Question 1

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?

Accepted Answer

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

Question 2

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.

Accepted Answer

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

Question 3

Why would it be very improbable for our universe to have Ω mass+ ΩΛ =0.9?

Accepted Answer

A) It would quickly evolve to have a much different value of Ωmass +ΩΛ. 
B) In order to exist,every universe must have Ωmass + ΩΛ =1. 
C) We know Ωmass = 1,based on the average density of galaxies. 
D) The fluctuation in the CMB tell us that Ωmass + ΩΛ = 0.7. 
E) Dark energy studies tell us ΩΛ = 0.9. 
A) It would quickly evolve to have a much different value of Ωmass +ΩΛ. 
B) In order to exist,every universe must have Ωmass + ΩΛ =1. 
C) We know Ωmass = 1,based on the average density of galaxies. 
D) The fluctuation in the CMB tell us that Ωmass + ΩΛ = 0.7. 
E) Dark energy studies tell us ΩΛ = 0.9.

Question 4

In the early universe,which type of particle and anti-particle first stopped being spontaneously formed out of photons in the CMB?

Accepted Answer

A) Protons and neutrons,because their formation requires a larger number of photons 
B) Electrons and positrons,because their formation requires a smaller number of photons 
C) Protons and antiprotons,because their formation requires higher energy photons 
D) Electrons and neutrinos,because their formation requires lower energy photons 
E) Protons,antiprotons,electrons,and neutrinos stopped forming at the same time. 
A) Protons and neutrons,because their formation requires a larger number of photons 
B) Electrons and positrons,because their formation requires a smaller number of photons 
C) Protons and antiprotons,because their formation requires higher energy photons 
D) Electrons and neutrinos,because their formation requires lower energy photons 
E) Protons,antiprotons,electrons,and neutrinos stopped forming at the same time.

Question 5

From the analysis of distant Type I supernovae and the Cosmic Microwave Background,we know that the Universe is approximately

Accepted Answer

A) 4.6 million years old 
B) 4.6 billion years old 
C) 6.5 thousand years old 
D) 13.7 million years old 
E) 13.7 billion years old 
A) 4.6 million years old 
B) 4.6 billion years old 
C) 6.5 thousand years old 
D) 13.7 million years old 
E) 13.7 billion years old

Question 6

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

Accepted Answer

A) Ωmass +ΩΛ= 0 
B) Ωmass +ΩΛ =1 
C) Ωmass +Ωluminous =1 
D) Ωluminous +ΩΛ =1 
E) Ωluminous+ ΩΛ =0 
A) Ωmass +ΩΛ= 0 
B) Ωmass +ΩΛ =1 
C) Ωmass +Ωluminous =1 
D) Ωluminous +ΩΛ =1 
E) Ωluminous+ ΩΛ =0

Question 7

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

Accepted Answer

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 
E) there were more stars in the past than at the present time 
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 
E) there were more stars in the past than at the present time

Question 8

In a closed (spherical)universe,the sum of the angles in a triangle is:

Accepted Answer

A) 180 degrees 
B) 180 degrees 
E) 240 degrees 
A) 180 degrees 
B) 180 degrees 
E) 240 degrees

Question 9

In a universe with no dark energy,what will happen to the expansion of the universe in the future if: (a)Ωmass> 1, (b)Ωmass= 1,and (c)Ωmass <1?

Accepted Answer

For each case:
(a)The universe's expansi

Question 10

In order to produce an electron and a positron,two photons must have a combined energy of:

Accepted Answer

A) E > 2mec2 
B) E > mec2 
C) E > 1⁄2mec2 
D) E = mec2 
E) This cannot happen. 
A) E > 2mec2 
B) E > mec2 
C) E > 1⁄2mec2 
D) E = mec2 
E) This cannot happen.

Question 11

In the 1990s,astronomers found that distant Type I supernova were __________ than they expected,leading them to conclude that __________.

Accepted Answer

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 
E) fainter;the universe was finite in size 
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 
E) fainter;the universe was finite in size

Question 12

The ratio of the density of luminous matter in our universe to the critical density is 0.3.

Accepted Answer

A) True 
 B)False

Question 13

The universe can be infinite in size for which shapes of the universe?

Accepted Answer

A) open 
B) closed 
C) flat 
D) closed and flat 
E) open and flat 
A) open 
B) closed 
C) flat 
D) closed and flat 
E) open and flat

Question 14

If the Hubble constant were larger than it is,how would that change the measured age of the universe? Explain your answer.

Accepted Answer

If the Hubble constant were larger,then

Question 15

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

Accepted Answer

A) GUT 
B) quantum mechanics 
C) TOE 
D) inflation 
E) dark energy 
A) GUT 
B) quantum mechanics 
C) TOE 
D) inflation 
E) dark energy

Question 16

Current observations suggest that the density of luminous matter,all matter,and dark energy are:

Accepted Answer

A) Ω luminous = 0.1,Ω mass = 0.3,Ω Λ = 0.7 
B) Ω luminous = 0.02,Ω mass = 0.5,Ω  Λ = 0.5 
C) Ω luminous = 0,Ω mass = 0.1,Ω Λ = 0.9 
D) Ω luminous = 0.02,Ω mass = 0.3,Ω Λ = 0.7 
E) Ω luminous = 0.1,Ω mass = 0.2,Ω Λ = 0.7 
A) Ω luminous = 0.1,Ω mass = 0.3,Ω Λ = 0.7 
B) Ω luminous = 0.02,Ω mass = 0.5,Ω  Λ = 0.5 
C) Ω luminous = 0,Ω mass = 0.1,Ω Λ = 0.9 
D) Ω luminous = 0.02,Ω mass = 0.3,Ω Λ = 0.7 
E) Ω luminous = 0.1,Ω mass = 0.2,Ω Λ = 0.7

Question 17

Quantum chromodynamics describes how __________ works.

Accepted Answer

A) gravity 
B) the strong nuclear force 
C) electricity 
D) magnetism 
E) light 
A) gravity 
B) the strong nuclear force 
C) electricity 
D) magnetism 
E) light

Question 18

The theory of inflation assumes that at some point in the future dark energy will decay and the universe will expand rapidly by a factor of 1030.

Accepted Answer

A) True 
 B)False

Question 19

What was the temperature of the universe when a typical CMB photon was no longer able to spontaneously create an electron and positron pair? Note that a photon has an energy equal to E = hc/λ,the CMB at any point in time has a blackbody spectrum that peaks at a wavelength λpeak = (2900 μm K)/T,and the mass of a single electron is 9 × 10−31 kg.

Accepted Answer

A) 2000 K 
B) 400,000 K 
C) 2 million K 
D) 40 million K 
E) 2 billion K 
A) 2000 K 
B) 400,000 K 
C) 2 million K 
D) 40 million K 
E) 2 billion K

Question 20

How does the existence of dark energy affect the expansion of the universe?

Accepted Answer

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 mass 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. 
E) It is impossible for the mass density of the universe to be above the critical density and still expand forever. 
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 mass 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. 
E) It is impossible for the mass density of the universe to be above the critical density and still expand forever.

Exam 22: Modern Cosmology

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?

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.

Why would it be very improbable for our universe to have Ω mass+ ΩΛ =0.9?

In the early universe,which type of particle and anti-particle first stopped being spontaneously formed out of photons in the CMB?

From the analysis of distant Type I supernovae and the Cosmic Microwave Background,we know that the Universe is approximately

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

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

In a closed (spherical)universe,the sum of the angles in a triangle is:

In a universe with no dark energy,what will happen to the expansion of the universe in the future if: (a)Ωmass> 1, (b)Ωmass= 1,and (c)Ωmass <1?

In order to produce an electron and a positron,two photons must have a combined energy of:

In the 1990s,astronomers found that distant Type I supernova were __________ than they expected,leading them to conclude that __________.

The ratio of the density of luminous matter in our universe to the critical density is 0.3.

The universe can be infinite in size for which shapes of the universe?

If the Hubble constant were larger than it is,how would that change the measured age of the universe? Explain your answer.

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

Current observations suggest that the density of luminous matter,all matter,and dark energy are:

Quantum chromodynamics describes how __________ works.

The theory of inflation assumes that at some point in the future dark energy will decay and the universe will expand rapidly by a factor of 1030.

How does the existence of dark energy affect the expansion of the universe?

Why Learn Astronomy

Patterns in the Skymotions of Earth

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Birth and Evolution of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquid the Giant Planets

Planetary Adornments Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

Star Formation and the Interstellar Medium

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

The Expanding Universe

Galaxies

The Milky Waya Normal Spiral Galaxy

Large-Scale Structure in the Universe

Life

Filters

Why would it be very improbable for our universe to have Ω _mass+ Ω_Λ =0.9?

In a universe with no dark energy,what will happen to the expansion of the universe in the future if: (a)Ω_mass> 1, (b)Ω_mass= 1,and (c)Ω_mass <1?

In the 1990s,astronomers found that distant Type I supernova were than they expected,leading them to conclude that .

The theory of inflation assumes that at some point in the future dark energy will decay and the universe will expand rapidly by a factor of 10³⁰.