Deck 16: The Evolution of the Universe

Question 1

How does the addition of a nonzero cosmological constant affect the expansion of the universe?

A) It is possible for the mass density of the universe to be below the critical density and still collapse.
B) It is possible for the density of the universe to be below the critical density and still expand forever.
C) It is impossible to have a collapsing universe, regardless of its density.
D) It is impossible to have an expanding universe, regardless of its density.

Answer 1

It is possible for the density of the universe to be below the critical density and still expand forever.

Question 2

If Wmₐttₑᵣ = 0.5 today and there were no dark energy,the universe would:

A) expand forever.
B) slow its expansion but never reverse it.
C) stop expanding and eventually collapse.
D) oscillate between expansion and collapse.

Answer 2

expand forever.

Question 3

Observations of Type Ia supernovae in distant galaxies have shown that:

A) the star formation rate in galaxies decreases with increasing redshift.
B) the expansion rate of the universe is increasing.
C) the cosmological constant is zero.
D) dark energy is negligible at the present time.

Answer 3

the expansion rate of the universe is increasing.

Question 4

Why was the discovery of dark energy unexpected?

A) The gravity provided by the mass contained within the universe was predicted to slow the expansion.
B) The acceleration of the universe was predicted to increase.
C) Astronomers had not anticipated being able to observe supernovae at such large distances.
D) The universe was expected to lose, not gain energy.

Question 5

Why does the expansion of space cause redshifts of distant galaxies?

A) The amount of space in between the galaxies is increasing.
B) All galaxies are moving away from us because we are at the center of the universe.
C) All galaxies are moving toward us because we are at the center of the universe.
D) Galaxies do not show redshifts.

Question 6

Why does the overall mass and energy density of the universe decide its ultimate fate?

A) The greater the density of the universe, the more black holes will form, which will devour surrounding material more quickly.
B) The greater the density of the universe, the more gravitationally bound the universe will be.
C) The greater the density of the universe, the more massive stars it will contain, and the faster it will evolve.
D) The greater the density of the universe, the more stars it will form over time, and the longer the universe will last.

Question 7

After the Big Bang,as the universe cooled and protons and electrons combined so that the universe became neutral,what important consequence happened?

A) Photons began to travel freely through the universe.
B) Neutrinos ceased to interact with normal matter.
C) Dark matter ceased to interact with normal matter.
D) Protons and neutrons combined to form nuclei such as deuterium and helium.

Question 8

Was the Big Bang an explosion that flung debris throughout space?

A) Yes, the debris made the first stars.
B) Yes, the debris made protons, neutrons, and electrons.
C) No, the Big Bang formed space and time.
D) No, the debris was already present.

Question 9

Where in the universe did the Big Bang take place?

A) near the Milky Way Galaxy
B) near the Virgo Cluster
C) near some unknown location on the other side of the universe
D) everywhere in the universe

Question 10

The critical density of the universe is approximately equal to:

A) 1 proton/m3.
B) 1 kg/m3.
C) 1 Earth mass/m3.
D) 1 solar mass/m3.

Question 11

Which of the following is NOT a prediction of the standard Big Bang theory that has been successfully verified by observations?

A) The universe is expanding.
B) The faintest galaxies look redder because their stars are younger.
C) Helium, lithium, and beryllium were made as the universe cooled after the initial Big Bang.
D) The early universe was very hot and dense.

Question 12

Why is it NOT possible to look all the way back to the Big Bang itself?

A) Photons are not produced until the stars form.
B) At such high redshifts, photons are gravitationally lensed by the dark matter in the universe.
C) At such high redshifts, most of the photons are blocked by large amounts of cold gas and dust.
D) At such high redshifts, photons are heavily altered because they easily react with individual protons and electrons in the universe.

Question 13

Because we live in a universe with an accelerating expansion rate,the actual age of the universe is ________ the Hubble time.

A) larger than
B) smaller than
C) the same as
D) independent of

Question 14

In the early 1960s,physicists named Penzias and Wilson detected a persistent noise at a wavelength of 1 mm in their radio telescope.The persistent noise that Penzias and Wilson detected came from all directions in the sky due to:

A) synchrotron emission from the Crab Nebula.
B) emission from newly formed stars in the Orion Nebula.
C) cell phone usage.
D) photons leftover from the Big Bang.

Question 15

If the fate of the universe were determined SOLELY by what we currently know to be the total mass of the universe in luminous and dark matter (excluding dark energy),astronomers would predict that we live in a universe that will:

A) expand forever.
B) slow its expansion but never reverse it.
C) stop expanding and eventually collapse.
D) oscillate between expansion and collapse.

Question 16

The inverse of the value of H₀ is a:

A) time.
B) mass.
C) density.
D) size.

Question 17

Current observations suggest that the density of luminous matter (Wlᵤmᵢnₒᵤs),all matter (Wmₐttₑᵣ),and dark energy (WL)are:

A) Wluminous = 0.1, Wmatter = 0.3, WL = 0.7
B) Wluminous = 0.02, Wmatter = 0.5, WL = 0.5
C) Wluminous = 0, Wmatter = 0.1, WL = 0.9
D) Wluminous = 0.02, Wmatter = 0.3, WL = 0.7

Question 18

The current temperature of the cosmic microwave background radiation of 2.73 K means that the peak of its spectrum occurs at a wavelength of:

A) gamma rays.
B) infrared.
C) microwaves.
D) ultraviolet.

Question 19

In the 1990s,astronomers found that distant Type Ia supernovae were ________ than they expected,leading them to conclude that ________.

A) brighter; the universe's expansion rate was decreasing with time
B) brighter; the universe was finite in size
C) fainter; the universe's expansion rate has been increasing with time
D) fainter; the universe was infinite in size

Question 20

The existence of the cosmic microwave background radiation tells us that the early universe was:

A) much hotter than it is today.
B) much colder than it is today.
C) composed entirely of radiation at early times.
D) composed entirely of stars at early times.

Question 21

By the time the universe was a few minutes old,the majority of the normal matter in the universe was hydrogen,and the remainder was mostly ________.

A) helium
B) neutrons
C) neutrinos
D) protons

Question 22

Which of the following was NOT created in the early universe as a result of the Big Bang?

A) helium
B) lithium
C) carbon
D) deuterium

Question 23

The flatness problem arises because only a universe with ________ can have that value forever.

A) Wmass + WL= 0
B) Wmass + WL = 1
C) Wluminous + WL = 1
D) Wluminous + WL = 0

Question 24

Grand unified theories are very attractive because they can explain:

A) why the universe consists mostly of matter.
B) why the Big Bang never made any antimatter.
C) why we have five fundamental forces in the universe today.
D) why the cosmic microwave background radiation is very smooth.

Question 25

What can simultaneously solve both the flatness and horizon problems in cosmology?

A) GUTs
B) quantum mechanics
C) inflation
D) dark energy

Question 26

In some particle physics theories,the universe must have more than three spatial dimensions,but we experience only three.Why would we not see the other spatial dimensions?

A) The other six spatial dimensions are tightly wrapped around each other and have not expanded.
B) The other nine spatial dimensions are too small to be noticeable.
C) The other seven spatial dimensions undergo inflation and flatten themselves out.
D) The other nine spatial dimensions wrap around each other and form the temporal dimension.

Question 27

Why is the fact that the cosmic microwave background radiation is very smooth considered a problem?

A) A universe as smooth as predicted by the cosmic microwave background radiation should not have formed as many galaxies as have been observed.
B) A universe as smooth as predicted by the cosmic microwave background radiation should have collapsed by now.
C) A universe as smooth as predicted by the cosmic microwave background radiation should be expanding much faster than we are now.
D) A universe as smooth as predicted by the cosmic microwave background radiation should never have occurred occur because quantum mechanical fluctuations would have been imprinted on it.

Question 28

A grand unified theory unites which forces?

A) only electromagnetism, weak nuclear, and strong nuclear
B) only gravity and strong nuclear
C) only electromagnetism, gravity, and weak nuclear
D) all four known forces

Question 29

What would the universe be like if there were complete symmetry between matter and antimatter?

A) It would look similar to our universe, but half of it would be composed of antimatter.
B) We would observe two universes, one an antimatter reflection of the other.
C) There would be no universe because all of the matter and antimatter would have been annihilated.
D) There would be a universe, but it would be completely composed of energy.

Question 30

List the four fundamental forces of nature.

A) electromagnetic, gravity, strong nuclear, and weak nuclear
B) electroweak, gravity, magnetic, and nuclear
C) gravity, magnetism, strong nuclear, and weak nuclear
D) electrostrong, gravity, magnetic, and nuclear

Question 31

The standard model of particle physics is incomplete because it leaves which question(s)unanswered?

A) Why do neutrinos have mass?
B) Why is the strong nuclear force much stronger than the weak nuclear force?
C) How is gravity related to the other three fundamental forces?
D) all of the above

Question 32

Even with infinitely powerful telescopes,we can look back in time only until:

A) when galaxies were first formed.
B) when hydrogen and helium were formed.
C) when gravity was quantum mechanical.
D) the time of recombination.

Question 33

If Wmₐttₑᵣ + WL = 1 today and dark energy was a cosmological constant,the universe will:

A) expand forever.
B) slow its expansion but never reverse it.
C) stop expanding and eventually collapse.
D) oscillate between expansion and collapse.

Question 34

How would astronomers describe the antiparticle of an electron?

A) It would have the same mass but opposite charge.
B) It would have the same charge but opposite spin.
C) It would have the opposite charge and higher mass.
D) It would have the opposite spin and higher mass.

Question 35

Inflation happened when:

A) the universe was <10-33 seconds old.
B) the universe expanded by a factor of approximately 1030.
C) the average energy of the vacuum of spacetime changed.
D) all of the above

Question 36

If multiverses exist,which of the following is correct?

A) Each universe is identical to every other.
B) Multiverses are not allowed by the laws of physics as we understand them.
C) The universes can never communicate with each other.
D) You have lived your exact same life in every universe.

Question 37

Whether or not parallel universes exist is hard to determine because:

A) our universe is so big.
B) the parallel universes cannot communicate with each other.
C) the other universes do not emit any light.
D) parallel universes destroy each other if they come into contact.

Question 38

About what was the temperature of the universe when a typical cosmic microwave background radiation photon was no longer able spontaneously to create an electron and positron pair?

A) 1000 K
B) 100,000 K
C) 1 million K
D) 1 billion K

Question 39

At what stage in the universe's history do we think the asymmetry between matter and antimatter was created?

A) at the very moment the Big Bang occurred
B) about the time gravity separated out of the theory of everything
C) about the time the strong force separated out of the grand unified theory
D) about the time the weak force and electromagnetism separated

Question 40

Soon after the Big Bang,we believe the four fundamental forces of nature were united into one superforce,and ________ was the first to split off from the others.

A) the strong force
B) electromagnetism
C) gravity
D) nucleosynthesis

Question 41

Describe the four fundamental forces of nature by listing their names and describing what effect each force has on objects in the universe.

Question 42

Why does the sum of Wmₐss and WL determine the shape of our universe?

Question 43

Explain why astronomers cannot accurately model the exact history of the universe in the first few fractions of a second after the Big Bang.

Question 44

Name two predictions of the standard Big Bang theory that have been verified by observations.

Question 45

Why does the critical mass density of the universe depend on the value of the Hubble constant,H₀?

Question 46

What is the "flatness problem" in cosmology?

Question 47

The COBE and WMAP satellites detected fluctuations in the cosmic microwave background radiation.On average,how big were these fluctuations,and what does that tell us about the very early universe?

Question 48

Assuming the Hubble constant is equal to 72 km/s/Mpc,estimate the age of the universe (or Hubble time).Note that 1 Mpc = 3.1 × 10¹⁹ km,and 1 year = 3.17 × 10⁷ seconds.

Question 49

If dark energy is currently causing the expansion rate of the universe to increase with time,does this mean that you should worry that the Sun,Earth,and your body itself are expanding? Why or why not?

Question 50

The cosmic microwave background radiation has a temperature of approximately 2.7 K and a Planck blackbody spectrum.Calculate the wavelength where the cosmic microwave background radiation spectrum peaks.

Question 51

What will happen to the expansion of the universe in the future if (a)W > 1,(b)W = 1,and (c) W < 1?

Question 52

What is the difference between a grand unified theory (GUT)and a theory of everything (TOE)?

Question 53

What can solve the flatness and horizon problem in cosmology,and why?

Question 54

What important event in the universe's history marked the creation of the cosmic microwave background radiation?

Question 55

Why is the universe made up of matter as opposed to antimatter?