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# Why is summer hot?

Year 7 Earth and space · The Earth and the sun

<!-- Speaker note: Students explain seasons by the Earth's axial tilt, link tilt to the height of the noon sun and day length, and use opposite hemispheres and the distance data to reject the distance explanation (AC9S7U03, node 4, a hinge node). About 22 minutes (Engage and Explore 7 min · Explain 9 min · The other hemisphere 3 min · Evaluate 3 min · Wider adds about 4 min). -->

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## Today

**We are learning to** seasons are caused by the Earth's tilted axis, not its distance from the sun. Leaning towards the sun gives a higher noon sun (concentrated light) and longer days: summer. The two hemispheres have opposite seasons.

- I can explain that seasons are caused by the tilt, not distance from the sun.
- I can link the tilt to the height of the noon sun and the length of the day.
- I can explain why the two hemispheres have opposite seasons.

<!-- Speaker note: Before class: A concept tutorial for introducing or revising the idea; pair it with a torch shone straight and at a slant onto grid paper. Set the width with `?width=minimum`, `typical` (default) or `wider`. The hinge misconception is that summer happens because the Earth is closer to the sun. The board shows the real distance for each date: closest (147 million km) in early January, farthest (152) in early July. Board notes: day lengths and noon sun heights are calculated for each city's latitude and date (ignoring the bending of light by the air, which adds a few minutes). The wider tier's tilt slider is a "what if": the real tilt is 23.4°. The Kakadu six seasons are described by Parks Australia with Bininj/Mungguy people; check local sources if you want students to explore a calendar from your own area. -->

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## Why it matters

> On 4 January the Earth is at its closest to the sun all year, five million kilometres closer than in July. That day it's summer in Canberra and winter in London.

<!-- Speaker note: The Earth's axis is tilted and always points the same way. This lesson: what that does across a year. -->

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<span style="background:#dbeafe; color:#1a1a1a; border:1.5px solid #3b82f6; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">💬 Discussion</span>

## Engage: predict

**Why is it hotter in Canberra in December than in June?**

- The Earth is closer to the sun in December
- There are fewer clouds in December
- The sun gives out more heat in December
- The Earth's tilt makes the Southern Hemisphere lean towards the sun in December

<!-- Speaker note: What happens: The tilt. In December the Southern Hemisphere leans towards the sun: the noon sun is high and the days are long. The Earth is in fact closest to the sun in early January, but that changes the sunlight by only about 7%. Take two or three predictions before anyone runs it. -->

<!-- Speaker note: Teacher: count how many chose 'closer to the sun'. -->

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<span style="background:#fef3c7; color:#1a1a1a; border:1.5px solid #f59e0b; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✍️ Activity</span>

## Explore it

{{embed: https://studio.learningwaypoints.com/tutorials/_playground-board/index.html?id=deck%2Fscience%2Fearth-7%2Fseasons%2Fstep-2&code=widget%3A+sky%0Amode%3A+earth%0Aplace%3A+Canberra%0A&fresh=1}}

[Open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/science/earth-7/seasons/?full=step-2#step-2)

<!-- Speaker note: Move the **Date** slider between December and June. Note the daylight, how high the sun is at noon, and the distance from the sun each time. -->

<!-- Speaker note: Teacher: ask what the distance was in December and in June. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## What happened?

* The tilt. In December the Southern Hemisphere leans towards the sun: the noon sun is high and the days are long. The Earth is in fact closest to the sun in early January, but that changes the sunlight by only about 7%.

<!-- Speaker note: Reveal after running. Ask who predicted it, and what made them think so. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Distance

**In late December, when it's summer in Canberra, how far is the Earth from the sun compared with late June?**

- About 5 million km closer
- Twice as close
- The same distance
- About 5 million km farther

* Answer: About 5 million km closer

<!-- Speaker note:  -->

<!-- Speaker note: Teacher: 'If distance caused seasons...' is the checkpoint. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## A test of distance

**If distance caused seasons, what would be true?**

- Both hemispheres would have summer at the same time
- Australia would have summer in December
- Nothing would change
- Seasons would be opposite in the two hemispheres

* Answer: Both hemispheres would have summer at the same time

<!-- Speaker note:  -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Summer and winter

**Which go with Canberra's summer, and which with its winter?**

Groups: Summer · Winter

Southern Hemisphere leans towards the sun · Noon sun high in the sky · About 9½ hours of daylight · Sunlight hits the ground at a low angle, spread over a bigger area · About 14½ hours of daylight

* Answer: Southern Hemisphere leans towards the sun → Summer; Noon sun high in the sky → Summer; About 9½ hours of daylight → Winter; Sunlight hits the ground at a low angle, spread over a bigger area → Winter; About 14½ hours of daylight → Summer

<!-- Speaker note:  -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Mix it up

**Looking back at the Earth's spin and orbit: as the Earth goes round the sun, what does its tilted axis do?**

- It keeps pointing the same way in space
- It stands straight up
- It flips over halfway through the year
- It always leans towards the sun

* Answer: It keeps pointing the same way in space

<!-- Speaker note: The axis keeps pointing the same way in space. That is why each hemisphere leans towards the sun for half the year. What this step is for: The tilt that causes the seasons only works because the axis keeps pointing the same way as the Earth goes round the sun. -->

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<span style="background:#fef3c7; color:#1a1a1a; border:1.5px solid #f59e0b; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✍️ Activity</span>

## the other hemisphere

{{embed: https://studio.learningwaypoints.com/tutorials/_playground-board/index.html?id=deck%2Fscience%2Fearth-7%2Fseasons%2Fstep-5&code=widget%3A+sky%0Amode%3A+earth%0Aplace%3A+London%0A&fresh=1}}

[Open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/science/earth-7/seasons/?full=step-5#step-5)

<!-- Speaker note: What this step is for: Seeing opposite seasons on the same date in London and Canberra is the strongest evidence for the tilt explanation. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Why opposite

**On 22 June, London has about 16½ hours of daylight and Canberra about 9½. Why?**

- London is nearer the equator
- The sun is bigger in London
- London is closer to the sun
- The Northern Hemisphere leans towards the sun in June, and the Southern Hemisphere leans away

* Answer: The Northern Hemisphere leans towards the sun in June, and the Southern Hemisphere leans away

<!-- Speaker note:  -->

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<span style="background:#fef3c7; color:#1a1a1a; border:1.5px solid #f59e0b; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✍️ Activity</span>

## Elaborate: no tilt

{{embed: https://studio.learningwaypoints.com/tutorials/_playground-board/index.html?id=deck%2Fscience%2Fearth-7%2Fseasons%2Fstep-6&code=widget%3A+sky%0Amode%3A+earth%0Aplace%3A+Canberra%0Atilt%3A+choose%0A&fresh=1}}

[Open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/science/earth-7/seasons/?full=step-6#step-6)

<!-- Speaker note: What this step is for: Removing the tilt in the model and watching the seasons disappear shows tilt is the cause, not just a correlation. -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Seasons without tilt

**With no tilt, what happens to Canberra's seasons?**

- They disappear: about 12 hours of daylight and the same noon sun all year
- Nothing changes
- They swap
- They get stronger

* Answer: They disappear: about 12 hours of daylight and the same noon sun all year

<!-- Speaker note:  -->

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Six seasons

**In Kakadu, Bininj people recognise six seasons, marked by changes in rain, wind, plants and animals, rather than four. Why can both systems be useful?**

- The six seasons are caused by a different tilt
- The tilt model explains why the year changes; a six-season calendar describes the changes people actually observe in that place
- Kakadu has no seasons
- Only the four-season model is science

* Answer: The tilt model explains why the year changes; a six-season calendar describes the changes people actually observe in that place

<!-- Speaker note:  -->

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## Evaluate: look back

Write one sentence: "At first I thought… Now I think… because…"

**Revision summary**

- Seasons are caused by the Earth's **tilt**, not its distance from the sun (we are closest in January).
- Leaning **towards** the sun: the noon sun is **higher** (light concentrated on a smaller area) and days are **longer**: summer.
- The two hemispheres have **opposite** seasons. Near the equator the changes are small.

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<span style="background:#dcfce7; color:#1a1a1a; border:1.5px solid #22c55e; padding:6px 18px; border-radius:8px; font-size:1em; font-weight:500;">✅ Check</span>

## Exit ticket

**Explain why Canberra is hotter in December than in June.**

* In December the Southern Hemisphere leans towards the sun (the tilt), so the noon sun is higher, concentrating the light, and days are longer. It isn't distance: the Earth is actually slightly closer to the sun in January.

<!-- Speaker note: Students answer on paper or a mini whiteboard before the reveal. Anyone who cannot answer needs the main idea again next lesson. Where this leads: Next: the moon (nodes 2, 3 and 5). In class: the torch-and-grid-paper practical; a sunrise and sunset table for your town from the Bureau of Meteorology or Geoscience Australia. -->