Which of the following has your “cosmic address” in the correct order?
You, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
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
Could we see a galaxy that is 20 billion light-years away? (Assume that we mean a “lookback time” of 20 billion years.)
No, because it would be beyond the bounds of our observable universe.
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 _________.
the same as the number of grains of sand on all the beaches on Earth
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.
If we imagine the history of the universe compressed into one year, dinosaurs became extinct _________.
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.
Where is our solar system located within the Milky Way Galaxy?
Roughly halfway between the center and the edge of the visible disk of the galaxy
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 is not a general difference between a planet and a star?
All planets are made of rock and all stars are made of gas.
Our solar system consists of _________.
the Sun and all the objects that orbit it
A typical galaxy is a _________.
collection of a few hundred million to a trillion or more stars, bound together by gravity
Which of the following best describes what we mean by the universe?
The sum total of all matter and energy
An astronomical unit (AU) is _________.
the average distance between Earth and the Sun
A light-year is _________.
about 10 trillion kilometers
A television advertisement claiming that a product is light-years ahead of its time does not make sense because _________.
it uses “light-years” to talk about time, but a light-year is a unit of distance
The term observable universe refers to _________.
that portion of the universe that we can see in principle, given the current age of the universe
On a scale in which the distance from Earth to the Sun is about 15 meters, the distance from Earth to the Moon is _________.
small enough to fit within your hand
On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars besides the Sun?
About the distance across the United States
The number of stars in the Milky Way Galaxy is approximately _________.
a few hundred billion
What do astronomers mean by the Big Bang?
The event that marked the beginning of the expansion of the universe
What do we mean when we say that the universe is expanding?
Average distances between galaxies are increasing with time.
Based on observations of the universal expansion, the age of the universe is about _________.
14 billion years
What is the ecliptic plane?
The plane of Earth’s orbit around the Sun
How long does it take the Earth to complete one orbit around the Sun?
Consider a raisin cake expanding uniformly in an oven. Viewed from one of the raisins, you would see _____.
all other raisins moving away from you, with more distant raisins moving faster