Teaching sequence

Work through this resource material in the following sequence:

5 minutes – The story so far...
15 minutes – Tune in: The sound from the start of the universe
20 minutes – Find out: The Redshift theory of an expanding universe
15 minutes – Take action: Proof of Redshift experiment
5 minutes – Reflection

Presentation slides

We strongly encourage you to use the Presentation Slides as a guide for yourself and your students through this lesson.

The story so far...

Step 1.

Revisit the story so far, using the Threshold Cards as a guide to retell the story of the history of the universe. Students should be involved in the retelling - you might nominate different students each lesson to be responsible for a different threshold. Prompt them to explain what ingredients were present in the universe at the time, what goldilocks conditions existed to enable a change, and the new complexity it resulted in.

Remember, students' explanations can't be wrong, but you might supplement them with the information below.

In the beginning, we weren't sure there was anything in the universe. If there was, we don't know what it was. We also don't know what the conditions were like. However, something happened, which we know as the Big Bang. This caused the universe to change so much that we recognise it as a new complexity - almost a totally new place. After that, we had space, time, matter (hydrogen and helium), and energy (gravity and electromagnetism).

The universe had changed once again.

Tune in: The sound from the start of the universe

You can also use the Presentation Slides to guide you through these steps.

Step 1.

Explain that Professor Cramer is a physicist at Brookhaven National Laboratory in New York. He has been part of a large collaboration studying what the universe might have been like moments after the Big Bang.

As the universe cooled and expanded, it stretched the wavelengths to create a low sound. The sound was, in fact, so low that he had to boost the frequency 100 septillion times (that’s a 100 followed by 24 more zeroes!) just so the recordings could be heard by humans.

Step 2.

As the universe gets bigger, the sound waves have to stretch longer to fill more space. Whereas in the beginning, the soundwaves are able to be quick (compressed) in the smaller space of the universe.

This graphic will help students understand - and is important for our understanding later.

A picture demonstrating the difference between short and long wavelengths for light and sound

Find out: The Redshift theory of an expanding universe

Step 1.

Narrate this video to students.

Note: As you read the words in this video, make sure to substitute the word ‘humans’ for ‘man’ in this video. Women need to be included too!

Watch:

Introduction to the Big Bang (https://www.youtube.com/watch?v=dMBqa5BdN_8)

Step 2.

Did your students notice a wrong date at the end of this video? 13.7 BYA is now thought to be 13.82BYA.

It is good that you model questioning for the students, of what they see and hear - the universe story keeps changing and they are allowed to question it too!

Step 3.

Discuss any new vocabulary and the meaning of any unknown words that came up in these videos.

If you are keeping a word wall across the course of this unit, update it with new terms and definitions. Students should be picking up on words such as Big Bang, astronomy, cosmology, energy, matter, atoms, claim, authority, intuition, logic, evidence, hydrogen, helium, redshift, forces, gravity, electromagnetism, time, space, and building blocks of the universe

Step 4.

Where is the evidence for the Big Bang?

Remind students of their duty to be claims testers while researching the Big History of our universe. Do we just trust scientists when they say the big bang happened?

While scientists are credible sources, remember that science is constantly changing, evolving, and improving as new things are discovered. We think we currently have a pretty good idea of how things happened, however. That's based on our current understanding of the universe, and could change if we discover something new.

What we have currently is a reasonably informed theory.

And we should test that theory to see if it makes sense to us as amateur cosmologists, rather than blindly trusting a scientist who says it is so.

Step 5.

Watch:

What Is a Redshift? (https://www.youtube.com/watch?v=FhfnqboacV0)

Step 6.

In summary: in 1929, with his new telescope, Edwin Hubble discovered that all the galaxies and stars were moving away from each other by observing their light.

IF stars are moving away from Earth, THEN the observable (UV) light that reaches earth will appear to be red on the visible spectrum of light because the wavelength of the light will be longer, due to the Doppler effect. Hence the name Redshift.

This is indeed what Hubble observed - red light from stars he theorised were moving away from us.

Scientists believe that IF the universe is slowly expanding and growing bigger THEN it must have begun as a small ‘singularity’ - one tiny point that the Big Bang expanded from.

Step 7.

So, let's do an experiment to test this theory. This simple experiment shows how 13.82 billion years ago the universe was compressed into an infinitely small space, known as a singularity.

It inflated in a sudden burst of energy and created our universe that began to expand in all directions. Even right now objects are still moving away from each other.

Step 8.

Split students into partners or small groups.

Distribute the balloons, other materials, and Student Worksheets.

Take action: Proof of Redshift experiment

These instructions are also available on the Student Worksheet.

Step 1.

Make one person in the group responsible for inflating the balloon.

The other student(s) will be responsible for measuring and recording data.

This is important because one student will have to have their fingers on the balloon the entire experiment!

Step 2.

Inflate your balloon until it is about 10cm in diameter (a couple of big breaths.) Diameter is the distance from one side to the other. Do not tie the end, just hold it closed.

Step 3.

Using the felt-tip marker, make four random dots on the balloon in widely scattered locations. Label one dot "Earth" and the others are stars A, B and C.

Step 4.

Add three squiggly lines on your balloon to represent light waves. Make sure the light waves are close together to begin with.

Step 5.

Without letting air out of the balloon, use the string to measure the distance from the 'Earth' dot to each 'star' dot.

Use your ruler to measure the string to find the distance between the Earth and these stars.

Record the distances in the worksheet table under the heading "Time 1".

Step 6.

Inflate the balloon so that its diameter is about 5cm bigger (another big breath). Again measure the distances from the ‘Earth’ dot to each of the star dots, and record the distances under "Time 2" on the worksheet.

Step 7.

Inflate the balloon about 5cm one more time. After each inflation, measure and record the distances under "Time 3" on the worksheet.

Step 8.

Answer the following questions:

How did the distance from the Earth dot to each of the star dots change each time you inflated the balloon?
Did the stars nearest Earth, or those further away, appear to move the greatest distance?
What did you observe with the light waves each time you inflated the balloon? Think about what we learnt earlier and try to use words such as compressed and expanded.
Explain the Redshift and Big Bang theories of the universe in your own words.
How does what you've seen here support or disprove the Redshift and Big Bang theories of the universe?

Reflection

Reflection

Ask students to share their responses to the last question with the whole class.

Suggested answer: The Redshift theory says that the universe is constantly expanding. Stars are moving away from the centre of the universe.

Time 1 is supposed to represent a time closer to the start of the universe and the events of the Big Bang, while Time 3 might be closer to the present time.

This experiment showed that stars were indeed getting further away from Earth as the universe (balloon) continued to expand. We also saw that the light waves, which began quite tight and condensed, slowly stretched out and became longer as the universe expanded. This supports Hubble's theory that longer lightwaves at the red end of the visible light spectrum are emanating from stars as they move away from us.

Threshold crossed

Before this, we weren't sure there was anything in the universe. If there was, we don't know what it was. We also don't know what the conditions were like.

However, something happened, which we know as the Big Bang.

This caused the universe to change so much that we recognsie it as a new complexity - almost a totally new place.

Now we have space, time, matter (hydrogen and helium), energy (gravity and electromagnetism).

Stick your Threshold 1 Card up around the classroom somewhere as an indicator of a threshold being crossed!

Where to next?

Students' learning throughout Big History is leading them towards designing future cities. As Big Historians, we are travelling through 13.82 billion years of our universe’s history to find solutions to the United Nations' Sustainable Development Goal #11: to make cities inclusive, safe and resilient.

Remind students that the Sustainable Development Goals are the world’s to-do list for people and the planet. We all need to be a part of the process. 193 nations came together and agreed on one common list for all of us that helps make the planet and our communities stronger.

What will be our second touchdown threshold in the next lesson? Stars and chemical elements: Why are stars important to us?

Big History Passport check-in

After this lesson, students should have added to their Big History Passport:

Student Worksheet - Proof of redshift experiment
Threshold 1 Reflection Page.

Differentiated learning

Extension: For students who would like to learn more about the Big Bang. Watch: Looking into the Past. Discuss:
- How quickly does light travel? (0:48)
- What evidence did Hubble have for the expansion of the universe? (4:10)
- What is the significance of the Hubble eXtreme Deep Field? (5:40)
- What is the goal of the James Webb space telescope? (6:20)

Big History - Evidence for the Big Bang

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