Earth & Space Science

Earth & Space Science

  • About This Project
    • Preface/About
    • Author/Contributors
    • For Investors/Donors
    • Teaching Guide
  • Ch 1 – Our Place in the Universe
    • Chapter Introduction
    • 1.1 Our Cosmic Address
    • 1.1.1 Overview
    • 1.1.2 What do we mean when we say “Earth is a planet”?
    • 1.1.3 What is our solar system?
    • 1.1.4 What is a galaxy?
    • 1.1.5 What is the universe?
    • 1.1 Review: Our Cosmic Address
    • 1.2 The Scale of Space
    • 1.2.1 Overview
    • 1.2.2 How Big is the Earth–Moon System?
    • 1.2.3 How Big is our Solar System?
    • 1.2.4 How far are the stars?
    • 1.2.5 How big is the Milky Way Galaxy?
    • 1.2.6 How big is the universe?
    • 1.2 Review: The Scale of the Universe
    • 1.3 Spaceship Earth
    • 1.3.1 How is Earth moving in our solar system?
    • 1.3.2 How is our solar system moving in the Milky Way Galaxy?
    • 1.3.3 How does our galaxy move relative to other galaxies in the universe?
    • 1.3 Review
  • Ch 2 – Understanding the Sky
    • Chapter Introduction
    • 2.1 Our Everyday View of the Universe
    • 2.1.1 What do we see in the local sky?
    • 2.1.2 What is the celestial sphere?
    • 2.1.3 Why do stars rise and set?
    • 2.1.4 Why do we see different constellations at different times of year?
    • 2.1 Review
    • 2.2 Seasons
    • 2.2.1 What causes the seasons?
    • 2.2.2 How do seasons differ around the world?
    • 2.2.3 Does the orientation of Earth’s axis ever change?
    • 2.2 Review
    • 2.3 Viewing the Moon: Phases and Eclipses
    • 2.3.1 Why do we see phases of the Moon?
    • 2.3.2 When do we see different phases of the Moon in our sky?
    • 2.3.3 Why do we always see the same face of the Moon?
    • 2.3.4 What are eclipses?
    • 2.3 Review
    • 2.4 Planets in the Night Sky
    • 2.4.1 How do we recognize planets in the sky?
    • 2.4.2 Why do the planets “wander”?
    • 2.4 Review
  • Ch 3 – How Science Discovered the Earth
    • Chapter Introduction
    • 3.1 The Ancient View of Earth
    • 3.1.1 How did the ancient Greeks learn that Earth is round?
    • 3.1.2 Why didn’t the ancient Greeks realize that Earth orbits the Sun?
    • 3.1 Review
    • 3.2 The Copernican Revolution
    • 3.2.1 How did the idea of Earth as a planet gain favor?
    • 3.2.2 How did Galileo seal the case for Earth as a planet?
    • 3.2 Review
    • 3.3 The Nature of Modern Science
    • 3.3.1 How does science work?
    • 3.3.2 What is a “theory” in science?
    • 3.3.3 What is the value of science?
    • 3.3 Review
    • 3.4 The Fact and Theory of Gravity
    • 3.4.1 What is gravity?
    • 3.4.2 How does gravity hold us to the ground and make objects fall?
    • 3.4.3 Why does gravity make planets round?
    • 3.4.4 How does gravity govern motion in the universe?
    • 3.4 Review
  • Chapter 4 – Planet Earth
    • Chapter Introduction
    • 4.1 A Planetary Overview
    • 4.1.1 What does Earth look like on the outside?
    • 4.1.2 What does Earth look like on the inside?
    • 4.1.3 How has Earth changed through time?
    • 4.1.4 How do we study the Earth?
    • 4.1 Review
    • 4.2 Earth System Science
    • 4.2.1 What are Earth’s four major systems?
    • 4.2.2 What drives Earth system changes?
    • 4.2.3 What IS energy and how do we measure it?
    • 4.2 Review
    • 4.3 Earth In the Context of Other Worlds
    • 4.3.1 How does Earth compare to other worlds of our solar system?
    • 4.3.2 Could there be life on other worlds?
  • Chapter 5 – Earth Through Time
    • Chapter Introduction
    • 5.1 Learning from Rocks and Fossils
    • 5.1.1 How do rocks form?
    • 5.1.2 What are fossils?
    • 5.1.3 How do we learn the ages of rocks and fossils?
    • 5.1 Review
    • 5.2 Shaping Earth’s Surface
    • 5.2.1 How do continents differ from oceans?
    • 5.2.2 What processes shape continents?
    • 5.2.3 What dangers do geological changes pose?
    • 5.2 Review
    • 5.3 Plate Tectonics — The Unifying Theory of Earth’s Geology
    • 5.3.1 What evidence led to the idea that continents move?
    • 5.3.2 How does the theory of plate tectonics explain Earth’s major features?
    • 5.3 Review
    • 5.4 A Brief Geological History of Earth
    • 5.4.1 What major changes mark Earth’s fossil record?
    • 5.4.2 What killed the dinosaurs?
    • 5.4.3 Have we humans started a new geological epoch?
    • 5.4 Review
  • Chapter 6 – Air and Water
    • Chapter Introduction
    • 6.1 Atmosphere and Hydrosphere
    • 6.1.1 What exactly is the atmosphere?
    • 6.1.2 How is water distributed on Earth?
    • 6.1.3 How does water cycle through the hydrosphere and atmosphere?
    • 6.1 Review
    • 6.2 Global Winds and Currents
    • 6.2.1 What drives global winds and currents?
    • 6.2.2 What is the general pattern of winds on Earth?
    • 6.2.3 What is the general pattern of ocean currents?
    • 6.2 Review
    • 6.3 Weather and Climate
    • 6.3.1 What is the difference between weather and climate?
    • 6.3.2 How and why does climate vary around the world?
    • 6.3.3 How do we measure and predict the weather?
  • Chapter 7 – Human Impact on the Climate
    • Chapter Introduction
    • 7.1 The Basic Science of Global Warming
    • 7.1.1 What is the greenhouse effect?
    • 7.1.2 How is human activity strengthening Earth’s greenhouse effect?
    • 7.1.3 How do we know that global warming is really happening and is human-caused?
    • 7.1.4 How does human-caused climate change compare to natural climate change?
    • 7.1 Review
    • 7.2 Consequences of Global Warming
    • 7.2.1 What are the major consequences of global warming?
    • 7.2.2 How do scientists predict future consequences of global warming?
    • 7.2.3 How will climate changes affect you and others around the world?
    • 7.2 Review
    • 7.3 Solutions to Global Warming
    • 7.3.1 What existing technologies could solve the problem of global warming?
    • 7.3.2 What future technologies might help even more?
    • 7.3.3 What does it take to implement a solution?
    • 7.3.4 What will your world look like AFTER we solve global warming?
    • 7.3 Review
cropped-Ch03-Opener-(McCandless)-NASA-576200main_s84-27017_full-copy

Astronaut Bruce McCandless orbits Earth as if he were a tiny moon during Space Shuttle mission STS-41-B. Credit: NASA

Chapter 3 - How Science Discovered the Earth

CHAPTER INTRODUCTION

Imagine yourself as a satellite, orbiting Earth like the astronaut in the photo above. As you look down at the thin layer of atmosphere that separates our homes from the blackness of space, you’d be seeing Earth in a way that most of our ancestors could never have imagined.

Think back on all the ideas we’ve discussed in the first two chapters. We’ve talked about why ancient villagers would have assumed that they lived on a small, flat surface covered by a domed sky, and we’ve contrasted that idea with the facts we know today: Earth is a planet, orbiting a star, located in a galaxy that is one among billions in a vast, expanding universe.

How did we go from ancient beliefs to our modern understanding of Earth? The answer is through science. In this chapter, we’ll explore how modern science arose largely through human efforts to understand the kinds of sky phenomena that you studied in Chapter 2. We’ll also see how the methods of modern science have made it possible to produce reliable knowledge about how the universe works —so reliable that we can use this knowledge to launch astronauts into space, let them float freely above our planet, and then return them safely to Earth.

Journal Entry

What is Science?

Write a paragraph or two in your journal to describe how you would define science, and how you would distinguish something we consider science (such as Earth science or astronomy) from something that is not science. Leave plenty of space after your entry so that you can come back and revise your answer later.

Show Teachers Notes

This journal entry is designed to help you as a teacher understand how much your students know or remember about the nature of science from earlier grades, which will help you plan how much time you need to teach the concepts in this chapter. As usual for journal entries, grading should be based on effort, not on whether they answer correctly or not. Later, students should go back to this journal entry to evaluate for themselves whether their initial ideas were correct or whether they have modified them based on what they learned.

Group Discussion

Gravity

One of the great achievements of modern science has been in the way it has helped us understand gravity and the many roles in plays in our lives. We’ll discuss gravity in some detail later in this chapter. To help you start thinking about it, hold a group discussion in which you try to do the following as best you can for now.

  1. Make a list of as many things as you can that are explained by gravity.
  2. For each item on your list, discuss how you think gravity explains them.
  3. Based on your list and discussion, try to come up with a definition of gravity that is as simple as possible.
Show Teachers Notes

This discussion can be done in small groups but is probably better done with you leading the whole class to keep the discussion focused and on track. Notes on possible answers:

  1. Once you get students started on the right track, they should be able to come up with many good answers to this question. For example:
    • Gravity holds us to the ground.
    • Gravity makes objects fall when dropped.
    • Gravity keep the Moon in orbit of Earth.
    • Gravity keeps satellites and the International Space Station in orbit of Earth.
    • Gravity holds Earth in orbit around the Sun.
    • Gravity makes planets and stars round.
    • Gravity holds galaxies together.
  2. This “how” question will be more difficult for students. Try to get them to begin to realize that gravity must be an attractive force between objects, and one that acts toward a center. It will be relatively easy for most students to grasp how this idea leads to gravity holding us to the ground and making objects fall. Somewhat more advanced students will recognize that larger masses have more gravity and this, along with acting toward a center leads to the idea that gravity makes smaller objects orbit larger ones, and also makes larger objects like planets and stars round. A few students will also recognize that orbits involve objects moving and “falling” at the same time.
  3. The goal here should be to get them to realize that their definition should at minimum include the fact that gravity is an attractive force between masses. Some students will already know more, such as that it depends on the masses and the distance between the masses.

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