ES 2123 Earth as a Dynamic Planet Life Sciences Research (Essay Sample)

Earth as a Dynamic Planet
Name
Institution
Earth as a Dynamic Planet
Earth’s gravitational field and change in Earth’s rotational axis
Gravity is considered to be a natural phenomenon which makes all objects possessing mass to gravitate towards each other. In classical mechanics, Newton’s Law of Universal Gravitation argues that, objects in the universe attract each other with a force which is directly proportional to their masses and inversely proportional to the square of the distance between their centers of mass. Gravity is considered to be the weakest known force in nature. As such, it plays a very small role in shaping the internal properties of materials. However, despite its so small magnitude, it controls the trajectories of objects moving within the universe. Processes such as the evolution of stars, cosmos and galaxies are greatly influenced by this force. To determine the degree of influence which gravity has on objects, the amount of acceleration of falling bodies is measured. Freely falling bodies are given an acceleration of 9.8m/s2 on the surface of the Earth while on the Moon’s surface, the value is 1.6m/s2 (Rovelli, 1991).
In quantum mechanics, Einstein considers gravity as caused by the warping of space-time. If a massive object is placed on a piece of stretched fabric, it causes it to sag. As such, if a light marble ball is placed on the fabric near the warped region, it enters the created hole occupied by the massive object. Similarly, massive bodies like the sun cause the bending of space-time so that when the Earth passes nearby, it is attracted to the sagged space occupied by the sun. The bending of space-time is to the effect that light travels slower than it would do in straight line. Moreover, the trajectories of other objects are altered as they traverse the warped space-time. The planet Earth is a dynamic planet whose axis of rotation keeps on changing (Buis, 2016; Rovelli, 1991).
Since time immemorial, gravity has played a pivotal role in shaping the dynamic processes in the Earth’s interior. As such, scholars in geophysics endeavor to understand this phenomenon as it is through this that they can succeed in geophysical explorations. Spatial variations in gravitational acceleration are vital in eliciting important information regarding the dynamical state of the planet Earth. If the Earth is sliced along a plane perpendicular to the equator, then it realized to be elliptical with its widest portion aligning itself with the equator itself. This model of the planet was first proposed by Sir Isaac Newton in the year 1687. In coming up with this model, Newton was facilitated by observations given to him by his friend Richer who was a ship navigator. Richer made observations that, a pendulum clock could operate accurately in London but lost up to 2 minutes daily when a ship carrying it approached the equator. Newton therefore concluded that the planet Earth had a larger diameter near the equator than at the poles. Precisely, Newton discovered that the Earth had a radius difference of 22km in favor of the equator, thereby, representing a 0.3% change. Owing to this difference, it can be concluded that, the gravitational acceleration of the planet varies with latitude (Buis, 2016; Chang et al., 1987).
As shown in figure 1, the Earth’s gravitational acceleration is inversely proportional to the square of the distance from its center of mass. As such, qualitatively, this acceleration is larger at the poles than it is at the equator. The rotation of the planet Erath is the second factor determining its acceleration. This variation is attributable to the fact that the gravimeter used to measure this acceleration also rotates with the planet as one takes the readings. As the Earth rotates, the gravimeter rests on it hence the obtained reading captures information associated with the rotation. As an object moves in a curved path, it experiences a force known as centrifugal force, normally directed towards the outer side. The magnitude of this force is usually proportional to the distance of the object from the axis of rotation. Moreover, the size of the centrifugal force experienced is proportional to the rate of rotation. Scholars have discovered that the amount of centrifugal force is large at the equator but reduces to zero at the poles. Its direction on the other hand is always away from the axis of rotation. As such, centrifugal force serves to lower the amount of gravitational acceleration owing to rotation. If the planet was not rotating, the size of the acceleration would be higher (Chang et al., 1987; Buis, 2016).
Gravity on the Earth’s surface also undergoes time dependent variations. These temporal changes in gravitational pull are as a result of factors such as lunar-solar tides, changes in the volume of underground water, atmospheric and oceanic mass redistribution, changes in the amount of snow cover, earthquakes, post-glacial rebound in the Earth’s mantle and long-term mantle convection. These geophysical alterations have serious implications and should therefore be understood very well for researchers to effectively monitor global climatic changes, rotation of the planet Earth and changes in sea level. Moreover, redistribution in the mass of planet Earth alters the position of its center of mass. Although temporal variations in gravitational pull owing to oceanic and solid earth tides are easy to determine, non-tidal changes are comparatively harder to detect (Buis, 2016; Chang et al., 1987).
According to Chandler (2002), data gathered from various satellites since the year 1998 indicates a bulge in the Earth’s gravitational field around the equator. This change according to her is attributable to factors such as fluctuations in the volumes of water held by oceans. The period preceding the year 1998 was witnessing relatively smaller gravitational bulges in the equator owing to post-glacial rebounds. Moreover, the comparatively smaller changes are attributable to the melting of ice sheets after the last Ice Age. After the ice melt, the land that had been covered by the ice started to rise. This rebound of the ground led to changes in gravity. Presently, the land forming the equatorial region has been noted to bulge upwards while that at the poles has registered a downward bulge. The corresponding changes in the Earth’s gravity can be sensed through the use of ultra-precise laser tracking satellites. Additionally, the changes can be realized through tracking alterations in day length and the Earth’s rotation (Buis, 2016).
Scholars have noted variations in the Earth’s gravity in West Antarctica which they have attributed to a massive loss of ice occasioned by global warming. Using measurements obtained by a satellite named the European Space Agency’s (ESA) Gravity Field and Steady-State Ocean Circulation Explorer (GOCE), researchers were able to note a drastic weakening in the planet’s gravity a couple of years back. This satellite was ideally created to map the planet’s gravitation field. The findings obtained using this satellite were combined with data gathered using the Gravity Recovery and Climate Experiment (GRACE). This investigation was basically a joint venture involving the U.S National Aeronautics and Space Administration and the German Aerospace Center with the main focus being mapping out variations in the gravitational field of the planet Earth (Buis, 2016).
According to ESA, although the redistribution of the Earth’s mass causes slight gravitational alterations, between 2009 and 2012, a large scale melting of ice was incurred in the West Antarctica and it resulted in a large scale change in the Earth’s gravitational force in this region. By combining the observations recorded by both GRACE and GOCE, researchers were able to estimate the total loss in ice in the West Antarctica at 209 billion metric tons. Over the same period of time, Pine Island Glacier lost a total of 67 billion metric tons of ice per year (Buis, 2016).
The Earthquake that was registered in Japan on the 11th of March in the year 2011 may have altered the planet’s rotational axis, thereby, shortening the length of a day. NASA’s scientists by the names Richard Gross and Pasadena Calif utilized a complex model to execute a preliminary theoretical calculation aimed at determining how this temblor affected the rotation of the planet Earth. This Earthquake was the fifth strongest ever to strike Earth since 1900 and it had a magnitude of 9.0. According to these scholars, the quake changed the distribution of the Earth’s mass, thereby, causing the planet to rotate faster. Effectively, the length of a day on the planet got shortened by approximately 1.8 microseconds (Buis, 2016).
The magnitude of the Earth’s gravity is not constant everywhere on the planet but changes from place to place. One major reason as to why gravitational pull varies from place to place is inhomogeneity and unevenness in the distribution of material inside the Earth’s surface. When temblors strike a region, rocks and other materials are moved tens of kilometers below the surface. As a result of these alterations, small changes in local gravity are registered. When quakes occur in oceans such as the one recorded in Japan in 2011, the shape of the sea bed gets altered, thereby, occasioning the displacement of water and an eventual change in gravity (Buis, 2016).
After staying in orbit for a span of time twice its earlier planned life, GOCE ran out of fuel and reentered the atmo...