What causes the earth to rotate
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Causes of Earth's Rotation
Understanding the causes of Earth's rotation involves examining both the fundamental principles of physics and the various geophysical processes that influence this rotation over time. This article synthesizes insights from multiple research papers to provide a comprehensive overview of the factors contributing to Earth's rotation.
Fundamental Physics of Earth's Rotation
Conservation of Angular Momentum
The primary cause of Earth's rotation is the conservation of angular momentum. This principle states that an object will continue to rotate unless acted upon by an external torque. Earth's rotation began during its formation from the solar nebula, where the conservation of angular momentum caused the planet to spin as it coalesced from a cloud of gas and dust6.
Gravitational Influences
Gravitational forces from celestial bodies, particularly the Sun and the Moon, also play a significant role in Earth's rotation. These forces cause tidal effects, which in turn lead to variations in the rotation rate and the position of the rotation axis. The gravitational pull of the Moon, for example, causes nutational motion, a type of axis motion that occurs with nearly diurnal periods as seen from Earth2.
Geophysical Processes Affecting Rotation
Atmospheric and Oceanic Dynamics
Changes in the distribution of mass within Earth's atmosphere and oceans can cause fluctuations in the rotation rate. Seasonal shifts in air masses and variable winds are significant contributors to short-period fluctuations in Earth's rotation1. Additionally, the exchange of angular momentum between the atmosphere and the mantle, particularly during events like El Niño, can lead to noticeable changes in the length of the day (LOD)9.
Core and Mantle Interactions
Processes occurring within Earth's core and mantle also influence its rotation. Variations in the motion of the liquid metallic core, where the geomagnetic field originates, can cause irregularities in the rotation rate. These processes are linked to the dynamics of the Earth-Moon system and the topography of the core-mantle boundary4. The westward drift of Earth's magnetic field is another indicator of core-related motion affecting rotation3.
Tidal Forces and Secular Changes
Tidal forces exerted by the Sun and Moon not only cause nutational motion but also contribute to long-term changes in Earth's rotation. These forces lead to a gradual increase in the length of the day over millennia. Historical records of lunar and solar eclipses, as well as geological evidence from fossil growth rhythms, support the observation of these secular changes7.
Observational Advances
Space Geodetic Techniques
Recent advancements in space geodetic techniques, such as satellite laser ranging (SLR), very long baseline interferometry (VLBI), and the global positioning system (GPS), have significantly improved our ability to measure variations in Earth's rotation. These techniques provide precise data on changes in the rotation rate, polar motion, and nutation, enhancing our understanding of the underlying geophysical processes8.
Conclusion
The rotation of Earth is a complex phenomenon influenced by fundamental physical principles and a variety of geophysical processes. While the conservation of angular momentum initiated Earth's rotation, ongoing variations are driven by atmospheric dynamics, core-mantle interactions, and tidal forces. Advances in observational techniques continue to refine our understanding of these processes, offering deeper insights into the intricate mechanisms governing Earth's rotation.
Sources and full results
Most relevant research papers on this topic
Astronomy-Geophysics. (Book Reviews: The Rotation of the Earth. A geophysical discussion)
This book explores irregularities in the Earth's rotation, revealing factors such as seasonal shifts, variable winds, and climate changes, as well as a secular increase in the length of day.
Highly CitedThe Earth’s Rotation
Earth's rotation, influenced by various processes, is influenced by the length of a day, the gravitational attraction of celestial objects, and the Earth's rotation rate.
ON THE GEOPHYSICAL INTERPRETATION OF IRREGULARITIES IN THE ROTATION OF THE EARTH
Variations in the Earth's rotation over decades can be accounted for by a variable motion in the core, with processes in the atmosphere, ocean, and crust being insufficient to fully explain them.
Earth's Variable Rotation
Earth's rotation fluctuations impact core-mantle boundary topography, interior processes, and atmospheric variations, with implications for oceans and climate.
Highly Cited