Question 1

In quantum electrodynamics (QED),what mediates the electromagnetic force between particles?

Accepted Answer

In QED,the electromagnetic for

Question 2

Which of the following are NOT considered carrier particles used to mediate forces between other particles?

Accepted Answer

A)  Photons 
B)  Gluons 
C)  Quarks 
D)  W+ particles 
A)  Photons 
B)  Gluons 
C)  Quarks 
D)  W+ particles

Question 3

When the universe was __________ old,approximately 24 percent of the normal matter in it had been turned into helium.

Accepted Answer

A)  5 minutes 
B)  8 hours 
C)  1,000 years 
D)  4.5 billion years 
A)  5 minutes 
B)  8 hours 
C)  1,000 years 
D)  4.5 billion years

Question 4

Dark energy is a force that continually decreases the expansion rate of the universe.

Accepted Answer

A) True 
 B)False

Question 5

Which was a triumph of quantum electrodynamics (QED)?

Accepted Answer

A)  QED predicted the existence of three carrier particles before they were discovered in laboratory experiments. 
B)  QED unites the strong and weak nuclear forces. 
C)  QED is an example of a theory of everything. 
D)  QED successfully explains the origin of quantum mechanical fluctuations in the CBR. 
A)  QED predicted the existence of three carrier particles before they were discovered in laboratory experiments. 
B)  QED unites the strong and weak nuclear forces. 
C)  QED is an example of a theory of everything. 
D)  QED successfully explains the origin of quantum mechanical fluctuations in the CBR.

Question 6

The critical mass density of the universe today is   .Using the current observed value of   ,what is the average density of protons in the universe? If they were spread evenly throughout the universe,what would be their typical separation? Note that the mass of the proton is   .

Accepted Answer

The average density of protons

Question 7

In order to produce an electron and a positron,a photon must have

Accepted Answer

A)    . 
B)    . 
C)    . 
D)  an infinite energy. 
A)    . 
B)    . 
C)    . 
D)  an infinite energy.

Question 8

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

Accepted Answer

A) True 
 B)False

Question 9

To verify whether or not some grand unified theories are correct,physicists are searching for

Accepted Answer

A)  the Big Rip. 
B)  mini-black holes. 
C)  protons that decay. 
D)  dark matter that decays. 
A)  the Big Rip. 
B)  mini-black holes. 
C)  protons that decay. 
D)  dark matter that decays.

Question 10

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

Accepted Answer

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

Question 11

The fact that   is very close to 1 means that its value has always been very close to 1.

Accepted Answer

A) True 
 B)False

Question 12

During inflation when the universe was approximately 1 second old,its size grew by a factor of   .

Accepted Answer

A) True 
 B)False

Question 13

The force that binds three quarks together to make up a proton or neutron is called the weak force.

Accepted Answer

A) True 
 B)False

Question 14

Directly after the Big Bang,the universe was filled with a variety of charged particles,antiparticles,and photons.

Accepted Answer

A) True 
 B)False

Question 15

In the superstring theory that successfully unites gravity and quantum mechanics,the universe must have

Accepted Answer

A)  11 dimensions (10 spatial and 1 temporal). 
B)  4 dimensions (3 spatial and 1 temporal). 
C)  9 dimensions (8 spatial and 1 temporal). 
D)  6 dimensions (3 spatial and 3 temporal). 
A)  11 dimensions (10 spatial and 1 temporal). 
B)  4 dimensions (3 spatial and 1 temporal). 
C)  9 dimensions (8 spatial and 1 temporal). 
D)  6 dimensions (3 spatial and 3 temporal).

Question 16

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

Accepted Answer

At the very moment of its creation,the u

Question 17

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

Accepted Answer

A)      ,   . 
B)    ,   ,   . 
C)    ,   ,   . 
D)    ,   ,   . 
A)      ,   . 
B)    ,   ,   . 
C)    ,   ,   . 
D)    ,   ,   .

Question 18

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

Accepted Answer

A)    
B)    
C)    
D)    
A)    
B)    
C)    
D)

Question 19

Why does a unified force split to become two separate forces?

Accepted Answer

A)  The universe expands so much that carrier particles become too dense. 
B)  The energy in the CBR becomes less than the mass of the unified force's carrier particles. 
C)  Dark energy becomes significant at later times and forces the two to split. 
D)  The spatial dimensions split and so must the forces. 
A)  The universe expands so much that carrier particles become too dense. 
B)  The energy in the CBR becomes less than the mass of the unified force's carrier particles. 
C)  Dark energy becomes significant at later times and forces the two to split. 
D)  The spatial dimensions split and so must the forces.

Question 20

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

Accepted Answer

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. 
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.

Exam 21: Modern Cosmology

In quantum electrodynamics (QED),what mediates the electromagnetic force between particles?

Which of the following are NOT considered carrier particles used to mediate forces between other particles?

When the universe was __________ old,approximately 24 percent of the normal matter in it had been turned into helium.

Dark energy is a force that continually decreases the expansion rate of the universe.

Which was a triumph of quantum electrodynamics (QED)?

The critical mass density of the universe today is .Using the current observed value of ,what is the average density of protons in the universe? If they were spread evenly throughout the universe,what would be their typical separation? Note that the mass of the proton is .

In order to produce an electron and a positron,a photon must have

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

To verify whether or not some grand unified theories are correct,physicists are searching for

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

The fact that is very close to 1 means that its value has always been very close to 1.

During inflation when the universe was approximately 1 second old,its size grew by a factor of .

The force that binds three quarks together to make up a proton or neutron is called the weak force.

Directly after the Big Bang,the universe was filled with a variety of charged particles,antiparticles,and photons.

In the superstring theory that successfully unites gravity and quantum mechanics,the universe must have

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

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

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

Why does a unified force split to become two separate forces?

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

Why Learn Astronomy

Patterns in the Skymotions of Earth

Gravity and Orbitsa Celestial Ballet

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 Liquidthe Giant Planets

Gravity Is More Than Keplers Laws

Planetary Adornmentsmoons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

A Run-Of-The-Mill G-Type Starour Sun

Star Formation and the Interstellar Medium

Stars in the Slow Lanelow-Mass Stellar Evolution

Live Fast,die Younghigh-Mass Stellar Evolution

Our Expanding Universe

Galaxies

The Milky Waya Normal Spiral Galaxy

The Origin of Structure

Life

Filters