--- marp: true theme: default html: true --- # Why does the moon change shape? Year 7 Earth and space · The moon --- ## Today **We are learning to** the sun always lights half of the moon. As the moon goes round the Earth (29.5 days from new moon to new moon), we see more or less of that lit half: the phases. They are not caused by Earth's shadow. - I can put the eight phases of the moon in order. - I can explain the phases by the moon's position, not Earth's shadow. - I can predict the phase seen from Earth for a given position. --- ## Why it matters > The moon looks like a thin smile one week and a bright full disc two weeks later. Nothing about the moon itself has changed. --- 💬 Discussion ## Engage: predict **What causes the moon's phases?** - The moon changing shape - Earth's shadow covering part of the moon - Clouds covering part of the moon - How much of the moon's sunlit half we can see from Earth, as it goes round us --- ✍️ Activity ## Explore it {{embed: https://studio.learningwaypoints.com/tutorials/_playground-board/index.html?id=deck%2Fscience%2Fearth-7%2Fphases%2Fstep-2&code=widget%3A+sky%0Amode%3A+moon%0Ashadow%3A+on%0A&fresh=1}} [Open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/science/earth-7/phases/?full=step-2#step-2) --- ✅ Check ## What happened? * How much of the sunlit half we can see. The sun always lights half the moon; as the moon goes round the Earth, we see more or less of that half. Earth's shadow is only involved in a lunar eclipse. --- ✅ Check ## Order **Put the phases in order, starting from new moon.** ```science Waning gibbous First quarter Full moon Waning crescent Waxing gibbous New moon Last quarter Waxing crescent ``` --- ✅ Check ## The shadow **At first quarter, where is Earth's shadow?** - Pointing away from the sun, nowhere near the moon: half the moon is dark only because we see half of its lit side - In front of the sun - Covering half the moon - Covering the whole moon * Answer: Pointing away from the sun, nowhere near the moon: half the moon is dark only because we see half of its lit side --- ✅ Check ## Full moon **At full moon, where is the moon?** - Between the Earth and the sun - On the far side of the Earth from the sun, so we see its whole lit half - At a right angle to the sun - Closest to the sun * Answer: On the far side of the Earth from the sun, so we see its whole lit half --- ✅ Check ## Phase or eclipse **In a lunar eclipse, a full moon goes dark and reddish for an hour or two. How is that different from the moon's phases?** - A lunar eclipse happens at new moon, when the moon is dark - An eclipse is the moon going through all its phases in an hour - An eclipse is Earth's shadow falling on the moon, only at some full moons; the phases come from how much of the lit half we see, every month - There is no difference: a lunar eclipse is just a very dark phase * Answer: An eclipse is Earth's shadow falling on the moon, only at some full moons; the phases come from how much of the lit half we see, every month --- ✅ Check ## Mix it up **Looking back at spinning and orbiting: about how many times does the Earth spin during one trip round the sun?** - About 365 - About 12 - About 24 - Once * Answer: About 365 --- ✍️ Activity ## name the phase {{embed: https://studio.learningwaypoints.com/tutorials/_playground-board/index.html?id=deck%2Fscience%2Fearth-7%2Fphases%2Fstep-5&code=widget%3A+sky%0Amode%3A+moon%0Aquiz%3A+on%0Aneed%3A+5%0A&fresh=1}} [Open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/science/earth-7/phases/?full=step-5#step-5) --- ✅ Check ## Elaborate: a month of evidence **A student sees a full moon on 1 March. On about what day of March will the next full moon be?** * Answer: 30 --- ✍️ Activity ## Elaborate: the view from Japan {{embed: https://studio.learningwaypoints.com/tutorials/_playground-board/index.html?id=deck%2Fscience%2Fearth-7%2Fphases%2Fstep-7&code=widget%3A+sky%0Amode%3A+moon%0Aview%3A+north%0A&fresh=1}} [Open this step in the tutorial](https://studio.learningwaypoints.com/tutorials/science/earth-7/phases/?full=step-7#step-7) --- ✅ Check ## Elaborate: the view from Japan **From Australia a waxing crescent is lit on the left. From Japan it is lit on the right. Why?** - People in the Northern Hemisphere see the moon 'upside down' compared with us, so left and right swap - The moon's phase is different in Japan - Japan sees a different moon - It's lit on the left everywhere * Answer: People in the Northern Hemisphere see the moon 'upside down' compared with us, so left and right swap --- ## Evaluate: look back Write one sentence: "At first I thought… Now I think… because…" **Revision summary** - The sun always lights **half** the moon. The **phase** is how much of that lit half we can see, which depends on where the moon is in its orbit. - New moon → waxing crescent → first quarter → waxing gibbous → full moon → waning gibbous → last quarter → waning crescent (about 29.5 days). - Phases are **not** caused by Earth's shadow. From Australia a waxing moon is lit on the left. --- ✅ Check ## Exit ticket **Why do we see a half-lit moon at first quarter?** * The moon is a quarter of the way round its orbit, at right angles to the sun; we see half of its sunlit half. It isn't Earth's shadow.