Question 1

The 2003 observation of a very distant galaxy,the light from which passed through a less distant galaxy cluster on its way to us,showed an overall blueshift.What is the significance?

Accepted Answer

A)   The observation shows that the most distant galaxies have already started to fall back to the center of the universe (the Big Crunch) , and their light experiences a Doppler blueshift.
B)   The mass density at our location is larger than the mass density in the vicinity of the very distant galaxy, so light experiences a gravitational blueshift as it moves toward us.
C)   The apparent blueshift is not unusual. Most distant galaxies look blue because of the predominence of blue stars in the early universe.
D)   The gravitational blueshift experienced by the light approaching the cluster (at an earlier time)  outweighed the gravitational redshift it experienced (at a later time)  while moving away from the cluster. This suggests an outward cosmological acceleration. D

Question 2

At the present time,we believe the structure and behavior of the universe are dominated by:

Accepted Answer

A)   radiation.
B)   ordinary matter.
C)   dark matter.
D)   dark energy. D

Question 3

During the first one-ten-thousandth of a second (10-⁴ s)of the life of the universe,antiprotons were very common.For every billion antiprotons,how many protons were there?

Accepted Answer

A)   exactly 1 billion since protons and antiprotons were created in equal numbers
B)   slightly more than 1 billion, thus producing the matter we see today
C)   a totally unknown number since the early universe was opaque and we cannot see what conditions were like then
D)   10 billion, thus producing the dark matter we see today B

Question 4

Immediately after the cosmological singularity,the four forces were indistinguishable.Then they began to "branch off" and become separate.Which was the LAST of the four to branch off?

Accepted Answer

A)   gravitation
B)   weak force
C)   strong force
D)   electromagnetism

Question 5

If space were flat and there were no "dark energy," what would be the future of the universe?

Accepted Answer

A)   The universe would hardly expand forever; if it had any more matter in it than it does, it would eventually stop expanding and start to collapse.
B)   The universe would expand to a maximum size and then collapse into a Big Crunch.
C)   The future of the universe is not related to the geometry of space.
D)   The universe would have more than enough energy to expand forever, not stopping, even when infinite time has elapsed.

Question 6

The cosmic microwave background was discovered by:

Accepted Answer

A)   rocket-borne telescopes that also discovered X-ray sources in space.
B)   the Voyager 2 spacecraft during one of its "coasting" periods between planetary encounters.
C)   scientists testing a new antenna and receiver for satellite communications.
D)   the IRAS satellite, which produced an all-sky infrared survey.

Question 7

Within the first second after the Big Bang,the universe was filled with high-energy,gamma-ray photons.These photons created huge numbers of elementary particles and their antiparticles through pair production.What happened to these particles?

Accepted Answer

A)   They are still here. They combined to create the first atoms and molecules that compose the physical universe.
B)   The particles are still with us as atoms and molecules, but almost all of the antiparticles disappeared.
C)   These particle-antiparticle pairs annihilated to produce more photons.
D)   This pair production was followed by the era of cosmic inflation during which these particles spread out to produce the matter densities that we see today.

Question 8

What method is being used to discover whether we live in an unbounded universe,in which expansion will continue forever,or a bounded universe,in which expansion will eventually turn into contraction and lead us to re-collapse?

Accepted Answer

A)   careful monitoring of the Moon-Earth distance to detect the slowdown of the expansion of the universe
B)   measurement of the deviation from uniformity of the cosmic background radiation
C)   measurement of the curvature of the Hubble relationship, v = H₀ d, at large distances
D)   measurement of the bending of light by distant galaxies as it follows the curvature of space

Question 9

The physical force that controls the structure of the nucleus and binds together protons and neutrons is the _____ force.

Accepted Answer

A)   gravitational
B)   weak nuclear
C)   electromagnetic
D)   strong nuclear

Question 10

How was the cosmic microwave background radiation discovered?

Accepted Answer

A)   using a microwave detector on the Hubble Space Telescope
B)   using the Cosmic Background Explorer (COB
E)   spacecraft
C)   using a horn antenna on Earth's surface
D)   using the BOOMERANG balloon circling above Antarctica

Question 11

In which period of time are we now living?

Accepted Answer

A)   the inflationary period, in which the universe expands rapidly
B)   the era of recombination, in which electrons and protons combine to form hydrogen atoms
C)   the Planck era, in which all four forces of nature are unified
D)   the period of confinement, in which quarks are unable to travel freely

Question 12

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

Accepted Answer

A)   The universe will expand to a maximum size and then collapse into a Big Crunch.
B)   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.
C)   The future of the universe is not related to the geometry of space.
D)   The universe will expand forever.

Question 13

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

Accepted Answer

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.

Question 14

What is the Great Attractor?

Accepted Answer

A)   a fifth fundamental force, in addition to the strong, weak, electromagnetic, and gravitational forces
B)   a massive supercluster of galaxies that is gravitationally pulling on our Local Group
C)   a supermassive black hole at the center of the Virgo cluster of galaxies
D)   a concentration of primordial quantum fluctuations

Question 15

Two light beams that are initially parallel to each other will eventually converge in what kind of universe?

Accepted Answer

A)   flat only
B)   hyperbolic only
C)   either flat or hyperbolic
D)   closed

Question 16

The farther away a galaxy is,the more its light is redshifted,as observed from Earth.This relationship between redshift and distance is caused by:

Accepted Answer

A)   the Doppler shift of light leaving a moving object. More distant galaxies are moving faster through space, so their light is more strongly Doppler-shifted (redshifted) .
B)   energy losses. The universe does not really expand; photons simply lose energy (wavelength lengthens)  as they travel. Photons from more distant galaxies have traveled farther and so are more redshifted.
C)   the expansion of space itself, which stretches the wavelength of the photon. The longer the time the photon has traveled, the more space has expanded and therefore the more the photon has been redshifted.
D)   the gravitational redshift. Photons leaving a more distant galaxy have traveled farther through the galaxy's gravitational field, so they have lost more energy and are more redshifted.

Question 17

At what times during the Big Bang were all four fundamental forces unified?

Accepted Answer

A)   until 10-²⁴ s, after the start of the Big Bang, when the inflationary era ended
B)   during the first 500,000 years from the start of the Big Bang, when the universe was dominated by radiation
C)   until 10-⁶ s after the start of the Big Bang, when the era of quark confinement ended
D)   during the Planck era, up to 10-⁴³ s, after the start of the Big Bang

Question 18

When we use H₀ to calculate the age of the universe,we are making all of the following assumptions EXCEPT ONE.Which is the exception?

Accepted Answer

A)   The universe is isotropic, that is, it has the same properties in all directions.
B)   The Milky Way Galaxy is the center of the universal expansion.
C)   The value of H₀ is indeed constant.
D)   The speed of the expansion has been constant through time.

Question 19

Why are the youngest galaxies that we see in distant parts of the universe bluer and brighter than the older galaxies we see closer to us?

Accepted Answer

A)   The red light has been partially absorbed by gas and dust between us and the galaxies.
B)   Young galaxies have more dust, and dust scatters blue light better than it scatters red light.
C)   The light from the most distant galaxies has been bent by gravitational lenses and focused on Earth.
D)   Young galaxies have a burst of star formation that produces many hot, bright, blue stars.

Question 20

How do the youngest,most distant galaxies compare with the older galaxies we see closer to us today?

Accepted Answer

A)   The youngest galaxies are bluer and brighter than the older ones.
B)   The youngest galaxies have the same color as the older ones but are significantly brighter.
C)   There is no observable difference between the youngest galaxies and the older ones.
D)   The youngest galaxies are redder and fainter than the older ones.

Exam 14: Cosmology