Deck 26: Cosmology

Question 1

Suppose we were to discover that the distances to other galaxies had all been overestimated by a factor of two.How would this discovery affect our estimate of the age of the universe?

A)The estimate would be cut in half
B)The estimate would remain the same
C)The estimate would be cut by about a factor of 1000
D)The estimate would double

Answer 1

The estimate would be cut in half

Question 2

An observer now located at a distance of 3 billion light years from us could look in our general direction and see

A)Most of the galaxies approaching him or her
B)The same Hubble's law that we see
C)About equal numbers of red and blue shifted galaxies
D)Everything rushing away from a point near the Milky Way galaxy

Answer 2

The same Hubble's law that we see

Question 3

What produced the radiation that we see as the 3 degree background radiation?

A)Stars
B)Glowing gas
C)Neutrinos
D)Supernovae

Answer 3

Glowing gas

Question 4

Which of the following is a statement of the cosmological principle?

A)The universe has always looked the same
B)The universe looks the same to all observers everywhere
C)The mass and composition of a star determine its entire evolution
D)The universe will eventually begin to collapse

Question 5

Which statement is true of the cosmic background radiation?

A)It comes primarily from one hemisphere of the sky
B)It is still being produced in the universe
C)It is greatly redshifted
D)It was produced in the first second of the Big Bang

Question 6

In a universe that is isotropic

A)The Big Bang never occurred
B)Things look the same in all directions
C)Nothing ever changes
D)All clusters contain the same number of galaxies

Question 7

If we were to discover that Hubble's constant is actually twice as large as it is now thought to be,how would that alter our estimate of the expansion age of the universe?

A)Our estimate would be cut in half
B)Our estimate would double
C)Our estimate would be unchanged
D)Our estimate would increase to 4 times its present value

Question 8

Which of the following is true of the cosmic background radiation?

A)It is brighter in the northern hemisphere than in the southern
B)It was produced by stars
C)It was produced a few 100,000 years after the beginning of the expansion
D)It is brightest in the ultraviolet part of the spectrum

Question 9

If the universe is flat,where is its center?

A)There is no center
B)At the place that is the center of expansion
C)Near the Coma cluster
D)At the place where the value of Hubble's constant is zero

Question 10

In which part of the sky is the cosmic background radiation brightest?

A)Equally bright in all parts of the sky
B)Toward the Virgo cluster
C)Toward the center of the universe
D)Toward the spot where the Big Bang took place

Question 11

The expansion age of the universe is about

A)1 billion years
B)10 billion years
C)100 billion years
D)1000 billion years

Question 12

Which of the following is NOT an implication of Hubble's law?

A)The universe is expanding
B)We are in the center of the universe
C)The universe had a beginning
D)The universe was once denser than it now is

Question 13

The universe is generally assumed to be isotropic.What does "isotropic" mean?

A)Looks the same in all directions
B)Is the same from place to place
C)Is centered on the Sun
D)Has always been the same

Question 14

Which of the following is true for a universe in which space is flat?

A)It has an infinite volume and a well-defined center
B)It has an infinite volume and no center
C)It has a finite volume and a well-defined center
D)It has a finite volume and no center

Question 15

Which of the following is true of the universe if it is made of flat space?

A)It will eventually begin to collapse
B)It has a center
C)It is infinite
D)The expansion of the universe began at a point in the Virgo cluster

Question 16

Why is the cosmic background radiation found primarily in the radio part of the spectrum?

A)The visible part of it was absorbed by intergalactic dust
B)It was emitted by cool,intergalactic clouds
C)It is primarily synchrotron radiation
D)It is highly redshifted

Question 17

In which part of the spectrum is the cosmic background radiation brightest?

A)Radio
B)X-ray
C)Ultraviolet
D)Visible

Question 18

Suppose our universe has negative curvature.Which of the following statements would be FALSE?

A)The universe has a center
B)The universe will never begin to contract
C)The universe has an infinite volume
D)The universe has no boundary

Question 19

In which respect are flat and positively curved universes alike?

A)They are both infinite
B)Neither can expand
C)Neither has a center
D)The sum of the angles of a triangle is 180 degrees in both

Question 20

If the universe is closed,where is its center?

A)Trick question,it has no center
B)Near the Virgo cluster
C)Beyond the visible part of the universe
D)Within the local group of galaxies

Question 21

Which of the following observations motivated the suggestion that the early universe experienced a brief period of extremely rapid inflation?

A)The extreme isotropy of the cosmic background radiation
B)The large number of black holes in the universe
C)The fact that some globular clusters are older than the universe
D)The presence of helium in the universe

Question 22

About 25% of the mass in the universe is helium? Where did most of the helium come from?

A)It was produced in early,massive stars
B)It was present in the universe at the moment the expansion began
C)It was produced in supernovae
D)It was produced during the first few minutes of the expansion

Question 23

What is one of the things that have been learned from measurements of the fluctuations in the cosmic background radiation (CBR)?

A)The extent to which foreground objects block the CBR
B)Space is very nearly flat
C)The CBR was produced long after the first stars formed
D)The CBR was emitted primarily by galaxies

Question 24

If the universe is open (negatively curved),the present expansion will

A)Stop and be followed by contraction to another singular state
B)Continue for an infinite time
C)Slow down but never quite stop in a finite time
D)Stop at the cosmic time of 20 billion years and remain stationary

Question 25

The conversion of hydrogen into helium began about 2 minutes after the beginning of the expansion of the universe.Why was there no helium in the universe during the first 2 minutes?

A)There was no matter in the universe during the first 2 minutes
B)Collisions were too violent for helium to be stable during that time
C)No collisions occurred during the first two minutes
D)Neutrino disruption dominated during the first two minutes

Question 26

What has been learned from extremely distant (high-z)supernovae?

A)The events that took place before the Big Bang
B)The history of the expansion of the universe
C)The location of the center of the universe
D)The age of the Sun

Question 27

What was the chemical makeup of the universe several hours after the expansion began?

A)Almost entirely hydrogen and helium
B)All of the known elements were present
C)Entirely hydrogen
D)A range of elements up to and including iron

Question 28

Which of the following combinations will lead to an eventual contraction of the universe?

A)High density,large expansion rate,no dark energy
B)Low density,large expansion rate,dominated by dark energy
C)High density,small expansion rate,no dark energy
D)Low density,small expansion rate,dominated by dark energy

Question 29

Imagine that a year from now you read that astronomers have discovered a group of
50 billion-year-old stars.What would you conclude from such a discovery?

A)They must be spectral class O and B stars
B)They must be in a late stage of stellar evolution
C)Our present ideas on evolution of the universe are seriously in error
D)We would have to revise our theories of stellar energy sources

Question 30

Why can't we see radiation produced during the first 300,000 years of the history of the universe?

A)It was all absorbed and destroyed soon after it was emitted
B)It hasn't reached us yet
C)It has been deflected by black holes
D)It passed by our part of the universe a few billion years ago

Question 31

What evidence do we have for the existence of "dark energy"?

A)It blocks our view of distant parts of the universe
B)The universe contains more light than has ever been emitted by stars
C)Expansion seems to be accelerating
D)We see the cosmic background radiation in all directions

Question 32

Where in the universe did the Big Bang occur?

A)Very close to the Milky Way galaxy
B)Everywhere
C)Near the Virgo cluster
D)At the center

Question 33

What important event happened about 300,000 years after the universe began to expand?

A)Helium was produced
B)The first stars formed
C)The universe became ionized for the first time
D)The universe became transparent

Question 34

What will happen if there is no "dark energy" and the density of the universe is greater than the critical density?

A)The universe will eventually contract.
B)The universe will contract and then rebound
C)The universe will stop expanding,but not begin to contract
D)The universe will expand forever

Question 35

The underlying cause of inflation is believed to be

A)Scalar fields
B)Radiation pressure
C)Nuclear fusion
D)The isotropy of the universe

Question 36

Which of the following statements about the first few minutes of the Big Bang is true?

A)The universe was transparent
B)The universe was very cool
C)Hydrogen was converted to helium
D)Galaxies began to form

Question 37

What do we need to know in order to predict whether the expansion of the universe will continue forever?

A)The curvature of space
B)The age of the universe and the speed of light
C)The lifetime of the proton and the distance to the Virgo cluster
D)The temperature of the cosmic background radiation and the age of the universe

Question 38

Which of the following is true of the expansion of the universe if there is no dark energy?

A)The expansion rate will increase
B)The expansion rate will decrease
C)The expansion rate will remain constant
D)The expansion rate will first increase and then decrease

Question 39

Approximately how long after the expansion of the universe began was the radiation that we now see as the 3 K background radiation produced?

A)3 billion years
B)1 microsecond
C)7 minutes
D)300,000 years

Question 40

How could we tell (in principle)whether we live in a universe in which space is flat or in a universe in which space is positively curved?

A)Find out if the universe has a center
B)Find out if the universe has boundaries
C)Determine whether there is cosmic background radiation
D)Measure the sum of the angles of a very large triangle