Refresh yourself: Facts about the earth

Danny Massawe · 2014-12-12T11:38:00+00:00

Nimesoma mahali nikajifunza mengi, ningependa kama unapenda na wewe upitie.... 1.HAIJULIKANI DUNIA IPO UPANDE GANI MWA ULIMWENGU. A precocious child might write his or her full address as Main Street, Toronto, Canada, the Earth, the Solar System, Orion Arm, the Milky Way, the Local Group, the Virgo Supercluster, the Universe. The Solar System consists of the Sun and those objects bound to it by gravity (the terrestrial planets, Mercury, Venus, Earth and Mars; the gas giants, Jupiter, Saturn, Neptune and Uranus; and various dwarf planets, proto-planets and asteroids). However measured, it is less than a light year across. The Milky Way galaxy is a barred spiral galaxy with a diameter of about 100,000 light-years and containing about 200 billion stars. Our Solar System is located towards the edge of one of the Milky Way's outer spiral arms, known as the Orion Arm or Local Spur, about 25,000 to 28,000 light years from the galactic centre. The Local Group is a small group or cluster of gravitationally-boundgalaxies, which includes the Milky Way, the Andromeda galaxyand the much smaller Triangulum galaxy (which has a diameter of around 10 million light-years), along with smaller satellite and dwarfgalaxies such as the Large Magellanic Cloud, the Sagittarius Dwarf Galaxy and Canis Major Dwarf Galaxy. The Virgo Supercluster is an irregular group of clusters of galaxies, between 100 and 200 million light years in diameter, which incorporates our Local Group of galaxies and about 100 other clusters. The Local Group is located in a small filament on the outskirts of the supercluster. It is thought that superclusters may also be arranged in even larger structures called walls (such as the Sloan Great Wall, which is about 1.5 billion light years long), although these may not be true structures as their parts are not gravitationally bound together. The universe is what we usually think of as the totality of known or supposed objects and phenomena throughout space. The observable part alone contains over ten billion trillion stars arranged in about 100 billion galaxies, and is estimated to be around 156 billion light years in diameter. By definition, we are at the centre of our observable universe, but it is totally unknown where we are in the universe as a whole. 2.SPIDI YA DUNIA A person on the equator is rotating around the Earth at about 1,660 kilometres per hour. A person at the north or south pole actually has a rotational speed of zero, and is effectively turning on the spot. Somewhere in between, a person's rotational speed decreases as they move from the equator towards the pole: for example, a person in Toronto, at around 45°N, is travelling about 1,230 kilometres per hour. Actually, rotational speed around the Earth is also dependent on altitude above sea level, and a person at the top of a mountain on the Equator is actually travelling faster than 1,660 kilometres per hour (as he has further to go with each revolution). Taking this to an extreme, an object in geostationary orbit around the Earth at an altitude of about 36,000 kilometres above the ground has to travel at about 11,000 kilometres per hour. But that is not all. The Earth circles around the Sun at about 107,000 kilometres per hour. Our Solar System is rotating around the Milky Way galaxy at about 700,000 kilometres per hour. The galaxy is also travelling at huge speed away from every other galaxy as the universe continues to expand, although with vastly differing relative speeds depending on the distances of the galaxies from us. To give some indication, scientists have calculated that our galaxy is travelling at about 2.2 million kilometres per hour relative to the cosmic background radiation which pervades the universe 3.SPIDI YA MWANGA light travels at exactly 299,792,458 metres per second in a vacuum (about 300,000 kilometres per second or just over 1 billion kilometres per hour). As a comparison, sound waves travel at a paltry 343.14 metres per second (about 1,235 kilometres per hour), almost a million times slower than light waves, and the fastest military airplane, the SR-71 Blackbird, can fly at about 980 metres per second (about 3,500 kilometres per hour). At that speed light takes: 0.0000033 seconds to travel 1 kilometre 1.3 seconds to reach us from the Moon 8.32 minutes to reach us from the Sun 4.37 years to reach us from Alpha Centauri, the nearest star system to the Solar System (Alpha Centauri is therefore said to be 4.37 light years away) 26,000 years to reach us from the centre of our Milky Way galaxy 2,500,000 to reach us from the Andromeda Galaxy, our next nearest galaxy (and the most distant object visible to the naked eye, although only as a barely perceptible smudge) 59 million years to reach us from the Virgo Cluster, the nearest large galaxy cluster and, theoretically, about 78 billion years to reach us from the edge of the observable universe(this is actually longer ago than the 13.7 billion year age of the universe, because the continued expansion of space has significantly increased the distance the light from these early objects has had to travel). 4.DUNIA IMEACHANA NA JUA NA NYOTA KWA UMBALI GANI? Earth's atmosphere is divided up into several layers: the troposphere from about 6 - 20 kilometres up; the stratosphere from 20 - 50 kilometres; the mesosphere from 50 - 85 kilometres; the thermosphere from 85 - 690 kilometres; and the exosphere out to about 10,000 kilometres. "Space" is often considered to start at about 100 kilometres up, known as the Kármán line, where the Earth's atmosphere becomes too thin for aeronautical purposes. The International Space Station orbits the Earth about 350 kilometres up (in the thermosphere). The Moon is about 360,000 kilometres away from the Earth (and it is receding from us at a rate of about 4 centimetres a year as its orbit gradually speeds up). The nearest planet to the Earth is either Venus, which varies between 42 million kilometres and 258 million kilometres away (its orbit is highly irregular), or Mars which varies between 56 million kilometres and 100 million kilometres away. The Sun is about 150 million kilometres away from the Earth (sometimes referred to as 1 astronomical unit, or 1 AU). The next nearest star to us (other than the Sun) is Proxima Centauri, in the Alpha Centauri starsystem (still part of our Milky Way galaxy), which is about 40 trillion (40,000,000,000,000) miles away or, using the more convenient unit based on the distance light travels in a year (which is about 9.46 trillion kilometres), 4.24 light years. Sirius A and B, in the Sirius star system, are about 81 trillion (81,000,000,000,000) kilometres or 8.58 light years away. The centre of the Milky Way galaxy is about 26,000 light years, or roughly 245 quadrillion (245,000,000,000,000,000) kilometres. Our next closest galaxy is the Andromeda Galaxy, which is about 2.5 million light years away, or roughly 26,000,000,000,000,000,000 kilometres. The best estimate of the size of the observable universe (given that it has been expanding for 13.7 billion years), is about 156 billion light years (1,560,000,000,000,000,000,000,000 kilometres) across. 5.KUNA NYOTA NGAPI? About 3,000 stars are visible to the unaided eye on a clear moonless night. About 100,000 stars can be seen using a small telescope. There are an estimated one hundred billion (100,000,000,000) stars in our own Milky Way galaxy, although some estimates range up to four times that many, much depending on the number of brown dwarfs and other very dimstars. A typical galaxy may contain anywhere between about ten million and one trillion stars. Therefore, using a very rough estimate of a hundred billion galaxies in the observableuniverse, and the number of stars in our own galaxy as a reasonable average, there may be around ten billion trillion (10,000,000,000,000,000,000,000 or 1022) stars in the observable universe, or quite possibly anywhere up to 1024. 6.AINA ZA NYOTA brown dwarfs - "failed stars", which form from clouds of interstellar gas, as other stars do, but never reach sufficient mass, density and internal heat to start thenuclear fusion process (i.e. less than 8% of the mass of our Sun). Although they may glow dimly when newly formed (and are therefore in fact red not brown), they start to cool soon after and so are very difficult to spot. They may actually be among the most common type ofstars. red dwarfs - small and relatively cool stars, bigger than brown dwarfs, but less than 40 - 50% of the mass of our Sun. Most of the stars in our galaxy (excluding possible unseen brown dwarfs) are red dwarfs. They are much dimmer than our Sun (even the largest red dwarf has only about 10% of the Sun's luminosity), burn much more slowly, and typically live much longer. yellow dwarfs - main-sequence stars like our own Sun, Alpha Centauri A, Tau Ceti, etc, typically about 80 - 100% of the size of the Sun, and actually more white than yellow. They are also known as G Vstars for their spectral type G and luminosity class V. white stars - bright, main-sequence stars with masses from 1.4 to 2.1 times the mass of the Sun and surface temperatures between 7,600°C and 10,000°C, such as Sirius A and Vega. red giants - luminous giant stars of low or intermediate mass (usually between 0.5 and 10 solar masses) in a late phase of stellar evolution, such as Aldeberan and Arcturus. When a main-sequence star has fused all its hydrogen into helium, it then starts to burn its helium to produce carbon and oxygen, and expands to many times its previous volume to become a red giant. After a relatively short time (in the region of two hundred million years), the red giant puffs out its outer layers in a gas cloud called a nebula and collapses in on itself to form a white dwarf. The largest red giants are known as red supergiants, and are the largest stars in the universe in terms of volume (well-known examples are Antares and Betelgeuse). white dwarfs - small, dense, burnt-out husks of stars, no longer undergoing fusion reactions, and representing the final evolutionary state of most of the stars in our galaxy. When a red giant has used up its helium to produce carbon and oxygen, and has insufficient mass to generate the core temperatures required to fuse carbon, it sheds its outer layers to form a planetary nebula, and leaves behind an inert mass of carbon and oxygen. A white dwarf is typically only the size of the Earth, but 200,000 times more dense. black dwarfs - hypothetical stellar remnants created when a white dwarf becomes cool and dark after about ten billion years of life. Black dwarfs are very hard to detect, and very few would exist yet anyway in a universe only 13.7 billion years old. blue giants - bright, giant stars, between 10 and 100 times the size of the Sun, and between 10 and 1,000 times its luminosity. Because of their mass and hotness, they are relatively short-lived and quickly exhaust their hydrogen fuel, ending as red supergiants or neutron stars. The biggest and most luminous stars are referred to as blue supergiants and hypergiants. The best known blue supergiant is Rigel, the brightest star in the constellation of Orion, which has amass about 20 times that of the Sun and a luminosity more than 60,000 times greater. The biggest and brightest ever found is 10 million times as bright as the Sun. neutron stars - stellar remnants that can result from the gravitational collapse of massive starsduring a supernova event. They are composed almost entirely of crushed neutrons, and are very hot and very dense. Although a typical neutron star has a mass of only between 1.35 and about 2.1 times that of our Sun, it is 60,000 times smaller than the Sun (usually in the region of just 20 - 30 kilometres across) and, because of this huge density, has a gravity of over 200 billion times that we experience on Earth. They rotate very fast (especially soon after thesupernova explosion) and some emit regular pulses of radiation and are known as pulsars. Smaller collapsed stars will usually become white dwarfs, and larger ones (over about 5 solar masses) will collapse completely into a black hole singularity. variable stars - stars that grow and shrink in size periodically and appear to pulsate. The changes in apparent brightness may be due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth. binary stars - two stars in close proximity which orbit around their common centre of mass. In fact, the majority of stars are part of binary, triplet or multiple star systems, and well-known examples are Sirius in the Canis Major constellation and Alpha Centauri.

Thread starter Danny Massawe
Start date Dec 12, 2014

Danny Massawe

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Refresh yourself: Facts about the earth

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