Answers to Questions in Astronomy Essay Example for Free

Answers to Questions in Astronomy Essay 1. How do astronomers measure the distances to galaxies and how does that allow the sizes, luminosities and masses of galaxies to be determined? A distance indicator is an object within a galaxy that functions as a marker to that galaxy. It may be a Cepheid star, globular cluster, H II region, planetary nebula or supernova. The distance to a galaxy, especially if it is very far away, is approximated by employing the Hubble Law which is expressed as Recession Velocity (Vr) = Hubble’s Constant (H) x distance (d). After obtaining the distance, it is possible to determine diameter through the small angle formula and luminosity from distance and apparent magnitude where both formulas are derived equations (Garber). Meanwhile mass can be estimated in three ways. Rotation curves reveal the calculation of rotational velocities for varying distances from the galactic center so that once distance and velocity are known, mass can be obtained (Garber). Another is through the cluster method which focuses on the motion of a galaxy within a galactic cluster. The size of the galaxy as well as range of velocity determines the total mass of the cluster (Garber). The third is through the velocity dispersion method where the spectra of the galaxy are used to approximate mass. Broad spectral lines indicate high velocity which in turns suggests a large mass (Garber). 2. Discuss how individual stars and the shapes of galaxies are affected by collisions. As a galaxy approaches another in a collision, the gravitational fields of the stars in each of them start to interweave and the resulting powerful tidal forces disturb and radically alter the shape of the galaxy, similar to the manner in which the gravitational pull of the moon causes the tide to rise in regions of the earth nearest to it but magnified a thousand times. A collision initiates the formation of tidal tails, bars or rings and colliding gas clouds produce knots of newly formed blue stars while the nucleus of the galaxy becomes deformed (sciencedaily.com). On the other hand, when stars collide, they merge together as one star that displays unusual brightness and heat relative to age so that they become very prominent in their globular cluster. These stars are referred to as â€Å"blue stragglers†. When stars increase in age and use up their hydrogen, they become cooler, less massive and red in color but through collisions, they obtain extra mass causing them to turn blue (Masters). This permits them to remain longer in the main sequence – the phase in a star’s life where it burns its hydrogen. 3. Explain the differences between the three types of galaxies and what happens to change their shape. An elliptical galaxy is rounded or oval in shape, do not have visible gas and dust or bright, hot stars and consists of population II stars. Elliptical galaxies are also surrounded by globular clusters. A spiral galaxy has a disc component, consists of both populations of stars, exhibits a nucleus and may have arms with differing orientations (Garber). An irregular galaxy does not present a regular pattern and includes new and old stars alike. Galactic interaction, collision and merging, which involve the effects of the gravitational fields of galaxies, are the primary events that change the shape of galaxies. The subsequent structure depends on both the type of the galaxies involved and the directions of their orbits (Keel). Collision, mentioned earlier, may not result in a merger if both galaxies have enough force to continue moving away from each other after the event. Galaxies are said to be interacting when they do not collide but both their gravitational attractions cause distortion and exchange of gas and dust (astro.umd.edu). In interactions that occur at slow speeds and involve galaxies with unequal masses, spiral formations may assume irregular-lenticular shapes (Than). Gases being pulled to the central region, as a result of tidal disturbances, clear away the spiral configuration, leaving behind a disk structure. The most drastic interaction is the merging of two galaxies and occurs when they collide but lose their momentum to slide past one another. Instead, they fall back into each other and unite into one galaxy, losing their original shapes in the process (astro.umd.edu). When a significantly more massive galaxy collides and merges with a smaller one in a type of interaction known as galactic cannibalism, the bigger galaxy does not exhibit a visible change in shape but the less massive galaxy is ripped apart, loses its shape and becomes integrated into the bigger one. Answers to Questions in Astronomy. (2016, Nov 07).

Matrices and function Coursework Example | Topics and Well Written Essays - 1000 words

Matrices and function - Coursework Example 0.0072 = 0.9928 are alive at the end of the year. Some of this number will have reached the age of 15 during the 1 year and become adults. We shall assume that15 of the surviving juveniles become adults. So the proportion of juveniles still alive and still juveniles at 14 the end of the year is . (b) The network model above can be written as a matrix equation of the form where M is a 2 x 2 matrix. Write down the matrix M (c) (i) Edit the matrix M, and the vector whose entries are the initial subpopulation sizes J0 and A0, in a copy of a worksheet so that the worksheet shows the predicted changes in population size for the country considered in this question. Set N = 50, so that the worksheet covers 50 years. Here we have: For n=0, For n= 2, As the value is influenced by the previous value the table has the accurate calculation: Table below shows the juvenile population, Adult population and total population, while the first column shows the increase in the years startind from 2007 an d ending at 2057. n Jn An Tn 0 8.3 30.1 38.4 1 8.82254 30.09562 38.91816 2 9.306561 30.12591 39.43247 3 9.756194 30.18769 39.94388 4 10.17515 30.2781 40.45324 5 10.56675 30.39457 40.96132 6 10.93398 30.53483 41.46882 7 11.27954 30.69682 41.97636 8 11.60582 30.87871 42.48453 9 11.91499 31.07884 42.99384 10 12.209 31.29576 43.50476 11 12.48958 31.52816 44.01774 12 12.7583 31.77485 44.53315 13 13.01658 32.03479 45.05137 14 13.26567 32.30705 45.57272 15 13.50671 32.59079 46.0975 16 13.74073 32.88526 46.626 17 13.96865 33.18981 47.15846 18 14.19129 33.50384 47.69513 19 14.40939 33.82683 48.23623 20 14.62363 34.15832 48.78195 21 14.83461 34.49789 49.3325 22 15.04287 34.84518 49.88805 23 15.2489 35.19987 50.44877 24 15.45315 35.56167 51.01482 25 15.65601 35.93033 51.58634 26 15.85784 36.30564 52.16348 27 16.05896 36.68741 52.74637 28 16.25968 37.07546 53.33514 29 16.46026 37.46966 53.92992 30 16.66093 37.86989 54.53083 31 16.86193 38.27604 55.13797 32 17.06344 38.68802 55.75146 33 17.26566 39.10576 56.37142 34 17.46873 39.5292 56.99793 35 17.67283 39.95829 57.63112 36 17.87807 40.393 58.27108 37 18.0846 40.8333 58.9179 38 18.29252 41.27917 59.57169 39 18.50195 41.7306 60.23254 40 18.71297 42.18758 60.90056 41 18.9257 42.65013 61.57582 42 19.14019 43.11825 62.25844 43 19.35655 43.59195 62.9485 44 19.57484 44.07126 63.6461 45 19.79512 44.55621 64.35133 46 20.01747 45.04681 65.06428 47 20.24195 45.54311 65.78506 48 20.46861 46.04513 66.51374 49 20.69751 46.55292 67.25044 50 20.92871 47.06652 67.99523 51 21.16224 47.58598 68.74822 (ii) What behaviour does the model predict for the total population size over 50 years? Find the sizes of the total population predicted by the model for the years 2032 and 2057, giving your answers to the nearest thousand. The population of the juveniles and the adults in total is increasing by the ration of 1.013 and the population is increasing in the geometric manner. The size of the population in the year 2032 will be at 51.58634 million w hich is approximately 1.343 times the total population in the year 2007. In the 2057, the total population of juveniles and adults will be 67. 99523 million, which is 1.77 times the population in the year 2007. (iii) What does the model predict for the ratio of successive total populations over the 50 years? Your answer should include both a description of behaviour and numerical information. Years Tn Ratio Tn/Tn-1 2007

American Wartime Music Composers - Cohan & Berlin Term Paper

American Wartime Music Composers - Cohan & Berlin - Term Paper Example The 20th century was such a juxtaposition of styles, forms, and genres of music that it was difficult to chose two "composers" who had something in common. Perception is one of the most important tools of propaganda. For the first time aural perception was combined with the visual. Audiences became more demanding as the subjective choice of music was more diverse and more complicated . The radio was a significant factor in the mass distribution of different types of music. By World War II, composers of all genre were put in the forefront for the first time in history . Contrary to social believe, composers were highly touched by the effects of the number of deaths of the World War I and the number of deaths by the flue pandemic which closed theaters for almost 3 years. The two World Wars created different levels of propaganda and thus music was used differently. By World War II, audiences expected to be entertained by going to dance halls, jazz bands, musicals, music revues†¦. A s radio was a major form of entertainment in the majority of American households, music stations flourished. By World War II, it was common to go to cinema once a week. The United States War Office had a "Wartime Music Committee". (Sheppard 304) Audiences at home were under the influence that all was going well in both wars and soldiers were played music when they were in the mess hall; saw movies and were fed propaganda that the Americans were winning battles. Music was an important part of the war effort Each soldier was given a book of military songs. Over 9 000 songs were composed from the start of World War 1. Composers and producers were drafted or volunteered to entertain the troops. At the turn of the century, Musical theatre was a juxtaposition of a group of songs with a slight story line. George Cohan (b. 1878 d.1942) was raised in a family of vaudeville performers. (Kenrick) In the early 1900's the US was in a state of economic stability and patriotism. American Musical t heater was in its infancy. Vaudeville performances were still common. A group of diverse traveling performers would perform on stage with no continuity in the program. He is quoted as saying his family was making $1 000.00 a week in the late 1800's. (Kenrick)When he came to New York, he began writing and composing his own songs and "sketches". They were the equivalent of musicals but they were simplistic and missed the continuity of full musicals of today. They were a group of songs, perhaps in different keys without any or a few common musical themes. He is considered the father of American Musical Theatre.(Ewan 68) As a proud chauvinist, his song writing was one of the first to be used to promote national cause or "national propaganda". As soon as President Wilson declared war, his most famous song "Over There" became a national hit. (Kenrick) It showed the value of fighting the war. His war songs showed the negative side of staying out of the war. His songs did not take into acco unt the human emotional side of fighting a war. Irving Berlin (1888-1989) was one of many Jewish immigrants who came to the US as a child. He lived in abject poverty. His father was a singer (cantor) in the synagogue so his son would have had vocal religious training. This fact is not to be neglected as a young orthodox Jew he chanted his studies. (Kenrick) Once in the US, his father died within 2 years and as a child I Berlin went to work on the streets to help support his family. Little by little