Practically All Expert TA Homework Questions and Answers
Scientific models and hypotheses can change as new experiments or observations are done, often with better equipment.
TRUE
The Moon keeps roughly the same "face" (same side) toward the Earth; so there is a near side (Earth-facing side) and a far side (facing-away-from-Earth side).
TRUE
The stars we see in the night sky are other suns, which only look like points of light because they are so far away.
TRUE
When the Moon is new, the Sun is shining on the side of the Moon facing away from the Earth.
TRUE
Order the objects. Please use the drag-and-drop environment to label the missing parts of the figure from nearest to furthest. (Option: Sun, Andromeda Galaxy, Moon, Coma Cluster of Galaxies, Pleiades Star Cluster)
(Nearest) Moon, Sun, Pleiades Star Cluster, Andromeda Galaxy, Coma Cluster of Galaxies (Farthest)
(a) Suppose you looked up in the sky from the Northern Hemisphere and observed the Moon illuminated as it appears above. At which lettered position in its orbit is the Moon located at this moment? (b) What phase is the Moon in when it appears this way?
(a) G (right half of the moon is shaded so it would need to be above Earth in the image so that the sun would be hitting its left side) (b) Third Quarter
Distinguish among the statements below which were reasons, and which were not reasons, why Copernicus wanted to develop a completely new system for predicting planetary positions.
(Reasons:) The Ptolemaic model lacked beauty or symmetry in his eyes; The equant point violated Aristotle's principle of uniform circular motion; The Ptolemaic model required revisions to remain accurate over time (Not Reasons:) Local clergy hired him to calculate a more accurate calendar to properly place Easter; He thought highly of his mathematical skills and knew that only he would be able to fix Ptolemaic model's inaccuracies
Distinguish among the statements below which were reasons, and which were not reasons, why the geocentric model persisted for so long.
(Reasons:) There was no explanation for why people and objects would remain stuck to the Earth; No sense of Earth's motion was felt; Stellar parallax was not observed; The Ptolemaic model made reasonably accurate predictions; The Aristotelian view of uniform circular motion was very popular. (Not Reasons:) Nobody ever had any interest in changing the model until Copernicus came along; The equant had been observed in the sky, which was evidence that Ptolemy was right; The Ptolemaic model made perfect predictions such that no improvement was ever needed.
Put these in order of size. Please use the drag-and-drop environment to put the astronomical objects in the big box in order of size from smallest to largest. (Options: Moon, Sun, Jupiter, Galaxy)
(Smallest) Moon, Jupiter, Sun, Galaxy (Largest)
While ancient thinkers expected the motions of the planets to be circles, Kepler used Tycho Brahe's data to show that planets moved around the Sun in ellipses.
TRUE
Nebulae are regions rich with gas and dust which glow with light and other radiation. Here we see different nebulae with their approximate distances given in (light-years). Please use the drag-and-drop environment to label the missing parts of the figure from youngest to oldest light. (Options: Orion 1300, Rosette 5000, Crab 6500, Ring 2600, Dumbbell 1200)
(Youngest) Dumbbell 1200, Orion 1300, Ring 2600, Rosette 5000, Crab 6500 (Oldest)
(a) Suppose you looked up in the sky from the Northern Hemisphere and observed the Moon illuminated as it appears above. At which lettered position in its orbit is the Moon located at this moment? (b) What phase is the Moon in when it appears this way?
(a) B (3/4 of the moon is shaded on the left so it would have to be below Earth in the image in order for our POV from earth to see the sun hitting the moon's right side) (b) Waxing Crescent
a) Suppose you looked up in the sky from the Northern Hemisphere and observed the Moon illuminated as it appears above. At which lettered position in its orbit is the Moon located at this moment? (b) What phase is the Moon in when it appears this way?
(a) C (left side of the moon is shaded so it would have to be below Earth in the image in order for our POV from earth to see the sun hitting the moon's right side) (b) First Quarter
(a) Suppose you looked up in the sky from the Northern Hemisphere and observed the Moon illuminated as it appears above. At which lettered position in its orbit is the Moon located at this moment? (b) What phase is the Moon in when it appears this way?
(a) F (Sun is left of earth, and moon is 1/3 shaded on right side so it must be top-right of Earth) (b) Waning gibbous
Place each image in the bucket corresponding to where it is found - either Inside the Universe or Outside the Universe. Please use the drag-and-drop environment to label the missing parts of the figure. (Options: M51 Galaxy, Stefan's Quintet, Earth, Centauri, Saturn)
(Inside the Universe): M51 Galaxy, Stefan's Quintet, Earth, Centauri, Saturn (Outside the Universe:) None
Several astronomers have found intriguing, but complicated, evidence that there might be another planet in our solar system, far beyond the orbit of Neptune. For now it's being called Planet Nine. Suppose Planet Nine turns out to be a solid planet, and you could someday land there. Please put the planets in order of what you would weigh, from least to most.
(Least) Planet 9: 4x Earth's mass and radius; Planet 9: 1/2 Earth's mass, same radius as Earth; Planet 9: same mass and radius as Earth; Planet 9: 1/2 Earth's mass and radius; Planet 9: same mass as Earth, 1/2 Earth's radius (Most)
Suppose Earth took exactly 284 days to go around the Sun and everything else (the days, the months, etc.) stayed exactly the same. (a) How many lunar months (as determined by a full cycle of the Moon's phase) would there be in that year? Your answer should include fractional months if you do not get a whole number result. (b) How many seasons would the Earth have after this change, assuming that the tilt remained the same?
(a) Lunar months = 9.617 months (b) Number of seasons = 4.000 seasons
(a) Play the simulation for one full orbit. The default distance between the star and planet is two grid cells. Which of the following statements accurately describes what you see? (b) Now decrease the distance between the star and planet to one grid cell. What do you need to do to the planet's orbital speed in order to maintain a circular orbit? (c) Which of the following statements best explains why you need to increase the planet's orbital speed to maintain a circular orbit?
(a) the planet follows a circular orbit (b) Increase the speed (c) Decreasing the separation distance increases the force pulling on the planet, requiring the planet to travel faster in its orbit to avoid falling into the star.
In this diagram of the Celestial Sphere, there are five lines that point to different parts of the picture. Please use the drag-and-drop environment to label the indicated parts of the figure.
--Earth's equator is the imaginary [black] line that spans across the middle of the earth from east to west. --North Celestial Pole is the imaginary [white] line that rises from the arctic (north pole). --Your zenith is the imaginary [yellow] line that rises from the person icon. (It is always above you) --Your Horizon is the imaginary [red] line that circles the earth and the person icon. --Celestial equator is the imaginary [white] line that is parallel to the earth's equator.
Written in correct scientific notation, the number 13.8 billion becomes:
1.38 × 10^10
From horizon to opposite horizon, the sky takes up how much angular distance?
180 degrees
A star is 230 light-years away. The light we see tonight from that star left it:
230 years ago
Light travels 3 x 10^5 kilometers every second. That number in words is:
300,000 kilometers
In this diagram sunlight is coming from the right, and we see the Moon in various positions as it goes around the Earth in a month. We want to ask what phase of the Moon a person on Earth (who is facing the Moon) will see in the four positions. Drag the correct labels to those four positions.
A = New Moon C = First Quarter E = Full H = Waxing Crescent
Problem 13: What is Out There (drag-and-drop)
Astronomers have found many different kinds of objects beyond Earth. The Sun is an example of a star, which is *a giant glowing ball of gas that shines from nuclear reactions*. Round objects that revolve around (orbit) a star are called *planets*. Large collections of billions of stars, like the Milky Way, are called *galaxies*. Moons are smaller objects that orbit a planet. Astronomers call the sum total of everything that is out there *the universe*.
The diagram below shows the seasons that our planet Earth undergoes for the Northern Hemisphere. The position of the Earth is labeled for one of the key seasonal dates, the Autumnal (Fall) Equinox. Please label the other three positions correctly. Note the blue arrow on the circle of the Earth's orbit, which shows which way the Earth moves.
Autumnal Equinox (completely shaded) Winter Solstice (right side shaded) Vernal Equinox (no shading) Summer Solstice (left side shaded)
Problem 22: Light-Years and Light Travel Time
Because cosmic distances are so vast, astronomers use light-years as their unit of distance. One light-year is defined as *the distance light travels in a year*. The nearest star isa little more than *four* light-years away from us. When we see light from a galaxy 2million light-years away, it has taken *2 million years* to reach us. Light from the Sun takes *a little more than 8 minutes* to reach us.
Suppose you are on a strange planet and observe, at night, that the stars do not rise and set, but instead circle parallel to the horizon. You then walk in the same direction for 8910 miles, and at your new location on the planet you find that all stars rise straight up in the east and set straight down in the west. Based on these observations, what is the circumference, in miles, of this alien planet?
Circumference = 3.564×10^4 miles
Suppose Eratosthenes had found that in Alexandria at noon on the first day of summer, the line to the Sun makes an angle 13° with the vertical. How many times the distance between Syene and Alexandria would he have calculated the Earth's circumference to be?
Circumference of the Earth = 27.69 times the distance between the cities
The figure below illustrates the heliocentric model, but depicting only the orbits of Earth and Venus. Using the drag-and-drop environment, place the phases of Venus in the correct orbital position relative to Earth and the Sun where each phase would be seen as viewed from Earth.
Crescents (sliver not shaded) are between the earth and sun, half (half shaded) are to the left or right of the sun, and Gibbous (sliver shaded) are behind the sun
The orbit shown on the left has a semimajor axis of 1 (in arbitrary units)
D (ellipse with width of 2)
The light-year is a unit of:
Distance
The circumference of the giant planet Jupiter at its equator is 439,264 km. The diameter of planet Earth at its equator is 12,756 km. How many Earth diameters could we fit side by side into the circumference of Jupiter?
Earths = 34.44
A "New Age" bride and groom, who are enchanted by the Sun, want to get married on the day when it gets to be highest in the sky. If they live in the United States, around what day of the year will the wedding take place?
summer solstice
From which location could you observe all of the stars during the course of a year?
Equator
Problem 13: Ancient Thinkers (drag-and-drop)
Even though ancient thinkers considered the circle to be the perfect form and thus imagined that the planets followed orbits that were circles, in fact the orbit of a planet is in the shape of an *ellipse*. Planets orbit the Sun, which is located at one of the *foci* of this figure. The line across the widest part of this figure is called its *major axis*. Some of the planets' orbits are almost circles and others are more stretched out. *eccentricity* is a measure of how round or squashed the shape of the orbit is.
After studying the stars, astronomers have concluded that the most abundant element in the universe is oxygen.
FALSE
In the United States, at night, the direction north is always directly above your head.
FALSE
In the southern hemisphere, the longest nights (and shortest days) occur during their summer solstice in December.
FALSE
The Sun revolves around (orbits) the Earth in about 365 days (what we call one year.)
FALSE
The first coronavirus stimulus bill, signed into law March 2020 was for 2.2 trillion dollars. In scientific notation, this is written as 2.2 x 10^6.
FALSE
The main reason we on Earth have seasons is that the orbit of the Earth is an ellipse and we are sometimes further from the Sun and sometimes closer.
FALSE
The same side of the Moon (with the same craters) is always in sunlight and the other side of the Moon is always in darkness.
FALSE
According to the U.S. Census Bureau, the population of the U.S. in June 2019 was estimated at 329 million people. The population of the world was estimated at 7.58 billion people. Calculate what fraction of the world's population lived in the U.S. in 2019.
Fraction = 0.04340
The fastest human spaceship leaving the solar system is Voyager 1, which is traveling at 61,146 kilometers per hour. Imagine it is traveling to a star system 5.4 light-years away. Calculate how long, in years, it will take for Voyager 1 to arrive.
t = 9.530 × 10^4
The figure above shows the Moon's orbit as seen from above Earth's North Pole. What position (indicated by roman numeral) would the moon need to be for observers on Earth to see a lunar eclipse?
III (Earth is directly between it and the sun)
Problem 20: Travel Advice (drag-and-drop)
If you want to have 12 hours of day and 12 hours of night every day of the year, you should travel to the *equator*. If you want to see Sun directly overhead (at the zenith) on June 21, you need to travel to the circle of latitude known as *Tropic of Cancer*. If you want to see the Sun directly overhead on December 21, on the other hand, you must go to the *Tropic of Capricorn*. To see the Sun up for 24 hours on December 21, you must be at a latitude higher than the altitude of the *Antarctic Circle*. To be in darkness for 24 hours on the December 21, you must be at a latitude higher than the latitude of the *Arctic Circle*. (That's clearly why Santa Claus leaves his workshop around that time of year; it's too dark and depressing.)
The Earth is closest to the Sun in which month of the year?
January
Problem 19: Joe, Bernie, and Julian (drag-and-drop)
Joe, Bernie, and Julian are roommates in a big apartment building that has a nice roof garden. On a weekend day, they decide to spend all day in that garden while the Sun is up. They notice that the Sun is up for more than 14 hours that day. From this they conclude that the date must be near the *summer solstice*. Elizabeth and Kamala also live in the building, and also enjoy the roof garden. On another day, they are disappointed to find that the Sun is up less than 8 hours and then it's dark. They conclude that this date must be near the *winter solstice*. Donald and Mike live near that address, although there is a chance they might be moving, since they don't get along so well with the other tenants in their building. They go up to their roof three months after Joe, Bernie, and Julian have been there, and notice that there are 12 hours of daylight that day. They conclude that the date must be near the *autumnal equinox*.
Suppose astronomers find an Earth-like planet with 13 times the radius of the Earth. What must be the mass of this planet so that the gravitational force at the surface would be identical to the Earth's? Give your answer as a multiple of the Earth's mass (so entering 2 would be 2x the Earth's mass).
Mass = 169.0 times
When NASA and a group of astronomers sent up a spacecraft designed to find planets orbiting other stars, they named it after Kepler. Why was this an appropriate name?
Kepler figured out the rules of planetary motion, which planets in our solar system and planets elsewhere must obey
Suppose the Earth were tilted by 15 degrees instead of 23 degrees. What would be the latitude of the Arctic Circle? Answer in degrees.
Latitude = 75.00°
Problem 15: Some words are missing from the following related paragraph. (drag-and-drop)
Like all stable orbits, the orbits of this spacecraft will be in the shape of *an ellipse*. When the craft orbits the Earth, the point where it is closest to our planet is its *perigee*. When the craft is in orbit around the Sun, the point in its orbit when it's furthest from the Sun is its *aphelion*. As "planet Amazon" orbits the Sun, its speed will be the highest when it is at *perihelion*. If the craft's orbit has a significant difference between its closest and farthest point from the Sun, this means it will have *an eccentricity* greater than zero.
Suppose you live on a planet with a moon that makes one full trip around the planet with respect to the stars in about 12 days. How many degrees per day does the Moon move relative to the stars?
Movement = 30.00°
Using the drag-and-drop environment, correctly arrange the steps in the scientific method shown. Please use the drag-and-drop environment to label the missing parts of the figure. (Options: Hypothesis is supported by the test, Run experiment or collect data, Hypothesis is not supported by the test, Make a prediction, Form a hypothesis, and Make an observation.)
Make an observation \/ Form a hypothesis \/ Make a prediction \/ Run experiment or collect data Hypothesis is supported by the test [arrow to make a prediction] Hypothesis is not supported by test [arrow to form hypothesis]
In the units used in the U.S., the speed of light is roughly 670 million miles per hour. Using the information in the problem statement, find approximately how many miles there are in a light-year.
Miles in a light year = 5.873 × 10^12 miles
Why do astronauts (and cans of soft drink) float around in the International Space Station instead of falling?
the Station is falling around the Earth (and everything aboard is in free fall)
Which of the following is NOT an argument for showing that the Earth must be round:
the Sun is seen blocking different constellations in the course of a year
Which of the following is an important part of the reason it is hotter in summer in North America than in winter?
the Sun's rays hit the Earth more directly in the Summer, and spread out less
The Astronomical Unit (AU) as defined by astronomers is:
the average distance between the Earth and the Sun
A light-year is...
the distance that light travels in one year
In 1996, astronomers discovered an icy object beyond Pluto that was given the designation 1996 TL 55. it has a semimajor axis of 84 AU. What is its orbital period in years according to Kepler's third law?
Period = 769.9 years
When a planet temporarily moves westward in the sky over the course of several weeks or months (instead of eastward, as it typically does), we call it:
Retrograde Motion
Two stars are the same size and are located at the same distance from us. Star A has a surface temperature of 2800 K and star B has a surface temperature of 11200 K. How many times brighter will star B appear to us in the night sky as compared to star A?
Relative Brightness = 256.0 times
Some college students decide to form a secret society that would meet each year after graduation at a time when the day and night were the same length. Which of the following would be a time they could meet?
September 23
The figure below shows a blackbody spectrum. Based on Wien's Law, what temperature does this spectrum correspond to in Kelvins?
T = 5455 K
Astronomers call the point directly above your head in the sky your zenith.
TRUE
By looking billions of light-years out into space, astronomers are actually seeing billions of years into the past.
TRUE
If we condense the history of the universe since the Big Bang into one calendar year, in that year, human beings first appear on the last day of December.
TRUE
In its elliptical orbit, the Earth is closest to the Sun in January.
TRUE
On the autumn equinox, our days and nights are the same length.
TRUE
Of these which is the closest to us?
The Moon
Problem 9: Ancient Astronomical History (drag-and-drop)
The ancient Greeks had good arguments for why the Earth must be round. When the Earth's shadow is visible on the Moon during a lunar *eclipse*, it always shows a round shape. In the northern hemisphere, the height of the north star *decreases* as a traveler moves south. The size of the round Earth was measured by *Eratosthenes*; he measured the angle that sunlight made with a vertical line in different cities at the same time on the same day. In the second century BCE, Hipparchus measured and described *precession*, the idea that the north celestial pole (the point around which stars in the sky seem to turn) had changed its position over long periods of time. The astronomer *Ptolemy* made a geometric model of our solar system, with the Earth in the center, and circles upon circles to explain the movements of the planets in the sky.
From the list below, select the main reason that the following happens (match the phenomenon in the left column with the reason for it).
The cycle of day and night = The Earth turns The different amounts of daylight during the cycle of the seasons = The Earth's axis is tilted The phases of the Moon = The Moon orbits the Earth Eclipses don't happen every month = The Moon's orbit is tilted relative to the ecliptic
The figure above shows the Moon's orbit as seen from above Earth's North Pole. What position (indicated by roman numeral) would the moon be one week after observers on Earth see a solar eclipse?
V (It takes roughly four weeks for the moon to orbit Earth. Since VII was the solar eclipse to the left of Earth, and V was at the bottom of earth, that means that V would have been one week since it was a 25% rotation.)
The figure above shows the Moon's orbit as seen from above Earth's North Pole. What position (indicated by roman numeral) would the moon need to be for observers on Earth to see a total solar eclipse?
VII (it is directly between the sun and earth)
According to a recent survey, the chief executive at a fast-food company earned $23.7 million in one year, while the median wage of workers at the company was $7160 that year. Use scientific notation to figure out how many times the median wage the chief executive was earning.
Wage factor = 3310
Hydrogen is the most common element in the universe. (Harlan Ellison, a science fiction writer, popularized the expression "The two most common elements in the universe are hydrogen and stupidity.") Cold hydrogen between the stars tends to give off radio waves at a frequency of 1420 MHz (megahertz, or millions of cycles per second). What is the wavelength in meters of this radiation?
Wavelength = 0.2113 m
A carrier wave on a campus radio is broadcasting at a frequency f = 89.1 MHz. What is the wavelength of the carrier wave of this radio in meters?
Wavelength = 3.367 m
Consider an asteroid with an orbital period P = 7 years. What is the average distance, a, from the sun to the asteroid in astronomical units?
a = 3.659 AU
A friend of yours (who has not had the benefit of an astronomy course) tells you about a report he has read in a tabloid newspaper. They claim that on the dark side of the Moon, which is never in sunlight, there is a secret base of aliens who cannot stand light, and who send UFO's to Earth under the cover of darkness. Ignoring the UFO claim for a moment, what is the scientific error in this story?
all sides of the Moon are illuminated by sunlight in the course of a month; there is no dark side
From a city in the U.S., where in the sky would you look to see a star that is not turning with the motion of the sky in the course of a night?
at the north celestial pole
How fast do electromagnetic waves travel?
at the speed of light
How did Eratosthenes measure the size of the Earth?
by measuring the height of the Sun in the sky on the same day in two cities at different latitudes
According to Kepler's third law, there is a relationship between the time a planet takes to revolve around the Sun and its
distance from the sun
According to Kepler's 2nd Law, comets (which have eccentric orbits) should spend a lot more of their time:
far from the Sun
When it comes to our place in the solar system today, which model do we accept?
heliocentric
In Australia (in the Southern Hemisphere), when are the days the shortest and the nights the longest?
in late June
The idea that objects (in the absence of an outside force) tend to continue doing what they are already doing is called the law of
inertia
Which of the following statements about the force of gravity is FALSE?
its strength is inversely proportional to the mass: the more mass, the less gravity
In Newton's Law of Gravity, the force of gravity goes up as the:
more than one of these
When a planet, in its orbit, is closer to the Sun, it:
moves faster than average
A writer of mystery novels wants to portray something gruesome happening just as the full moon is at its highest point in the sky. What time of day will the gruesome event occur?
roughly midnight
If there really were a Santa Claus at the North Pole, what would the cycle of the seasons be like for him and Mrs. Claus?
six months of light, followed by six months of darkness (or at least dark twilight)
Which of the following statements about the nucleus of a typical atom (such as a carbon atom in your little finger) is FALSE:
the nucleus repels the electrons which move around it
The celestial sphere turns once around each day because:
the planet on which we live is rotating
In Ptolemy's system, the planets orbit the Earth and not the Sun. How did the system explain the retrograde motion of planets like Jupiter?
the planets moved on a small circle whose center, in turn, circled a point near the Earth
The period of the moon's rotation on its axis is:
the same as its revolution around the Earth
Someone who observes the sky every clear night in Boston for many years will NEVER get to see:
the south circumpolar zone
The point in the sky directly above your head at any given time is called the:
zenith
