Up until only about 400 years ago, most people believed that Earth was the center of the universe, and that the Sun, Moon, planets, and stars all circled around us once each day. Today, we know that Earth is just one planet orbiting our Sun, that our Sun is just one star in our Milky Way Galaxy, and that our galaxy is just one of billions of galaxies in the universe.
In this section, we’ll discuss the meanings of all these ideas, so that you will understand “our cosmic address,” by which we mean our location in the universe.
Audio
A View of Earth
Narration: Jeff Bennett (Duration, 0:43)Look at this picture. It was taken on Christmas Eve, 1968, from the Apollo 8 spacecraft as it circled around the Moon. Below we see the Moon’s gray surface, and in the sky we see our beautiful blue world.
Notice how small our world looks from the Moon; the astronauts noticed that they could cover the entire world with the thumb of an outstretched arm. What do you think when you look at a picture like this one?
Does it change your perspective on Earth, or on your own existence? Does it make you want to learn more about the universe? Let’s continue on by talking about what we might call our cosmic address, meaning our location in this amazing universe.
Section Learning Goals
By the end of this section, you should be able to answer the following questions:
- What do we mean when we say Earth is a planet?
- What is our solar system?
- What is a galaxy?
- What is the universe?
Before you continue, take a few minutes to discuss the above Learning Goal questions in small groups or as a class. For example, you might discuss what (if anything) you already know about the answers to these questions; what you think you’ll need to learn in order to be able to answer the questions; and whether there are any aspects of the questions, or other related questions, that you are particularly interested in.
Journal Entry
Planet Earth
Spend at least 15 seconds looking closely at the photo of Earth as it appears from the Moon. Does it affect the way you think about yourself or our planet? On today’s page in your journal, start an entry with the title “Seeing Earth from the Moon” and write about how this photo affects your thinking. You can use any format you wish; for example, you can write an essay, a set of sentences, or even a poem. Feel free to draw illustrations as well.
Teacher Notes: For this journal entry, note that the instructions allow many different formats for the responses, so focus your grading on whether the students are thoughtful in their work.