Exam 25: Cosmology: The Origin and Evolution of the Universe

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Suppose the ionization energy of hydrogen were larger than 13.6 eV and the decoupling of radiation and matter had occurred earlier, say at z = 2000. What would the temperature have been at that time?

(Multiple Choice)

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Question 21

In Newton's model of an infinite universe with stars distributed smoothly throughout, an individual star would feel:

(Multiple Choice)

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Question 22

If the Hubble constant is 73 km/s/Mpc then the age of the universe is 13.4 billion years, assuming a uniform expansion. Suppose it were discovered that the Hubble constant is actually larger than 73 km/s/Mpc. What effect would this have on the calculated age of the universe?

(Multiple Choice)

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Question 23

Which one of the following statements represents a correct description of the expansion of the universe?

(Multiple Choice)

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Question 24

Where in the universe does the "general" expansion occur?

(Multiple Choice)

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Question 25

What is the lookback time (i.e., how long ago did the light leave its source) for an object with a redshift z = 0.05, assuming that the Hubble constant is 22.4 km/s/Mly? (Assume nonrelativistic speed for this object.)

(Multiple Choice)

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Question 26

What will happen if the universe is bounded?

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Question 27

At present, the energy density of matter greatly exceeds that of radiation. But in the early universe, radiation energy was dominant. Why was this?

(Multiple Choice)

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Question 28

In cosmology, to what does the phrase "critical density" refer?

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Question 29

The Sun presently consists of about 25% helium. Where did this helium come from?

(Multiple Choice)

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Question 30

The discovery that the Sun and similar stars consist of about 25% helium posed a dilemma: There was too much helium in the universe to be accounted for by nucleosynthesis in stars in the contemporary cosmological models. How was this dilemma resolved?

(Multiple Choice)

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Question 31

A few decades ago many astronomers used a value 42 km/s/Mpc for the Hubble constant. What was the age of the universe based on this value?

(Multiple Choice)

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Question 32

If, as we now believe, the rate of expansion of the universe was slower in the past than at present, then in the past the value of the Hubble ratio, H = v/d, was: (See Figure 25-16 of Universe, 11th ed.)

(Multiple Choice)

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Question 33

What will happen if the universe is unbounded?

(Multiple Choice)

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Question 34

In our description of the universe, what does the word "homogeneous" mean?

(Multiple Choice)

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Question 35

In which of the following universe scenarios will the present universe recollapse at some time in the future?

(Multiple Choice)

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Question 36

If space has a hyperbolic geometry (unbounded universe), what will happen to two initially parallel flashlight beams as they traverse billions of light years of space?

(Multiple Choice)

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Question 37

If there is dark energy in the universe with a positive energy density, what is the future of the universe? (See Figure 25-18 of Universe, 11th ed.(in the text))

(Multiple Choice)

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Question 38

An object has a lookback time of 1 billion years. Assuming it is nonrelativistic, and that the Hubble constant is 22.4 km/s/Mly, what is its velocity?

(Multiple Choice)

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Question 39

How is it that we can detect evidence of sound waves in the early universe?

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Question 40

Showing 21 - 40 of 68

Exam 25: Cosmology: The Origin and Evolution of the Universe

Suppose the ionization energy of hydrogen were larger than 13.6 eV and the decoupling of radiation and matter had occurred earlier, say at z = 2000. What would the temperature have been at that time?

In Newton's model of an infinite universe with stars distributed smoothly throughout, an individual star would feel:

If the Hubble constant is 73 km/s/Mpc then the age of the universe is 13.4 billion years, assuming a uniform expansion. Suppose it were discovered that the Hubble constant is actually larger than 73 km/s/Mpc. What effect would this have on the calculated age of the universe?

Which one of the following statements represents a correct description of the expansion of the universe?

Where in the universe does the "general" expansion occur?

What is the lookback time (i.e., how long ago did the light leave its source) for an object with a redshift z = 0.05, assuming that the Hubble constant is 22.4 km/s/Mly? (Assume nonrelativistic speed for this object.)

What will happen if the universe is bounded?

At present, the energy density of matter greatly exceeds that of radiation. But in the early universe, radiation energy was dominant. Why was this?

In cosmology, to what does the phrase "critical density" refer?

The Sun presently consists of about 25% helium. Where did this helium come from?

The discovery that the Sun and similar stars consist of about 25% helium posed a dilemma: There was too much helium in the universe to be accounted for by nucleosynthesis in stars in the contemporary cosmological models. How was this dilemma resolved?

A few decades ago many astronomers used a value 42 km/s/Mpc for the Hubble constant. What was the age of the universe based on this value?

If, as we now believe, the rate of expansion of the universe was slower in the past than at present, then in the past the value of the Hubble ratio, H = v/d, was: (See Figure 25-16 of Universe, 11th ed.) ​ ​

What will happen if the universe is unbounded?

In our description of the universe, what does the word "homogeneous" mean?

In which of the following universe scenarios will the present universe recollapse at some time in the future?

If space has a hyperbolic geometry (unbounded universe), what will happen to two initially parallel flashlight beams as they traverse billions of light years of space?

If there is dark energy in the universe with a positive energy density, what is the future of the universe? (See Figure 25-18 of Universe, 11th ed.(in the text))

An object has a lookback time of 1 billion years. Assuming it is nonrelativistic, and that the Hubble constant is 22.4 km/s/Mly, what is its velocity?

How is it that we can detect evidence of sound waves in the early universe?

Astronomy and the Universe

Knowing the Heavens

Eclipses and the Motion of the Moon

Gravitation and the Waltz of the Planets

The Nature of Light

Optics and Telescopes

Comparative Planetology I: Our Solar System

Comparative Planetology II: the Origin of Our Solar System

The Living Earth

Our Barren Moon

Mercury, Venus, and Mars: Terrestrial, yet Unique

Jupiter and Saturn: Lords of the Planets

Jupiter and Saturns Satellites of Fire and Ice

Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Asteroids, Comets, and Impacts

Our Star, the Sun

The Nature of the Stars

The Birth of Stars

Stellar Evolution: on and After the Main Sequence

Stellar Evolution: The Death of Stars

Stellar Remnants: Neutron Stars and Black Holes

Our Galaxy

Galaxies

Quasars and Active Galaxies

Exploring the Early Universe

The Search for Extraterrestrial Life

Filters

If, as we now believe, the rate of expansion of the universe was slower in the past than at present, then in the past the value of the Hubble ratio, H = v/d, was: (See Figure 25-16 of Universe, 11th ed.)