Instructor Manual: Seeds/Backman/Wegryn, Foundations of Astronomy, 15e, 2026, 9798214193328; Chapter 1: Here and Now
Instructor Manual
Seeds/Backman/Wegryn, Foundations of Astronomy, 15e, 2026,
9798214193328; Chapter 1: Here and Now
TABLE OF CONTENTS
Purpose and Perspective of the Chapter.....................................................................2
Chapter Objectives........................................................................................................2
Key Terms.....................................................................................................................2
What’s New in this Chapter.........................................................................................3
Chapter Outline............................................................................................................3
Key Concepts.................................................................................................................4
Answers to Review Questions.......................................................................................5
Answers to Active Inquiry Questions...........................................................................7
Answers to Problems....................................................................................................7
Answers to Sense of Proportion...................................................................................8
Answers to Learning to Look.......................................................................................8
Additional Resources....................................................................................................9
a
© 2026 Cengage Learning, Inc. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly
accessible website, in whole or in part.
1
, Instructor Manual: Seeds/Backman/Wegryn, Foundations of Astronomy, 15e, 2026, 9798214193328; Chapter 1: Here and Now
PURPOSE AND PERSPECTIVE OF THE CHAPTER
Guidepost
As we study astronomy, we also learn about ourselves. We are planet-walkers, and this chapter offers a
preview of what that means. The planet we live on whirls around a star that moves through a space filled
with other stars and galaxies. We owe it to ourselves to know where we are located in the Universe and
when we are living in its history, because those are important steps to knowing what we are.
CHAPTER OBJECTIVES
In this chapter, we consider the following three important questions:
Where is Earth in the Universe?
How does human history fit into the history of the Universe?
Why study astronomy?
[return to top]
KEY TERMS
The glossary for the 15th edition has been thoroughly reviewed by authors Backman and Wegryn, and
extensively revised for improved clarity, consistency, and cross-references. Terms are presented here in
order of occurrence.
field of view: the area visible in an image; usually given as the (angular) diameter of the region
scientific notation: the system of recording very large or small numbers by using powers of 10
planet: a non-stellar body orbiting the Sun or another star that has strong enough gravity to compress it
into a spheroidal shape and to have cleared its orbital zone of debris (contrast with dwarf planet)
star: celestial object like the Sun, composed of gas held together by its own gravity and supported by
nuclear fusion occurring in its interior, which generates energy
terminator: the dividing line between daylight and darkness on a planet or moon
Solar System: the Sun and all the objects gravitationally bound to it, including Earth and the other
planets, dwarf planets, planetary satellites and rings, asteroids, comets, Kuiper Belt Objects, and Oort
Cloud objects; an example of a planetary system
satellite: object revolving around (orbiting) a planet or other larger primary; may be natural, like the
Moon or moons of other worlds, or artificial, like the International Space Station
astronomical unit (AU): the average distance from Earth to the Sun: 1.50 × 108 km
light-year (ly): the distance light travels in one year; 9.5 × 1012 km
a
© 2026 Cengage Learning, Inc. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly
accessible website, in whole or in part.
2
, Instructor Manual: Seeds/Backman/Wegryn, Foundations of Astronomy, 15e, 2026, 9798214193328; Chapter 1: Here and Now
Milky Way: the hazy band of light that circles the sky, produced by the combined light of billions of
stars in our Milky Way Galaxy
Milky Way Galaxy: the spiral galaxy containing our Solar System; visible on Earth at night as the
hazy band of light (Milky Way) that circles the sky, produced by the combined light of billions of stars in
our galaxy
galaxy: very large collection of gas, dust, and stars orbiting a common center of mass. The Sun and
Earth are located in the Milky Way Galaxy.
spiral arm: long, spiral pattern of bright stars, star clusters, gas, and dust that extends from the center
to the edge of the disk of spiral galaxies
Big Bang: the well-supported theory that the Universe began expanding from a moment of extreme
conditions of high density and temperature
scientific method: the reasoning process by which scientists make observations and test theories with
predictions to understand how nature works.
[return to top]
WHAT’S NEW IN THIS CHAPTER
The following elements are improvements in this chapter from the previous edition:
· New chapter opener image (as in other chapters as well) — for Chapter 1,
a rare and puzzling double double rainbow (courtesy of our new coauthor,
Dr. Erıc Wegryn)
· More reliance on international (SI) units of measurement
[return to top]
CHAPTER OUTLINE
The following outline reflects the organization of topics in this chapter.
1-1 Where Are We?
a
© 2026 Cengage Learning, Inc. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly
accessible website, in whole or in part.
3
, Instructor Manual: Seeds/Backman/Wegryn, Foundations of Astronomy, 15e, 2026, 9798214193328; Chapter 1: Here and Now
Figur Description Ideas Presented Diameter of View
e
1-1 Campus scene Scale 52 feet (15 m)
1-2 A small city Metric System & distances 1 mile (1.6 km)
1-3 Mountains and rivers Evolving planet 160 km
1-4 Earth Earth's structure 12,756 km
1-5 The Moon's orbit Scientific notation 1.6 × 106 km
1-6 The inner Solar System Astronomical Unit (AU) 1.6 × 108 km (1.07 AU)
1-7 The Solar System Light travel time & distance 107 AU
1-8 Interstellar space Emptiness of space 11,000 AU
1-9 The nearby stars Light-year 1.07 × 106 AU (17 ly)
1-10 Stars & star clusters Star clusters and gas clouds 1,700 ly
1-11 The Milky Way Galaxy Our galaxy 170,000 ly
1-12 Neighboring galaxies Clusters of galaxies 1.7 × 107 ly
1-13 Filaments & voids Superclusters, filaments, 1.7 × 109 ly
& voids
1-2 When Is Now?
1-3 Why Study Astronomy?
[How Do We Know? 1-1 The Scientific Method]
[What Are We? Participants]
[return to top]
KEY CONCEPTS
The goal of this chapter is to illustrate the vastness of the universe through a series of images that
gradually step further and further away from scenes that are part of our everyday experience. It is
important that students understand the concept of scale. This chapter gives an excellent brief overview of
the structure of our Universe: planets, solar systems, galaxies, clusters and superclusters of galaxies, and
filament and void structure.
This is a good chapter to discuss the uniqueness of astronomy among the sciences. Astronomy is
observational, so we cannot change the initial conditions of an experiment and redo it. We must make the
most out of every photon that comes our way if we are to further our understanding of the universe.
International (metric) units of measurement and other units specific to astronomy (i.e., astronomical unit,
light year, parsec, and perhaps solar units for mass, luminosity, and radius) should be introduced early in
a
© 2026 Cengage Learning, Inc. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly
accessible website, in whole or in part.
4
Instructor Manual
Seeds/Backman/Wegryn, Foundations of Astronomy, 15e, 2026,
9798214193328; Chapter 1: Here and Now
TABLE OF CONTENTS
Purpose and Perspective of the Chapter.....................................................................2
Chapter Objectives........................................................................................................2
Key Terms.....................................................................................................................2
What’s New in this Chapter.........................................................................................3
Chapter Outline............................................................................................................3
Key Concepts.................................................................................................................4
Answers to Review Questions.......................................................................................5
Answers to Active Inquiry Questions...........................................................................7
Answers to Problems....................................................................................................7
Answers to Sense of Proportion...................................................................................8
Answers to Learning to Look.......................................................................................8
Additional Resources....................................................................................................9
a
© 2026 Cengage Learning, Inc. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly
accessible website, in whole or in part.
1
, Instructor Manual: Seeds/Backman/Wegryn, Foundations of Astronomy, 15e, 2026, 9798214193328; Chapter 1: Here and Now
PURPOSE AND PERSPECTIVE OF THE CHAPTER
Guidepost
As we study astronomy, we also learn about ourselves. We are planet-walkers, and this chapter offers a
preview of what that means. The planet we live on whirls around a star that moves through a space filled
with other stars and galaxies. We owe it to ourselves to know where we are located in the Universe and
when we are living in its history, because those are important steps to knowing what we are.
CHAPTER OBJECTIVES
In this chapter, we consider the following three important questions:
Where is Earth in the Universe?
How does human history fit into the history of the Universe?
Why study astronomy?
[return to top]
KEY TERMS
The glossary for the 15th edition has been thoroughly reviewed by authors Backman and Wegryn, and
extensively revised for improved clarity, consistency, and cross-references. Terms are presented here in
order of occurrence.
field of view: the area visible in an image; usually given as the (angular) diameter of the region
scientific notation: the system of recording very large or small numbers by using powers of 10
planet: a non-stellar body orbiting the Sun or another star that has strong enough gravity to compress it
into a spheroidal shape and to have cleared its orbital zone of debris (contrast with dwarf planet)
star: celestial object like the Sun, composed of gas held together by its own gravity and supported by
nuclear fusion occurring in its interior, which generates energy
terminator: the dividing line between daylight and darkness on a planet or moon
Solar System: the Sun and all the objects gravitationally bound to it, including Earth and the other
planets, dwarf planets, planetary satellites and rings, asteroids, comets, Kuiper Belt Objects, and Oort
Cloud objects; an example of a planetary system
satellite: object revolving around (orbiting) a planet or other larger primary; may be natural, like the
Moon or moons of other worlds, or artificial, like the International Space Station
astronomical unit (AU): the average distance from Earth to the Sun: 1.50 × 108 km
light-year (ly): the distance light travels in one year; 9.5 × 1012 km
a
© 2026 Cengage Learning, Inc. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly
accessible website, in whole or in part.
2
, Instructor Manual: Seeds/Backman/Wegryn, Foundations of Astronomy, 15e, 2026, 9798214193328; Chapter 1: Here and Now
Milky Way: the hazy band of light that circles the sky, produced by the combined light of billions of
stars in our Milky Way Galaxy
Milky Way Galaxy: the spiral galaxy containing our Solar System; visible on Earth at night as the
hazy band of light (Milky Way) that circles the sky, produced by the combined light of billions of stars in
our galaxy
galaxy: very large collection of gas, dust, and stars orbiting a common center of mass. The Sun and
Earth are located in the Milky Way Galaxy.
spiral arm: long, spiral pattern of bright stars, star clusters, gas, and dust that extends from the center
to the edge of the disk of spiral galaxies
Big Bang: the well-supported theory that the Universe began expanding from a moment of extreme
conditions of high density and temperature
scientific method: the reasoning process by which scientists make observations and test theories with
predictions to understand how nature works.
[return to top]
WHAT’S NEW IN THIS CHAPTER
The following elements are improvements in this chapter from the previous edition:
· New chapter opener image (as in other chapters as well) — for Chapter 1,
a rare and puzzling double double rainbow (courtesy of our new coauthor,
Dr. Erıc Wegryn)
· More reliance on international (SI) units of measurement
[return to top]
CHAPTER OUTLINE
The following outline reflects the organization of topics in this chapter.
1-1 Where Are We?
a
© 2026 Cengage Learning, Inc. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly
accessible website, in whole or in part.
3
, Instructor Manual: Seeds/Backman/Wegryn, Foundations of Astronomy, 15e, 2026, 9798214193328; Chapter 1: Here and Now
Figur Description Ideas Presented Diameter of View
e
1-1 Campus scene Scale 52 feet (15 m)
1-2 A small city Metric System & distances 1 mile (1.6 km)
1-3 Mountains and rivers Evolving planet 160 km
1-4 Earth Earth's structure 12,756 km
1-5 The Moon's orbit Scientific notation 1.6 × 106 km
1-6 The inner Solar System Astronomical Unit (AU) 1.6 × 108 km (1.07 AU)
1-7 The Solar System Light travel time & distance 107 AU
1-8 Interstellar space Emptiness of space 11,000 AU
1-9 The nearby stars Light-year 1.07 × 106 AU (17 ly)
1-10 Stars & star clusters Star clusters and gas clouds 1,700 ly
1-11 The Milky Way Galaxy Our galaxy 170,000 ly
1-12 Neighboring galaxies Clusters of galaxies 1.7 × 107 ly
1-13 Filaments & voids Superclusters, filaments, 1.7 × 109 ly
& voids
1-2 When Is Now?
1-3 Why Study Astronomy?
[How Do We Know? 1-1 The Scientific Method]
[What Are We? Participants]
[return to top]
KEY CONCEPTS
The goal of this chapter is to illustrate the vastness of the universe through a series of images that
gradually step further and further away from scenes that are part of our everyday experience. It is
important that students understand the concept of scale. This chapter gives an excellent brief overview of
the structure of our Universe: planets, solar systems, galaxies, clusters and superclusters of galaxies, and
filament and void structure.
This is a good chapter to discuss the uniqueness of astronomy among the sciences. Astronomy is
observational, so we cannot change the initial conditions of an experiment and redo it. We must make the
most out of every photon that comes our way if we are to further our understanding of the universe.
International (metric) units of measurement and other units specific to astronomy (i.e., astronomical unit,
light year, parsec, and perhaps solar units for mass, luminosity, and radius) should be introduced early in
a
© 2026 Cengage Learning, Inc. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly
accessible website, in whole or in part.
4
