Monday, November 11, 2019
Earth is the planet on which we live. Earth is the third planet from the sun. The particles which compose of the mass of the earth but more particularly the particles which from the mould on the surface of Earth. The Earth is the largest member of the group of inner planets and is also the most massive. When the Earth is compared with its planetary neighbors, marked similarities as well marked differences are found. Of course, what singles the Earth out from any other planets is the fact that it has an oxygen-rich atmosphere and a temperature that makes it suitable for life of the kind we can understand. Were the Earth slightly close to the sun and slightly farther away, life here might not have developed. The purpose of this research is to let us learn more about our Planet that we are living and also aims to help us understand more about our planet. Even we have an idea what Planet Earth is all about, we must dig deeper and know the characteristics of Earth that we havenÃ¢â¬â¢t yet know. `The completion of this paper was made possible through my research in library, and computers. Some books, encyclopedia, dictionary, some magazines computer encyclopedia and other website, I got all I want to know. They are very helpful for my research, and thanks be to God for giving me wisdom to do this term paper alone and by myself. Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar SystemÃ¢â¬â¢s four terrestrial planets. It is sometimes referred to as the world, the Blue Planet, or by its Latin name, Terra. Earth formed approximately 4. 54 billion years ago, and life appeared on its surface within one billion years. EarthÃ¢â¬â¢s biosphere then significantly altered the atmospheric and other basic physical conditions, which enabled the proliferation of organisms as well as the formation of the ozone layer, which together with EarthÃ¢â¬â¢s magnetic field blocked harmful solar radiation, and permitted formerly ocean-confined life to move safely to land. The physical properties of the Earth, as well as its geological history and orbit, have allowed life to persist. Estimates on how much longer the planet will be able to continue to support life range from 500 million years (myr), to as long as 2. billion years (byr). EarthÃ¢â¬â¢s crust is divided into several rigid segments, or tectonic plates, that migrate across the surface over periods of many millions of years. About 71% of the surface is covered by salt water oceans, with the remainder consisting of continents and islands which together have many lakes and other sources of water that contribute to the hydrosphere. EarthÃ¢â¬â¢s poles are mostly covered with ice that is the solid ice of the Antarctic ice sheet and the sea ice that is the polar ice packs. The planetÃ¢â¬â¢s interior remains active, with a solid iron inner core, a liquid outer core that generates the magnetic field, and a thick layer of relatively solid mantle. Earth gravitationally interacts with other objects in space, especially the Sun and the Moon. During one orbit around the sun, the Earth rotates about its own axis 366. 26 times, creating 365. 26 solar days, or one sidereal year. The EarthÃ¢â¬â¢s axis of rotation is tilted 23. 4Ã ° away from the perpendicular of its orbital plane, producing seasonal variations on the planetÃ¢â¬â¢s surface with a period of one tropical year (365. 24 solar days). The Moon is EarthÃ¢â¬â¢s only natural satellite. It began orbiting the Earth about 4. 53 billion years ago (bya). The MoonÃ¢â¬â¢s gravitational interaction with Earth stimulates ocean tides, stabilizes the axial tilt, and gradually slows the planetÃ¢â¬â¢s rotation. The planet is home to millions of species, including humans. Both the mineral resources of the planet and the products of the biosphere contribute resources that are used to support a global human population. These inhabitants are grouped into about 200 independent sovereign states, which interact through diplomacy, travel, trade, and military action. Human cultures have developed many views of the planet, including its personification as a planetary deity, its shape as flat, its position as the center of the universe, and in the modern Gaia Principle, as a single, self-regulating organism in its own right Formation The earliest material found in the Solar System is dated to 4. 5672Ã ±0. 0006 bya; therefore, it is inferred that the Earth must have been forming by accretion around this time. By 4. 54Ã ±0. 04 bya. The primordial Earth had formed. The formation and evolution of the Solar System bodies occurred in tandem with the Sun. In theory a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disk, and then the planets grow out of that in tandem with the star. A nebula contains gas, ice grains and dust (includingprimordial nuclides). In nebular theory planetesimals commence forming as particulate accrues by cohesive clumping and then by gravity. The assembly of the primordial Earth proceeded for 10Ã¢â¬â20 myr. The Moon formed shortly thereafter, about 4. 53 bya. The MoonÃ¢â¬â¢s formation remains a mystery. The working hypothesis is that it formed by accretion from material loosed from the Earth after a Mars-sized object, dubbed Theia, had a giant impact with Earth, but the model is not self-consistent. In this scenario the mass of Theia is 10% of the EarthÃ¢â¬â¢s mass, it impacts with the Earth in a glancing blow, and some of its mass merges with the Earth. Between approximately 3. 8 and 4. 1 bya, numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the greater surface environment of the Moon, and by inference, to the Earth. EarthÃ¢â¬â¢s atmosphere and oceans formed by volcanic activity and outgassing that included water vapor. The origin of the worldÃ¢â¬â¢s oceans was condensation augmented by water and ice delivered by asteroids, proto-planets, and comets. In this model, atmospheric Ã¢â¬Å"greenhouse gasesÃ¢â¬ kept the oceans from freezing while the newly forming Sun was only at 70% luminosity. By 3. 5 bya, the EarthÃ¢â¬â¢s magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind. A crust formed when the molten outer layer of the planet Earth cooled to form a solid as the accumulated water vapor began to act in the atmosphere. The two models that explain land mass propose either a steady growth to the present-day forms or, more likely, a rapid growthearly in Earth history followed by a long-term steady continental area. Continents formed by plate tectonics, a process ultimately driven by the continuous loss of heat from the earthÃ¢â¬â¢s interior. Ontime scales lasting hundreds of millions of years, the supercontinents have formed and broken up three times. Roughly 750 mya (million years ago), one of the earliest known supercontinents, Rodinia, began to break apart. The continents later recombined to form Pannotia, 600Ã¢â¬â540 mya, then finally Pangaea, which also broke apart 180 mya. Evolution of life Highly energetic chemistry is thought to have produced a self-replicating molecule around 4 bya and half a billion years later the last common ancestor of all life existed. The development of photosynthesis allowed the SunÃ¢â¬â¢s energy to be harvested directly by life forms; the resultant oxygen accumulated in the atmosphere and formed a layer of ozone (a form of molecular oxygen [O3]) in the upper atmosphere. The incorporation of smaller cells within larger ones resulted in the development of complex cells called eukaryotes. True multicellular organisms formed as cells within colonies became increasingly specialized. Aided by the absorption of harmful ultraviolet radiation by the ozone layer, life colonized the surface of Earth. Since the 1960s, it has been hypothesized that severe glacial action between 750 and 580 mya, during the Neoproterozoic, covered much of the planet in a sheet of ice. This hypothesis has been termed Ã¢â¬Å"Snowball EarthÃ¢â¬ , and is of particular interest because it preceded he Cambrian explosion, when multicellular life forms began to proliferate. Following the Cambrian explosion, about 535 mya, there have been five major mass extinctions.  The most recent such event was 65 mya, when an asteroid impact triggered the extinction of the (non-avian) dinosaurs and other large reptiles, but spared some small animals such as mammals, which then resembled shrews. Over the past 65 myr, mammalian life has diversified, and several million years ago an African ape-like animal such as Orrorin tugenensis gained the ability to stand upright. This enabled tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain, which allowed the evolution of the human race. The development of agriculture, and then civilization, allowed humans to influence the Earth in a short time span as no other life form had, affecting both the nature and quantity of other life forms. The present pattern of ice ages began about 40 mya and then intensified during the Pleistocene about 3 mya. High-latitude regions have since undergone repeated cycles of glaciation and thaw, repeating every 40Ã¢â¬â100,000 years. The last continental glaciation ended 10,000 years ago.