Which of the following has your address in the right order?
You, earth, solar system, milky way, local group, local supercluster
About where is our solar system located in the milky way galaxy?
about two-thirds of the way from the center of the galaxy to the outskirts of the galactic disk
Roughly how many stars are in the milky way galaxy?
100 billion
Suppose we imagine the sun to be about the size of a grapefruit. How big an area would the orbits of the nine planets of the solar system cover?
the size of a typical campus
What do we mean when we say that the universe is expanding?
average distances are increasing between galaxies
The age of the universe is
between 10 billion and 16 billion years
The earth is made mostly of metal and rocks. Where did this material come from?
It was produced by nuclear fusion in stars
Why does Carl Sagen say that we are star stuff?
nearly every atom from which we are made once (before the solar system formed) was inside of a star
Which of the following statements does not use the term light-year in an appropriate way?
It will take me light-years to complete this homework assignment
Suppose we look at a photograph of many galaxies. Assuming that all galaxies formed at about the same time, which galaxy in the picture is the youngest?
the one that is farthest away
Suppose we imagine the sun to be about the size of a grapefruit. Which of the following describes the size and distance of the earth on the same scale?
the earth is the size of a point about 15 meters away from the sun
Which of the following is smallest?
size of a typical planet
Which of the following is the largest?
size of a typical galaxy
Suppose we imagine the sun to be about the size of a grapefruit. How far away are the nearest stars (the three stars of Alpha Centauri)?
2,500 miles
If we use 1 millimeter to represent 1 light-year, how large in diameter is the milky way galaxy?
100 meters
Which of the following best describes the milky way galaxy?
a spiral galaxy with a disk about 100,000 light-years in diameter and containing between 100 billion and 1 trillion stars
How long would it take to count all the stars in the milky way galaxy at a rate of one star per second?
several thousand years
How many galaxies are there in the observable universe?
roughly (with a factor of 10) the same as the number of stars in our galaxy
If you represented each star by a grain of sand, how much sand would it take to represent all the stars in the universe?
more than all the sand on all the beaches on earth
On the scale of the cosmic calendar, in which the history of the universe is compressed into one year, how long is the average human life span?
0.2 seconds
Approximately how fast are you moving with the rotation of the earth?
1,300 km/hr
What is an astronomical unit?
the average distance from the earth to the sun
Patterns of stars in constellations hardly change in appearance over times of even a few thousand years. Why?
The stars in our sky actually move rapidly relative to us--thousands of kilometers per hour--but are so far away that it takes a long time for this motion to make a noticeable change in the patterns in the sky.
How long does it take for our solar system to complete one orbit around the milky way galaxy?
230 million years
Which of the following statements about the milky way galaxy is not true?
Our solar system is located very close to the center of the milky way galaxy
Which of the following correctly lists speeds from slowest to fastest?
Earth's speed of rotation on its axis, typical speeds of stars in the local solar neighborhood, earth's speed of revolution about the sun, the speed of our solar system's orbit, the speeds of the very distant galaxies relative to us
The distribution of the mass of the milky way galaxy is determined by
studying the rotation of the galaxy
From the fact that virtually every galaxy is moving away from us and more distant galaxies are moving away from us at a faster rate than closer ones, we conclude that
the universe is expanding
By studying distant galaxies in the 1920's, Hubble made the following important discovery that led us to conclude that the universe is expanding:
all galaxies located outside the Local Group are moving away from us, and the farther away they are, the faster they are going
Which scientists played a major role in overturning the ancient idea of an earth-centered universe, and about when?
Copernicus, Kepler, and Galileo; about 400 years ago
The names of the seven days of the week are based on the
seven naked eye objects that appear to move among the constellations
Suppose the planet Uranus was 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?
A week would have eight days instead of seven
What do the structures of Stonehenge, the Templo Mayor, the Sun Dagger, and the Big Horn Medicine Wheel have all in common?
They were all used by ancient peoples for astronomical observations.
At the Sun Dagger in New Mexico, a dagger-shaped beam of sunlight pierces a spiral
at noon on the summer solstice
The muslim fast of Ramadan occurs
during the ninth month of a 12-month lunar cycle
The jewish calendar is kept roughly synchronized with a solar calendar by
adding a thirteenth lunar month to 7 out of every 19 years
Which ancient culture had the greatest known success in predicting ellipses?
Mayans
Ptolemy was important in the history of astronomy because he
developed a model of the solar system that made sufficiently accurate predictions of planetary motions to remain in use for many centuries
When did Ptolemy live?
about 2000 years ago
How did the Ptolemaic model explain the apparent retrograde motion of the planets?
It held that the planets moved along small circles that moved on larger circles around the earth
Where was the sun in Ptolemy's model of the universe?
between the orbits of Venus and Mars
When Copernicus first created his sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions that the Ptolemaic model. Why not?
Copernicus used perfect circles for the orbits of the planets
One of the "nails in the coffin" for the earth-centered universe was
Galileo's observations of the moons of jupiter
Kepler's third law p^2=a^3, means that
1. All orbits with the same semimajor axis have the same period 2. The period of a planet does not depend on its mass 3. Planets that are farther from the sun move at slower average speeds than nearer planets 4. A planet's period does not depend on the eccentricity of its orbit
From Kepler's third law, a hypothetical planet that is twice as far from the sun as the earth should have a period of
more than 2 earth years
From Kepler's third law, an asteroid with an orbital period of 8 years lies at an average distance from the sun equal to
4 astronomical units
Kepler's second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, means that
a planet travels faster when it is nearer to the sun and slower when it is farther from the sun
All of the following statements are true. Which one follows directly from Kepler's third law?
Venus orbits the sun at a slower average speed than mercury
