ASTRO 1: MIDTERM QUESTIONS

The blackbody curve of a star moving toward Earth would have its peak shifted...

toward higher energies.

waxing crescent moon

visible near western horizon about an hour after sunset. sets 2-3 hours after the Sun sets.

When a thin crescent of the Moon is visible just before sunrise, the Moon is in its...

waning phase.

Compared with ultraviolet radiation, infrared radiation has a greater...

wavelength.

Heliocentric

Explained planetary motions and brightness changes most simply.

PART A: What is a scientific theory?

A theory is a framework of ideas and assumptions that represents our initial explanation for something.

annular eclipse. total lunar eclipse. penumbra. total solar eclipse. umbra. node.

1. A solar eclipse that occurs when the new moon is too far from Earth to completely cover the Sun can be either a partial solar eclipse or a(n) ANNULAR ECLIPSE. 2. Anyone looking from the night side of Earth can, in principle, see a(n) TOTAL LUNAR ECLIPSE 3. During some lunar eclipses, the Moon's appearance changes only slightly, because it passes only through the part of Earth's shadow called the PENUMBRA. 4. A(n) TOTAL SOLAR ECLIPSE can occur only when the Moon is new and has an angular size larger than the Sun in the sky. 5. A partial lunar eclipse begins when the Moon first touches Earth's UMBRA. 6. A point at which the Moon crosses Earth's orbital plane is called a(n) NODE.

FOCUS, APHELION, ELLIPSE, SEMIMAJOR AXIS, PERIHELION, ECCENTRICITY.

1. Earth is located at one FOCUS of the Moon's orbit. 2. According to Kepler's second law, Jupiter will be traveling most slowly around the Sun when at APHELION. 3. Earth orbits in the shape of a/an ELLIPSE around the Sun. 4. The mathematical form of Kepler's third law measures the period in years and the SEMIMAJOR AXIS in astronomical units (AU). 5. According to Kepler's second law, Pluto will be traveling fastest around the Sun when at PERIHELION. 6. The extent to which Mars' orbit differs from a perfect circle is called its ECCENTRICITY.

PART A: Suppose that instead of being inclined to Earth's orbit around the Sun, the Moon's orbit was in the same plane as Earth's orbit around the Sun. (Click "Show Moon with flat orbit" to see this situation.) In this hypothetical situation, approximately how many solar eclipses would occur each year?

12. CORRECT: If the Moon orbited Earth in the same plane that Earth orbits the Sun (the ecliptic plane), we would have a solar eclipse at every new moon. Because there are about twelve new moons in a year, we would have twelve solar eclipses. Of course, this isn't what really happens. Continue to Part B to study the real situation.

PART B: In reality, the Moon's orbit about Earth is tilted (by about 5°) with respect to Earth's orbit about the Sun. As a result, the actual number of solar eclipses that occur each year is approximately _____.

2. CORRECT: There are generally two periods of time each year when eclipses are possible — the "eclipse seasons" — and there is a solar eclipse of some type (partial, total, or annular) during each of these eclipse seasons. (Because the time between eclipse seasons is less than six months, in some years there is a third eclipse season and hence a third solar eclipse.)

ESSAY QUESTION 3: In terms of its blackbody curve, describe what happens as a red-hot glowing coal cools.

A blackbody curve is the basic characteristic in which the intensity of radiation emitted by a hot object depends on its frequency. This means that if the frequency of the object increases then this is the indication of the object's temperature, also called the "Planck Curve". In a blackbody curve, when a red-hot glowing coal cools then the frequency of the coal declines. As the frequency of the red-hot coal cools then the coal will move to the left and decline with a longer wavelength. According to Wien's Law, the complete relation between the wavelength at which a blackbody curve peaks and the temperature of the object is balanced, so the hotter the object the bluer it's radiation. Since the object of the blackbody curve is red-hot then the relation between the wavelength and the temperature declines because of the color is not blue, it is red which means that the object was already cool to begin with. According to Stefan's Law, the energy within an object inclines rapidity in the the temperature of the object, proportional to the temperature "raised to the fourth power". This means that the temperature of the red-hot glowing coal will decline because the total area declining, making both the temperature and the area in the object proportional to one another.( CORRECT) ANSWER KEY: As the coal cools off, its temperature decreases. According to Wien's law, more of its radiation will be emitted at longer wavelengths. According to Stefan's law, it will emit less radiation as it cools. The net result is that it gets fainter and redder with time.

PART B: If you throw a rock into a pond, it creates a wave in the water. What is responsible for creating an electromagnetic wave?

A vibrating charged particle. CORRECT: The production of an electromagnetic wave requires a vibrating charged particle. The changing position of the particle causes its associated electric field to change in a wavelike manner, creating an electromagnetic wave.

According to Figure 1.15 in the textbook ("The Zodiac"), in January the Sun is in the constellation...

Aquarius.

ESSAY QUESTION 1A( 2ND): What does an astronomer mean by "the universe"?

Astronomers study the universe, meaning that they study the totality of space, time, matter, and energy. Space is what holds the sun, moon, stars, and planets together and what divides them apart from one another. Time is the distance it takes to get from one planet to another. Matter is the density of each planet, which is the measure of how big each planet is from one another. Energy is the ray that the planet puts off, which is measured through energy, time, matter, and space. All in all, astronomy is the study of the entire universe. This means that the study of the entire universe is also the study of space,time,matter,and energy. The study of the universe is an eye opening observation that makes us compare and contrast and even change our views about the world.( CORRECT) ANSWER KEY: The universe is defined as the sum total of all space, time, energy, and matter.

Compared with red light, blue wavelengths of visible light travel...

At the same speed.

ESSAY QUESTION 3( 2nd): What's so special about c?

C is the definition for the speed of light. The value of the speed of light is approximately 299 792 458 m s−1 while the "relative uncertainty" is "defined". The speed of light, also seen as a type of vacuum, is exact in length because it's meter being characterized as the distance it takes to travel during a certain time interval, that is 1/299792458 seconds. C is the certain extend of speed which matter in all shapes of information can travel. Even though this type of speed is used for light, it can also be associated to find the "speed in certain massless particles which may change to a certain extent in a vacuum." ( "including electromagnetic radiation and gravitational waves"). C can also appear in the acclaimed equation, relating to space and time, as " E = mc2" , mass-energy equivalence.(CORRECT) ANSWER KEY: The speed of light is symbolized by the letter c. The speed of light is actually the speed of all electromagnetic radiation in a vacuum and is a constant.

PART A: Light is a wave, and, like all waves, it is characterized by specific physical characteristics. Identify the key physical characteristics of a wave in the figures below. Figure A shows a wave as a function of time, and Figure B shows a wave as a function of space. Drag the appropriate labels to their respective targets.

CORRECT: All waves have properties related to both time and distance. The wave period is the time it takes for a wave to travel from crest to crest. The wavelength is the distance of a wave from crest to crest. The amplitude is half the distance between the crest of a wave and the trough. The two figures show the correlation between wavelength and wave period: The longer the wavelength, the longer the wave period.

PART A: The circles in the diagrams below represent energy levels in an atom, and the arrows show electron (blue dot) transitions from one energy level to another. (The spacing between circles represents differences in energy: A larger spacing means a greater difference in energy.) Assuming that the transitions occur as photons are emitted, rank the atoms based on the photon energy, from highest to lowest.

CORRECT: As your answer correctly shows, the emitted photon must have exactly the same amount of energy that the electron loses in moving from the higher to the lower energy level. Therefore the ranking of the photon energies must be in the same order as the amounts of energy lost by the electrons, and longer arrows mean greater changes in energy.

PART B: Shown following are five different phases of the Moon as seen by an observer in the Northern Hemisphere. Imagine that tonight the Moon is in the waxing gibbous phase (as shown at the far left (labeled "first") in the following ranking box). Rank the pictured phases from left to right based on the order in which you would see them over the next four weeks, from first seen to last.

CORRECT: Remember that "waxing" phases mean on the way to full moon and "waning" phases mean after full moon. So if tonight is a waxing gibbous moon, then we are headed toward full moon in about three to four days. Because the full moon is not shown, we'd next see a waning gibbous moon, then a third-quarter moon, and then a waning crescent. From there we'd have new moon (which isn't shown), then the waxing crescent, and then first-quarter. Finally, a full four weeks from now (actually 29 1/2 days), we'd once again have a waxing gibbous moon.

PART E: If you could change the layout of the solar system, which of the following would cause a lunar eclipse to occur at least once every month in this hypothetical situation?

Change the Moon's orbital plane so it is in the same plane as Earth's orbit around the Sun. CORRECT: Good work! You correctly visualize that the Moon's orbit has to be in line with Earth's orbit in order for a lunar eclipse to happen just about every month.

ESSAY QUESTION 1A: Compare the size of Earth with that of the Sun, the Milky Way galaxy, and the entire universe.

Earth is an odd rocky planet, a solid object that holds liquid in the ocean and the core, and gas in the atmosphere. The earth is approximately 15,000 kilometers wide/big or 3,959 mi, that means that earth is approximately 14,999.99 bigger that humans! The sun, a bigger star among millions of other stars, is known to be an "extremely hot ball of gas composed mainly of hydrogen and helium." The sun is approximately 1,500,000 kilometers or 0.5 light seconds, meaning that the sun is about 100 times larger in diameter than the earth. The Milky Way galaxy is an assortment of a "hundred billion stars", each divided by massive regions of empty space, the sun being the center region of the space. The Milky Way galaxy is about 100 quadrillion kilometers or 10,000 light years, also about 1,490,000 kilometers bigger than the sun. The entire universe, also known as the " Galaxy cluster", is a broad "cluster of galaxies", reaching about 2 million light years and encompassing more than 100 galaxies. The entire universe is about 2,000,000 light years which is bigger than the sun, the Milky Way, and the earth combined. All in all, the universe consists of the total amount of space, time, matter, and energy between the earth, the sun, the milky way, and the entire universe.( CORRECT) ANSWER KEY: Looking at the data in the text, we can see that the diameter of the Sun is about 100 times that of Earth, about 1 500 000 km for the Sun compared to about 12 000 km for Earth. A galaxy such as the Milky Way is about 100 000 light-years in diameter. Since a light-year is about 10^13 km, this means the Galaxy has a diameter of approximately 10^18 km, or about 10^14 times (100 million million times) the radius of Earth. The most distant objects visible define the limits of the visible universe (which is likely only a small part of the entire universe). These objects are about 10 billion light-years away, or 10^23 km. This is 10^19 times (10 billion billion times) the radius of Earth.

Testable by science

Earth orbits the Sun every 365.25 days. Bacteria acquire resistance to antibiotics through changes in their DNA. There will be a solar eclipse nextTuesday at 11 a.m. Mars once had liquid water on its surface. People born under the sign of Sagittarius are twice as likely to be teachers as anyone else.

FIELDS, PERPENDICULAR, PARALLEL, VACUUM, 300,000 KM/S,

Electromagnetic waves consist of co-oscillating electric and magnetic FIELDS. The wave amplitudes are directed PERPENDICULAR, to the direction of wave motion. Energy and information flows PARALLEL to the direction of wave motion. Electromagnetic waves are able to travel through a VACUUM. Electromagnetic waves travel at a speed of 300,000 KM/S.

PART C: An important line of hydrogen occurs at a rest wavelength (as measured in a laboratory) of 656 nm (a nanometer (nm) is a billionth of a meter). Each diagram below has this line labeled with its wavelength in the spectrum of a distant star. Rank the motion of the stars along our line of sight (radial motion) based on their speed and direction, from moving fastest toward Earth, through zero (not moving toward or away from Earth), to moving fastest away from Earth.

FASTEST TOWARD EARTH: 646 MM, 650 MM, 656 MM, FASTEST AWAY FROM EARTH: 657 MM, 663 MM.

PART C: The following diagrams are the same as those from Parts A and B. This time, rank the planets from left to right based on their average orbital speed, from fastest to slowest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Distances are to scale, but planet and star sizes are not.)

FASTEST: Smallest, round circle. Smallest, oval circle. Medium, round circle. SLOWEST: Medium/ Big oval circle. Big, round circle.

PART B: The following diagrams are the same as those from Part A. This time, rank the five positions of the spaceship from left to right based on the strength of the gravitational force that the Moon exerts on the spaceship, from strongest to weakest.

STRONGEST FORCE Spaceship is past the midpoint line and right next to the moon. Spaceship I past the midpoint line and is heading to the moon( not close). Spaceship is right on the midpoint line. WEAKEST Spaceship is past the midpoint line, heading to earth. Spaceship is really close to the earth.

Stefan's law says that if the Sun's temperature were to double, its energy emission would...

Increase 16 times.

Johannes Kepler used decades of Tycho Brahe's observational data to formulate an accurate description of planetary motion. Kepler spent almost 30 years of his life trying to develop a simple description of planetary motion based on a heliocentric model that fit Tycho's data. What conclusion did Kepler eventually come to that revolutionized the heliocentric model of the solar system?

Kepler determined that the planetary orbits are elliptical.

ESSAY QUESTION 2B(2ND) If radio waves cannot be reflected from the Sun, how can radar be used to find the distance from Earth to the Sun?

Kepler's third law of periods clearly states that, "The square of the period of any planet is proportional to the cube of the semimajor axis of its orbit." This means that even though the radio waves are not being reflected from the sun, we can find the distance from Earth to the Sun by the Astronomical Unit(A.U). This means that since the astronomical unit of earth to the sun is relatively one astronomical unit, the length between the earth and sun is around 93 million miles(150 million kilometers), or 8 light minutes.This ultimately conveys that Earth is farther away from the sun by about 3 percent but is not too close to the perihelion point.(CORRECT) ANSWER KEY: The astronomical unit, defined as the average distance between the Earth and the Sun, was used to provide an estimate of the distances between the planets long before its actual numerical value was known. By reflecting radar waves off the planet Venus and timing how long it takes them to return, we can determine the distance to Venus in kilometers. Comparing this to the distance to Venus in AU, the length in kilometers could be determined, and with it, the distance between the Earth and the Sun.

PART A: The diagrams below each show the motion of a distant star relative to Earth (not to scale). The red arrows indicate the speed and direction of the star's motion: Longer arrows mean faster speed. Rank the stars based on the Doppler shift that we would detect on Earth, from largest blueshift, through no shift, to largest redshift.

LARGEST BLUESHIFT: Line points from sun to earth(long), Line points from sun to earth(short), Line points from away from sun, Line points from earth to sun(small), Line points earth to earth to sun( long) CORRECT: As your correct answer indicates, the star moving fastest toward Earth will have the greatest blueshift, the star moving across our line of sight will have no shift at all, and the star moving fastest away from us will have the greatest redshift.

PART A: The following diagrams all show the same star, but each shows a different planet orbiting the star. The diagrams are all scaled the same. (For example, you can think of the tick marks along the line that passes through the Sun and connects the nearest and farthest points in the orbit as representing distance in astronomical units (AU).) Rank the planets from left to right based on their average orbital distance from the star, from longest to shortest. (Distances are to scale, but planet and star sizes are not.)

LONGEST: Biggest circle. Oval like median circle. Small, round median looking circle. SHORTEST: Oval looking, small circle. Really small, round circle.

PART D: Each of the following diagrams shows a planet orbiting a star. Each diagram is labeled with the planet's mass (in Earth masses) and its average orbital distance (in AU). Assume that all four stars are identical. Use Kepler's third law to rank the planets from left to right based on their orbital periods, from longest to shortest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Distances are to scale, but planet and star sizes are not.)

LONGEST: 2AU: One Earth Mass & Three Earth Mass(ARE EQUAL) SHORTEST: - 1AU: One Earth Mass & Two Earth Mass(EQUAL)

ESSAY QUESTION 1B: Why do we see different stars at different times of the year?

MY ANSWER: We view different stars at different times of the year because of the movement of the earth in its orbit around the sun. The measurement of how much the sky alternates is approximately one degree per day. This means that since we have 365 days per year, that the degree of a circle is also 360. The alteration of the sky is the movement of the earth around the sun. The sky doesn't completely rotate because of apparent motion, which is the "shift in objects in the sky due to the earth's orbit around the axis."( CORRECT) ANSWER KEY: At any given time during the year, we can only see the part of the Galaxy that the "night side" of Earth is facing as it orbits the Sun. In July, this part of the Galaxy includes, for example, the stars of Scorpio. Six months later, Earth has moved over to the other side of the Sun, and the night side of Earth is facing an entirely different section of the Galaxy. We cannot see the stars of Scorpio in January because the Sun is between them and us.

ESSAY QUESTION 1B: What is a constellation? Why are constellations useful for mapping the sky?

MY ANSWER: A constellation is the grouping of stars in the night sky resulting in recognizable patterns. Constellations are helpful when mapping out the sky because they can be seen by the naked eye and are attached to the celestial sphere, which is a a hypothetical sphere that surrounds the earth and all of the objects that are connected to the sky. ANSWER KEY: In the common usage of the term, a constellation is a pattern of stars in the sky. Officially, however, a constellation is a section of sky that contains stars, galaxies, nebulae, and many more celestial objects. Just as every section of Earth's land surface is considered part of a country, every part of the sky is within the borders of a constellation. Constellations are thus useful in naming and locating celestial objects.

PART C: The law of physics state that a magnetic field must accompany a changing electric field, and a change in one must create a change in the other. Together, electric and magnetic fields make up electromagnetic waves, which carry energy and information from one part of the universe to another. Electromagnetic waves share many properties with ordinary waves, but they also have a number of unique characteristics. Using the figure below and your knowledge from Parts A and B, complete the following statements about the specific properties of electromagnetic radiation.

Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer. LOOK AT NEXT SLIDE...

ESSAY QUESTION 2B: What are Newton's laws of motion and gravity?

Newton's laws of motion and gravity clearly states the universal reason for the movement of everyday objects. Newton's first law conveys that an object will stay in its state of motion unless force is exerted onto it. This means that an object that is in a still state will remain in a still position until a force pushes or pulls it forward or backward. If the object is moving forward, then it will continue to move forward at a constant speed unless a force is exerted onto it. Newton's second law of motion states that force is balanced or equal to the mass of an object times its speed. This means that since force is generally equal to the mass of an object, in order for an object to move at an increased or decreased speed, one would have to know how big the force of an object is. Newton's third law of motion and gravity states that for each force that acts upon an object by another object, each force will be equal to one another.This means that by making each force of a certain object equal to the other force of another object, both objects will move in opposite directions from one another, because the forces and masses of both objects are equal, the acceleration of each object is different. ( CORRECT) ANSWER KEY: First law of motion: Every object continues in a state of rest or in a state of uniform motion in a straight line unless it is compelled to change that state of motion by an unbalanced force acting on it. Second law of motion: When an unbalanced force (F) acts on a body of mass (m), the body experiences an acceleration (a) equal to the force divided by the mass. Thus, a = F/m, or F = ma. Third law of motion: To every action there is reaction equal in size and opposite in direction to the original action. Law of gravity: Every particle of matter in the Universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between their centers.

Both geocentric and heliocentric

Planetary orbits and motions based on Greek ideologies of perfect form and motion. Predicted planetary positions accurately over relatively short time periods.

Geocentric

Rooted in widely accepted religious beliefs regarding Earth's place in the universe.

PART C: The following diagrams are the same as those from Part A. This time, rank the pairs from left to right based on the size of the acceleration the asteroid on the left would have due to the gravitational force exerted on it by the object on the right, from largest to smallest.

SAME AS PART A AND PART B: STRONGEST FORCE: astroid= sun, astroid= earth, astroid= moon, WEAKEST FORCE: astroid= astroid, astroid= hydrogene atom.

PART B: The following diagrams are the same as those from Part A. This time, rank the planets from left to right based on the amount of time it takes each to complete one orbit, from longest to shortest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Distances are to scale, but planet and star sizes are not.)

SAME AS PART A. LONGEST: Biggest circle. Oval like median circle. Small, round median looking circle. SHORTEST: Oval looking, small circle. Really small, round circle

PART B: The following diagrams are the same as those from Part A. Again considering only the two objects shown in each pair, this time rank the strength, from strongest to weakest, of the gravitational force acting on the object on the right.

SAME AS PART A. STRONGEST FORCE: astroid= sun, astroid= earth, astroid= moon, WEAKEST FORCE: astroid= astroid, astroid= hydrogene atom.

PART B: Copernicus's heliocentric model and Ptolemy's geocentric model were each developed to provide a description of the solar system. Both models had advantages that made each an acceptable explanation for motions in the solar system during their time.

SEE NEXT SLIDE...

PART C: The following diagrams show five pairs of asteroids, labeled with their relative masses (M) and distances (d) between them. For example, an asteroid with M=2 has twice the mass of one with M=1 and a distance of d=2 is twice as large as a distance of d=1. Rank each pair from left to right based on the strength of the gravitational force attracting the asteroids to each other, from strongest to weakest.

STRONGEST d=1, m=2, m=2, d=1, m=1, m=2, d=1, m=1, m=1, d=2, m=1, m=2, d=2, m=1, m=1

PART A: Each of the following diagrams shows a spaceship somewhere along the way between Earth and the Moon (not to scale); the midpoint of the distance is marked to make it easier to see how the locations compare. Assume the spaceship has the same mass throughout the trip (that is, it is not burning any fuel). Rank the five positions of the spaceship from left to right based on the strength of the gravitational force that Earth exerts on the spaceship, from strongest to weakest.

STRONGEST FORCE spaceship is right next to earth Spaceship coming from earth, closer to midpoint Spaceship is right on the midpoint line. WEAKEST spaceship is past the midpoint( heading to the moon) spaceship very close to the moon.

PART A: The following five diagrams show pairs of astronomical objects that are all separated by the same distance d. Assume the asteroids are all identical and relatively small, just a few kilometers across. Considering only the two objects shown in each pair, rank the strength, from strongest to weakest, of the gravitational force acting on the asteroid on the left.

STRONGEST FORCE: astroid= sun, astroid= earth, astroid= moon, WEAKEST FORCE: astroid= astroid, astroid= hydrogene atom.

measurable quantities and testable predictions, that can be tested, fit totally within, testable, not testable, that cannot be tested, untestable assumptions, do not fit within,

Science therefore relies on MEASURABLE QUANTITIES AND TESTABLE PREDICATIONS to search for answers. Pseudosciences such as astrology typically make predictions THAT CANNOT BE TESTED, and offer explanations that DO NOT FIT WITHIN a coherent framework of ideas. If a claim is NOT TESTABLE, it cannot be considered scientific.

Listed following are various physical situations that describe how light interacts with matter. Match these to the appropriate category.

TRANSMISSION: Visible light meets clear glass. Cell phone signals pass through walls. ABSSORPTION: Visible light does not pass through a black wall. Blue light hits a red sweatshirt. REFELECTION OR SCATTERING: Red light hits a red sweatshirt. White light hits a white piece of paper. EMISSION: Light comes from a light bulb. Light comes from your computer screen.

Each of the following items states a temperature, but does not tell you whether the temperature is measured on the Fahrenheit, Celsius, or Kelvin scale. Match the items to the appropriate temperature scale.

Temperature scale( F): A hot summer day might be 100. Ice cream is stored in freezers at 26. Temperature scale(C): Water freezes into ice at 0. A typical room temperature is 24. Liquid water boils at 100. Temperature scale( K): The coldest possible temperature is 0. Water boils into gas phase at 373.15.

Galileo Galilei was the first scientist to perform experiments in order to test his ideas. He was also the first astronomer to systematically observe the skies with a telescope. Galileo made four key observations that challenged the widely accepted philosophical beliefs on which the geocentric model was based, thus providing support for the heliocentric model. From the following list of observations, which are the key observations made by Galileo that challenged widespread philosophical beliefs about the solar system?

The Moon has mountains, valleys, and craters. Venus goes through a full set of phases. The Sun has sunspots and rotates on its axis. Jupiter has orbiting moons.

PART C: As you found in Part A, your weight will be greater than normal when the elevator is moving upward with increasing speed. For what other motion would your weight also be greater than your normal weight?

The elevator moves downward while slowing in speed. CORRECT: When the elevator is moving downward, a downward acceleration would mean an increasing downward speed. Therefore, as your answer correctly states, an upward acceleration would mean a decreasing downward speed.

ESSAY QUESTION 2A: The benefit of our current knowledge lets us see flaws in the Ptolemaic model of the universe. What is its basic flaw?

The most basic flaw in the Ptolemaic model of the universe is how retrograde motion is not being explained. The Ptolemaic model was invented in the old ages by astronomer Claudius Ptolemy, who foresaw the great "accuracy" of the arrangement of the planets. Retrograde motion is a backwards loop that is being sketched out by a planet with respect to the fixated stars.This model does not describe retrograde motion relating to the reversal of the rotation of the sun, the moon, the planets, and earth, analogous to the stars and their normal onward motion. The Retrograde motion is the motion is a motion described as the backwards movement along a "epicyclic" path around earth. ANSWER KEY: The most obvious flaw in the Ptolemaic model is in its basic premise, since the Earth is not at the center of the solar system, let alone the entire universe. The unquestioned acceptance of perfectly circular orbits is another problem. However, a deeper flaw is that the Ptolemaic model did not attempt to explain why the motions are the way the model depicts them. The model may describe the motions, but it does not explain them. Today we would require any such explanation to be based on fundamental physical laws.

PART D: What conditions must exist for a lunar eclipse to occur?

The phase of the Moon must be full and the Moon must be passing through Earth's orbital plane. CORRECT: The two points at which the Moon's orbit crosses the Earth's orbital plane are called the nodes of the Moon's orbit. So another way to state the conditions for a lunar eclipse is that (1) it must be full moon, and (2) the Moon must be at or quite near one of the nodes of its orbit.

PART C: What conditions must exist for a solar eclipse to occur?

The phase of the Moon must be new and the Moon must be passing through Earth's orbital plane. CORRECT: The two points at which the Moon's orbit crosses the Earth's orbital plane are called the nodes of the Moon's orbit. So another way to state the conditions for a solar eclipse is that (1) it must be new moon, and (2) the Moon must be at or quite near one of the nodes of its orbit.

PART B: Can a theory ever be proved to be absolutely true?

Theory can never be proven to be absolutely true.

Astronomers have made many observations since the days of Galileo and Kepler to confirm that the Sun really is at the center of the solar system, and that the planets revolve around the Sun in elliptical orbits. Which observation(s) could you make today that Galileo and Kepler could not have made to confirm that the heliocentric model is correct?

Transit of an extrasolar planet Stellar parallax in nearby stars Doppler shifts in stellar spectra of nearby stars

Not testable by science

Vince Young is the greatest quarterback of all time. Hurricane Katrina was an act of God.

PART E: In Ptolemy's Earth-centered model for the solar system, Venus always stays close to the Sun in the sky and, because it always stays between Earth and the Sun, its phases range only between new and crescent. The following statements are all true and were all observed by Galileo. Which one provides evidence that Venus orbits the Sun and not Earth?

We sometimes see gibbous (nearly but not quite full) Venus. CORRECT: In the Ptolemaic system, we should never see more than a crescent in Venus. Because we do in fact see more, the Ptolemaic model must be wrong. The full range of phases that we see for Venus is consistent only with the idea that Venus orbits the Sun. Galileo was the first to observe the phases of Venus — and hence to find this evidence in support of the Sun-centered system — because he was the first to observe Venus through a telescope. Without a telescope, we cannot tell that Venus goes through phases.

discarded or modified, discovering, hypothesis, accepted, guessing, theory, data,

What is the scientific method? The scientific method is a process for DISCOVERING the best possible explanation as to why something occurs. The process begins when observations lead to the formulation of a HYPOTHESIS, a preliminary explanation that makes testable. Investigators gather information - called DATA - to test the predictions through observation and experimentation. The information is analyzed to find patterns in the DATA. If the patterns agree with the predictions, the HYPOTHESIS is considered a viable theory. If they do not agree, the HYPOTHESIS must be DISCARDED OR MODIFIED.

In Figure 1.28 in the textbook ("Triangulation"), using a longer baseline would result in...

a smaller angle at point B.

PART C: A new Venus occurs when Venus is directly between the Sun and Earth, which means a new Venus will be highest in the sky at the same time that the Sun is highest in the sky, which is around noon (local time).

at noon. CORRECT: A new Venus occurs when Venus is directly between the Sun and Earth, which means a new Venus will be highest in the sky at the same time that the Sun is highest in the sky, which is around noon (local time).

PART B: Imagine that Venus is in its full phase today. If we could see it, at what time would the full Venus be highest in the sky?

at noon. CORRECT: Because Venus is full when it is on the opposite side of the Sun from Earth, the Sun and Venus both appear to move through the sky together at that time. Venus therefore rises with the Sun, reaches its highest point at noon, and sets with the Sun.

Figure 2.21 in the textbook ("Gravity"), showing the motion of a ball near Earth's surface, depicts how gravity...

causes the ball to accelerate downward.

If the Sun and its mass were suddenly to disappear, Earth would...

fly off into space.

PART A: In Ptolemy's Earth-centered model for the solar system, Venus's phase is never full as viewed from Earth because it always lies between Earth and the Sun. In reality, as Galileo first recognized, Venus is __________.

full whenever it is on the opposite side of the Sun from Earth, although we cannot see the full Venus because it is close to the Sun in the sky. CORRECT: A full Venus always occurs when it is on the opposite side of the Sun as viewed from Earth. (However, we cannot see the full Venus, because it is always very close to the Sun in the sky at that time.) Galileo used this fact as evidence for the Sun-centered view of the solar system: The fact that Venus goes through all the phases must mean it goes all the way around the Sun. In contrast, in the Ptolemaic model, Venus only varies between new and crescent phases.

PART A: Suppose you are in an elevator. As the elevator starts upward, its speed will increase. During this time when the elevator is moving upward with increasing speed, your weight will be __________.

greater than your normal weight at rest. CORRECT: Increasing speed means acceleration, and when the elevator is accelerating upward you will feel a force pressing you to the floor, making your weight greater than your normal (at rest) weight.

An asteroid with an orbit lying entirely inside Earth's...

has an orbital semimajor axis of less than 1 AU.

PART B: Suppose you are in an elevator that is moving upward. As the elevator nears the floor at which you will get off, its speed slows down. During this time when the elevator is moving upward with decreasing speed, your weight will be __________.

less than your normal weight at rest CORRECT: Even though the elevator is still moving upward, the fact that its speed is slowing means that the acceleration is downward; the situation is rather like that of a ball that is still on its way up after you throw it, even though it is being pulled downward with the acceleration of gravity. Because the acceleration of the elevator is downward, your weight is lower than normal.

summer solstice

longest day (most daylight) of the year. The noontime Sun reaches its highest point of the year.

If the Moon's orbit were a little larger, solar eclipses would be...

more likely to be annular.

If Earth's orbit around the Sun were twice as large as it is now, the orbit would take...

more than two times longer to traverse.

Figure 2.26(b) in the textbook ("Orbits") shows the orbits of two stars of unequal masses. If one star has twice the mass of the other, then the more massive star

moves more slowly than the less massive star.

PART D: When would you expect to see Venus high in the sky at midnight?

never. CORRECT: For Venus to be high in the sky at midnight, it would have to be on the opposite side of our sky from the Sun. But that never occurs because Venus is closer than Earth to the Sun.

waning crescent moon

occurs about 3 days before new moon. visible near eastern horizon just before sunrise.

As shown in Figure 2.12 in the textbook ("Venus Phases"), Galileo's observations of Venus demonstrated that Venus must be...

orbiting the Sun.

An electron that collides with an atom will...

produce an electromagnetic wave.

A star much cooler than the Sun would appear...

red.

Planets near opposition...

rise in the east.

full moon

rises at about the time the Sun sets. occurs 14 days after the new moon. visible due south at midnight.

PART D: Consider Earth and the Moon. As you should now realize, the gravitational force that Earth exerts on the Moon is equal and opposite to that which the Moon exerts on Earth. Therefore, according to Newton's second law of motion __________.

the Moon has a larger acceleration than Earth, because it has a smaller mass. CORRECT: Newton's second law of motion, F=ma, means that for a particular force F, the product mass x acceleration must always be the same. Therefore if mass is larger, acceleration must be smaller, and vice versa.

fall equinox

the Sun has declination 0 degree today, but will have a negative declination tomorrow.

spring equinox

the Sun rises due east today, but will rise slightly north of due east tomorrow

PART D: If you are standing on a scale in an elevator, what exactly does the scale measure?

the force you exert on the scale. CORRECT: You probably recognize that neither your mass nor the gravitational force exerted on you change when you are in an elevator. The scale measures the force that is exerted on it, which in an elevator is a combination of the force due to your normal weight and a force due to the elevator's acceleration.

winter solstice

the noontime Sun casts the longest shadows the Sun crosses the meridian 23.5 degrees lower in altitude than the celestial equator. sunset occurs at its farthest point south of due west for the year.

According to Wien's law, the hottest stars also have...

the shortest peak wavelength.

A calculation of how long it takes a planet to orbit the Sun would be most closely related to Kepler's...

third law of planetary distances.