Archive For September 26, 2018

Western Ghats

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The Western Ghats or SahyÄdri runs north to south along the western edge of the Deccan Plateau, and separates the plateau from a narrow coastal plain along the Arabian Sea. The range starts near the border of Gujarat and Maharashtra, south of the Tapti River, and runs approximately 1600 km through the states of Maharashtra,…

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Coal Resources in India

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Most of the coal mined in India comes from the rock formations of two geological ages viz. Lower Gondwana and Tertiary. About 80 per cent of the coal deposits in India is of bituminous type and is of non-coking grade. This is one of the reasons that India has to rely upon imports of coking…

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Demographic Transition Theory

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The demographic transition theory studies the relationship between economic development and population growth. It discusses about changes in birth rate and death rate and consequently growth rate of population in assonance with the process of growth and development. It is also used to describe and predict the future population of any area. The theory tells…

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Population Pyramids : Meaning and Types

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The age-sex structure of a population refers to the number of females and males in different age groups. An age sex pyramid or population pyramid is used to show the age-sex structure of the population. The shape of the population pyramid reflects the characteristics of the population and also indicates whether the population is experiencing…

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Demographic Dividend, Longevity Dividend and Zero Population Growth

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India is a nation of young people – out of a population of above 1.1 billion, 672 million people are in the age-group 15 to 59 years, – which is usually treated as the “working age populationâ€. A few years back, it was proposed that India in near future (30 years) will see a sharp…

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Key Facts about Universe

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The universe is all of space, time, matter, and energy that exist. Universe is not just space, but space is just the framework or the scaffolding in which the universe exists. As Space and time are intimately connected in a four-dimensional fabric called space-time. Contents Age of Universe Size of Universe Cosmic Horizon Structure of…

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Hubble Constant, Doppler Effect, Blue and Red Shift in Galaxies

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The expansion rate of the universe is called the Hubble Constant in honor of Edwin Hubble (1889–1953). Currently the best measured value of the Hubble Constant is about 73 kilometers per second per megaparsec. This implies that if a location in space is one million parsecs from another location, then in the absence of any…

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Black Holes : Key Facts and Types of Black Holes

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Each object has its own gravity which depends on its size and mass. The objects which have highest mass in smallest size would exert most gravity. The ultimate combination of large mass and small size is called a black hole. A black hole exerts such massive gravitational force that its escape velocity is equal or…

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Dark Matter and Dark Energy

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In 1930s, astronomers noticed that in some galaxy clusters, some of the galaxies were moving extra fast than possible with available matter (and its gravitational force). The question was – Is there any matter which is not visible to us but exerts its gravitation responsible for keeping the galaxies put together? Again in 1970s researchers…

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Galaxies: Types, Distribution, Clusters and Super Clusters

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A galaxy is a vast collection of stars, gas, dust, and dark matter that forms a cohesive gravitational unit in the universe. In a way, galaxies are to the universe what cells are to the human body: each galaxy has its own identity, and it ages and evolves on its own, but it also interacts…

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Key Facts and Comparison of Milky Way and Andromeda Galaxies

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The Milky Way is the galaxy we live in. It contains the Sun and 100 to 500 billion other stars. It is a barred spiral galaxy as grouped in the Hubble tuning fork diagram. It is located at the  outskirts of the Virgo supercluster. The centre of the Virgo cluster is about 50 million light-years…

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