The Cosmic Engine Research Essay Example

The Cosmic Engine Research Essay Example The Cosmic Engine Research Essay The Cosmic Engine Research Essay Compare the views of Hubble and Friedman about the expansion of the universe: Edwin Hubble’s observation In 1929, Edwin Hubble announced that his observations of galaxies outside our own Milky Way showed that they were systematically moving away from us with a speed that was proportional to their distance from us. The more distant the galaxy, the faster it was receding from us. The universe was expanding after all, just as General Relativity originally predicted! Hubble observed that the light from a given galaxy was shifted further toward the red end of the light spectrum the further that galaxy was from our galaxy.The specific form of Hubbles expansion law is important: the speed of recession is proportional to distance. Hubble expressed this idea in an equation distance/time per megaparcec. A megaparcec is a really big distance (3. 26 million light-years). Alexander Friedman’s theory In the early 1920’s Friedman for told a theory were universe begins with a B ig Bang and continues expanding for untold billions of years (that’s the stage we’re in now. ) But after a long enough period of time, the mutual gravitational attraction of all the matter slows the expansion to a stop. The universe will eventually start to contract in a big crunch. Friedman embraced the idea that the equation in Einstein’s theory of relativity shows a universe that is in motion, and not constant.* A flow chart to show and describe the transformation of radiation into matter which followed the â€Å"big bang†: * Einstein’s view of the connection between matter and energy: Association between  mass  (m) and  energy (E) in Albert Einstein’s theory of relativity, complete by the formula E=  mc2, where  c  equals 300,000 km (186,000 miles) per second i. e. he  speed of light. In physical theories prior to that of  special relativity, mass and energy were seen as distinct entities. The energy of a body at rest cou ld be assigned an arbitrary value. In special relativity, the energy of a body at rest is determined to be  mc2. There for, each body of  rest mass  m  possesses  mc2  of â€Å"rest energy,† which potentially is available for conversion to other forms of energy. The mass-energy relation implies that if energy is released from the body as a result of such a conversion, then the rest mass of the body will decrease.Such a switch of rest energy to other forms of energy occurs in ordinary chemical reactions, but much larger conversions occur in  nuclear reactions. This is particularly true in the case of nuclear-fusion reactions that transform  hydrogen  to  helium, in which 0. 7 % of the original rest energy of the hydrogen is converted to other forms of energy. Although the  atomic bomb  proved that vast amounts of energy could be liberated from the  atom, it did not demonstrate the precision of Einstein’s equation. * Accretion of galaxies and st arsAfter a few hundred thousand years after the Big Bang, the Universe was cooled down and atoms were formed. As the Universe was further expanding and cooling, the atom particles lost kinetic energy and gravity began to attract them together forming regions of high mass density. The regions of high mass density began to attract nearby material and gain mass. This process is known as accretion. At some time or another, all matter in the universe formed discrete gas clouds known as protogalaxies. As further accretion occurred, galaxies were formed. Accretion also occurred inside galaxies, forming stars.As the average temperature of matter in the universe, then as the universe expands there is less hot matter such as stars and colder dark space/matter between it, so when you average things out, you get a lower temperature. * Relationship between the temperature of a star to the wavelength and color emitted from that star. Stars appear to be exclusively white at first glance. If we loo k carefully, we can see that there are a range of colors blue, white, red etc. stars are small blackbodies and their color variation is a direct consequence of their surface temperature.Cool stars radiate most of their energy in the red and infrared region of the electromagnetic spectrum and there for appear red, while hot stars emit mostly at blue and ultra-violet wavelengths, making them appear blue or white. To estimate the surface temperature of a star, we can use the known relationship between the temperature of a blackbody and the wavelength of light where its spectrum peaks. That is, as you increase the temperature of a blackbody, the peak of its spectrum moves to shorter bluer wavelengths of light.This simple method is conceptually correct, but it cannot be used to obtain stellar temperatures accurately, because stars are  not perfect blackbodies. The presence of various elements in the stars atmosphere will cause certain wavelengths of light to be absorbed. Because these absorption lines are not uniformly distributed over the spectrum, they can alter the position of the spectral peak. Moreover, obtaining a usable spectrum of a star is a time-intensive process and is prohibitively inefficient for large samples of stars. Propose an experiment that can be conducted at home to find the mathematical relationship between brightness to its luminosity and distance. Shine a clear 100 Watt light bulb through a square hole in a piece of paper and see how many squares it illuminates on a piece of grid paper as you move the grid paper different distances away from the hole. Throughout the experiment, keep the light bulb and the piece of paper with the hole in it exactly 10 cm apart while you move the grid paper progressively farther away.The experiment works best if you turn the light bulb so that the shadow it casts through the hole is as sharp as possible this will usually be when the filament is held perpendicular to the paper. 1. Place the grid paper right a gainst the square hole, so it is also 10 cm from the light bulb. The bulb should illuminate one square on your grid paper. Now move the grid paper 20 cm from the bulb and see how many squares are illuminated. Repeat this measurement for distances of 30 cm and 40 cm from the bulb. 2.At each successive distance tested above, determine how many times farther away the grid paper was from the light bulb than it was at the first distance 10 cm. 3. Throughout this experiment, the amount of light passing through the square hole has remained constant since the distance between the light bulb and the hole has not changed. Thus, if the light is spread out over N squares, then only 1/N as much light falls on each individual square on the grid paper. Determine what fraction of the light coming through the square hole falls on any one square on the grid paper at each of the distances you examined. . Examine your data for trends and relationships. * Hertzsprung Russell diagram: Average mass (the s un = 1) Average luminosity (the sun = 1) * Main Sequence: A main sequence star is not really a type of star but a period in a stars life. When a star is in main sequence it is converting hydrogen into energy. It is then usually called a dwarf star. This is the longest period in a stars lifetime. Our Sun is a yellow dwarf in main sequence. A main sequence star’s mass ranges from 0. 10 M/M to 60 M/M the luminosity can start at 0. 008 L/L and reach 500,000 L/L. their surface temperature which is measured in kalvins can reach from 3000 K to 38,000 K. Once a protostar starts burning hydrogen in its core, it quickly passes through the T-Tauri stage (in a few million years) and becomes a main sequence star where its total mass determines all its structural properties. The three divisions in a stellar interior are the nuclear burning core, convective zone and radioactive zone. Energy, in the form of gamma-rays, is generated solely in the nuclear burning core.Energy is transferred tow ards the surface either in a radioactive manner or convection depending on which is more efficient at the temperatures, densities and opacities. Red Giants: Towards the end of a  star’s life, the temperature near the core rises and this causes the size of the star to expand. This is known to transform a main sequence star into a â€Å"Red Giant†. The average mass of a Red Giant is around 0. 4 to 0. 9 Betelgeuse is a red giant, it is 20 times bigger than the sun about 14,000 times brighter and its surface temperature is no more than 6,500 K.A stars evolution after the red giant phase depends on its mass. For stars greater than 1 solar mass, but less than 2 solar masses, the hydrogen burning shell eats its way outward leaving behind more helium ash. As the helium piles up, the core becomes more massive and contracts. The contraction heats the core as it becomes more dense. * White Dwarfs: Stars that have a lot of mass may end their lives as black holes neutron stars. A low or medium mass star, with a mass less than about 8 times the mass of our Sun will become a white dwarf.A typical white dwarf is about as massive as the Sun, yet only slightly bigger than the Earth. This makes white dwarfs one of the densest forms of matter, surpassed only by neutron stars and black holes. The average mass of a White Dwarf ranges from 1. 1 to 1. 7, the luminosity ranges from 1. 2 to 6. White dwarfs are quite common, being found in binary systems and in  clusters. Since they are remnants of stars born in the past, their numbers build up in the Galaxy over time. It is only because they are so faint that we fail to detect any except for the very closest ones. * Neutron star:A neutron star is a very small, super-dense star which is composed mostly of tightly-packed  neutrons. It has a thin atmosphere of  hydrogen. It has a diameter of about 5-10 miles (5-16 km) and a density of roughly 10  15  gm/cm3. Its mass is between 1 and 2 solar masses. * Proton â⠂¬â€œ Proton Cycle   and carbon cycle Proton-proton cycle,  also called  Proton-proton Reaction,  chain of  reactions that is the chief source of the energy radiated by the  Sun  and other cool main-sequence  stars. Another sequence of thermonuclear reactions, called the carbon cycle, provides much of the energy released by hotter stars.In a proton-proton cycle, four  hydrogen  nuclei (protons) are combined to form one  helium  nucleus; 0. 7 percent of the original mass is lost mainly by conversion into  heat energy, but some energy escapes in the form of  neutrinos  (? ). First, two hydrogen nuclei (1H) combine to form a hydrogen-2 nucleus (2H, deuterium) with the emission of a  positive electron  (e+, positron) and a neutrino (? ). The hydrogen-2 nucleus then rapidly captures another proton to form a helium-3 nucleus (3He), while emitting a  gamma ray  (? ). In symbols:

Sedentism, Community-Building, Began 12,000 Years Ago

Sedentism, Community-Building, Began 12,000 Years Ago Sedentism refers to the decision made first by humans at least 12,000 years ago to start living in groups for long periods of time. Settling down, picking a place and living in it permanently for at least part of the year, is partially but not entirely related to how a group gets required resources. This includes gathering and growing food, stone for tools, and wood for housing and fires. Hunter-Gatherers and Farmers In the 19th century, anthropologists defined two different lifeways for people beginning in the Upper Paleolithic period. The earliest lifeway, called hunting and gathering, describes people who were highly mobile, following herds of animals like bison and reindeer, or moving with normal seasonal climatic changes to collect plant foods as they ripened. By the Neolithic period, so the theory went, people domesticated plants and animals, necessitating permanent settlement to maintain their fields. However, extensive research since then suggests that sedentism and mobility - and hunter-gatherers and farmers - were not separate lifeways but rather two ends of a continuum that the groups modified as circumstances required. Since the 1970s, anthropologists use the term complex hunter-gatherers to refer to hunter-gatherers who have some elements of complexity, including permanent or semi-permanent residences. But even that doesnt encompass the variability that is now apparent: in the past, people changed how mobile their lifestyles were depending on circumstances, sometimes due to climatic changes, but for a range of reasons, from year to year and decade to decade. What Makes a Settlement Permanent? Identifying communities as permanent ones is somewhat difficult. Houses are older than sedentism. Residences such as brushwood huts at Ohalo II in Israel and mammoth bone dwellings in Eurasia occurred as early as 20,000 years ago. Houses made of animal skin, called tipis or yurts, were the homestyle of choice for mobile hunter-gatherers throughout the world for an unknown period of time before that. The earliest permanent structures, made from stone and fired brick, were apparently public structures rather than residences, ritual places shared by a mobile community. Examples include the monumental structures of Gobekli Tepe, the tower at Jericho, and the communal buildings at other early sites such as Jerf el Ahmar and Mureybet, all in the Levant region of Eurasia. Some of the traditional features of sedentism are residential areas where houses were built close to one another, large-scale food storage and cemeteries, permanent architecture, increased population levels, non-transportable toolkits (such as massive grinding stones), agricultural structures such as terraces and dams, animal pens, pottery, metals, calendars, record-keeping, slavery, and feasting. But all of these features are related to the development of prestige economies, rather than sedentism, and most developed in some form prior to permanent year-round sedentism. Natufians and Sedentism The earliest potentially sedentary society on our planet was the Mesolithic Natufian, located in the Near East between 13,000 and 10,500 years ago (BP). However, much debate exists about their degree of sedentism. Natufians were more or less egalitarian hunter-gatherers whose social governance shifted as they shifted their economic structure. By about 10,500 BP, the Natufians developed into what archaeologists call Early Pre-Pottery Neolithic as they increased in population and reliance on domesticated plants and animals and began living in at least partially year-round villages. These processes were slow, over periods of thousands of years and intermittent fits and starts. Sedentism arose, quite independently, in other areas of our planet at different times. But like the Natufians, societies in places such as Neolithic China, South Americas Caral-Supe, the North American Pueblo societies, and the precursors to the Maya at Ceibal all changed slowly and at different rates over a long period of time. Sources Asouti, Eleni. A Contextual Approach to the Emergence of Agriculture in Southwest Asia: Reconstructing Early Neolithic Plant-Food Production. Current Anthropology, Dorian Q. Fuller, Vol. 54, No. 3, The University of Chicago Press Journals, June 2013. Finlayson, Bill. Architecture, sedentism, and social complexity at Pre-Pottery Neolithic A WF16, Southern Jordan. Steven J. Mithen, Mohammad Najjar, Sam Smith, Darko MariÄ ević, Nick Pankhurst, Lisa Yeomans, Proceedings of the National Academy of Sciences of the United States of America, May 17, 2011.   Inomata, Takeshi. Development of sedentary communities in the Maya lowlands: Coexisting mobile groups and public ceremonies at Ceibal, Guatemala. Jessica MacLellan, Daniela Triadan, Jessica Munson, Melissa Burham, Kazuo Aoyama, Hiroo Nasu, Flory Pinzà ³n, Hitoshi Yonenobu, Proceedings of the National Academy of Sciences of the United States of America, April 7, 2015. Railey, Jim A. Reduced Mobility or the Bow and Arrow? Another Look at Expedient Technologies and Sedentism. Volume 75, Issue 2, American Antiquity, January 20, 2017. Reed, Paul F. Sedentism, Social Change, Warfare, and the Bow in the Ancient Pueblo Southwest. Phil R. Geib, Wiley Online Library, June 17, 2013. Rosen, Arlene M. Climate change, adaptive cycles, and the persistence of foraging economies during the late Pleistocene/Holocene transition in the Levant. Isabel Rivera-Collazo, Proceedings of the National Academy of Sciences of the United States of America, March 6, 2012.