Tehran vs Sun

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Tehran (; Persian: تهران‎ Ťehrân [tehˈɾɒːn] (listen)) is the capital of Iran and Tehran Province. With a population of around 8.7 million in the city and 15 million in the larger metropolitan area of Greater Tehran, Tehran is the most populous city in Iran and Western Asia, and has the second-largest metropolitan area in the Middle East (after Cairo). It is ranked 24th in the world by the population of its metropolitan area.In the Classical era, part of the territory of present-day Tehran was occupied by Rhages, a prominent Median city. It was subject to destruction through the medieval Arab, Turkic, and Mongol invasions. Its modern-day inheritor remains as an urban area absorbed into the metropolitan area of Greater Tehran. Tehran was first chosen as the capital of Iran by Agha Mohammad Khan of the Qajar dynasty in 1786, in order to remain within close reach of Iran's territories in the Caucasus, before being separated from Iran as a result of the Russo-Iranian Wars, and to avoid the vying factions of the previously ruling Iranian dynasties. The capital has been moved several times throughout history, and Tehran is the 32nd national capital of Persia. Large-scale demolition and rebuilding began in the 1920s, and Tehran has been a destination for mass migrations from all over Iran since the 20th century.Tehran is home to many historical collections, including the royal complexes of Golestan, Sa'dabad, and Niavaran, where the two last dynasties of the former Imperial State of Iran were seated.

Tehran's most famous landmarks include the Azadi Tower, a memorial built under the reign of Mohammad Reza Shah of the Pahlavi dynasty in 1971 to mark the 2,500th year of the foundation of the Imperial State of Iran, and the Milad Tower, the world's sixth-tallest self-supporting tower which was completed in 2007. The Tabiat Bridge, a newly built landmark, was completed in 2014.The majority of the population of Tehran are Persian-speaking people, and roughly 99% of the population understand and speak Persian, but there are large populations of other ethno-linguistic groups who live in Tehran and speak Persian as a second language.Tehran has an international airport (Imam Khomeini Airport), a domestic airport (Mehrabad Airport), a central railway station, the rapid transit system of Tehran Metro, a bus rapid transit system, trolleybuses, and a large network of highways. There have been plans to relocate Iran's capital from Tehran to another area, due mainly to air pollution and the city's exposure to earthquakes. To date, no definitive plans have been approved. A 2016 survey of 230 cities by consultant Mercer ranked Tehran 203rd for quality of life. According to the Global Destinations Cities Index in 2016, Tehran is among the top ten fastest growing destinations.October 6 is marked as Tehran Day based on a 2016 decision by members of the City Council, celebrating the day when the city was officially chosen as the capital of Iran by the Qajar dynasty back in 1907.

Source: Wikipedia

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The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy mainly as light and infrared radiation. It is by far the most important source of energy for life on Earth. Its diameter is about 1.39 million kilometres (864,000 miles), or 109 times that of Earth, and its mass is about 330,000 times that of Earth. It accounts for about 99.86% of the total mass of the Solar System. Roughly three quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron.The Sun is a G-type main-sequence star (G2V) based on its spectral class. As such, it is informally and not completely accurately referred to as a yellow dwarf (its light is closer to white than yellow). It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core. It is thought that almost all stars form by this process.

In its core the Sun currently fuses about 600 million tons of hydrogen into helium every second, converting 4 million tons of matter into energy every second as a result. This energy, which can take between 10,000 and 170,000 years to escape the core, is the source of the Sun's light and heat. When hydrogen fusion in its core has diminished to the point at which the Sun is no longer in hydrostatic equilibrium, its core will undergo a marked increase in density and temperature while its outer layers expand, eventually transforming the Sun into a red giant. It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury and Venus, and render Earth uninhabitable – but not for about five billion years. After this, it will shed its outer layers and become a dense type of cooling star known as a white dwarf, and no longer produce energy by fusion, but still glow and give off heat from its previous fusion. The enormous effect of the Sun on Earth has been recognized since prehistoric times. The Sun has been regarded by some cultures as a deity. The synodic rotation of Earth and its orbit around the Sun are the basis of solar calendars, one of which is the predominant calendar in use today.

Source: Wikipedia