accelerates Earth's rotation rather than decelerating it.
Throughout Earth's history, the lunar tides have predominantly outweighed the solar tides, leading to a decrease in our planet's rotational speed and an increase in the length of the day. Nevertheless, around two billion years ago, an intricate interplay between the temperature of the atmosphere, its natural resonance, and Earth's rotational rate emerged.
The scientists, led by theoretical astrophysicist Norman Murray, delved into geological evidence and employed advanced atmospheric research tools to unravel the connection between the atmosphere's temperature and Earth's rotational rate. They discovered that the atmospheric bulges were more pronounced during this period due to a warmer atmosphere.
As our planet's temperature rises due to global warming and climate change, the resonance of the atmosphere undergoes a shift. This shift disrupts the previous alignment, resulting in less torque from the sun and an accelerated lengthening of the day. It is indeed remarkable to consider that climate change is contributing to longer days in our current era.
The study's findings shed light on the fascinating dynamics between Earth's rotation, the moon's gravitational pull, the sun's atmospheric tide, and the effects of climate change on day length. Understanding these intricate mechanisms allows us to grasp the complexities of our planet's history and the ongoing changes it experiences.