Chapter 17 Mastering Astronomy

Question 1

During the history of the universe, what important even occurred about 0.001 seconds after the big bang?

Answer 1

Most matter in the early universe was annihilated by antimatter.

Question 2

Which of the following important events occurred earliest in the history of the universe?

Answer 2

Spacetime rapidly expanded during a brief period of inflation.
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Question 3

During the history of the universe, what important even occurred about 380,000 years after the Big Bang?

Answer 3

Light began to travel freely through the universe.

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Question 4

Essentially all the hydrogen nuclei that will ever exist in our universe was created __________.

Answer 4

by the time the universe was about 3 minutes old

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Question 5

Compared to when the cosmic microwave background was first released, the radiation of the cosmic microwave background today is __________.

Answer 5

fainter and has most of its photons at longer wavelengths

Question 6

Hydrogen nuclei are protons, and protons were formed during the particle era. During the next three minutes, many of these protons fused and then broke back apart, but by the end of that period these reactions stopped. Essentially all the hydrogen that will ever exist was therefore present in the universe when the universe was just 3 minutes old, because subsequent fusion in stars has consumed some of this hydrogen but has not made any more.

Answer 6

Hydrogen nuclei are protons, and protons were formed during the particle era. During the next three minutes, many of these protons fused and then broke back apart, but by the end of that period these reactions stopped. Essentially all the hydrogen that will ever exist was therefore present in the universe when the universe was just 3 minutes old, because subsequent fusion in stars has consumed some of this hydrogen but has not made any more.

Question 7

Mathematically bubble’s law is expressed as:

v=HoXd
v stands for?
Ho?
d?

Answer 7

v= recession velocity
d= distance from earth
Ho= hubble's constant which is the relationship between distance and time

Question 8

Based on our current understanding of physics, it would seem that we can understand the conditions that prevailed in the early universe as far back in time as _________.

Answer 8

one ten-billionth of a second after the Big Bang

Question 9

What happens when a particle of matter meets its corresponding antiparticle of antimatter?

Answer 9

The combined mass-energy of the two particles is completely transformed into radiation-energy (two photons).

Question 10

What is the significance of the Planck time?

Answer 10

Before it, conditions were so extreme that our current understanding of physics is insufficient to predict what might have occurred.

Question 11

The four fundamental forces that operate in the universe today are _________.

Answer 11

strong force, weak force, electromagnetic force, gravity

Question 12

A “GUT” (grand unified theory) refers to theories that _________.

Answer 12

unify the strong force with the electromagnetic and weak forces

Question 13

What do we mean by inflation?

Answer 13

We mean a sudden and rapid acceleration of the universe that went on for a tiny fraction of a second at the time the strong force froze out from the GUT force.

Question 14

Of the statements below, which one correctly summarizes the events in the early universe according to the Big Bang theory?

The universe began with the forces ________.
During the first fraction of a second, the forces __________ and there was a brief but important episode of _____________.

Answer 14

The universe began with the forces UNIFIED.
During the first fraction of a second, the forces SEPARATED and there was a brief but important episode of INFLATION. SUBATOMIC PARTICLES of both matter and antimatter then began to appear from the ENERGY PRESENT in the universe.
Most of the particles annihilated to make PHOTONS, but some became PROTONS NEUTRON ELECTRONS, and NEUTRINOS.
The protons and neutrons underwent some fusion during the first 3 MINUTES, which determined the BASIC CHEMICAL COMPOSITION OF THE UNIVERSE.

Question 15

Which statement about the cosmic microwave background is NOT true?

Answer 15

It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.

Question 16

The Big Bang theory is supported by two major lines of evidence that alternative models have not successfully explained. What are they?

Answer 16

1) the theory predicts the existence of and the specific characteristics of the observed cosmic microwave background; (2) the theory correctly predicts the observed overall chemical composition of the universe.

Question 17

Measuring the amount of deuterium in the universe allows us to set a limit on _________.

Answer 17

the density of ordinary (baryonic) matter the universe

Question 18

Based on the Big Bang theory, what do observations of the cosmic microwave background and of chemical abundances in the universe suggest about dark matter?

Answer 18

Much of the dark matter must be made of non-ordinary (nonbaryonic) matter, such as WIMPs.

Question 19

Which of the following observations cannot be explained by the Big Bang theory unless we assume that an episode of inflation occurred?

Answer 19

The fact that the temperature of the cosmic microwave background is almost the same everywhere

Question 20

The idea of inflation makes one clear prediction that, until quite recently, seemed to contradict the available observations. What is this prediction?

Answer 20

The universe should be geometrically “flat” (in the four dimensions of spacetime).

Question 21

Olbers’s paradox is an apparently simple question, but its resolution suggests that the universe is finite in age. What is the question?

Answer 21

Why is the sky dark at night?

Question 22

Bubbles law is based on the relationship stating…

Answer 22

velocity is proportional to the galaxy’s distance from earth

Question 23

as Distance from earth increases, velocity…

Answer 23

increases

Question 24

galaxies move in relation to Earth due to

Answer 24

gravity of other galaxies and expansion of space

Question 25

Why do you think we see dark space between the galaxies?

Answer 25

the universe has a finite age so there is a maximum distance something can be before we can see the light emitted. Galaxies more than 14 billion light years away ‘s light has not had enough time to reach earth

Question 26

One reason Hubble’s constant is not known is because

Answer 26

the exact distance of a galaxy is hard to measure

Question 27

When the four fundamental forces behaved as one

Answer 27

Planck Era

Question 28

gravity became distinct at the end of

Answer 28

GUT Era

Question 29

electromagnetism and the weak force became distinct at the end of

Answer 29

Electroweak Era

Question 30

Matter particles annihilated all the antimatter particles by the end of the

Answer 30

particle era

Question 31

Fusion of protons and neutrons into helium ceased at the end of the era of

Answer 31

nucleosynthesis.

Question 32

Hydrogen nuclei captured all the free electrons, forming hydrogen atoms at the end of the era of

Answer 32

nuclei.

Question 33

Galaxies began to form at the end of the era of

Answer 33

atoms

Question 34

radiation left over from the Big Bang is called

Answer 34

cosmic microwave background