Deck 18: Cosmology: the Big Bang and the Fate of the Universe

Question 1

The density of the universe is large enough that gravity alone will eventually halt its expansion.

Answer 1

False

Question 2

The critically bound universe, with omega = 1, is saddle shaped.

Answer 2

False

Question 3

If the value of H is doubled, it would also double the age of the universe.

Answer 3

False

Question 4

In the Big Bang model, two possible fates exist: expansion forever, or cosmic collapse.

Question 5

If the value of H has not changed since the Big Bang, then H = 70 km/s/Mpc will give a Hubble Time of about 14 billion years.

Question 6

In a closed universe, if you could send out a powerful enough light, it would eventually return from behind you.

Question 7

The cosmological principle is the ultimate extension of the Copernican principle to the entire universe, in that there is no center at all.

Question 8

Olbers's paradox seeks the explanation for why the night sky is dark.

Question 9

An infinite universe is a basic assumption of the cosmological principle.

Question 10

Galaxies are moving away from us and into the vast, empty space of the outer universe beyond the Big Bang.

Question 11

The latest observations of distant Type I supernovae suggest the universe is slowing down more than we had expected.

Question 12

The cosmological redshift is not really a velocity at all, but a measure of the expansion of space- time.

Question 13

Hubble's law implies that, at some time in the past, all the matter in the universe was at one place.

Question 14

Euclidean geometry is useful for most common problems, but the geometry of space requires general relativity as well.

Question 15

The universe has been expanding at the same rate since its formation.

Question 16

The darkness of the night is due in part to the cosmological redshift, with the energy of the most distant objects diluted in the universal expansion.

Question 17

A gravitationally bound universe, with omega greater than 1.0, will expand forever.

Question 18

The Big Bang was an expansion of matter into empty space.

Question 19

The cosmological redshift is a direct measure of the expansion of the universe, thus independent of direction.

Question 20

Olbers's paradox is solved in part by the fact that the universe is neither infinitely large nor infinitely old.

Question 21

The background hiss that Bell Labs detected was the best observational evidence for the Big Bang.

Question 22

Primordial nucleosynthesis implies the Big Bang makes all elements up to iron.

Question 23

The Big Bang has time in primordial nucleosynthesis to make only H and He in abundance.

Question 24

Einstein originally added a cosmological constant to his equations to prevent a presumably static universe from either contracting or expanding. Modern cosmologists have reintroduced it to their equations, where as the source of dark energy it causes the universe to expand ever faster.

Question 25

At decoupling, the protons and electrons formed transparent hydrogen atoms, allowing the radiation to escape and become the present microwave background.

Question 26

Decoupling refers to the separation of matter and antimatter during inflation.

Question 27

The 3 K background radiation is just the redshifted gamma wavelength radiation of the decoupling.

Question 28

In the Big Bang, about 75% of the normal matter by mass was hydrogen atoms, and the other 25% almost entirely helium.

Question 29

At decoupling, the electrons and protons were made from neutron decay.

Question 30

The carbon in your DNA was fused in the first few minutes of the Big Bang.

Question 31

Perhaps as much as 95% of the matter in superclusters is dark matter.

Question 32

The majority of dark matter is normal protons and neutrons.

Question 33

Of normal matter, about 25% of it by mass is still primordial helium even today.

Question 34

The fate or future of the universe depends only on the total number of galaxies and quasars.

Question 35

From the best current data, we infer the universe will expand forever.

Question 36

Like dark matter, dark energy will also retard the expansion of the universe.

Question 37

The cosmic microwave background is the total of all the radio emissions from all the galaxies and quasars in the universe.

Question 38

The radiation era lasted for only the first few billion years of the Big Bang.

Question 39

During the epoch of decoupling, nuclei and electrons combined to form atoms.

Question 40

Deuterium abundance suggests that normal matter makes up only 3- 4% of the critical density.

Question 41

The COBE satellite was designed to image the microwave cosmological background radiation and thus study the earliest stages of the universe.

Question 42

The concept that the direction of observation does NOT matter overall is

A) geometry.
B) universality.
C) homogeneity.
D) relativity.
E) isotropy.

Question 43

In the cosmological principle, we can easily test cosmic homogeneity with the redshift surveys, but isotropy cannot be so tested.

Question 44

The darkness of the night sky in an infinite universe is addressed in

A) Olbers's paradox.
B) Steady State Physics.
C) General Relativity.
D) Special Relativity.
E) the Cosmological principle.

Question 45

In which of the following models will the universe stop expanding?

A) open universe
B) steady state universe
C) critical density universe
D) closed universe
E) All have an ultimate collapse.

Question 46

If the inflation theory is correct, the geometry of the universe is flat and Euclidean.

Question 47

Because almost all galaxies show redshifted spectra, we know that

A) the universe is closed.
B) our understanding of redshift is wrong.
C) the sky must be dark at night.
D) the universe is expanding.
E) we must be at the center of the universe.

Question 48

The concept that on the grandest of scales, the universe is similar in appearance everywhere is

A) general relativity.
B) universality.
C) special relativity.
D) isotropy.
E) homogeneity.

Question 49

The horizon problem relates to the isotropy of the microwave background radiation.

Question 50

Homogeneity and isotropy, taken as assumptions regarding the structure and evolution of the universe, are known as

A) Olbers's paradox.
B) Wien's law.
C) Hubble's law.
D) the cosmological principle.
E) the Grand Unified Theory.

Question 51

The redshift of the galaxies is correctly interpreted as

A) the differences in temperatures and star formation in old and young galaxies.
B) a Doppler shift due to the random motions of galaxies in space.
C) an aging of light as gravity weakens with time.
D) space itself is expanding with time, so the photons are stretched while they travel through space.
E) placing our Galaxy near the center of the Local Group.

Question 52

If the accepted value of H were to double,

A) the age of the universe would be half what we believed.
B) the age of the universe would be twice as old as we originally believed.
C) the ages of the oldest globular clusters would be invalid.
D) the critical density would be halved.
E) the Copernican principle would not be valid beyond our solar system.

Question 53

In the GUT, electromagnetism and the strong nuclear force are the last to appear.

Question 54

COBE found the cosmic microwave background to be absolutely uniform everywhere.

Question 55

Cosmic inflation continues today in the cosmological redshifts and dark energy.

Question 56

The COBE data allow us to test the isotropy of the universe.

Question 57

If Euclid is right, then ▲o is

A) zero.
B) 0.3.
C) 1.0.
D) 2.0.
E) infinite.

Question 58

It appears that the universe is composed of nearly three times as much dark energy as normal and dark matter combined.

Question 59

There is a superforce that separates into the electromagnetic, weak, and strong nuclear forces below a critical temperature.

Question 60

What does Hubble's law imply about the history of the universe?

A) The universe had a beginning and has expanded since, giving it a finite age.
B) The redshifts will turn to blueshifts as universe contraction follows the expansion.
C) The Milky Way lies exactly at the center of this expansion.
D) The universe must be infinitely old and huge.
E) The redshifts will lengthen with time due to dark energy.

Question 61

The presently accepted value of the Hubble constant gives an age of

A) 4.5 billion years.
B) 8- 9 billion years.
C) 14 billion years.
D) 18 billion years.
E) 22 billion years.

Question 62

Why didn't elements heavier than helium form in the first minutes of creation?

A) The electrons slowed down enough to be captured into orbits by protons.
B) There was not enough matter in the universe at that time.
C) When He- 4 was formed, the expansion cooled the cosmos below 100 million K.
D) The first generation of stars used them up too quickly to observe them.
E) Only Type I supernovae can produce iron and heavier elements.

Question 63

In the closed universe model, the geometry of spacetime in two dimensions resembles the surface of a

A) saddle.
B) flat piece of paper.
C) cylinder.
D) sphere.
E) pyramid.

Question 64

How does the energy of the cosmic microwave background compare to the energy radiated by all the stars and galaxies that ever existed?

A) 73% cosmic background, 27% starlight
B) They are very close to being equal.
C) about ten times more from the Big Bang than from stars and galaxies
D) The starlight now dominates the background, as your eyes show clearly.
E) We have no way of comparing matter and energy this way.

Question 65

The major players in the discovery of the cosmic microwave background were at

A) Kitt Peak and the University of Arizona.
B) Cal Tech and Mt. Palomar.
C) Bell Labs and Princeton.
D) Jet Propulsion Lab and MIT.
E) Keck telescopes and the University of Hawaii.

Question 66

Before the decoupling,

A) deuterium produced electrons and positrons.
B) protons and electrons combined to form atoms.
C) the universe was opaque to radiation.
D) there was more helium than hydrogen.
E) the universe was transparent to radiation.

Question 67

What key event happened during the decoupling epoch?

A) Dark energy accelerated the cosmos on to infinity.
B) Electrons and positrons were created.
C) Expansion cooled the universe enough that protons could capture electrons in orbit.
D) Pairs of neutrons and protons were created.
E) The universe underwent a brief period of very rapid expansion.

Question 68

The Big Bang formed

A) only helium.
B) only hydrogen.
C) hydrogen and helium, but very little else.
D) all elements up to iron.
E) all elements found in nature now.

Question 69

If the density of the universe is greater than critical, then

A) the universe will continue expanding forever.
B) the universe will end up as nothing but black holes.
C) the universe is closed, gravity wins, and will shrink to the Big Crunch.
D) the universe is flat, and Euclid is right.
E) there is more matter than energy.

Question 70

What temperature has the Big Bang cooled to by now?

A) 5,800 K
B) just over 2.7 K
C) about 3,000 K
D) 1.4 K
E) about 300 K

Question 71

According to the turn- off points of the oldest globular clusters, they are about

A) 4.5 billion years old.
B) 6.8 billion years old.
C) 10 billion years old.
D) 12 billion years old.
E) 16 billion years old.

Question 72

Concerning dark energy, we do know

A) that it is created when matter annihilates anti- matter.
B) that it was revealed with Type II supernovae distances in the late 1990s.
C) its density remains constant over time, so it is not important in the early universe.
D) that it makes up 90% of all the matter and energy in the whole universe.
E) combined with dark matter, it will ultimately produce a closed universe.

Question 73

With a Hubble constant of 70 km/sec/Mpc, the critical density would be

A) 3 × 10- 31 g/cc.
B) 9 × 10- 27 kg/m3.
C) 6.23 × 10- 23 g/mole.
D) 4 × 10- 36 g/cc.
E) 1.4 g/cc.

Question 74

If ▲o is less than one, then

A) no matter could have existed.
B) only dark energy exists in the universe.
C) the universe will expand forever.
D) there is more matter than energy in the universe.
E) the universe is closed, and must recycle.

Question 75

What is the meaning of a "closed" universe?

A) The universe will disappear into a white hole in time.
B) The universe is in a steady- state.
C) The universe will stop expanding in an infinite amount of time.
D) The universe will expand forever.
E) The universe will someday stop expanding and start to collapse.

Question 76

The expansion rate of the universe is

A) constant.
B) increasing.
C) independent of time.
D) decreasing.
E) different in different directions.

Question 77

Studies from _ led to the discovery of "dark energy."

A) the gravitational lensing by MACHOs
B) Cepheid variables in the Virgo Cluster
C) Type II supernovae in the Large Magellanic Cloud
D) Type I supernovae at very large redshifts
E) the COBE microwave ripples

Question 78

The discovery of the cosmic microwave background was important because

A) its detection was a major advance in microwave testing.
B) it established a firm center of the universe.
C) it proved that astronomy at radio wavelengths was possible.
D) it showed the universe must be closed, with more than the critical density here.
E) it was experimental verification of a prediction from the Big Bang theory.

Question 79

Most of the deuterium formed right after the Big Bang

A) turned into dark matter.
B) was found in the globular clusters.
C) broke down into electrons and neutrons.
D) quickly burned into helium nuclei.
E) is still around today.

Question 80

In the critical density universe now proposed, the ratio of dark energy to matter is about

A) 1 to 1.
B) 10 to 1.
C) 1 to 5.
D) 1 to 100.
E) 3 to 1.