Written Expressions 3rd Year Classes
Collected by GUELLIL MABROUK (mgbay13.com)
Unit Five: Are we alone?
Astronomy
Topic56:
It was only thanks to the astronomers that the world all-around is well-known to us. Discuss.
Typical Essay:
An astronomer is a person who studies, classifies, and describes the phenomena of the heavens. The
astronomer has been one of the most important roles in the modern scientific world, with some of the great
leaps in methodology coming from the realm of astronomy. In the modern day, there are not many who
identify as an astronomer, with the American Astronomical Society having less than 7,000 members, for
example. Nonetheless, the concept of astronomer continues to fascinate the public as a romantic figure gazing
skyward.
One of the most well-known people to bear the name astronomer was the 16th century astronomer, Nicolaus
Copernicus. Copernicus developed a heliocentric model of our solar system, placing the sun at the center and
the Earth orbiting it, and in doing so turned most of the predominant world views of the time on their heads.
Although a heliocentric model had been put forth by various brilliant minds from the world of islam , India,
and Greece, Copernicus laid his out in the West in such a way that it was impossible for the world to ignore.
Not long after Copernicus, the astronomer galileoGalilei expanded on Copernicus’ views. He made the
telescope substantially more effective than it had been, allowing the astronomer to make much more detailed
observations, including viewing craters on the moon, sunspots , and four of the moons of Jupiter. galileowas a
devout Catholic, and in fact traveled to Rome to show the moons of Jupiter to the Jesuit College Romano as
evidence of the Copernican heliocentric model. The Church rejected Galileo’s views, and eventually found him
highly suspected of heresy and placed under house arrest.
Sir Isaac Newton, in addition to his many other accomplishments, was an influential astronomer. Many of his
observations led him to develop some of his grand theories of motion, gravitation, and physical dynamics.
Edmond Halley, an 18th century astronomer, conceived of a new wave of astronomers to crop up, but these
are often amateurs. With a relatively small investment now, anyone can be an astronomer. In fact, some
important discoveries over the past two decades have been by those who are far from professional astronomers.
As technology continues to improve, it is likely that the role the amateur astronomer plays in identification of
celestial phenomena with only increase.
Topic57:
Write a composition on the solar system.
Typical Essay:
The Solar System is made up of all the planets that orbit our Sun. In addition to planets, the Solar System also
consists of moons, comets, asteroids, minor planets, and dust and gas.
Everything in the Solar System orbits or revolves around the Sun. The Sun contains around 98% of all the
material in the Solar System. the larger an object is the more gravity it has .because the sun is so large, its
powerful gravity attracts all the other objects in the Solar System towards it. At the same time, these objects,
which are moving very rapidly, try to fly away from the Sun, outward into the emptiness of outer space. The
result of the planets trying to fly away, at the same time that the Sun is trying to pull them inward is that they
become trapped half-way in between. Balanced between flying towards the Sun, and escaping into space, they
spend eternity orbiting around their parent star.
How Did The Solar System form?
This is an important question, and one that is difficult for scientists to understand. After all, the creation of our
Solar System took place billions of years before there were any people around to witness it. Our own evolution
is tied closely to the evolution of the Solar System. Thus, without understanding from where the Solar System
came from, it is difficult to comprehend how mankind came to be.
Scientists believe that the Solar System evolved from a giant cloud of dust and gas. They believe that this dust
and gas began to collapse under the weight of its own gravity. As it did so, the matter in this could begin
moving in a giant circle, much like the water in a drain moves around the center of the drain in a circle.
At the center of this spinning cloud, a small star began to form. This star grew larger and larger, as it collected
more of the dust and gas that were collapsing into it.
Further away from the star that was forming in the center were smaller clumps of dust and gas that were also
collapsing. The star in the center eventually ignited forming our Sun, while the smaller clumps became the
planets, minor planets, moons, comets, and asteroids.
Topic58:
Many theories were formulated about the creation of the world. Choose one and discuss it.
Typical Essay:
In fact, it is difficult for scientists to understand how our world was created. After all, the creation of our world
took place billions of years before there were any people around to witness it. Our own evolution is tied closely
to the evolution of the Solar System. Thus, without understanding from where the Solar System came from, it
is difficult to comprehend how mankind came to be.
Scientists believe that our world evolved from a giant cloud of dust and gas. They believe that this dust and
gas began to collapse under the weight of its own gravity. As it did so, the matter in this could begin moving in
a giant circle, much like the water in a drain moves around the center of the drain in a circle.
At the center of this spinning cloud, a small star began to form. This star grew larger and larger, as it collected
more of the dust and gas that were collapsing into it.
Further away from the star that was forming in the center were smaller clumps of dust and gas that were also
collapsing. The star in the center eventually ignited forming our Sun, while the smaller clumps became the
planets, minor planets, moons, comets, and asteroids.
Topic59:
Suppose a comet collided with the earth. Write a composition predicting the consequences of such a collision.
Typical Essay:
For the most part, a comet is an object in the solar system that orbits the sun sometimes has a coma (or
atmosphere) and a tail. These characteristics are added mostly because of the effects of solar radiation upon the
comet's nucleus (the nucleus is made of rock, dust, ice, etc.).
The interesting thing is that comets' orbits are highly variable. First, they are almost always highly affected by
close calls with major planets, sometimes even being moved into orbits that destroy them due to their nearness
to the Sun. One of the reasons why comets are so easily moved is because the outgassing that creates their
comas and tails propels them in mysterious and unpredictable ways. But if a comet collided with the earth,
what would happen then?
If the comet were small enough (and we survived), probably something similar to the situation on the 15th of
April 1815, when volcanic eruptions of Mount Tambour ejected immense amounts of volcanic dust into the
upper atmosphere, would happen." The year of 1816 (the year after) was often referred to as the Year Without
a Summer.
This is because so much dust, from only one volcano, blocked out so much sunlight that several people froze
to death and crops around the world died. Prices for food skyrocketed and it caused a major problem in
economy.
The meteor that hit the Earth and resulted in the extinction of the dinosaurs probably kicked up 100 times to
1000 times as much dust as this volcano explosion.
So the consequences of such a supposed collision really depend on the size of the comet. The bigger it is, the
more devastating its outcomes are.
Topic60:
Write a composition on the importance of astronomy.
Typical Essay:
Astronomy is the study of celestial objects, phenomena, and origins. One of the oldest sciences, astronomy has
been practiced since prehistoric times. Modern astronomy depends highly on accepted physical theories, such
as Newton's Laws of Motion and general relativity . In the past, astronomy was something anyone could do,
and many seers and sages made reputations for themselves by using the stars for useful functions, such as
telling what time of the year it is, or navigating the seas. Columbus and his contemporaries used the stars to
navigate across the Atlantic ocean.
It wasn't until the renaissance that the <http://www.wisegeek.com/what-is-a-hypertelescope.htm>
hypertelescopes," which use a network of telescopes working cooperatively to resolve images. These could
develop to the point where we can observe extrasolar planets with telescopes directly, instead of just detecting
Topic61:
galileois often called “the Father of Observational Astronomy”. Discuss.
Typical Essay:
galileoGalilei was an Italian HYPERLINK "http://www.wisegeek.com/what-is-physics.htm" physicist, mathematician, HYPERLINK "http://www.wisegeek.com/what-is-an-astronomer.htm" astronomer and philosopher who has been called “the Father
of Modern Science”. Born on 15 February 1564 in Pisa, Italy, galileois known for greatly improving the
telescope from only 3X magnification to 32X magnification, discovering the moons of Jupiter, observing hills
and valleys on the Moon, discovering and analyzing HYPERLINK "http://www.wisegeek.com/what-is-a-legend.htm" legend that galileodropped objects off the Leaning Tower
of Pisa as a way of HYPERLINK "http://www.wisegeek.com/what-is-the-difference-between-troubleshooting-testing-and-debugging.htm" testing the different speeds at which they fell, but this was more likely a thought
experiment. In reality, galileoperformed similar experiments with inclined planes that led to the same
conclusion. The conclusion, contrary to the Aristotlean wisdom which had held for over a thousand years
before, was that objects fall at the same speed regardless of their weight. Heavier objects are just often larger,
and therefore slightly more susceptible to air friction. galileowas not the first modern thinker to realize this, but
he played a crucial role in popularizing it.
Because of all his contributions to HYPERLINK "http://www.wisegeek.com/what-is-physics.htm" physics, engineering, and HYPERLINK "http://www.wisegeek.com/what-is-astronomy.htm" astronomy, galileois often called “the Father of
Observational Astronomy,” “the Father of Modern Physics,” and other such titles. His basic insights about
physics are taught in high schools worldwide.
Topic62:
Long ago, astronomers spotted a galaxy far away and wondered why it was giving birth to so many stars.
Discuss.
Typical Essay:
A galaxy is a cluster of stars, nebulae, HYPERLINK "http://www.wisegeek.com/what-is-dark-matter.htm" dark matter, and other astronomical objects. Most galaxies are tens of
thousands of light years in diameter, and contain billions of stars. Galaxies come in three primary shapes; spiral
galaxies are thin disks, with spiral arms surrounding a central hub; elliptical galaxies are uniform, oval-shaped
agglomerations; and irregular galaxies have little or no definite structure.
A spiral galaxy centers around a hub, which is roughly spherical and bulges outward from the disk. The hub
is the gravitational center of the galaxy, and usually contains a supermassive black hole. Surrounding the hub
are spiral arms, which are bunched-up HYPERLINK "http://www.wisegeek.com/what-were-the-waves.htm" waves of stars and gas orbiting the center. The spiral arms usually have
more gas and dust, and they contain most of the newly formed stars, which make them appear blue in color
imagery. A spiral galaxy may have a horizontal bar passing through its hub; our own galaxy, the HYPERLINK "http://www.wisegeek.com/what-is-the-milky-way.htm" Milky Way,
is believed to contain a bar.
Elliptical galaxies have a large, central hub, but they lack the arms of a spiral galaxy; they usually appear
more yellowish in color imagery from old, reddish stars. Irregular galaxies often have no discernible structure,
but often they can be recognized as having a distorted spiral or elliptical shape. Elliptical and irregular galaxies
often result from collisions, which cause large bursts of star formation and distort the galaxies' structure due to
the complex gravitational interactions. Eventually, the two galaxies usually merge to form one large galaxy,
which has cast off most of its gas and dust clouds.
There are roughly a hundred billion galaxies in the visible universe; most of them occur in large
agglomerations called galaxy superclusters. Between these superclusters are voids with few or no galaxies, often
for a hundred million light years or more. By studying the rotation of spiral galaxies, astronomers found that
most of the matter in the universe is not stars and gas, but invisible “dark matter” which cannot be seen but
still exerts HYPERLINK "http://www.wisegeek.com/what-is-gravity.htm" gravity. Dark matter is thought to be responsible for these large clusters, as the gravitational
attraction of the dark matter pulled galaxies together.
Topic63:
Unlike the other small bodies in the solar system, comets have been known since antiquity. Discuss.
Typical Essay:
A comet is a small astral body, similar in construction to a planet. A comet may have an unusual orbit, which
may at times bring the comet close to the sun and make it visible to the naked eye, or through relatively low
strength telescopes. When such a comet can be viewed it is usually noted as having a tail, made of gasses,
which early astronomers often mistook for a HYPERLINK "http://www.wisegeek.com/what-is-a-shooting-star.htm" shooting star.
Most observable comets in our solar system derive from the HYPERLINK "http://www.wisegeek.com/what-is-the-oort-cloud.htm" Oort Cloud, a hypothesized cloud made up of
leavings from the sun. These materials form comets, which orbit the sun because are then affected by the
gravitational pull of the sun and other planets. While passing by individual planets, the comet may be affected
by the gravitational forces of the planets, thus causing an elliptical or oval-type orbit.
Usually, people on earth see a comet when the comet passes in between earth and the sun. It is thought that
the comet and its tail, sometimes called the HYPERLINK "http://www.wisegeek.com/what-is-a-coma.htm" coma and tail, reflect the light of the sun, enhancing visibility. Since
comets may orbit the sun in such strange patterns, people may only see the passage of one comet in a lifetime.
In fact, comets are usually classed by the length of time it takes them to orbit the sun. A short period comet
takes about 200 years or less to make a full trip around the sun. A long period comet may take far more than
200 years to complete a trip.
For example Halley’s Comet can be viewed on earth about every 75 years. This marks it as a short period
comet. Its last sight on earth was in 1986, and it is expected to be seen again in 2061.
A planet may capture a comet and the result can cause significant damage to the comet. Such a gravitational
capture may result in the comet breaking into many small pieces, and these smaller pieces can then break off
from the comet and hit the capturing planet. Comet Shoemaker-Levy 9, was observed as broken in 1993, and
astronomers were able to witness it hitting the atmosphere of Jupiter in 1994.
Most often people looking at the night sky may think that they see “HYPERLINK "http://www.wisegeek.com/what-is-a-shooting-star.htm" falling stars” which are actually HYPERLINK "http://www.wisegeek.com/what-is-a-meteor.htm" meteors
or comets. There are thousands of tiny comets that do not attract much interest. The once in a lifetime comet
like Halley’s are often thought of as exciting, since most people will only see them with the naked eye once.
ليست هناك تعليقات: