This activity asks you to explore how planet formation is connected to star formation. Although you learned about star formation in Unit 3, you haven’t yet studied the process of planet formation. The purpose of this activity is to give you an opportunity to use your intuition and logic to make deductions about what might happen next to the matter that is left over after a star has formed.

Look at the photos of the different stages in the formation of a planet. Order the images from a planet’s beginning until it is fully formed, based on your knowledge and intuition. You probably know more than you think you do. You have only 5 minutes so make your best guess (don’t worry; you’ll dig into how planets form in more detail soon). As you arrange the images, discuss the differences among them. What does your knowledge about how stars form tell you about how planets might form?

While the Universe got its start 13.8 billion years ago, our Solar System and Earth are relatively young by comparison. In this video, Rachel Hansen will explain how clouds of gases eventually came together under the force of gravity to create new complexity—including our pale blue dot of a planet. But four billion years ago, the early Earth wasn’t exactly a cool place to live. In fact, during the Hadean Eon, it was a super-hot ball of lava bombarded by asteroids!

Collective learning is a core concept in Big History. This video focuses on how collective learning changed our understanding of Earth. But new theories often need a lot of time, evidence, and new technologies before people accept them. In this video, you’ll learn how our knowledge of the Solar System and Earth changed over time.

Preview

As a reminder, open and skim the transcript, and read the questions before you watch the video.

Key Ideas – Factual

Think about the following questions as you watch this video:

1. What theory did meteorologist Alfred Wegener propose and how did most geologists react to this theory?
2. What led to the acceptance of the theory of plate tectonics?
3. What types of evidence did earlier scholars discover that contributed to collective learning and the eventual acceptance of plate tectonics?
4. What are the ingredients and Goldilocks Conditions for Threshold 4—the creation of our Solar System and Earth?
5. What was the Hadean Eon?
6. How are we all lava surfers?

Thinking Conceptually

1. Why do you think it can take many years for theories such as plate tectonics to become accepted?
2. How do the earlier thresholds (Big Bang, Stars Light Up, New Chemical Elements) contribute to the Unit 4 threshold (Our Solar System & Earth)?
3. Rachel ends the video on a fun note as she tries to think of tourism slogans for extraterrestrial visits. Based on what you’ve learned in this video, come up with two advertising slogans: one for the early Earth and one for today.

Understanding vocabulary helps you access course content, become a better reader, and a better communicator. This word wall activity will help you begin to learn some of the key vocabulary from Unit 4.

In this activity, you’ll work with your class to create a word wall using the Unit 4 vocabulary.

Your teacher will assign a vocab card to each of you. Once you get yours, take a few minutes to look it up in the Unit 4 Vocab Guide and then examine the unit itself (click around and quickly skim the content) to see where in the unit your word might be most applicable. Then, add as many antonyms to your card for your word as possible. Be careful if you decide to use the related words section from the vocab guide—it doesn’t distinguish between synonyms and antonyms. Your teacher will give you a limited amount of time to write antonyms. Then, the people with the most correct antonyms will put their words on the word wall first.

Your teacher may add some fun twists to this assignment, so be sure to listen closely for directions!

Take out the Thresholds Graphic you worked on in earlier Narrative and Thresholds activities. If you skipped those activities, you can use the Threshold Graphic included in the PDF for this activity.

Big History research has shown that repeated activities help build a stronger grasp of concepts than activities you only do one time. This activity will continue the Narrative and Thresholds progression’s mission, which is to deepen your understanding of the BHP narrative and specific, key ideas and events in the course. You will have a number of opportunities to demonstrate what you’ve learned, as you’ll perform an image analysis, synthesize information, watch a video, and participate in a collaborative conversation about the Big History story line.

Reading, writing, causation
You’ll engage in reading through an image analysis, which will make use of your comprehension skills by requiring you to reflect on an image and describe the key points in a short summary. Generally, you’ll practice summarization in this activity. Causation is a key concept in this as in all the thresholds. Think about what caused each threshold of increasing complexity to occur, and what the effects of that threshold have been over vast time periods.

Take out your BHP Thresholds Graphic. Reflect on the images and your writing from the previous thresholds. What changes would you make to your summaries to better represent the BHP narrative?

Next, watch Threshold 4: Earth & the Solar System, and then write a tweet (288 characters or less) that characterizes this threshold and add it to the relevant spot on the graphic.

Remember that a few Narratives and Threshold activities ago you wrote down your version of the Big History story at that time in the course? You’re going to try that again now that you’ve learned so much more; however, this time, you’ll tell the story in an “elevator pitch.”

In case you aren’t familiar with the term, an elevator pitch is a short speech that is meant to spark someone’s interest about what you are telling them. A good elevator pitch will last about 20 to 30 seconds. So, here is your task: Imagine you just got onto the elevator on the first floor of the Empire State Building and you have to tell your version of the Big History story before you reach the observation deck on the top floor. That means you have less than 60 seconds. Go!

Your teacher will let you know how you can deliver this pitch (live, video, or written as a monologue, for example). Once you’re done making your elevator pitch, think about the Big History story you wrote earlier in the course, for the Narrative and Thresholds activity for Threshold 2: The Stars Light Up. How does your elevator pitch support, extend, or challenge your initial thinking about the BHP narrative?

This unit will explore the process of how planets form. Planets can be large and made of gasses, or smaller and rocky, like our Earth. The formation process determines the chemical composition of our planet but also can result in the Goldilocks Conditions that enable life on Earth to exist.

The formation of our Solar System including Earth marks the fourth threshold in the course. In order to understand why the Earth is such a unique planet, you must learn the ingredients and Goldilocks Conditions that made the formation of the Sun, Earth, and the rest of our Solar System possible.

Preview

Large clouds of dust and gas remain in the aftermath of the death of stars. These chemically complex areas in space begin to pull together and the process of star formation happens all over again. In the aftermath of star formation, the leftover materials can coalesce to form planets.

Understanding Content

As you watch this video, use these questions to help you check for understanding. Keep in mind that some videos may require watching more than once to really understand all of the materials.

1. What enabled planets to form?
2. When did the Earth form?

Thinking Conceptually

Do you think there could be Earth-like planets in other solar systems? Do you think that other solar systems are currently forming in different parts of the Universe? What evidence might there be for this?

Planets form by a process called accretion in the aftermath of star formation. In our Solar System, the lighter elements were pushed far from the Sun, and this led to the formation of the gas planets, which lie far from the Sun. The heavier elements remained closer to the Sun and formed the rocky planets like our Earth.

The process of planet formation is a complex one, involving the forces of gravity and electromagnetism and the discipline of chemistry. To understand why the formation of planets and solar systems marks a new level of complexity in the Universe, one needs to understand how planets form and what makes them different from stars.

Preview

As the stars die out and explode in supernovae, we start to see a collection of elements floating across the Universe. Out of these elements, new stars and planets will form.

Understanding Content

As you watch this video, use these questions to help you check for understanding. Keep in mind that some videos may require watching more than once to really understand all of the material.

Part I

1. In the last unit, you learned that about 98 percent of the Universe was hydrogen and helium, and that about 2 percent was everything else. What percentage of the Earth is made up of these other elements?
2. How did all these elements get concentrated in planets like the Earth?
3. Can we predict the qualities of a molecule from the atoms that make it up?
4. Are the bonds between the atoms in molecules the same?

Part II

5. Are there molecules in space?
6. What is a protoplanetary disk?
7. Why are the planets closest to our Sun different from the planets further away?
8. What is accretion?
9. What’s the likely way the Moon was formed?
10. What is an exoplanet?

Part III

11. What makes planets more complex than stars?

Thinking Conceptually

Do you think that the Earth is still forming today? Can you think of other examples of accretion elsewhere in the Solar System?

The process that led to the formation of the Earth and the Solar System was slow and violent. Although gravity did much of the work drawing dust particles and other masses together slowly, collisions between these objects made for a spectacular beginning.

This article covers in depth the process that led to the formation of the Earth and the planets of our Solar System. At this point, you’ve heard about accretion and the formation of planets several times. This article provides a formal explanation of the process.

Skimming for Gist

The formation of the Sun left only a very small amount of matter for the formation of planets. Through the process of accretion, this small amount of matter was transformed into the planets of our Solar System.

Understanding Content

By the end of the second close read, you should be able to answer the following questions about the formation of our Earth:

1. How did the Earth form?
2. Was the process driven by small particles being drawn together or by large masses colliding together?
3. How old is our Solar System?
4. How are rocky planets different from gas planets?
5. How is the Earth different from the other rocky planets?
6. How did the Moon form?
7. How does the Moon impact life on Earth?

Thinking Conceptually

At the end of the third close read, you should respond to these questions: What were the factors working against life forming on the early Earth? Should we be surprised that life formed here at all?

Mary Golda Ross (1908–2008) was born in the Cherokee Nation. Her excellent math skills helped her become the first female Indigenous engineer. Over the course of the twentieth century, she worked at the Lockheed Corporation and helped design war planes during World War II, missiles during the Cold War, and spacecraft during the Space Race between the United States and Soviet Union. She also worked throughout her career to help other women and Indigenous people begin careers in science and engineering.

Traveling into outer space deepened our knowledge of the Solar System. To get to outer space, we depended on the work of engineers and mathematicians to develop spacecraft and mathematical models to guide us on our voyages. This graphic biography highlights the life of one woman whose story you probably don’t know. Yet, her work is an important piece of the story of our collective learning about this planet and our solar system. As humanity continues to reach toward our nearest neighbors, like Mars, Ross’s work remains relevant to the story of how we know what we know.

Read 1: Observe

As you read this graphic biography for the first time, review the Read 1: Observe section of your Three Close Reads for Graphic Bios Tool. Be sure to record one question in the thought bubble on the top-right. You don’t need to write anything else down. However, if you’d like to record your observations, feel free to do so on scrap paper.

Read 2: Understand

On the tool, summarize the main idea of the comic and provide two pieces of evidence that helped you understand the creator’s main idea. You can do this only in writing or you can get creative with some art. Some of the evidence you find may come in the form of text (words). But other evidence will come in the form of art (images). You should read the text looking for unfamiliar vocabulary words, the main idea, and key supporting details. You should also spend some time looking at the images and the way in which the page is designed. By the end of the second close read, you should be able to answer the following questions:

1. The comic describes Mary as a “computer.” What does this mean?
2. Why was Mary hired? How would you describe her career?
3. How has the artist designed the images in this comic to help you know in which order to read the text?
4. Looking at just the images, what do you think is the theme of this comic?

Read 3: Connect

In this read, you should use the graphic biography as evidence to support, extend, or challenge claims made in this unit of the course. On the bottom of the tool, record what you learned about this person’s life and how it relates to what you’re learning.

1. Had you heard about Mary Golda Ross before reading this comic? Why do you think some people, like Mary Golda Ross, often get left out of the big stories about our collective learning?

To Be Continued…

On the second page of the tool, your teacher might ask you to extend the graphic biography to a second page. This is where you can draw and write what you think might come next. Here, you can become a co-creator of this graphic biography!

This activity simulates accretion. The process of accretion is responsible for the formation of planets, so it’s really important that you understand how this process works. You’ve already been introduced to the idea, but this activity illustrates the process in a hands-on way that gets you out of your chair.

Your teacher will take you to a large open space such as a football field or park and give you a “dust particle” sign. Yes, that’s your role: dust particle. Your teacher—or a lucky substitute—will be the Sun and will stand at the center of the “Solar System.” Take your dust particle sign and move to a spot somewhere around the “Sun.”

When the Sun yells “Go,” all of the “dust particles”—that’s you and your classmates—are going to move around the Sun. You should all move in the same direction at a brisk walking pace. As you move, you have to follow a few rules):

1. They must move towards closer objects. (The word object refers to a student or group of students.)
2. They must move towards larger objects.
3. They must always move around a center point (the Sun).
4. When they’re close enough to someone else that their hands can reach each other, they must link hands (or arms) and then move as a unit, following the same rules as before.

As you link up with other students and groups of students, your “object” size will grow. Periodically, the Sun will yell, “Stop!” Once you’ve stopped, one student from each group must run to the Sun to swap out your object sign for one that reflects your group’s new role, which is, of course, determined by your new group size:

Continue the process until there is at least one planet orbiting the Sun. Your teacher might have you repeat the simulation more than once to see if there are differences in the resulting Solar System each time.