Uncovering the Phenomenon: How Tidal Forces Kept Earth’s Days at a Standstill for Over a Billion Years

An atmospheric effect that occurred billions of years ago caused various tidal forces to cancel out, resulting in Earth’s rotation slowing down and the lengthening of its days being put on pause. According to a recent study published in Science Advances, astrophysicists have discovered that from 2 billion to 600 million years ago, Earth’s days were approximately 19.5 hours long due to the cancellation of tidal forces. If this cancellation had not occurred, our present days might be over 65 hours long.

The research team emphasized that the fact that the day is currently 24 hours long is not a coincidence. The length of Earth’s days has gradually increased over time as lunar tidal forces have slowed down its rotation. These forces are generated by the Moon’s gravitational pull, causing bulges on the side of the planet closest to the Moon and the side furthest from it. These bulges, which result in high tides in the oceans, resist the spin of the Earth and create friction that slows down its rotation.

There are two types of solar tides that also affect Earth’s rotation. The first is the solar tidal torque, which operates similarly to the Moon’s tidal forces and causes small changes in ocean tides, further slowing down Earth’s spin. The second type is the thermal tidal torque, which occurs when sunlight heats the atmosphere, causing it to expand. This expansion creates another handle for the Sun’s gravity to interact with, pushing Earth to rotate faster. However, the lunar tides generate twice the force due to the Moon’s closer proximity to Earth.

Around two billion years ago, Earth’s atmosphere was warmer, affecting the thermal waves created by sunlight. Higher temperatures led to higher wave velocities, and the frequency at which these waves traveled through the atmosphere created an atmospheric resonance. This resonance and the length of the day remained in sync for approximately a billion years, with atmospheric waves resonating every time the Earth completed about half a rotation.

The resonance caused the atmospheric tides caused by the Sun to become stronger, countering the lunar tides. As a result, Earth’s rotation neither slowed down nor sped up. It wasn’t until 600 million years ago, a billion years after the resonance started, that days began to grow longer again.

The study’s findings were confirmed by examining geological evidence of high and low tides from ancient rock formations. The researchers concluded that the long duration and relatively recent occurrence of this resonant state may be responsible for the current 24-hour day.

However, there is concern that rising temperatures due to global warming could throw the resonance even more out of sync with rotation, further lengthening days. The more out of sync the resonance and rotation are, the less solar tidal forces can counter the lunar tidal forces that have gradually extended days on Earth over eons. While having a few extra hours in the day may seem appealing, it should not come at the expense of our planet.

The study was published in Science Advances in 2023, and the DOI is 10.1126/sciadv.add2499. Elizabeth Rayne, the author of the article, is a writer whose work has appeared on various platforms.

How have variations in air density and pressure affected Earth’s rotation over time?

Variations in air density and pressure. These variations create atmospheric tides that exert a torque on Earth’s rotation, slowing it down even more.

However, the recent study suggests that there was a period in Earth’s history when these forces were somehow balanced, resulting in the cancellation of tidal forces. This cancellation prevented the lengthening of Earth’s days and kept them relatively stable at around 19.5 hours for a period of 1.4 billion years.

The researchers used computer simulations to model the effects of different atmospheric conditions on Earth’s rotation. They found that during this period, the combination of solar and thermal tidal torques cancelled out the lunar tidal forces, keeping Earth’s days from getting longer.

If this cancellation had not occurred, our present days would be significantly longer, potentially exceeding 65 hours. This would have had profound implications for our planet and its ecosystems. The longer days would have affected climate patterns, temperature distributions, and even the evolution of life on Earth.

The study highlights the delicate balance between the various forces that shape our planet’s rotation. It shows that even subtle changes in atmospheric conditions can have significant effects on Earth’s rotation and the length of its days.

Understanding these processes is not only important for understanding Earth’s history but also for predicting and mitigating the impacts of future changes. As our climate continues to evolve, it is crucial to comprehend how these forces interact and what consequences they may have on our planet’s rotation and the length of our days. The research team’s findings contribute to this ongoing body of knowledge and provide further insight into Earth’s dynamic system.