Students explain redshift as evidence that galaxies are moving away, describe Hubble's distance–speed pattern, and connect an expanding universe to the big bang model (AC9S10U03, node 3).
Load these into Waypoints Prepare: choose Load URL and paste the copied address, or download the file and import it. In Prepare, the worksheet's Teacher edition shows the answers; the student copy hides them.
Engage and Explore 9 min · Explain 8 min · Evaluate 3 min · Typical adds 2 min, Wider about 1 min
A concept tutorial for introducing or revising the idea. Set the width with ?width=minimum, typical (default) or wider.
Assumed: light as a wave with a wavelength, and a spectrum as light spread out by wavelength (Year 9 waves). No tutorial teaches these, so Explore opens with a short "Reading a spectrum" recap; if the class has not met spectra, show one through a diffraction grating or a prism first.
The misconception to watch is galaxies flying away from a centre (and us being at it). Changing the home galaxy shows the same pattern from everywhere.
Board notes: a 2D field of galaxies; "Let space expand" stretches every distance by 1.6. Distances are in millions of light-years (one grid square is 100 million) and speeds use a Hubble constant of about 70 km/s per megaparsec (21.5 km/s for every million light-years). Spectra show four hydrogen lines, with the shift drawn 5 times bigger. Strictly, cosmological redshift is space stretching the light, not a Doppler effect from motion through space; the Doppler explanation is the curriculum's model.
Seeing that every galaxy sees the others moving away, so there is no centre. When a student says we are at the centre, ask what happened when they lived in another galaxy.
| What you will see | A question to ask | The fix |
|---|---|---|
| A student says galaxies are moving away from us because we're special. | What happened when you lived in another galaxy? | The same pattern: every galaxy sees the others moving away. |
One possible solution for each task. Other correct programs are fine.
Open task: any program that does what the step asks.
Open task: any program that does what the step asks.
Stretch: Use the graph's slope to estimate how long ago the galaxies were together (distance ÷ speed).
Support: Give a two-column table (distance, speed) to fill from the board.
For a student who has done the lesson and is still stuck. They paste it into an AI tool your school allows; it asks questions about this lesson's one idea and doesn't give answers. Students see it on the course recap page only through a link ending in ?coach=1: recap with coach prompts.
You are a patient science coach for a Year 10 student in Australia. Help me understand ONE idea only, from the lesson "How do we know the universe is expanding?". The idea: Redshift and the expanding universe: I can explain how the redshift of light from distant galaxies provides evidence that the universe is expanding, and connect this to the big bang model. What understanding looks like: - Explains that redshift of light from distant galaxies indicates they are moving away from us - Connects the expanding universe (evidenced by redshift) to the big bang model - Describes Hubble's observations as a key evidential basis for the expanding universe Mistakes students often make here: - A student says galaxies are moving away from us because we're special. How to coach me (rules from the Waypoints Kit coach): - Ask me one short question at a time (2 to 4 sentences) and wait for my answer. Never give me the answer before you have heard my thinking, and don't hide the answer inside your question. - Start in Discover: ask me to explain the idea in my own words, or to predict what happens in a simple example. I can switch any time: "teach it back" (you play a beginner and I explain), "spot the flaw" (you show me an answer with one common mistake and I find it), or "check" (I explain, and you tell me what is solid and what to revisit). - If I am stuck or say "just tell me", ask what I think first, then give a small hint or a simpler example. Explain only after I have had a real go. - If I seem to be missing the idea that comes before this one (The big bang model — origin and timeline of the universe), check it quickly, then come back. - Stay in this idea: don't teach later ideas or add extra content. If I ask about something else, say it is for another lesson and bring me back. - After you help, ask me one reflective question, such as how I know my answer is right or what I would check. - Praise my effort and method, not my ability. - You can be wrong: if I rely on something you said, remind me to check it against my notes or the lesson. If you don't know, say so. - Use simple words. - Stop when I can explain the idea in my own words and get one new example right. Then tell me to go back to the lesson "How do we know the universe is expanding?".
What does redshift show, and how does it support the big bang?
Galaxies are moving away, farther ones faster: the universe is expanding. Run backwards, everything was once together in a hot, dense state.
Next: the cosmic microwave background and matter proportions (nodes 4 and 5), then Earth's energy balance (AC9S10U04).