Galaxies:
Galaxies are large systems of stars, planets, etc which are bound together by gravity. The following brochure compares and contrasts the different types of galaxies.
Elliptical Galaxy:
An Elliptical Galaxy is one of the most common types of galaxies, and is classified as one of the main three types of galaxies by several astronomers such as Edwin Hubble. Elliptical Galaxies are true to their name and come in ellipsoidal shapes and appear very bright, but that is one of the only similarities between Elliptical Galaxies as far as appearance goes. The galaxies differ greatly in size and shape. Some galaxies are almost perfectly spherical, while others are flat like a pancake. In addition, the galaxies can contain anywhere from several hundred million to over one trillion stars.
Elliptical Galaxies are very similar in makeup and often consist of old low-mass stars and contain thin interstellar mediums(interstellar mediums are the.e matter that exists between star systems and fill interstellar space). They are also near to abundances of groups of stars which can also be known as globular clusters. In addition, since there is very little gas and dust in Elliptical Galaxies, the result of this is very little young stars because little amounts of gas and dust restrict star formation. This type of galaxy is also often found near the middle of galaxy clusters. It has also been long believed that Elliptical Galaxies have star formations that finish after the first burst of energy, which is another reason why the galaxies contain such old stars. In addition, Elliptical Galaxies often vary in size from a tenth of a parsec, to almost 100 parsecs which is a huge distance. There are also two forms of Elliptical Galaxies that are most common in the universe. The first one is the boxy, giant elliptical which can be brighter and larger than the other type of elliptical galaxy which is called the disky elliptical galaxy. These are smaller and not as bright as their counterparts.
The main theory behind the creation of Elliptical Galaxies is that they are formed when two galaxies collide and merge together, thus creating one entity. Currently, the Milky Way Galaxy is merging with several smaller galaxies, and scientists predict that in several billion years that the Milky Way will merge with the Andromeda which will create a huge elliptical galaxy.
Spiral Galaxy:
Spiral Galaxies are made up of flat disks that are constantly moving in rotary fashion. These galaxies contain large amounts of stars, dust, planets, and have a large central bulge made up of a dense group of stars. In addition, these galaxies contain bright "arms" that jut out from the central bulge going to the disk. These arms are collections of star formations and are brighter than the rest of the galaxy because of the young stars. In addition, almost half of all spiral galaxies have a quasi-bar component that extends from the central bulge, and makes up the start of some arms. The milky way has this bar feature. Spiral Galaxies are the most common type of galaxy in the universe and make up roughly 60% of the universe's galaxies when combined with irregular galaxies. The basic structure that all Spiral Galaxies consist are the fact that a dense group of old stars make up the central bulge. At the very center of the bulge, there is a large black hole. They consist of rotating interstellar and stellar matter, and are almost spherical in shape while constantly rotating.
Most of the stars in orbit in Spiral Galaxies lie on one plane, or in circular orbits near the center of the galaxy. However some stars follow irregular patterns, or move in halo orbits when other galaxies merge with spiral galaxies. An explanation of why the stars align themselves in spiral rotations is explained by Berti Linbland, and consists of the following: The angular speed and of a galactic disk varies with distance from the center of a galaxy, and gravity would act on the stars by a solar system gravitational model, which would curve spokes sticking out. These curved spokes would then wind around the galaxy tightly as they rotated more, thus causing the spiral galaxy, however nothing can explain the stability of this galaxy. Another force that acts on the rotating arms are density waves which are regions of increased density that rotate more than the galaxy's dust and stars, and when materials enter these regions, they are compressed and make new stars. In addition, when gas enters these regions, the density acts on the gas causing it to implode, collapse, and make new stars.
The Milky Way itself is a spiral galaxy, and spiral galaxies have several differences from elliptical galaxies. The first of which being that Spiral Galaxies have rotary orbits, elliptical galaxies have radial. In addition, Spiral Galaxies have vast amounts of gas while elliptical galaxies have little, which leads to another difference which is the fact that spiral galaxies consist of many new stars, but a small handful of older ones.However elliptical galaxies consist of mostly new stars. Spiral galaxies have constant star formation occurring, but elliptical galaxies have very small amounts of formation occuring because of the aformentioned reasons such as gas amounts etc. In addition, elliptical galaxies are mostly created by two galaxies colliding, but spiral galaxies are created when stars in orbit are pulled by gravity into arms which spiral around.
Lenticular Galaxies:
Lenticular Galaxies are galaxies that carry charcteristics of Elliptical and Spiral galaxies, and are one of the three main types of galaxies. They have lost most of their interstellar matter and therefore contain mainly older stars, and contain amounts of dust that are found near the center of the galaxies and bulges. Having bulges is a characteristic that Lenticular Galaxies share with Spiral galaxies, and they also have barely definable arms that are rotating, but they share most of their common properties with Elliptical galaxies. Lenticular galaxies also can contain bars just like spiral galaxies.
Comparing the Milky Way with Lenticular, Elliptical, and Spiral Galaxies:
The Milky Way is a barred spiral galaxy, and therefore shares some characteristics with Lenticular galaxies. It is also around thirty kiloparsecs in diameter, so it is in the same size range as a Elliptical Galaxy, and the Milky Way contains between 200 and 400 billion stars which is similar to the other types of galaxies as well. In addition, the Milky Way is engulfing other galaxies, and at some point will become an elliptical galaxy, because like an elliptical galaxy it consumes others and it will eventually collide with the Andromeda galaxy. The milky way also contains large amounts of rock and gas which feeds the star formation occuring in the area, unlike an elliptical galaxy. The large amounts rock and gas are typical of a spiral galaxy, and another common feature is that the milky way is a barred galaxy, which is a characteristic half of all spiral galaxies have, but elliptical galaxies do not have said feature. While most spiral galaxies have tightly wound "arms" that spiral around the galaxy, but the Milky Way has arms that are loosely wound around the galaxy, so that differs from the norm. The Milky way galaxy is a very old galaxy and its exact age is estimated to be around 13.2 billion years old, and is therefore one of the oldest galaxies in the universe. If the Milky Way Galaxy were in an elliptical galaxy, our own solar system would probably not have as many gas giants, because elliptical galaxies do not have much gas, which would somewhat limit the formation of planets. In addition, our sun would probably not be as young, because star formation is very limited, and we might therefore have a older star near the end of are life. If we were in a lenticular galaxy, we might still have the same cosmic makeup because they share qualities of spiral galaxies, and elliptical galaxies.
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"Spiral galaxy - Wikipedia, the free encyclopedia." Wikipedia, the free encyclopedia. N.p., n.d. Web. 5 Jan. 2011.
Second Proficiency
Second Proficiency
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century, the middle of the twentieth, this model suffered from a number of shortcomings: in particular, and Fred Lawrence Whipple. "Comet - Wikipedia, the free encyclopedia." Wikipedia, the free encyclopedia. N.p., n.d. Web. 19 Jan. 2011.
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Theories of the Universe
How the universe was created, or what it is composed of are questions that have confounded the world’s greatest thinkers for generations who have all made theories accepted by the public, but these were disproved after later research. As time has moved on throughout the centuries, the theories have only become more complicated, but closer to the Truth, however these new hypothesizes have been built off of information gathered by the scientists in the past, so it goes without saying that each hypothesis was important to getting humanity where it is now as far as knowledge.
Greek philosophers were the first people to wonder about what the universe is composed of, and began wondering about the physical object in the world. Plato and his pupils believed that the world, and universe was composed of flat circles, and that the world rose up from this base, which meant the Earth was a flat plain. However the philosopher Aristotle thought that the world and universe were composed of three dimensional spheres rather than a flat circle. While this hypothesis was advanced for the time period, Aristotle still though that the Earth was the center of the universe. In addition, almost all Greek philosophers believed that the universe was not endless, but ended where our solar system did and was therefore limited to the sun, planet, and stars.
In 150 A. D, Claudius Ptolemy, a cosmologist, created geometrical systems about the universe, and how it rotated around Earth. He believed that the Earth was the center of the universe, and that layers of three dimensional spheres rotated around the Earth. For example, if the Earth was at the center of the universe, then a sphere wrapped tightly around it rotated in a circular motion. This sphere carried planets, stars, etc. Around this sphere was a slightly larger sphere which rotated with the same motion, and carried the same components, and around this a larger sphere and so forth. Ptolemy hypothesized that the rotating motion of the spheres is caused because disorder in nature is not created by divine beings
The Greeks were a mathematically and scientifically advanced group of people, and they made many important discoveries about the universe that contradicted information that was previously accepted. However their lack of modern technology didn’t make their theories especially accurate. For example, they held the belief that universe was finite, or at least confined to the solar system, but modern research has disproven that statement with the use of technology such as the Hubble telescope.
For several thousands of years previous to the Greek society, people believed in the divine creation stories, and people still do. Stories that God created the world in seven days, and gave life to humanity may seem far-fetched to scientists, but there is no way to disprove this. Hindu’s believe that the god Brahma created the world at the orders of another god named Vishnu. Other religions have similar stories that are believed by the followers of those religions, and these mainly consist of the statement that God created the world, animals, universe, and people. Scientifically these creation theories do not seem very accurate, and mainly seem like old myths, but personally I believe that God created the world, so it would be strange to judge this theories credibility, but some of the more outlandish theories are too unrealistic, and therefore not accurate.
While theories of God’s creating the universe are bountiful, another common theory is the protouniverse. A Protouniverse means a developing universe, and the main component behind this is the white hole. A white hole hasn’t been scientifically proven to exist, but it is essentially the opposite of a black hole. A black hole sucks in matter at the speed of light, but a white hole, being the opposite, spews out and creates matter at the same speed. Therefore, the white hole creates a universe because it spews out matter at the speed of sound. This theory remains unlikely, because while there has been evidence of black holes, no evidence of white holes has been found.
George Lamaitre is a physicist who has been credited with some of the most profound and modern creation theories, and the bouncing theory reinforces Einstein’s renowned Big Bang theory which will be explained later. The Big Bang theory states that the universe was created when matter was concentrated at a single density, but the theory doesn’t tell of pre-bang time. However the bouncing theory states that the universe may have reached a point where it imploded upon itself because of gravity, and reached a point of maximum density where it reversed upon itself causing the big bang theory.
The Big Bang theory itself speaks of an explosion that started the universe. During the time right at and before the big bang, the universe was filled with huge pressures and densities which were quickly expanding and cooling. During this time of expansion, the universe grew rapidly and consisted of elementary particles and quark-gluon plasma, and because of high temperatures, these particles were moving at extraordinary speeds, and pairs of matter and anti-matter were colliding. A reaction to this called Baryogenesis occurred which is a physical process which produces asymmetry between baryons (composite particles that contain quarks, neutrons, etc) and anti-baryons creating lingering matter that exists today. This reaction led to an excess of quarks and other particles versus anti-quarks, and this is the reason that matter dominates anti-matter. The universe gradually grew in size and grew colder which cause particle energy levels to drop. This drop in temperature meant that it could no longer create proton and anti-proton pairs, so destruction occurred as a repercussion of this. The remaining protons were no longer moving much, so the universe was controlled by photons ( a type of elementary particles). After several minutes, neutrons combined with photons to create deuterium and helium nuclei, and after a span of time, dense spaces attracted matter which created stars, gas clouds, and galaxies.
These past two theories seem plausible, because it uses known particles, and follows probable reactions to components such as temperature and density. The only problem is it doesn’t describe the state of the universe previous to the big bang, and I thought that it didn’t really elaborate on where the components came from, etc. In addition, the theory follows scientifically accepted hypothesizes such as the Theory of General Relativity, etc.
Of all the theories, the Big Bang seems the most scientifically plausible, but really lacks a full explanation. For example, what started it? Aside from reactions described in it with temperature, etc, it doesn’t really say what the universe was like before the Big Bang, and then before the Big Bang, what reactions put it into full gear, because it didn’t “just happen,” it had to have been the result of some cosmic occurrence. This brings divine creation to mind, because that could’ve easily been the cause of something like the Big Bang. The Bang theory does not describe how the pressures and densities that occurred right at the start happened, and this is what bothers me. There isn’t evidence of a white hole, so I don’t believe that the Protouniverse theory exists, so I believe that the most plausible theory is that divine creation caused the universe to occur, and the Big Bang may have been part of it.
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