Date: 04/13/12                                        Name: __________________________

 

ASTRONOMY Major Test Chapter 18: Cosmology

 

 

PART I: Multiple Choice (75)

Determine which choice best completes the statement or answers the question. Carefully place your answer choice on your answer document.

 

 

1.

Which scientist discovered that the equations he had derived predicted an expanding universe, then modified his equations to eliminate this expansion?

 

A)

Albert Einstein

 

B)

Isaac Newton

 

C)

Stephen Hawking

 

D)

Edwin Hubble

 

 

2.

Why did Einstein introduce his cosmological constant into the original field equations for general relativity?

 

A)

The constant was necessary to make the solutions describe an expanding universe.

 

B)

Experimental evidence at this time (before Hubble) suggested a static universe, and this constant was required to produce static solutions.

 

C)

The constant represented the acceleration of gravity near Earth's surface, and it was necessary to make the nonrelativistic limit of the solutions compatible with Newton's results.

 

D)

The constant represented the speed of light, and its inclusion was necessary to produce solutions that were compatible with the postulates of special relativity.

 

 

3.

What is the “cosmological redshift”?

 

A)

stretching of the wavelengths of photons as they travel through expanding space

 

B)

stretching of the wavelengths of photons by the Doppler shift because they are emitted by galaxies that are moving away from us

 

C)

loss of energy from photons interacting with virtual particles in the vacuum, resulting in the wavelength of the photons gradually increasing as they travel toward us through space

 

D)

stretching of the wavelengths of photons as they pass through absorbing matter in galaxies between us and the emitting galaxy

 

 

4.

Where is the Earth?

 

A)

at the exact center of an expanding universe, as shown by the universal expansion away from Earth in all directions

 

B)

near the edge of an expanding universe, as shown by the microwave radiation coming to Earth from the edge

 

C)

near but probably not right at the center of the universe, as shown by the fact that the edge is so far away from Earth

 

D)

somewhere in an expanding universe but not in any special part of it

 

 

5.

Which single observation is perhaps the strongest argument against the steady-state model of the universe and for the Big Bang model?

 

A)

The number of supporters of the steady-state model is less than the number of supporters of the Big Bang model.

 

B)

We have not observed matter being created from nothing in the space around us.

 

C)

The universe is expanding.

 

D)

The universe is bathed in a sea of microwaves coming from the edge of the visible universe.

 

 

6.

In relation to the universe, what does isotropy mean?

 

A)

The universe has the same expansion speed at all distances.

 

B)

The universe is the same at all distances.

 

C)

The universe at any given distance is the same at all times.

 

D)

The universe looks the same in all directions.

 

 

7.

What do we mean when we say that the universe is homogeneous?

 

A)

At any given time, the universe looks the same at all locations.

 

B)

There are no mass concentrations anywhere in the universe.

 

C)

The universe is static and unchanging.

 

D)

At any given time, the universe looks the same in all directions.

 

 

8.

Why does the cosmic microwave background appear to be slightly warmer in one direction in the sky and slightly cooler in the opposite direction?

 

A)

The warmer direction is the direction in which the Big Bang occurred; hence, we are seeing the remnant of the explosion in this direction.

 

B)

The universe is younger in one direction and therefore warmer.

 

C)

The radiation in one direction is Doppler-shifted to shorter wavelengths by Earth's motion in space and to longer wavelengths in the other direction.

 

D)

Large amounts of matter in the warmer direction direction have focused the radiation slightly by gravitational lensing, making this direction appear hotter

 

 

9.

How many fundamental forces are there in nature at the present time under normal conditions?

 

A)

three: strong, electromagnetic, and gravitational

 

B)

six: color, strong, weak, magnetic, electric, and gravitational

 

C)

four: strong, weak, electromagnetic, and gravitational

 

D)

five: strong, weak, magnetic, electric, and gravitational

 

 

10.

The one physical force that extends farthest in our universe and is not canceled out by other effects is the

 

A)

weak nuclear force.

 

B)

strong nuclear force.

 

C)

electromagnetic force.

 

D)

gravitational force.

 

 

11.

When is the weak nuclear force encountered?

 

A)

when a neutron is transformed into a proton with the ejection of an electron and a neutrino

 

B)

when a positively charged nucleus repels another positively charged nucleus in the core of a star like the Sun

 

C)

when two quarks interact inside a proton or neutron

 

D)

when an atom absorbs a photon and one of the electrons in the atom is sent into a higher energy level

 

 

12.

In cosmology, what is the inflationary period?

 

A)

period when the cost of living rose faster than astronomers' salaries

 

B)

first 500,000 years of the life of the universe, when matter and radiation interacted vigorously

 

C)

period of universal expansion from the Big Bang to the present

 

D)

short period of extremely rapid expansion when the universe was very young

 

 

13.

What is the cosmic light horizon?

 

A)

The cosmic light horizon is the distance beyond which we cannot see because light cannot have traveled any farther in the finite age of the universe.

 

B)

The cosmic light horizon is the distance beyond which we cannot see because no stars or galaxies had yet formed at those distances (because we see back in time as we look out into space).

 

C)

The cosmic light horizon is the distance beyond which our own radio and television signals cannot have traveled through the universe.

 

D)

The cosmic light horizon is the distance beyond which we cannot see because of absorbing matter in the universe.

 

 

14.

The isotropy of the cosmic microwave background radiation (same temperature in all directions) indicates that

 

A)

the universe had an early period of inflation in which regions initially in contact were carried out of contact with each other.

 

B)

the universe did not begin to expand significantly until after the era of recombination.

 

C)

regions that appear to us to be on opposite sides of the visible universe are in fact in close contact with each other.

 

D)

the universe has always been dominated by matter.

 

 

15.

The fact that matter exists today is evidence that matter particles outnumber antimatter particles in the universe. This imbalance was caused by

 

A)

matter inflation.

 

B)

symmetry breaking.

 

C)

chirality.

 

D)

the cosmic overshift.

 

 

16.

Why does the observable universe have an “edge”?

 

A)

We cannot see any farther out into space than the distance that light has traveled over the lifetime of the universe

 

B)

The density of neutrinos at the “edge” becomes so large that photons cannot penetrate this barrier, and this prevents us from seeing beyond this point

 

C)

Absorbing matter prevents us from seeing beyond a certain distance

 

D)

There are so many galaxies in the universe that every line of sight eventually hits a galaxy, stopping us from seeing any farther

 

 

17.

Which of the following statements correctly describes the universe for the entire first 500,000 years of its life?

 

A)

The universe was filled with free quarks (not confined inside neutrons or protons).

 

B)

All the fundamental forces of nature were unified into one force.

 

C)

The universe was a filled with a sea of nuclear particles undergoing violent reactions.

 

D)

The universe was opaque.

 

 

18.

What appears to be the relationship between the distribution of dark matter and the distribution of luminous matter?

 

A)

There seems to be no correlation at all.

 

B)

There seems to be a separate distribution of dark matter—dark-matter galaxy clusters, voids in the dark matter, and so on. But these formations all occur in regions of space far from luminous matter.

 

C)

The distribution of dark matter seems to coincide with the distribution of luminous matter.

 

D)

The distribution of dark matter seems to be just the reverse of the distribution of luminous matter: Dark-matter galaxy clusters occur in the voids of luminous matter; luminous galaxy clusters occur in the voids of dark matter.

 

 

19.

In a primordial, pregalactic gas cloud, what is believed to have been the most important condition that caused the cloud to become a spiral galaxy?

 

A)

The cloud started off with a lot of dust and heavy elements.

 

B)

The initial rate of star formation was high.

 

C)

The cloud started off flattened and disk-shaped before it collapsed.

 

D)

The initial rate of star formation was low.

 

 

20.

In a primordial, pregalactic gas cloud, what is believed to have been the most important condition that caused the cloud to become an elliptical galaxy?

 

A)

The initial rate of star formation was high.

 

B)

The cloud started off with a lot of dust and heavy elements.

 

C)

The cloud started off flattened and disk-shaped before it collapsed.

 

D)

The initial rate of star formation was low.

 

 

21.

If the geometry of space is spherical, what is the future of the universe?

 

A)

The future of the universe is not related to the geometry of space.

 

B)

The universe will expand forever, not stopping even when infinite time has elapsed.

 

C)

The universe will hardly expand forever; if it has any more matter in it than it does, it will eventually stop expanding and start to collapse.

 

D)

The universe will expand to a maximum size and then collapse into a Big Crunch.

 

 

22.

Which parameter of the present universe is considered to be critical in determining the ultimate fate of the universe?

 

A)

amount of mass in black holes in the universe

 

B)

number of neutrinos in the universe

 

C)

amount of matter and energy in the universe

 

D)

number of photons of radiation in the universe

 

 

23.

What is the difference between dark matter and dark energy?

 

A)

Dark matter exists today, whereas dark energy existed only until the strong nuclear force became a separate force at the Planck time.

 

B)

Dark energy is the energy emitted by dark matter, much as luminous energy (light) is emitted by visible matter.

 

C)

There is no difference: Energy has mass by E = mc2, and dark matter and dark energy are two names for the same effect.

 

D)

Dark matter is attractive and slows the universal expansion, whereas dark energy is repulsive and accelerates the universal expansion.

 

 

24.

On the basis of recent results from very bright and very distant Type Ia supernovae, what seems to be our situation in the universe regarding the past and present motion of clusters of galaxies?

 

A)

We live in a “flat” universe with a decelerating rate of expansion.

 

B)

We live in an open universe with a constant rate of expansion given by the Hubble law.

 

C)

We live in a closed universe with a decelerating rate of expansion.

 

D)

We live in a “flat” universe with an accelerating rate of expansion.

 

 

25.

Why is flatness a problem in cosmology?

 

A)

The total amount of known matter (even if we include dark matter) is not enough to make the universe flat.

 

B)

The universe appears to be flat to within observational error, yet the universe is expanding, and it is impossible for an expanding universe to be flat.

 

C)

The universe appears to have a hyperbolic geometry to within observational error, yet the universe is expanding, and expanding universes have to be flat.

 

D)

Matter is known to create bumps in the geometry of spacetime; therefore, the universe cannot be flat.

 

 

PART II Short Answer (140)

Answer the questions below on your own paper. Be sure to put only one answer per page and be sure that each answer is 'a, 'b', 'c' bulleted while being answered in a complete sentence.

 

 

26.

Consider the shape of the universe.

a) How many possible shapes can the universe have?

b) Describe one shape and what that shape means regarding the fate of the universe.

c) Describe another shape and what that shape means regarding the fate of the universe.

d) Describe the third shape what what that shape means regarding the fate of the universe.

e) What is the shape of the universe for which astronomers have the best evidence?

 

 

27.

Consider the 'stages' through which our universe has passed:

a) Describe the radiation-dominated universe.

b) Describe the matter-dominated universe.

c) Describe the dark energy-dominate universe.

d) In which of the universes described do we presently live? Explain how you know.

 

 

28.

Consider the very early (sic!) universe:

a) What is the earliest era of the existence of the universe called?

b) What event ended this earliest era?

c) How much time passed between the big bang and the end of this first era?

d) What happened at 10-35s; to what extent did the universe change as a result of this event and for how long did this event take place?

e) When did the matter-dominated universe begin?

 

 


Answer Key

 

1.

A

2.

B

3.

A

4.

D

5.

D

6.

D

7.

A

8.

C

9.

C

10.

D

11.

A

12.

D

13.

A

14.

A

15.

B

16.

A

17.

D

18.

C

19.

D

20.

A

21.

D

22.

C

23.

D

24.

D

25.

A

26.

Considering the shapes of the universe:

a) The universe can have three shapes: spherical, flat or saddle-shaped.

b) If the universe is spherical it will expend to a point and then collapse back in on itself, this is the 'big crunch'.

c) If the universe is flat it will keep expanding forever and ever, with things in it getting further and further apart.

d) If the universe is saddle shaped or hyperbolic, it will expand forever with things in it getting further and further apart.

e) Modern astronomers have the best evidence for a flat universe.

27.

COnsidering the 'stages' through which our universe has passed:

a) During the radiation-dominated universe the energy density of the photons had the greatest gravitational effect on the development of the universe.

b) In a matter-dominated universe matter has the greatest gravitational effect on the development of the universe.

c) A dark energy dominated universe is one in which dark energy dominates the development of the universe.

d) We presently live in a dark energy-dominated universe. I know this because dark energy is driving the universe over matter and radiation. In other words dark energy is causing the universe to expand at an ever increasing rate.

28.

Considering the very early universe:

a) The earliest era of the existence of the universe is called the Plank era.

b) The Plank era ended when gravity separated itself as a force.

c) Plank time lasted all of 10-43s.

d) At t = 10-35s the universe underwent inflation during which the universe expanded to a size 1050 times larger than it was before and it lasted from 10-35 s to 10-33 s.

e) the matter-dominated universe began 300,000 years after the BB.