# Phenomenon

**Investigation Driving Question**

What can expansion reveal about the Universe?

**Storylines **

The storyline process is intended to be student-driven and connect lessons within the unit. The Expanding Universe investigation, including this phenomenon, would fit best into unit storylines geared toward understanding the evolution, structure, or expansion of the Universe.

Possible storylines include:

What can we know/observe/measure about the Universe?

How does the expansion of the Universe support the Big Bang theory?

**Instructions for Introducing Phenomenon**

This phenomenon can be introduced to students via a hands-on modeling experience or by using a video of the model. Choose an option below that best fits your needs.

- Before class starts, arrange a Driving Question Board (DQB) so it is visible to all students. This can be created using sticky notes or in a digital format (see other resources here). The DQB should include the investigation driving question, “What can expansion reveal about the Universe?” Students will be revisiting this DQB throughout the lesson. If you have a driving question for the unit or already created a DQB board, this investigation driving question can be used as a sub-question.
- Have students read and think about the driving question before doing the activity. (3 minutes)
- Begin the phenomenon activity by telling students they will be manipulating a physical model or viewing a video that represents the expansion of the Universe (with some limitations).

4.** Option 1** (Hoberman Sphere)

Provide student groups with a Hoberman Sphere or demonstrate the following steps with one Hoberman Sphere for the whole class.

Begin with the sphere folded to its smallest size and slowly expand the sphere into its maximum position. (Students can repeat these actions as needed to make their observations.)

**Option 2** (Hoberman Sphere Video)

Play the video.

You can continue to replay the video as students observe and think about their observations.

**Option 3** (Other Modeling Options)

Use one of the common models (inflating a balloon, the raisin bread (or chocolate chip cookie) analogy, stretching a rubber band) to demonstrate the expansion of space.

5. Ask students the following question to orient them with the components of the sphere and to check for previous understanding.

“There are two components to the Hoberman Sphere, the grid and the colored squares. What do each of these components represent about the Universe?” *Help students understand that the colored squares represent galaxies and the grid represents space or **spacetime**. *

6. Tell students, “In this model using the Hoberman Sphere, the spacetime of the Universe and these galaxies make up the *entire Universe* - there is nothing inside the sphere nor outside the sphere that is part of the Universe.”

7. Students should reflect on what they saw and try to figure out how this device represents the expansion of the Universe. They should think about what else they need to know and what questions they have about the expansion of the Universe. Students should record their questions and share them with the whole class. These questions should be displayed on the DQB for all students to refer to. (5 minutes)

8. As a whole class, facilitate a discussion about the questions. Begin by identifying and grouping common questions into categories. (10 minutes)

**Example Category****Example**Student QuestionsRates

Are galaxies moving at different speeds?

Does the expansion ever speed up or slow down?

Time

What will happen to the Universe in the future?

What was the Universe like in the past?

Did the Universe start as a point?

Space

How do we know the Universe is expanding?

How can space expand?

Where is the center of the Universe?

9. Revisit the investigation driving question and tell students they will be completing an investigation that will help them answer this driving question and their generated questions about the Hoberman sphere as a model of the Universe.

10. Begin the Expanding Universe Investigation.

**After the Investigation - Making Sense of the Phenomenon**

**Option 1 (student-driven)**

Replay the Hoberman Sphere video or pass out the device again to students as they discuss the remaining questions on the DQB and explain how the Hoberman Sphere acts as a model for the expansion of the Universe. Encourage students to independently investigate any remaining questions they have.

Facilitate a class discussion about the limitations of the Hoberman Sphere model.

Ask students if they can think of other models that would work for representing the expansion of the Universe.

**Option 2 (teacher-driven)**

This activity revisits the phenomenon and can be used as a recap of learned information from the investigation. This activity is designed to be more supportive for settings where differentiation is needed.

Play the guided Hoberman Sphere video for the entire class. Pause the video at the appropriately marked times to hold small group or whole-class discussions.

Conclude the activity by asking students if they can think of other models that would work for representing the expansion of the Universe.