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?
answer
1 year, which we know from Kepler's third law
Kepler's third law tells us that any object with the same average distance as Earth will orbit in the same time of 1 year.
question
Galileo challenged the idea that objects in the heavens were perfect by _________.
answer
observing sunspots on the Sun and mountains on the Moon
Both the Sun and Moon had been generally assumed to have "perfect" surfaces.
question
Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun?
A. Phases of Venus
B. Patterns of shadow and sunlight near the dividing line between the light and dark portions of the Moon's face
C. The Milky Way is composed of many individual stars.
D. Four moons of Jupiter.
answer
A. Phases of Venus
Galileo's observed that Venus goes through all the phases, which cannot be explained unless Venus is orbiting the Sun. (In the Ptolemaic system, Venus's phases vary only from new to crescent and back.)
question
Which of the following is not consistent with the major hallmarks of science?
A. Science progresses through the creation and testing of models that explain observation as simply as possible.
B. Scientific explanations should be based solely on natural causes.
C. Science consists of proven theories that are understood to be true explanations of reality.
D. A scientific model must make testable predictions.
answer
C. Science consists of proven theories that are understood to be true explanations of reality.
This is statement is not consistent with the hallmarks of science because scientific theories can never be proven beyond all doubt
question
Which of the following is not part of a good scientific theory?
A. A scientific theory must explain a wide variety of phenomena observed in the natural world.
B. A scientific theory must make testable predictions that, if found to be incorrect, could lead to its own modification or demise.
C. A scientific theory should be based on natural processes and should not invoke the supernatural or divine.
D. A scientific theory cannot be accepted until it has been proven true beyond all doubt.
answer
D. A scientific theory cannot be accepted until it has been proven true beyond all doubt
Scientific theories can never be proven true beyond all doubt; they can only be supported by a wide body of evidence.
question
Only one of the statements that follow uses the term theory in its correct, scientific sense. Which one?
A. I wrote a theory that is 152 pages long.
B. Evolution is only a theory, so there's no reason to think it really happened.
C. I have a new theory about the cause of earthquakes, and I plan to start testing it soon.
D. Einstein's theory of relativity has been tested and verified thousands of times.
answer
D. Einstein's theory of relativity has been tested and verified thousands of times.
The term theory is used in its correct scientific sense in this statement.
question
The astrology practiced by those who cast predictive horoscopes can be tested by __________
answer
comparing how often the predictions come true to what would be expected by pure chance.
And in such tests, astrological predictions have never proven to be more successful than is expected by chance
question
Which of these hypothetical observations (none of them are real) would force us to reconsider our modern, Sun-centered view of the solar system?
A. We discover that the universe is actually contracting, not expanding.
B. We discover a small planet beyond Saturn that rises in the west and sets in the east each day.
C. We discover an Earth-sized planet orbiting the Sun beyond the orbit of Pluto.
D. We find that we are unable to measure any parallax for a distant galaxy.
answer
We discover a small planet beyond Saturn that rises in the west and sets in the east each day
If Earth is rotating from west-to-east, then all celestial objects must move from east to west across our sky. (The only exception is satellites in low-Earth orbit, where they orbit faster than Earth rotates.) So a planet going in the opposite direction across the sky would pose a direct challenge to our view of Earth as a rotating planet
question
What practical value did astronomy offer to ancient civilizations?
answer
It helped them keep track of time and seasons, and it was used by some cultures for navigation.
Indeed, before the advent of mechanical or electrical clocks, the sky provided the only reliable means of timekeeping
question
Scientific thinking is _________.
answer
based on everyday ideas of observation and trial-and-error experiments
In that sense, modern science is just a formalization of ideas that innate to human beings.
question
The names of the 7 days of the week are based on _________.
answer
the seven naked-eye objects that appear to move among the constellations
These seven objects are the Sun (Sunday), the Moon (Monday), Mars (Tuesday), Mercury (Wednesday), Jupiter (Thursday), Venus (Friday), and Saturn (Saturday).
question
The Metonic cycle is
answer
used to keep lunar calendars approximately synchronized with solar calendars.
The Metonic cycle is the 19-year period over which the lunar phases occur on about the same dates, so using it ensures that a lunar calendar begins on the same solar date every 19 years.
question
Ptolemy was important in the history of astronomy because he _________.
answer
developed a model of the solar system that made sufficiently accurate predictions of planetary positions to remain in use for many centuries
His model was the culmination of the work of many other Greek astronomers in developing the Greek geocentric (Earth-centered) model of the universe.
question
The ancient Greeks get a lot of attention for their contributions to science because _________.
answer
they were the first people known to try to explain nature with models based on reason and mathematics, without resort to the supernatural
Although ancient Greek science was still different from modern science, many of the ideas of modern science originated in ancient Greece
question
What do we mean by a geocentric model of the universe?
answer
A model designed to explain what we see in the sky while having the Earth located in the center of the universe.
The geocentric model developed in ancient Greece and was generally accepted until the time of the Copernican revolution.
question
What was the Ptolemaic model?
answer
An Earth-centered model of planetary motion published by Ptolemy
The Ptolemaic model was published in about A.D. 150 and held sway for nearly the next 1,500 years.
question
The great contribution of Nicholas Copernicus was to _________.
answer
create a detailed model of our solar system with the Sun rather than Earth at the center
Although his model still had numerous flaws, it started the Copernican revolution and ultimately led to our modern understanding of the cosmos.
question
The great contribution of Tycho Brahe was to _________.
answer
observe planetary positions with sufficient accuracy so that Kepler could later use the data to discover the laws of planetary motion
Tycho's naked eye observations were accurate to within about 1 arcminute, making them far superior to any prior set of observations
question
Which of the following was not observed by Galileo?
A. Four moons orbiting Jupiter
B. Phases of Venus
C. Stellar parallax
D. Mountains and valleys on the Moon
answer
C. Stellar Parallax
Stellar parallax, which essentially offers direct proof that the Earth orbits the Sun, was not observed until some two centuries after Galileo.
question
Which of the following statements about an ellipse is not true?
A. The focus of an ellipse is always located precisely at the center of the ellipse.
B. The semimajor axis of an ellipse is half the length of the longest line that you can draw across an ellipse.
C. An ellipse with a large eccentricity looks much more elongated (stretched out) than an ellipse with a small eccentricity.
D. A circle is considered to be a special type of ellipse.
answer
A. The focus of an ellipse is always located precisely at the center of the ellipse.
An ellipse has two foci (not one), and neither one is located at the center of the ellipse unless the ellipse happens to be a perfect circle
question
Which of the following is not one of, nor a direct consequence of, Kepler's Laws?
A. The orbit of each planet about the Sun is an ellipse with the Sun at one focus.
B. As a planet moves around its orbit, it sweeps out equal areas in equal times.
C. A planet or comet in a noncircular orbit travels faster when it is nearer to the Sun and slower when it is farther from the Sun.
D. More distant planets orbit the Sun at slower speeds.
E. The force of attraction between any two objects decreases with the square of the distance between their centers.
answer
E. The force of attraction between any two objects decreases with the square of the distance between their centers.
This is part of Newton's universal law of gravitation, not Kepler's laws of planetary motion. (Note: although some might argue that Kepler's laws imply the inverse square law for gravity, the implication is clearly not direct; if it was, it wouldn't have taken some 70 years between the publication of the laws and the time when Newton explained them as consequences of the universal law of gravitation.)
question
Scientific models are used to _________.
answer
make specific predictions that can be tested through observations or experiments
A "model" that does not make such predictions cannot be tested and hence is not scientific.
question
In science, a broad idea that has been repeatedly verified so as to give scientists great confidence that it represents reality is called _________.
answer
a theory
Notice that this scientific definition of theory differs from the way the term is often used in everyday life
question
Which of the following best describes how modern astronomers view astrology?
A. Astrology is a synonym for astronomy.
B. Astrology is new age mumbo-jumbo that was a waste of time when it was invented thousands of years ago and remains a waste of time today.
C. Astrology was a great idea until it was disprove by the work of Copernicus, Tycho, Kepler, and Galileo.
D. Astrology played an important part in the development of astronomy in ancient times, but it is not a science by modern standards.
answer
D. Astrology played an important part in the development of astronomy in ancient times, but it is not a science by modern standards.
Whenever predictions of astrology have been tested, they have proven accurate only about as often as would be expected by pure chance
question
Summarize the development of the Greek geocentric model through Ptolemy. How did the Ptolemaic model account for apparent retrograde motion?
answer
The Ptolemiac model was able to explain retrograde motion by having the planets move on smaller circles attached to the larger circles on which they went around Earth.
question
In the Greek geocentric model, the retrograde motion of a planet occurs when:
answer
The planet actually goes backward in its orbit around Earth.
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