Astronomy Outline Essay Sample
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Introduction of TOPIC
Complete the outline following the instructions above. Use the example as a guide, using complete sentences for all subpoints.
1. Our place in the universe
a. The modern view of the universe
1) What is our Sun and what is its role in the solar system? a) The sun is the closest star to earth and makes up 98% of the solar system mass. b) The sun is made up of the hydrogen, helium, calcium, sodium, magnesium, and iron elements. c) The sun provides light, heat, and energy to the Earth.
2) What is our Milky Way galaxy and the sun’s position in it? a) The Milky Way is an island of hundreds of billions of stars, gas, and dust held together by gravity to form a disk that is surrounded by a halo of globular clusters, which are smaller spherical groups of stars. b) The sun is about 26,000 light-years from the center of the Milky Way Galaxy. 3) What is the Big Bang and what does it say about the age of the universe? a) The Big Bang is based off of telescopic observations of distant galaxies that are expanding with time. b) By considering the rate of expansion, going backward provides an idea of initialization. By observed rate of expansion it is estimated to have occurred about 14 billion years ago. 4) What is meant by the phase “looking out in the universe is looking back in time?” a) This phrase is meant to describe the time it takes time for light from distant objects to reach the Earth. We see the sun as it looked about 8 minutes ago, other stars as they looked years ago, and distant galaxies as they looked millions or even billions of years ago. b. Where are we in the universe?
1) What is Earth’s place in the solar system?
a) Earth is the third planet from the Sun.
2) How close are the nearest stars to the Sun as compared to the distance between the Sun and the Earth? a) The sun is approximately 8 light minutes away from Earth. b) The second nearest star is Proxima Centauri and 4.24 light years away. c) Coming in at a close third is Alpha Centauri which has been considered as a double star and is 4.36 light years away.
3) How large is our Milky Way galaxy?
a) The disk of the Milky Way galaxy spans a distance of about 100,000 light years (one light year is about 9.5 x 1015 meters). 4) How many stars are estimated to exist in our galaxy?
a) Our Galaxy contains about 200 billion stars. Most of the stars are located in the disk of our galaxy, which is the site of most of the star formation because it contains lots of gas and dust. 5) How old is the earth compared to the universe itself?
a) A recent study puts the age of the Milky Way at approximately 14.5 billion years, plus or minus more than 2 billion years. b) The Earth is approximated to be about 4.54 billion years old. c. Motion in the universe
1) How fast does the Earth move around the Sun? Compare that to fast things in day-to-day life. a) The average distance from the Earth to the Sun is approximately 92,955,819 mi. Therefore in one year the Earth travels this distance and the velocity based on days and hours reveals approximately 18.5 miles per second b) The muzzle loading velocity of a M16 machine gun only amounts to approximately .61 miles per second. 2) How is our Sun moving in the galaxy?
a) It orbits the galactic center at a distance of roughly 27,000 light years, and it also oscillates through the galactic plane on a scale of tens of millions of years. 3) How are the galaxies around the Milky Way galaxy moving from our point of view? a) The Earth sits inside an arm of stars which are always going to be in front of our view of other galaxies far beyond the stars of our own galaxy. b) The galaxies are getting farther apart (on very large distance scales), with the velocity of recession proportional to the distance between them. 2. The sky and the science of astronomy
a. Explain the significance of the celestial sphere.
1) What important directions and coordinate systems help you find your way around the sky? a) The Constellation Method uses some of the brighter stars to form patterns in the night sky and judges their positional relationship to each other forms. b) The Alt Azimuth Method does not use the patterns of the stars in the sky at all, but a grid reference or latitude and longitude references are used. c) The Celestial Method is much like the Alt Azimuth Method but is achieved by using an equatorial mounting. The difference between an equatorial and an Alt Azimuth mounting is that the equatorial rather than having its rotation bearing level. This allows the telescope tube to rotate around the same axis as the Earth’s axis. 2) Why are there different brightness of stars and how do we describe their brightness as compared to one another? a) Appa
rent magnitude refers to value of the magnitude depending on both how close the star is and how much
a) A constellation is a region of the sky with well-defined borders; the familiar patterns of stars merely help us locate the constellations. 4) What is Polaris and what is its significance in the sky?
a) Polaris is a star with an extreme luminosity and is also referred to as the North Star. b) Polaris is special not because of its brightness, but because it is so close to the north celestial pole and therefore very useful in navigation. 5) Why does the Moon change its phase, how does it move and how do these combine to create eclipses? a) The moon phases refer to its illumination by the sun. It is generally considered to have four phases: crescent, gibbous, waxing, and waning. b) The synodic period or lunation is approximately 29.5 days. It’s the time required for the moon to move to the same position (same phase) as seen by an observer on earth. c) When the moon blocks the sun or a part of it, it’s called a solar eclipse, and it can only happen during the new moon phase. When the earth casts a shadow on the moon, it’s called a lunar eclipse, and can only happen during the full moon phase. b. What is the science of astronomy?
1) Astronomy is the study of space and universe through careful observation and trial and-error experiments. c. What is the scientific method and how does it relate to the science of astronomy? 1) The scientific method is the process by which scientists, collectively and over time, endeavor to construct an accurate (that is, reliable, consistent and non-arbitrary) representation of the world. 2) In the field of astronomy, the earth-centered description of the planetary orbits was overthrown by the Copernican system, in which the sun was placed at the center of a series of concentric, circular planetary orbits.
Later, this theory was modified, as measurements of the planets motions were found to be compatible with elliptical, not circular, orbits, and still later planetary motion was found to be derivable from Newton’s laws. d. Who was Aristotle and what was his relationship to the science of astronomy? 1) Aristotle (384–322 B.C.) is among the best-known philosophers of the ancient world. He studied under Plato (428–348 B.C.) at Plato’s Academy. 2) Aristotle argued that the universe is spherical and finite; consequently that the Earth too was a sphere. However he also argued that gravity pulled heavy things toward the center of the universe (and allowed lighter things to float toward the heavens), thereby causing all the dirt, rock, and water of the universe to collect at the center and form the spherical Earth. e. What was the Copernican revolution?
1) Copernicus’ model, a rediscovery of the one proposed by Aristarchus centuries before, explained the observed motions of the planets more simply than Ptolemy’s by assuming a central sun around which all planets rotated, with the slower planets having orbits farther from the sun. f. What observations did Galileo make that proved that planets go around the sun? 1) In particular, he used experiments with rolling balls to demonstrate that a moving object remains in motion unless a force acts to stop it (an idea now codified in Newton’s first law of motion). 2) In reality, Venus orbits the Sun, so from Earth we can see it in many different phases. This is just what Galileo observed, allowing him to prove that Venus orbits the Sun and in turned helped to prove Copernicus’ theory. g. What laws tell us how the planets move around the star?
1) Kepler’s law states that planets move around the Sun in ellipses, with the Sun at one focus. 2) Kepler’s law states that the line connecting the Sun to a planet sweeps equals ares in equal times. 3) Kepler’s law states that the square of the orbital period of a planet is proportional to the cube of the mean distance from the sun. h. How does the Earth rotate and how does that relate to day and night or the seasons? 1) Rotation of the earth describes the spinning of the earth around its axis, resulting in the 24 hour phenomenon of day and night over the earth. i. How does the Earth revolve and how does that relate to day and night or the seasons? 1) Revolution on the other hand describes the movement of the earth around the sun over a period of one year, causing seasons to occur. j. What causes the seasons? Is it the tilt of the Earth’s axis or its changing distance from the Sun throughout the year? 1) Seasons are caused by the tilt of the Earth’s axis of rotation – the 23.4° offset of the axis from a direction perpendicular to the Earth’s orbital plane. The direction of the rotational axis stays nearly fixed in space, even as the Earth revolves around the Sun once each year. As a result, when the Earth is at a certain place in its orbit, the northern hemisphere is tilted toward the Sun and experiences summer. Six months later, when the Earth is on the opposite side of the Sun, the northern hemisphere is tilted away from the Sun and experiences winter. The seasons are, of course, reversed for the southern hemisphere. 3. Gravity, free fall, and orbits
a. What is gravity and how much weaker does it get as you get farther from the center of a body? 1) Gravity is the force of attraction by which terrestrial bodies tend to fall toward the center of the earth. 2) Gravity is weaker with regards to the greater the distance from the center of a body because The force of attraction between two objects is inversely proportional to the square of separation between the objects. b. Are objects in orbit of the Earth still under the influence of gravity? 1) Every planetary body (including the Earth) is surrounded by its own gravitational field, which exerts an attractive force on all objects. In space an object maintains its orbit because of the force of gravity acting upon it. c. An object in orbit falls around the Earth, what do planets, comets, and asteroids fall around? 1) Gravity attracts the planets to the sun.
In fact, the planets are constantly falling toward the sun in much the same way that a thrown ball falls down to the ground. The velocity is fast enough to keep the planets in orbit to continue “falling around” the Sun. 2) Most asteroids have unusual shapes because they have experienced many collisions and do not have a strong enough gravity to pull themselves back into a sphere. Many asteroids, including all of the largest asteroids, orbit the sun between Mars and Jupiter in the Asteroid Belt. 3) Comets orbit around the Sun just like planets, but their orbits are more elongated and take longer. Periodic comets are those that have an orbit of less than 200 years, but they make up the minority of known comets.
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