AST_101_Lesson_2_Homework_Rev_050823
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Arizona State University, Tempe *
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101
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Astronomy
Date
Feb 20, 2024
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Uploaded by ProfessorSheep4002
AST 101 Lesson 2 Homework
Student Name: Isabella Brown
Question 1 (10 points; 2 points each): This question has 5 parts. Consider the following 3 options for a location on the Earth:
Equator
North pole
Mid-northern or mid-southern latitude
For each question below, identify your location on Earth using one of the options above.
A)
All visible stars rise and set perpendicular to the horizon.
Answer: equator
B)
All visible stars circle the sky parallel to the horizon.
Answer: north pole
C)
The celestial equator passes through the zenith:
Answer: equator
D)
All the stars of the sky are above the horizon on some night of the year.
Answer: equator E)
The Sun rises on March 21 and does not set until September 21 (ideally).
Answer: northpole
Question 2 (5 points): Suppose a young astronomer more than 2,000 years ago repeated his famous colleague’s measurement of the Earth. Our young astronomer sent his assistant to the same location on the same day of the year as did his colleague, but he measured the Sun’s angle to be 10 degrees from vertical. What would our young astronomer have calculated for the Earth’s circumference in units of “stadia”? What would he have calculated in units of km? Assume there are 6 stadia in 1 km.
Show the formula you used and your calculations for both answers.
Answers: C=360/10 x 5,000 = 180,000 stadia Page 1 of 6
AST 101 Lesson 2 Homework
180,000/6 km = 30,000km Page 2 of 6
AST 101 Lesson 2 Homework
Question 3 (6 points, 3 points each): The drawing below shows the Earth, Moon, and Sun, along
with the direction pointed by your local meridian at times between 6am and 6pm. Suppose you observe the Moon on the meridian at 9 AM as shown. Answer the following two parts of this question below the diagram:
Page 3 of 6
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AST 101 Lesson 2 Homework
A)
What is the phase of the Moon?
Answer: waxing gibbous B)
Is it waxing or waning?
Answer: waxing Page 4 of 6
AST 101 Lesson 2 Homework
Question 4 ( points, 2 points each) Briefly describe one of the most significant scientific contributions of the following people. Give a detailed description of each contribution:
A)
Galileo:
Often referred to as the father of modern science. He pioneered the use of experiments and math to study nature. He improved the telescope and used it to study space and make important discoveries. He believed in the Copernican model of the solar system and expressed his opinion publicly. He got much backlash for this and was from there shunned by his community. B)
Copernicus:
An astronomer and mathematician proposed that the sun is in the center of our solar system, and we all revolve around it. His first model of this theory was a coherent heliocentric model. Prior to this the geocentric model was widely accepted. He also had theories that involved the season change, the lengths of the year, and earth axis and orbit. The year he died he release all
his theories explained in a book called On the Revolutions of the Heavenly Spheres 1543. Although his theory of us revolving around the sun was wrong, many of his findings were revolutionary. Question 5 (10 points): Describe Ptolemy’s geocentric model of the universe. In your answer, also describe the later observations that ultimately caused the heliocentric model to replace it.
Ptolemy’s geocentric model of the universe was a model that assumed that Earth was stationary
and at the center of the universe, and that the Sun, Moon, stars, and planets all orbited around it. The heliocentric model took the place of the geocentric. This offered the idea that the Sun was the center of the solar system and that the Earth and other planets revolved around it. Some of the later observations that caused the heliocentric model to replace the geocentric model were the phases of Venus, the elliptical orbits of the planets, and the laws of gravitation. Question 6 (5 points): Explain the origin of the “magnitude” system for determining the brightness of stars. In your answer, describe why it seems to go backward numerically, with smaller numbers indicating brighter stars.
The origin of the word magnitude comes
from an ancient Greek astronomer named Hipparchus.
He organized the stars into 6 different categories, ranked by brightness. The brightest stars were called first magnitude and the dimmest sixth. The systems seem to go backward numerically because the 6
th
is the dimmest, and not the biggest number for the brightest star. The way it was organized is based off the perception of the human eye. The eye sees light in a way that makes it hard to tell the difference between bright and very bright things., so because the magnitude scales is based on this, if something is five magnitudes brighter than another thing, it is actually 100 times brighter. Question 7 (10 points):
Although the Copernican system was correct to place the Sun at the center of all planetary motion, the model gave greatly improved but imperfect predictions for the positions of the planets. Explain the flawed assumption in the Copernican model that limited its accuracy.
Copernicus said that the sun was the center of the solar system and we umungst other plants revolved around it. One of the other flaws of this model was the prediction that the planets orbited in perfect circles. This is a flawed assumption becuase planets move in elipitcal orbits, which are more oval like. These oval motions explain why the planets sometimes appeat to spee up or slow down. Page 5 of 6
AST 101 Lesson 2 Homework
Question 8 (10 points): The primary cause of seasons on Earth is the tilt of its axis away from being perpendicular to its orbital plane. Explain why this tilt causes the seasons to occur at middle latitudes such as in the central United States.
The tilt of the Earth’s axis causes the seasons to occur at middles latitudes because it affects how much sunlight different parts of the Earth receive throughout the year. When the Northern Hemisphere is tilted toward th Sun, it gets more direct and longer lasting sunlight. This results in
more warmth. This is summer for the Northern Hemisphere. When the Norther Hemisphere is tilted away from the Sun, it gets less direct and shorter lastin sunlight, which makes it colder. This is winter. Page 6 of 6
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