Deck 18: Modern Cosmology

Question 1

Measured ages of globular clusters and a study of the time required for massive stars to build up the present abundance of heavy elements suggests that the universe is

A) at least 20 billion years old.
B) no more than 9 billion years old.
C) at least 13 billion years old.
D) flat.
E) closed.

Answer 1

at least 13 billion years old.

Question 2

The Great Wall

A) is a filament of superclusters of galaxies.
B) is a bridge of hydrogen stretching from the Milky Way to its Large Magellanic Cloud satellite.
C) is a structure in the Local Group composed of the most massive spiral galaxies.
D) is formed by gas and dust in the disk of the Milky Way.
E) is the result of a collision between three spiral galaxies.

Answer 2

is a filament of superclusters of galaxies.

Question 3

If gravity is unimportant and H equal 75 km/sec/Mpc,then (using the text's formula of 10¹²/H)the age of the universe is about ...

A) 8.9 billion years.
B) 13 billion years.
C) 16.6 billion years.
D) 26 billion years.
E) 74 billion years.

Answer 3

13 billion years.

Question 4

The best determination of the Hubble constant,using Cepheid variables found in distant galaxies by the Hubble telescope,suggests that the age of the universe is

A) less than 50 years.
B) about a billion years.
C) about 14 billion years.
D) about 200 billion years.
E) greater than 200 billion years.

Question 5

The age of the universe can be determined from

A) just the distances of galaxies outside our Local Group.
B) just the recession red shifts of galaxies outside our Local Group
C) just the slowing effect of the gravity of matter in the universe.
D) just the repulsive effects of dark energy
E) Actually all of the above can be used to improve the estimate

Question 6

The cosmic microwave background radiation contains small variations in temperature that are about a degree in size.What does the size and distribution of these variations tell us?

A) That the universe is closed.
B) That the universe is open.
C) That the universe is flat.
D) That the universe is expanding.
E) That Olbers' paradox implies that the universe is finite and bounded.

Question 7

The universe is said to be closed if

A) I & II
B) I & III
C) II & III
D) I,II,& III
E) none of the above

Question 8

The flatness problem is that

A) the density of the universe is very close to the critical density.
B) the density of the universe is much larger than the critical density.
C) the flat universe would expand forever,and we could never measure the density of the universe.
D) the laws of physics may not be different at different times in the history of the universe.
E) the red shift of a distant galaxy is caused by the curvature of space-time.

Question 9

The best scientific data and models suggest that the universe is

A) open,expanding,and accelerating.
B) open,expanding,but decelerating.
C) closed,expanding,and accelerating.
D) closed,expanding,but decelerating.
E) flat,expanding,and accelerating.

Question 10

If a two-dimensional saddle shaped universe has a negative curvature,

A) the area of a circle will be less than $\pi$ r².
B) the area of a circle will be equal to $\pi$ r².
C) the universe is infinite.
D) the universe is finite but bounded.
E) the universe will have a center.

Question 11

If a galaxy is found receding from us at 894 km/sec,and it is located at a distance of 12 Mpc,what is the age of the universe if it is flat?

A) about 20 billion years
B) about 1.4 billion years
C) about 14 billion years
D) about 9 billion years
E) about 90 billion years

Question 12

If the universe is flat and not accelerating,

A) the universe's age will be equal to 1/H.
B) the universe's age will be equal two-thirds of 1/H.
C) the universe it not isotropic.
D) the density of the universe is greater than the critical density.
E) dark energy accounts for a small fraction of the critical density of the universe.

Question 13

___________ and thus dark energy were discovered when astronomers found that supernovae in galaxies several billion light years away were slightly _______ than expected based on distances estimated from their redshifts..

A) Deceleration; brighter
B) Deceleration; fainter.
C) Acceleration; fainter
D) Acceleration; brighter
E) The dark night sky; fainter

Question 14

If galaxy A is four times more distant than galaxy B,then according to the Hubble Law,galaxy A will recede ____ than galaxy B.

A) 16 times faster
B) 4 times faster
C) 2 times faster
D) 1.2 times faster
E) 0.25 times faster

Question 15

If a galaxy is located at a distance of 18 Mpc,and it is found to have recessional velocity of 1170 km/sec,what is Hubble's constant based only on this galaxy?

A) 65 km/sec/Mpc
B) 75 km/sec/Mpc
C) 55 km/sec/Mpc
D) 85 km/sec/Mpc
E) 95 km/sec/Mpc

Question 16

The cosmic background radiation comes from the time in the evolution of the universe

A) when protons and neutrons were first formed.
B) when the big bang first began to expand.
C) known as the inflationary period.
D) when gamma rays had enough energy to destroy nuclei.
E) when electrons began to recombine with nuclei to form atoms.

Question 17

Voids are

A) regions in an elliptical galaxy where few clouds of gas and dust are found.
B) regions in the Local Group where light from distant galaxies is blocked by gas and dust.
C) regions in a cluster of galaxies where no spiral galaxies are found
D) regions in the universe that separate the filaments of superclusters.
E) regions swept clean by the hot intergalactic medium

Question 18

The resolution of Olbers' paradox suggests that it gets dark at night because the universe is

A) not infinite in age.
B) collapsing
C) the universe is closed.
D) the universe is flat.
E) the universe is isotropic.

Question 19

The assumption of isotropy states that

A) the universe looks the same at all epochs.
B) the universe looks the same in all locations.
C) the universe looks the same in all directions.
D) all of the above
E) none of the above

Question 20

During the first moments of the big bang,nuclear fusion reactions made few heavy elements because

A) all heavy nuclei are unstable.
B) no stable nuclei exist with masses of 5 or 8 hydrogen masses.
C) the helium nucleus was unstable.
D) the temperature and density were too low.
E) no nuclei heavier than helium could form since there weren't any electrons formed.

Question 21

The night sky is dark because the universe is neither static nor infinitely old.

Question 22

One explanation of the dark sky Olber's Paradox is that light can reach us only from objects in space out to a distance in light years _______ the age of the universe in years..

A) less than
B) greater than
C) equal to
D) less than or equal to
E) greater than or equal to

Question 23

Homogeneity is the assumption that the universe looks the same in all directions.

Question 24

How old is the universe since the Big Bang? Pick the best answer according to radioactive dating in the solar system,light travel times to most distant galaxies,time reversal of the Big Bang,and observations of the 3 degree K radiation.

A) 1400 years
B) 14,000 years
C) 14,000,000 years
D) 14,000,000,000 years

Question 25

What is the fate of an open universe?

A) Expansion forever
B) Eventual collapse
C) Gradual halt to the expansion
D) Can't be known

Question 26

Where did the cosmic microwave background (CMB)come from?

A) Photons emitted from hydrogen gas in our galaxy
B) Photons released from nearby stars in our galaxy
C) Photons released from our Sun
D) Photons released when electrons and nuclei combined for the first time.

Question 27

What evidence supports an acceleration in the expansion rate of the universe?

A) the discovery of super massive black holes at the center of quasars
B) the discovery that type Ia supernova in distant galaxies are 25 percent fainter than expected.
C) the discovery of MACHOs
D) the discovery of the grand unified theory
E) none of the above

Question 28

What observational evidence supports the fact that our universe is expanding?

A) The heliocentric nature of our Solar System
B) Unchanged wavelengths of distant galaxies compared to closer ones
C) Increasing redshift of galaxies with increasing distance
D) Increasing blueshift of galaxies with increasing distance

Question 29

Why is the cosmic microwave background (CMB)so cold if the early universe was so hot?

A) Enough time has passed for matter to release enough heat to cool down.
B) The CMB constantly interacts with atoms,which effectively cool down the photons.
C) The expansion of the universe has redshifted those photons to an effectively cooler temperature.
D) Misleading; The Big Bang was initially hot but the CMB was released from cold material much later on.

Question 30

Galaxy seeds around which galaxies,clusters,and walls grew may be

A) caused by hot dark matter.
B) baryons.
C) the result of the separation of the electromagnetic and weak forces.
D) the result of freezing water molecules shortly after the universe became transparent to photons.
E) defects in space-time.

Question 31

_____ in our Milky Way Galaxy's halo can cause sudden brightening of distant stars by gravitationally lensing the light from those stars.This process causes the distant stars to grow brighter over a period of a few tens of days.

A) WIMPs
B) Neutrinos
C) Globular clusters
D) MACHOs
E) none of the above

Question 32

Baryonic matter includes

A) I,II,& V
B) III & IV
C) I & II
D) I,II,& III
E) I,II,III,IV,& V

Question 33

If the universe is closed,then its age will be

A) less than two-thirds of 1/H.
B) more than two-thirds of 1/H.
C) equal to 1/H.
D) equal to H squared.
E) equal to the square-root of H.

Question 34

Evidence for a very early "super rapid" inflation of the universe is that the 3° K radiation from opposite sides of the skyand (180 degrees about 28 billion light years apart)is of nearly ________ intensity.This distance is ________ the age of the universe in years.

A) equal; greater than
B) unequal; greater than
C) equal; less than
D) unequal; less than

Question 35

Astronomers believe that the hydrogen atoms in your body were created ...

A) in the planets.
B) inside the stars.
C) in the sun.
D) in the big bang.
E) in neutron stars.

Question 36

Which of the following is not an assumption of today's cosmology?

A) Isotropy
B) The cosmological principle
C) Geocentrism
D) Homogeneity

Question 37

Measurements of the amount of deuterium and the presence of very little lithium-7 in the gas clouds near quasars tell us that

A) the universe is closed.
B) the universe is open.
C) the universe is flat.
D) the universe formed more than 13 billion years ago.
E) there can not be enough protons and neutrons to make the universe flat.

Question 38

What observation has prompted astronomers to ponder the possible existence of dark energy?

A) Discovery of quasars
B) Discovery of superclusters
C) Supernovae appear fainter than expected at large redshifts.
D) Uniform nature of the cosmic microwave background (CMB).

Question 39

A frame of the HST deep field image of distant galaxies is shown.By means of optical and radio telescopes astronomers can see distant objects like these as they ...

A) are right now.
B) will be in the distant future.
C) were in the distant past.
D) All of the above.
E) None of the above.

Question 40

The flatness problem and horizon problem

A) are solved if there was a sudden inflation of the universe at a very early time.
B) show that the universe cannot be described by the steady state theory.
C) show that dark matter must be a small fraction of the total mass of the universe.
D) imply that the universe was once much hotter than it is now.
E) imply that the inflationary theory is incorrect.

Question 41

A(n)____________________ universe is infinite and would have a density equal to the critical density.

Question 42

If the gravitating matter density of the universe is equal to the critical density,and H equals 50 km/sec/Mpc,then the true age of the universe is 13.3 billion years.There is no dark energy in this model.

Question 43

The inflationary theory of the universe may explain why the background radiation is so isotropic.

Question 44

The rate of expansion of the universe is currently increasing.

Question 45

Most of the elements heavier than helium were made during the first few minutes after the big bang.

Question 46

The cosmic microwave background radiation was released shortly after the formation of the first stars.

Question 47

Observations of type Ia supernovae reveal that the expansion of the universe is speeding up because of the presence of ____________________ in empty space.

Question 48

The amount of deuteriumversus ordinary hydrogen in Earth's oceans and in the interstellar medium suggests that the universe is open.

Question 49

The red shifts of the galaxies imply that the universe is expanding and that we are at the center.

Question 50

The cosmological principle states that any observer,in any galaxy,will see the same general features of the universe.

Question 51

The ____________________ states that the universe is both isotropic and homogeneous.

Question 52

If the average density of the universe is less than the critical density,the universe is open.