Astronomy Exam 1

Flashcard maker : Rae Jordan
Which of the following has your \”cosmic address\” in the correct order?
You, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe.
Using the ideas discussed in your textbook, in what sense are we \”star stuff\”?
Nearly every atom from which we are made was once inside of a star.
How are galaxies important to our existence?
Galaxies recycle material from one generation of stars to the next, and without this recycling we could not exist.
When we look at an object that is 1,000 light-years away we see it _________.
as it was 1,000 years ago
Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In that case _________.
we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2
Suppose we make a scale model of our solar system, with the Sun the size of a grapefruit. Which of the following best describes what the planets would look like?
The planets are all much smaller than the Sun. Four planets are within about 20 meters of the Sun, while the rest planets are spread much farther apart.
If you could count stars at a rate of about one per second, how long would it take to count all the stars in the Milky Way Galaxy?
Several thousand years
The total number of stars in the observable universe is about _________.
Where is our solar system located within the Milky Way Galaxy?
If we imagine the history of the universe compressed into one year, dinosaurs became extinct _________.
yesterday morning
Relative to the age of the universe, how old is our solar system?
It is about one-third the age of the universe.
How do the speeds at which we are moving with Earth’s rotation and orbit compare to the speeds of more familiar objects?
Earth’s rotation carries most people around the axis faster than a commercial jet travels, and Earth’s orbit carries us around the Sun faster than the Space Shuttle orbits Earth
Why do the patterns of the stars in our sky look the same from year to year?
Because the stars in the constellations are so far away
Astronomers infer that the universe is expanding because distant galaxies all appear to _________.
be moving away from us, with more distant ones moving faster
Which statement about motion in the universe is not true?
The mysterious dark matter is the fastest-moving material in the universe.
When did humans learn that the Earth is not the center of the universe?
Within the past 500 years.
Which of the following statements about the celestial sphere is NOT true?
The \”celestial sphere\” is another name for our universe.
The Andromeda Galaxy is faintly visible to the naked eye in the constellation Andromeda. Suppose instead it were located in the same direction in space as the center of the Milky Way Galaxy (but still at its current distance). How would it appear to the eye in that case?
We could not see it at all.
An angle of 1 arcsecond is _________.
less than the thickness of a human hair held at arm’s length
When traveling north from the United States into Canada, you’ll see the North Star (Polaris) getting _________
higher in the sky
Suppose you use the Southern Cross to determine that the south celestial pole appears 40 degrees above your horizon. Then you must be located at _________.
latitude 40 degrees south
Suppose you are facing north and you see the Big Dipper close to your northern horizon, with Polaris (and the Little Dipper) above it. Where will you see the Big Dipper in six hours?
To the right of Polaris; that is, 90 degrees counterclockwise from its current position.
In any particular place on Earth, certain constellations are visible in the evening only at certain times of the year because _________.
our evening view of space depends on where Earth is located in its orbit around the Sun
The Sun’s path, as viewed from the equator, is highest in the sky on _________.
the spring and fall equinoxes
Suppose Earth’s axis tilt was significantly greater than its current 23.5 degrees, but Earth’s rotation period and orbital period were unchanged. Which statement below would not be true?
The length of each season (for example, the number of days from the summer solstice to the fall equinox) would be significantly longer than it is now.
If our year were twice as long (that is, if Earth took twice as many days to complete each orbit around the Sun), but Earth’s rotation period and axis tilt were unchanged, then _________.
the four seasons would each be twice as long as they are now
How does Earth’s varying distance from the Sun affect our seasons?
It doesn’t — Earth’s orbital distance plays no significant role in the seasons.
Suppose you live in the United States and you see a crescent moon in your evening sky tonight. What will a friend in South America see tonight?
Your friend will also see a crescent moon.
Suppose it is full moon. What phase of Earth would someone on the Moon see at this time?
New Earth.
It’s 6 am and the Moon is at its highest point in your sky (crossing the meridian). What is the Moon’s phase?
Third quarter.
You observe a full moon rising at sunset. What will you see at midnight?
A full moon high in the sky.
All the following statements are true. Which one explains the reason that there is not a solar eclipse at every new moon?
The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane
For most of history, the lack of observable stellar parallax was interpreted to mean that _________.
Earth is stationary at the center of the universe
During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space?
Earth is catching up with and passing by Mars in their respective orbits.
Suppose you see a photo showing Jupiter half in sunlight and half in shadow (that is, a first quarter Jupiter). This photo might have been taken by _________.
the Galileo spacecraft that orbited Jupiter in the 1990s
About how many stars are visible to the naked eye on a clear, dark night away from city lights?
A couple thousand.
What do astronomers mean by a constellation?
A constellation is a region in the sky as seen from Earth
What is the ecliptic?
The path the Sun appears to trace around the celestial sphere each year.
What is the celestial sphere?
The celestial sphere is a representation of how the entire sky looks as seen from Earth.
What do we mean when we talk about the Milky Way in our sky?
The patchy band of light that outlines the plane of the Milky Way Galaxy as seen from Earth.
Which of the following statements does not use the term angular size or angular distance correctly?
The angular distance between those two bright stars in the sky is about 2 meters.
Which of the following correctly describes the meridian in your local sky?
A half-circle extending from your horizon due north, through your zenith, to your horizon due south.
The point directly over your head is called _________.
the zenith
Stars that are visible in the local sky on any clear night of the year, at any time of the night, are called _________.
We describe a location on Earth’s surface by stating its _________.
latitude and longitude
If you are located in the Northern Hemisphere, which of the following correctly describes a relationship between the sky and your location?
The altitude of the north celestial pole equals your latitude
Which of the following best describes why we have seasons on Earth?
The tilt of Earth’s axis causes different portions of the Earth to receive more or less direct sunlight at different times of year.
Each choice below describes how a few astronomical phenomena are related to time periods. Which list is entirely correct? (Careful: some lists are partially correct.)
Earth’s rotation defines a day.
The cycle of the Moon’s phases takes about a month.
Earth’s orbit defines a year.
Earth’s cycle of axis precession takes 26,000 years.
Earth’s rotation defines a day.
If we have a new moon today, when we will have the next full moon?
In about 2 weeks.
We cannot see a new moon in our sky because _________.
a new moon is quite near the Sun in the sky
The Moon always shows nearly the same face to Earth because ________.
Lunar eclipses can occur only during a _________.
What is the saros cycle?
The roughly 18-year cycle over which the pattern of eclipses repeats.
During the time that a planet is in its period of apparent retrograde motion: _________
Over many days or weeks, the planet moves westward relative to the stars, rather than the usual eastward relative to the stars.
What is stellar parallax?
It is the slight back-and-forth shifting of star positions that occurs as we view the stars from different positions in Earth’s orbit of the Sun
Suppose the planet Uranus were much brighter in the sky, so that it was as easily visible to the naked eye as Jupiter or Saturn. Which one of the following statements would most likely be true in that case?
A week would have eight days instead of seven.
How does a 12-month lunar calendar differ from our 12-month solar calendar?
It has about 11 fewer days.
Which of the following best describes a set of conditions under which archaeoastronomers would conclude that an ancient structure was used for astronomical purposes?
The structure has holes in the ceiling that allow viewing the passage of constellations that figure prominently in the culture’s folklore, and many other structures built by the same culture have ceiling holes placed in the same way.
How did the Ptolemaic model explain the apparent retrograde motion of the planets?
The planets moved along small circles that moved on larger circles around the Earth.
When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not?

Copernicus misjudged the distances between the planets.

Copernicus used perfect circles for the orbits of the planets.
Earth is farthest from the Sun in July and closest to the Sun in January. During which Northern Hemisphere season is Earth moving fastest in its orbit?
According to Kepler’s third law (p2 = a3), how does a planet’s mass affect its orbit around the Sun?
A planet’s mass has no effect on its orbit around the Sun.
All the following statements are true. Which one follows directly from Kepler’s third law (p2 = a3)?
Venus orbits the Sun at a slower average speed than Mercury.
Suppose a comet orbits the Sun on a highly eccentric orbit with an average (semimajor axis) distance of 1 AU. How long does it take to complete each orbit, and how do we know?
1 year, which we know from Kepler’s third law.
Galileo challenged the idea that objects in the heavens were perfect by ___
observing sunspots on the Sun and mountains on the Moon
Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun?
phases of Venus.
Which of the following is not consistent with the major hallmarks of science?
Science consists of proven theories that are understood to be true explanations of reality.
Which of the following is not part of a good scientific theory?
A scientific theory cannot be accepted until it has been proven true beyond all doubt.
Only one of the statements below uses the term theory in its correct, scientific sense. Which one?
Einstein’s theory of relativity has been tested and verified thousands of times.
The astrology practiced by those who cast predictive horoscopes can be tested by __________
comparing how often the predictions come true to what would be expected by pure chance.
Imagine for a moment that despite all the evidence, Earth actually is not rotating and orbiting the Sun. Which of these hypothetical observations (none of them are real) would be inconsistent with our Sun-centered view of the solar system?
We discover a small planet beyond Saturn that rises in the west and sets in the east each day.
What practical value did astronomy offer to ancient civilizations?
It helped them keep track of time and seasons, and it was used by some cultures for navigation.
Scientific thinking is _________.
based on everyday ideas of observation and trial-and-error experiments
The names of the seven days of the week are based on _________.
the seven naked-eye objects that appear to move among the constellations
The Metonic cycle is
used to keep lunar calendars approximately synchronized with solar calendars
Ptolemy was important in the history of astronomy because he _________.
developed a model of the solar system that made sufficiently accurate predictions of planetary positions to remain in use for many centuries
The ancient Greeks get a lot of attention for their contributions to science because _________.
they were the first people known to try to explain nature with models based on reason and mathematics, without resort to the supernatural
What do we mean by a geocentric model of the universe?
A model designed to explain what we see in the sky while having the Earth located in the center of the universe.
What was the Ptolemaic model?
An Earth-centered model of planetary motion published by Ptolemy.
The great contribution of Nicholas Copernicus was to _________.
create a detailed model of our solar system with the Sun rather than Earth at the center
The great contribution of Tycho Brahe was to _________
observe planetary positions with sufficient accuracy so that Kepler could later use the data to discover the laws of planetary motion
Which of the following was not observed by Galileo?
Stellar parallax.
Which of the following statements about an ellipse is not true?
Which of the following is not one of, nor a direct consequence of, Kepler’s Laws?
Scientific models are used to _________
make specific predictions that can be tested through observations or experiments
In science, a broad idea that has been repeatedly verified so as to give scientists great confidence that it represents reality is called _________.
a theory
Which of the following best describes how modern astronomers view astrology?
Astrology played an important part in the development of astronomy in ancient times, but it is not a science by modern standards.
Which of the following represents a case in which you are not accelerating?
Driving in a straight line at 60 miles per hour.
Suppose you drop a 10-pound weight and a 5-pound weight on the Moon, both from the same height at the same time. What will happen?
Both will hit the ground at the same time.
Why are astronauts weightless in the Space Station?
Because the Space Station is constantly in free-fall around the Earth.
A net force acting on an object will always cause a change in the object’s _________.
Suppose you are in an elevator that is traveling upward at constant speed. How does your weight compare to your normal weight on the ground?
It is the same.
The planets never travel in a straight line as they orbit the Sun. According to Newton’s second law of motion, this must mean that _________.
a force is acting on the planets
Suppose the Sun were suddenly to shrink in size but that its mass remained the same. According to the law of conservation of angular momentum, what would happen?
The Sun would rotate faster than it does now.
Suppose you kick a soccer ball straight up to a height of 10 meters. Which of the following is true about the gravitational potential energy of the ball during its flight?
The ball’s gravitational potential energy is greatest at the instant when the ball is at its highest point.
Suppose you heat an oven to 400^{circ}F and boil a pot of water. Which of the following explains why you would be burned by sticking your hand briefly in the pot but not by sticking your hand briefly in the oven?
The water can transfer heat to your arm more quickly than the air.
Which of the following scenarios involves energy that we would typically calculate with Einstein’s formula E=mc2?
A small amount of the hydrogen in of a nuclear bomb becomes energy as fusion converts the hydrogen to helium.
A rock held above the ground has potential energy. As the rock falls, this potential energy is converted to kinetic energy. Finally, the rock hits the ground and stays there. What has happened to the energy?
The energy goes to producing sound and to heating the ground, rock, and surrounding air.
Suppose that the Sun shrank in size but that its mass remained the same. What would happen to the orbit of the Earth?
Earth’s orbit would be unaffected
Imagine another solar system, with a star of the same mass as the Sun. Suppose a planet with a mass twice that of Earth (2MEarth) orbits at a distance of 1 AU from the star. What is the orbital period of this planet?
1 year.
Imagine another solar system, with a star more massive than the Sun. Suppose a planet with the same mass as Earth orbits at a distance of 1 AU from the star. How would the planet’s year (orbital period) compare to Earth’s year?
The planet’s year would be shorter than Earth’s.
Newton showed that Kepler’s laws are _________.
natural consequences of the law of universal gravitation
Each of the following lists two facts. Which pair of facts can be used with Newton’s version of Kepler’s third law to determine the mass of the Sun?
Earth is 150 million km from the Sun and orbits the Sun in one year.
When space probe Voyager 2 passed by Saturn, its speed increased (but not due to firing its engines). What must have happened?
Saturn must have lost a very tiny bit of its orbital energy.
Suppose that a lone asteroid happens to be passing Jupiter on an unbound orbit (well above Jupiter’s atmosphere and far from all of Jupiter’s moons.) Which of the following statements would be true?
The asteroid’s orbit around Jupiter would not change, and it would go out on the same unbound orbit that it came in on
Which of the following best describes the origin of ocean tides on Earth?
Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the Earth.
At which lunar phase(s) are tides most pronounced (for example, the highest high tides)?
Both new and full moons.
Which of the following best explains why the Moon’s orbital period and rotation period are the same?
The Moon once rotated faster, but tidal friction slowed the rotation period until it matched the orbital period.
Suppose the Moon’s orbit were unchanged, but it rotated faster (meaning it did not have synchronous rotation). Which of the following would be true?
We would no longer always see nearly the same face of the Moon.
The difference between speed and velocity is that _________.
velocity also includes a direction
The acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8 m/s2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?
30 m/s.
Momentum is defined as _________.
mass times velocity
Suppose you lived on the Moon. Which of the following would be true?
Your weight would be less than your weight on Earth, but your mass would be the same as it is on Earth.
In which of the following cases would you feel weightless?
While falling from a roof.
Which of the following statements is not one of Newton’s Laws of Motion?
What goes up must come down.
Newton’s Second Law of Motion tells us that the net force applied to an object equals its _________.
mass times acceleration
Suppose that two objects collide. Which of the following things is not the same both before and after the collision?
The total temperature of the objects
When a spinning ice skater pulls in his arms, he spins faster because _________.
his angular momentum must be conserved, so reducing his radius must increase his speed of rotation
The energy attributed to an object by virtue of its motion is known as _________.
kinetic energy
Radiative energy is _________.
energy carried by light
Absolute zero is _________.
0 Kelvin
What does temperature measure?
The average kinetic energy of particles in a substance
In the formula E=mc2, what does E represent?
The mass-energy, or potential energy stored in an object’s mass
According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them _________.
decreases by a factor of 9
What is the difference between a bound orbit and an unbound orbit around the Sun?
An object on a bound orbit follows the same path around the Sun over and over, while an object on an unbound orbit approaches the Sun just once and then never returns.
The allowed shapes for the orbits of objects responding only to the force of gravity are ______.
ellipses, parabolas, and hyperbolas
Why is Newton’s version of Kepler’s third law so useful to astronomers?
It can be used to determine the masses of many distant objects.
What do we mean by the orbital energy of an orbiting object (such as a planet, moon, or satellite)?
Orbital energy is the sum of the object’s kinetic energy and its gravitational potential energy as it moves through its orbit.
Which statement must be true in order for a rocket to travel from Earth to another planet?
It must attain escape velocity from Earth.
Approximately where is it currently high tide on Earth?
On the portion of Earth facing directly toward the Moon and on the portion of Earth facing directly away from the Moon

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