Chapter 3- Astronomy
EarlyCopernicanRevolution(about1543−1600)
Copernicus proposes Sun-centered model Planetary observations accurate within 1 minute of arc
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.
This figure shows the circle on circle motion of a planet in the Ptolemaic model. At which point(s) is the planet in the middle of its period of retrograde motion in our sky?
2 only
Earth-Centered only
A planet beyond Saturn rises in west, sets in east
Look carefully at this telescopic photo of the Moon. All the following statements are true. Which one is proved by the fact that the line dividing the dark and bright regions is not perfectly straight?
The Moon's surface is not perfectly smooth but rather has mountains and valleys.
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.
Assume you knew nothing else about the planets but what is shown in this diagram. What could you conclude?
The square of a planet's period in years is equal to the cube of its average distance from the Sun in AU.
Which of these hypothetical observations (none of them are real) would force us to reconsider our modern, 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.
Neither model
We sometimes see a crescent Jupiter
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.
We never see a crescent Jupiter from Earth because Jupiter __________.
is farther than Earth from the Sun
When would you expect to see Venus high in the sky at midnight?
never
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
This diagram shows a planet at four points in its orbit around the Sun. At which of the points shown is it traveling slowest in its orbit? (The planet is not real, as all the planets of our solar system have orbits much more circular than the one shown.)
4
Which of these four ellipses has the greatest eccentricity?
4
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.
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.
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 8 days instead of 7.
Central Africans learned long ago to use observations of the waxing crescent moon (once each month) to predict when the rainy season was coming. Use the graph for Central Africa. In what month(s) does this region get about 200 millimeters of rainfall?
April and August
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.
Jupiter orbits the Sun at an average distance of 5.203 AU and takes 11.86years to complete each orbit. Based on these facts, which statement is true?
11.86^2=5.203^3 Kepler's third law can be stated mathematically as p2=a3, where p is the planet's orbital period in years and a is its average orbital distance in AU.
Kepler's first law states that the orbit of each planet is an ellipse with the Sun at one focus. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's first law?
Earth is slightly closer to the Sun on one side of its orbit than on the other side. The Sun is located slightly off-center from the middle of each planet's orbit.
Only one of the statements that follow uses the term theory in its correct, scientific sense. Which one?
Einstein's theory of relativity has been tested and verified thousands of times.
In Carl Sagan's statement "Extraordinary claims require extraordinary evidence," what does he mean by "extraordinary evidence"?
Evidence that is extremely strong.
Which of the following were key pieces of evidence that led to widespread acceptance of the Sun-centered model "extraordinary claim" during the period from about 1609 to 1630?
Galileo's telescopic observations. The fact that Kepler's laws allowed virtually perfect prediction of planetary positions.
Kepler's third law states that a planet's orbital period, p, is related to its average (semimajor axis) orbital distance, a, according to the mathematical relationship p2=a3. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's third law?
Inner planets orbit the Sun at higher speed than outer planets. Venus orbits the Sun faster than Earth orbits the Sun.
How does a 12-month lunar calendar differ from our 12-month solar calendar?
It has about 11 fewer days.
Scientific thinking is _________.
based on everyday ideas of observation and trial-and-error experiments
This diagram shows a graphical interpretation of Kepler's third law. Suppose there were a planet in our solar system that orbited the Sun with an average speed of 11 km/s. In terms of its average distance, this planet would be located:
between Jupiter and Saturn
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.
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
Why wasn't the Sun-centered model of Copernicus immediately adopted after he proposed it?
it was not noticeably more accurate than the old Ptolemaic model
Consider again the diagrams from Part D, which are repeated here. Again, imagine that you observed the asteroid as it traveled for one week, starting from each of the positions shown. This time, rank the positions from left to right based on the distance the asteroid will travel during a one-week period when passing through each location, 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.
look up
Consider again the diagrams from Parts A and B, which are repeated here. Again, assume that all the shaded areas have exactly the same area. This time, rank the segments of the comet's orbit based on the speed with which the comet moves when traveling from Point 1 to Point 2, 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.
look up
Consider again the diagrams from Parts D and E, which are repeated here. Again, imagine that you observed the asteroid as it traveled for one week, starting from each of the positions shown. This time, rank the positions (A-D) from left to right based on how fast the asteroid is moving at each position, 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.
look up
Part complete Consider again the diagrams from Part A, which are repeated here. Again, assume that all the shaded areas have exactly the same area. This time, rank the segments of the comet's orbit from left to right based on the distance the comet travels when moving from Point 1 to Point 2, 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.
look up
Parts A through C all refer to the orbit of a single comet around the Sun. Each of the four diagrams below represents the orbit of the same comet, but each one shows the comet passing through a different segment of its orbit around the Sun. During each segment, a line drawn from the Sun to the comet sweeps out a triangular-shaped, shaded area. Assume that all the shaded regions have exactly the same area. Rank the segments of the comet's orbit from left to right based on the length of time it takes the comet to move from Point 1 to Point 2, 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.
look up
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.)
look up
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.)
look up
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.)
Look up
All of the following statements are true. Which one can be explained by Kepler's second law?
Mars moves faster in its orbit when it is closer to the Sun than when it is farther from the Sun.
NewtonandBeyond(afterabout1687)
Mathematical description of how gravity determines planetary orbits Observations of stellar parallax
Sun-centered only
Mercury goes through a full cycle of phases position of nearby stars shift slightly back and forth each year
Real (True Statement)
Mercury goes through fulll cycle of phases moon rises in east, sets in the west a distant galaxy rises in the east, sets in west each day stars circle daily around north or south celestial pole positions of nearby stars shift slightly back and forth each year
Both Models
Moon rises in east, sets in west a distant galaxy rises in east, sets in west each day stars circle daily around north or south celestial pole
As you learned in the video, Galileo's observations of Venus in gibbous (nearly full) phase showed conclusively that Venus orbits the Sun, not Earth. Which figure shows Venus's position when Galileo saw it in gibbous phase?
Notice that the gibbous phase occurs when Venus is farther from Earth than the Sun, and this could never happen in Ptolemy's system. That is how Galileo concluded that Venus must orbit the Sun.
Which of the following was not observed by Galileo?
Stellar parallax
AncientGreeceThroughPtolemy(about150A.D.)
Suggestion that Earth might orbit the Sun Recognition that Sun-centered model should lead to stellar parallax Ability to predict planetary positions within a few degrees of arc
What, if anything, is wrong with the planetary orbit shown?
The Sun is not at one focus, as Kepler's first law requires.
You discover an asteroid that orbits the Sun with the same 1-year orbital period as Earth. Which of the following statements must be true?
The asteroid's average (semimajor axis) distance from the Sun is 1AU.
Falsifiable (could be proven false)
The chemical content of the universe is mostly hydrogen and helium. Earth is at the center of the solar system. The Sun is at the center of the solar system. The observable universe contains approximately 100 billion galaxies.
The video states that the planetary orbits are shown to scale. Which statement correctly describes the way the planet sizes are shown compared to their orbits?
The planets are all much too large compared to their orbits.
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.
Not falsifiable (could not be proven false
The universe was created by God. The laws of nature are magnificent and beautiful. We are all playthings in a computer program created by advanced aliens
All of the following statements are true. Which one can be explained by Kepler's third law?
Venus orbits the Sun at a faster orbital speed than Earth.
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.
Which of the following can you observe about Venus with the naked eye? Select all that apply.
Venus sometimes shines brightly in the eastern sky shortly before dawn Venus sometimes shines brightly in the western sky shortly after sunset
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.
We'll now leave the comet behind, and instead consider the orbit of an asteroid in Parts D through F. Each of the four diagrams below represents the orbit of the same asteroid, but each one shows it in a different position along its orbit of the Sun. Imagine that you observed the asteroid as it traveled for one week, starting from each of the positions shown. Rank the positions based on the area that would be swept out by a line drawn between the Sun and the asteroid during the one-week period, from largest to smallest. 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.
look up
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.)
look up for diagram ^^
Which of the following orbits has the largest semimajor axis?
look up for picture
Which of the following orbits is the most eccentric?
look up for picture
Which of the following orbits shows the planet at aphelion?
look up for picture
Scientific models are used to _________.
make specific predictions that can be tested through observations or experiments
What do we mean by a geocentric model of the universe?
model designed to explain what we see in the sky while having the Earth located in the center of the universe.
In Ptolemy's Earth-centered model, when would Venus appear directly behind the Sun as viewed from Earth?
never
Study this diagram, which shows why we see phases of Venus, as first observed by Galileo. When should we expect to see a full Venus in our night sky?
never
Galileo challenged the idea that objects in the heavens were perfect by _________.
observing sunspots on the Sun and mountains on the Moon
The shadow cast by a simple stick or obelisk allowed ancient people to
tell the time of day
An original observation of Galileo's that helped to overturn the ancient Earth-centered model was
the phases of Venus
Consider the hypothetical observation "a planet beyond Saturn rises in west, sets in east." This observation is not consistent with a Sun-centered model, because in this model __________.
the rise and set of all objects depends only on Earth's rotation
The names of the 7 days of the week are based on _________.
the seven naked-eye objects that appear to move among the constellations
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
The Metonic cycle is
used to keep lunar calendars approximately synchronized with solar calendars.
Based on the video, which Venus phase would be impossible to see (from Earth) if Venus orbited Earth as described in Ptolemy's Earth-centered model?
gibbous (nearly full)
Part complete Which of the following paths could not be a real orbit for a planet around the Sun?
Look up for picture
LaterCopernicanRevolution(about1609−1630)
Ability to predict planetary positions within 1 minute of arc Observation of phases of Venus Sun-centered model with elliptical orbits
What was the Ptolemaic model?
An Earth-centered model of planetary motion published by Ptolemy
Earth is slightly closer to the Sun in January than in July. How does the area swept out by Earth's orbit around the Sun during the 31 days of January compare to the area swept out during the 31 days of July?
Both areas are the same.
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 used perfect circles for the orbits of the planets
Falsifiable (could be proven false)
Kennedy was the 35th president of the United States. Kennedy died from a bullet in his brain.
Not falsifiable (could not be proven false
Kennedy's death was the will of God. The murder of John F. Kennedy was an act of evil. If he'd lived, Kennedy would have ended the Vietnam War. Kennedy's murder was orchestrated by an undetectable shadow government of the United States.
In which of the four time periods did the Sun-centered model gain widespread acceptance, meaning that nearly everyone who looked at the evidence concluded that it was correct?
Later Copernican Revolution (about 1609-1630)
Each of these photos shows an ancient structure used for astronomical purposes. Which one is located in the United States?
PPt and Look up
Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun?
Phases of Venus
Kepler's second law states that as a planet orbits the Sun, it sweeps out equal areas in equal times. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's second law?
Pluto moves faster when it is closer to the Sun than when it is farther from the Sun.
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 are the three key hallmarks of science?
Science progresses through the creation and testing of models of nature that explain the observations as simply as possible Models must make testable predictions that will force us to revise or abandon the model if they do not agree with observations. Modern science seeks explanations for observed phenomena that rely solely on natural causes.
Which of the following statements about an ellipse is not true?
The focus of an ellipse is always located precisely at the center of the ellipse.
Which of the following is not one of, nor a direct consequence of, Kepler's Laws?
The force of attraction between any two objects decreases with the square of the distance between their centers.
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?
Winter
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
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
When would a new Venus be highest in the sky?
at noon
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
Earth is located at one focusof the Moon's orbit.
focus
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
Not real (false statements)
we sometime see a crescent jupiter a planet beyond Saturn rises in west, sets in east
