MS Earth and Space — every video script, narration first

Under each lesson: its atom, the script one beat per line (the on-screen column in grey), the attached question, the essential questions with keys shown, then the summary video with its three questions (the topic then goes straight to the PP100). Tap Fine or Change this under each; Copy all at the top pastes your rulings into the chat.

Topic 2 — The rock cycle

T02 intro video

119 spoken words, about 60 s.

1Here is Evan on a beach in California, letting sand run through his fingers.[Evan's labeled figure crouched on a wide beach, sand pouring from one hand; mountains far behind; no title card]
2Each grain of sand was once part of a solid rock, high in the mountains behind him.[a close view of a few grains in his palm; then the distant mountains]
3Rain and rivers broke that rock down and carried the pieces all the way to this beach.[a river winds from the mountains to the shore]
4So could this loose sand ever become solid rock again, and could that rock ever melt?[the grains in his palm; a question mark]
5Every rock on Earth, from a mountain to a pebble, is partway through the same slow story.[the beach, the river and the mountains in one frame]
6To find out, we will look at the three rock families, how each one forms, and the paths a rock can take from one to another.[the frame holds]
7Okay, so are you ready to follow a rock through its story?[the three replies appear]

A: Fine / B: Change this

T02 L01 — Sort a rock into its family from what you can see

EAR-010 · Sort a rock into igneous, sedimentary, or metamorphic from its observable features.

178 spoken words, about 89 s.

1Here is Farah at a table of rocks in science class, with a hand lens.[Farah's labeled figure at a table; six rock photos in a row (ph_granite, ph_obsidian, ph_sandstone, ph_limestone, ph_gneiss, ph_slate), no names yet; no title slide]
2To sort a rock into its family, look at its grains.[the hand lens moves over the first rock; chip LOOK AT THE GRAINS]
3This speckled rock is granite: its grains are locked in a jumble, so it is igneous.[ph_granite enlarges; label granite; chip GRAINS LOCKED IN A JUMBLE, then chip IGNEOUS beside it]
4This black rock is obsidian: it has a glassy look and no grains you can see, so it is igneous too.[ph_obsidian enlarges; label obsidian; chip GLASSY LOOK, then chip IGNEOUS]
5This tan rock is sandstone: it is pieces stuck together in flat layers, so it is sedimentary.[ph_sandstone enlarges; label sandstone; chip PIECES IN FLAT LAYERS, then chip SEDIMENTARY]
6This pale rock is limestone: its pieces of shell are stuck together in flat layers, so it is sedimentary too.[ph_limestone enlarges; label limestone; chip PIECES IN FLAT LAYERS, then chip SEDIMENTARY]
7This striped rock is gneiss: it has bands and wavy stripes, so it is metamorphic.[ph_gneiss enlarges; label gneiss; chip BANDS OR WAVY STRIPES, then chip METAMORPHIC]
8And this gray rock is slate: its grains are lined up so it splits into flat sheets, so it is metamorphic too.[ph_slate enlarges; label slate; a corner sheet lifts; chip GRAINS LINED UP IN FLAT SHEETS, then chip METAMORPHIC]
9So, here's what we've seen: grains locked in a jumble, or a glassy look, mean igneous; pieces stuck together in flat layers mean sedimentary; bands or wavy stripes, or grains lined up in flat sheets, mean metamorphic.[the six photos in three pairs under their family chips; closing screen: three bullets — • Grains locked in a jumble, or a glassy look: igneous. • Pieces stuck together in flat layers: sedimentary. • Bands or wavy stripes, or grains lined up in flat sheets: metamorphic.]
10Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. A student wants to sort a rock into its family. What does she look at to tell which family it is in?

  1. its grains ✓
  2. its color
  3. its size

Essential questions after the lesson (5)

1. A brown rock is made of thin flat layers of mud pressed together. Which family is it in?

  1. igneous
  2. sedimentary ✓
  3. metamorphic

2. A dark green rock is smooth and shiny like glass, with no grains you can see and no layers. Which family is it in?

  1. igneous ✓
  2. sedimentary
  3. metamorphic

3. A white rock has gray stripes that bend and wave across it. Which family is it in?

  1. igneous
  2. sedimentary
  3. metamorphic ✓

4. A gray rock's grains are lined up the same way, so it splits into thin flat sheets. Which family is it in?

  1. igneous
  2. sedimentary
  3. metamorphic ✓

5. A rock's pink, white and black grains are locked together in a jumble, with no layers. Which family is it in?

  1. igneous ✓
  2. sedimentary
  3. metamorphic

A: Fine / B: Change this

T02 L02 — Igneous rock forms when melted rock cools and hardens

EAR-011 · Explain that igneous rock forms when melted rock cools and hardens.

173 spoken words, about 86 s.

1Here is Gus on a hillside in Hawaii, watching red-hot lava creep down the slope.[Gus's labeled figure at a safe distance; a glowing lava flow moving slowly down a dark slope; no title slide]
2The melted rock that comes out of a volcano is called lava.[chip LAVA on the glowing flow]
3Deep under the ground, rock is so hot that it melts.[a cutaway under the hillside: a glowing pocket of melted rock far below, the volcano's pipe rising from it]
4Melted rock that is still under the ground is called magma.[chip MAGMA on the glowing pocket; chip LAVA stays on the flow above ground]
5On the slope, the lava cools in the air and hardens into black rock in days.[the flow darkens from the edges in; a day counter runs; ph_basalt appears beside it]
6This black rock is basalt: it cooled fast, so its grains are too small to see.[ph_basalt enlarges; chip COOLED FAST, chip TINY GRAINS]
7Lava that cooled fastest of all became obsidian, smooth like glass.[ph_obsidian beside the basalt; chip GLASS]
8Now suppose some magma stays deep under the ground.[back to the cutaway; the pocket of magma with no pipe to the surface]
9The rock around it keeps it warm, so it cools slowly, over thousands of years.[the pocket darkens very slowly; a counter in years climbs past 10 000]
10It cooled slowly, so its grains grew big, and the rock is granite.[ph_granite appears in the pocket's place; chip COOLED SLOWLY, chip BIG GRAINS]
11All three are igneous, because all three formed from melted rock that cooled and hardened.[the three photos in a row under one chip IGNEOUS]
12Here's the pattern: igneous rock forms when melted rock cools and hardens; fast cooling gives tiny grains or glass, and slow cooling gives big grains.[closing screen: one line — "Igneous rock forms when melted rock cools and hardens. Fast cooling gives tiny grains or glass; slow cooling gives big grains."]
13Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. Melted rock comes out of a volcano and hardens on the ground in a few days. Which family is the new rock in?

  1. igneous ✓
  2. sedimentary
  3. metamorphic

Essential questions after the lesson (4)

1. What must happen to melted rock for igneous rock to form?

  1. It cools and hardens. ✓
  2. It is pressed and cemented into layers.
  3. It is heated and squeezed without melting.

2. Melted rock pours onto the ground and hardens in a few days. What does the new rock look like close up?

  1. tiny grains or glass ✓
  2. big grains

3. Melted rock stays deep under the ground and hardens over thousands of years. What does the new rock look like close up?

  1. tiny grains or glass
  2. big grains ✓

4. Rock deep under the ground has melted and is still under the ground. What is this melted rock called?

  1. lava
  2. magma ✓
  3. sediment

A: Fine / B: Change this

T02 L03 — Sedimentary rock forms when sediment is pressed and cemented

EAR-012 · Explain that sedimentary rock forms when sediment is pressed and cemented together.

173 spoken words, about 86 s.

1Here is Hallie at the Grand Canyon in Arizona, looking at the layers of rock in its side.[Hallie's labeled figure at a railing; the canyon wall with flat layers in tan, red and gray; no title slide]
2One layer is sandstone, and it is made of sand grains stuck together.[ph_sandstone enlarges from one tan layer; chip SANDSTONE]
3But beach sand is loose, so how did loose sand become hard rock?[a handful of loose sand beside the sandstone; a question mark]
4Small pieces of rock, sand, mud or shell that settle to the bottom of water are called sediment.[a river running into the sea; grains sinking to the sea floor; chip SEDIMENT]
5The river drops sand on the sea floor, and the sand settles in a flat layer.[a cutaway of the sea floor: one flat tan layer forms]
6Year after year, more layers settle on top, and the first layer is buried deeper.[layer after layer piles on; the first layer sinks lower in the frame; a counter in years climbs]
7The weight of the layers above presses down on the layers below.[the stack of layers; the bottom layer thins as the pile grows]
8This pressing is called pressure.[chip PRESSURE on the bottom layer]
9The pressure packs the sand grains tightly together.[zoom into the bottom layer: round grains move closer until they touch]
10Water trickles between the grains and leaves tiny bits of mineral behind, which glue the grains to each other.[in the zoom, pale specks appear in the gaps between grains and join them]
11We say the grains are cemented together.[chip CEMENTED beside the joined grains]
12After millions of years, the loose sand has become sandstone.[zoom out: the bottom layer is now the tan sandstone layer in the canyon wall; a counter reads millions of years]
13So, when sediment is pressed and cemented together over millions of years, sedimentary rock forms.[closing screen: one line — "Sedimentary rock forms when sediment is pressed and cemented together, over millions of years."]
14Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. A river drops sand on the sea floor, and more layers bury it for millions of years. Which family will the new rock be in?

  1. igneous
  2. sedimentary ✓
  3. metamorphic

Essential questions after the lesson (4)

1. Mud settles in layers at the bottom of a lake. What has to happen to the mud, over millions of years, for it to become rock?

  1. It is pressed and cemented together. ✓
  2. It melts and then cools and hardens.
  3. It dries out in the sun.

2. A layer of sand lies buried under many other layers. What presses its grains together?

  1. the heat of the Sun
  2. the flow of the sea water
  3. the weight of the layers above it ✓

3. The grains of a buried sand layer are packed tightly. What glues them to each other?

  1. mineral left behind by water ✓
  2. heat from deep underground
  3. air trapped between the grains

4. The weight of the rock layers above pushes down on the layers below. What is this pushing down called?

  1. erosion
  2. pressure ✓
  3. weathering

A: Fine / B: Change this

T02 L04 — Metamorphic rock forms when heat and pressure change a rock without melting it

EAR-013 · Explain that metamorphic rock forms when heat and pressure change an existing rock without melting it.

176 spoken words, about 88 s.

1Here is Evan at the Lincoln Memorial in Washington, and the white stone around him is marble.[Evan's labeled figure on the memorial's steps; white marble columns; ph_marble inset; no title slide]
2His teacher tells him this marble was once limestone, a gray rock made of shell pieces.[ph_limestone beside ph_marble; an arrow between them with a question mark]
3So how did limestone turn into marble?[the question mark pulses]
4Over millions of years, more rock piles on top, so the limestone ends up deep underground.[a cutaway: a limestone layer sinks as layers pile above it; a counter in millions of years climbs]
5Deep underground, the rock above puts the limestone under great pressure.[chip PRESSURE; the layers above press down on the limestone]
6And deep underground, the rock is hot.[an orange glow around the layer; chip HEAT]
7Heat and pressure change the grains: the shell pieces turn into new, sparkling grains, and the limestone has become marble.[zoom into the layer: shell pieces blur and re-form as interlocking sparkling grains; ph_marble replaces ph_limestone]
8But the limestone stayed solid the whole time: it never melted.[chip STAYED SOLID; the layer keeps its shape through the change]
9If it had melted, it would have been magma, and then igneous rock, not marble.[a second cutaway beside the first: the layer glows and runs as magma; chip MAGMA; then hardens; chip IGNEOUS]
10Shale, a soft gray rock made of mud, changes the same way into slate.[a mud-rock photo slot beside ph_slate; chips HEAT and PRESSURE between them]
11And granite changes the same way into gneiss, its grains pressed into wavy bands.[ph_granite beside ph_gneiss; chips HEAT and PRESSURE between them]
12So, here's what we've seen: metamorphic rock forms when heat and pressure deep underground change a rock into a new rock, without melting it.[closing screen: one line — "Metamorphic rock forms when heat and pressure deep underground change a rock into a new rock, without melting it."]
13Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. Deep underground, heat and pressure change shale into slate. Does the shale melt while it changes?

  1. yes
  2. no ✓

Essential questions after the lesson (4)

1. A sandstone layer is buried deep underground, where heat and pressure change its grains while it stays solid. Which kind of rock does it become?

  1. igneous
  2. sedimentary
  3. metamorphic ✓

2. A rock is buried so deep that it melts. Later the melted rock cools and hardens. Which kind of rock has formed?

  1. igneous ✓
  2. sedimentary
  3. metamorphic

3. Limestone deep underground has changed into marble. What changed it?

  1. cooling and hardening
  2. heat and pressure ✓
  3. water and wind

4. Sand grains are pressed and cemented together over millions of years and never get hot. Which kind of rock forms?

  1. igneous
  2. sedimentary ✓
  3. metamorphic

A: Fine / B: Change this

T02 L05 — Predict what a rock becomes next

EAR-014 · Given a set of conditions, predict which rock type forms next.

177 spoken words, about 88 s.

1Here is Gus holding a piece of granite from a mountain in Colorado.[Gus's labeled figure on a rocky mountain trail; ph_granite in his hand; no title slide]
2He thinks a rock this hard will stay granite forever.[a thought bubble: the same granite with FOREVER under it]
3Suppose weathering breaks the granite into sediment, and a river carries it to the sea.[the granite cracks into grains; a river carries them to a sea floor; chip SEDIMENT]
4There it is buried, pressed and cemented, and over millions of years it becomes sedimentary rock.[layers bury the grains; chips PRESSED, CEMENTED; a counter in millions of years; ph_sandstone; chip SEDIMENTARY ROCK]
5Now suppose instead heat and pressure deep underground change the granite without melting it.[back to the whole granite; a cutaway buries it; chips HEAT and PRESSURE; the grains re-form into wavy bands]
6Then it becomes metamorphic rock.[ph_gneiss; chip METAMORPHIC ROCK]
7And suppose instead it is buried so deep that it melts into magma.[back to the whole granite; it sinks deeper and glows; chip MAGMA]
8When the magma cools and hardens, it becomes igneous rock.[the glow fades slowly to speckled rock: ph_granite again, as new igneous rock; chip IGNEOUS ROCK]
9So, when Gus said his granite would stay granite forever, he was not right.[the thought bubble's FOREVER is crossed out]
10Over millions of years, any rock can become any other kind of rock.[the three end rocks in a row with the granite above them]
11This diagram of every path a rock can take is called the rock cycle.[reg_cycle draws in, boxes first, then the arrows with their labels; chip THE ROCK CYCLE]
12To predict what a rock becomes next, ask what happens to it.[a pointer starts at IGNEOUS ROCK and follows the arrow labeled heat and pressure to METAMORPHIC ROCK]
13Here's the pattern: pressed and cemented sediment makes sedimentary rock; heat and pressure without melting make metamorphic rock; melting, then cooling, makes igneous rock.[reg_cycle holds; closing screen: three bullets — • Pressed and cemented sediment: sedimentary rock. • Heat and pressure, no melting: metamorphic rock. • Melted, then cooled and hardened: igneous rock.]
14Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. A diagram shows every path a rock can take from one kind of rock to another. What is this diagram called?

  1. the water cycle
  2. the rock cycle ✓
  3. the rock table

Essential questions after the lesson (5)

1. A layer of shale is buried deep underground, where heat and pressure change it without melting it. Which kind of rock forms next?

  1. igneous
  2. sedimentary
  3. metamorphic ✓

2. A marble boulder on a hillside is broken into sediment, and a river drops the sediment in a lake, where it is buried, pressed and cemented. Which kind of rock forms next?

  1. igneous
  2. sedimentary ✓
  3. metamorphic

3. A layer of limestone is buried so deep that it melts, and the melted rock later cools and hardens. Which kind of rock forms next?

  1. igneous ✓
  2. sedimentary
  3. metamorphic

4. A student finds a granite boulder in a park and says it will still be granite in a hundred million years, whatever happens to it. Is the student right?

  1. yes
  2. no ✓

5. Over millions of years, which kinds of rock can a piece of igneous rock become?

  1. only sedimentary rock
  2. only metamorphic rock
  3. any of the three kinds ✓

A: Fine / B: Change this

T02 L06 — Trace a path through the rock cycle

EAR-015 · Trace one route a rock can take through the cycle, showing the cycle has more than one path.

175 spoken words, about 88 s.

1Here is Farah in science class, with the rock cycle on the board.[Farah's labeled figure at the board; reg_cycle fills the board; no title slide]
2Her teacher asks how sand in sandstone could once have been granite.[ph_sandstone and ph_granite small, beside the board, with a question mark between them]
3To trace a path through the rock cycle, start at the first rock and follow one arrow at a time.[a pointer rests on the diagram; chip START AT THE FIRST ROCK]
4Granite is igneous, so start at igneous rock.[the IGNEOUS ROCK box highlights]
5Follow the arrow for weathering, erosion and deposition: the granite is broken into sediment.[the arrow from IGNEOUS ROCK to SEDIMENT highlights; the pointer slides along it; SEDIMENT highlights]
6Then follow the arrow for pressed and cemented: the sediment becomes sedimentary rock, and sandstone is sedimentary.[the arrow from SEDIMENT to SEDIMENTARY ROCK highlights; SEDIMENTARY ROCK highlights; chip PATH 1 along the two arrows]
7But there is a second path.[the first path fades to a thin highlight; the pointer returns to IGNEOUS ROCK]
8Follow the arrow for heat and pressure first, and the granite becomes metamorphic rock.[the arrow from IGNEOUS ROCK to METAMORPHIC ROCK highlights; METAMORPHIC ROCK highlights]
9Then follow weathering, erosion and deposition to sediment, and pressed and cemented to sedimentary rock.[the arrow from METAMORPHIC ROCK to SEDIMENT highlights, then SEDIMENT to SEDIMENTARY ROCK; chip PATH 2 along the three arrows]
10Two different paths lead from granite to sandstone, so the rock cycle has more than one path.[both paths highlighted together; chip MORE THAN ONE PATH]
11So, here's what we've seen: to trace a path, start at the first rock, follow one arrow at a time, and name each rock you reach; and the rock cycle has more than one path.[reg_cycle holds; closing screen: two bullets — • Start at the first rock, follow one arrow at a time, and name each rock you reach. • The rock cycle has more than one path.]
12Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. A student traces how a piece of basalt could become sandstone. Where on the rock cycle does the trace start?

  1. at igneous rock ✓
  2. at magma
  3. at sediment

Essential questions after the lesson (5)

1. A path has reached magma and is heading for igneous rock. Which arrow does it follow next?

  1. cools and hardens ✓
  2. weathering, erosion, deposition
  3. heat and pressure

2. A path starts at sedimentary rock and follows the arrow labeled melts. Which box does the path reach first?

  1. sediment
  2. magma ✓
  3. metamorphic rock

3. A path runs from metamorphic rock to sedimentary rock. Put these steps in the order they happen, first to last. (put in order)

Order: Weathering, erosion and deposition break the metamorphic rock into sediment. → The sediment is pressed and cemented. → Sedimentary rock forms.

4. Which arrow leads from igneous rock straight to metamorphic rock, in one step?

  1. cools and hardens
  2. melts
  3. heat and pressure ✓

5. Sedimentary rock can become igneous rock by melting and then cooling. Can it also become igneous rock by first becoming metamorphic rock, which then melts and cools?

  1. yes ✓
  2. no

A: Fine / B: Change this

T02 summary video

212 spoken words, about 106 s.

1Here is everything we found out about the rock cycle.[a still: the six rock photos in three pairs; no title chip]
2To sort a rock into its family, look at its grains.[chip LOOK AT THE GRAINS]
3Grains locked in a jumble, or a glassy look, mean igneous.[ph_granite and ph_obsidian under chip IGNEOUS]
4Pieces stuck together in flat layers mean sedimentary.[ph_sandstone and ph_limestone under chip SEDIMENTARY]
5Bands or wavy stripes, or grains lined up in flat sheets, mean metamorphic.[ph_gneiss and ph_slate under chip METAMORPHIC]
6Melted rock that is still under the ground is called magma.[a still cutaway: a glowing pocket under the ground; chip MAGMA]
7Igneous rock forms when melted rock cools and hardens.[chip IGNEOUS beside the cutaway]
8Fast cooling gives tiny grains or glass; slow cooling gives big grains.[ph_basalt under chip FAST, ph_granite under chip SLOW]
9The weight of the layers above presses down on the layers below.[a still stack of sediment layers]
10This pressing is called pressure.[chip PRESSURE on the bottom layer]
11Sedimentary rock forms when sediment is pressed and cemented together, over millions of years.[chip SEDIMENTARY beside the stack]
12Metamorphic rock forms when heat and pressure deep underground change a rock into a new rock, without melting it.[ph_limestone, an arrow, ph_marble; chips HEAT and PRESSURE on the arrow]
13Over millions of years, any rock can become any other kind of rock.[the still reg_cycle]
14The diagram of every path a rock can take is called the rock cycle.[chip THE ROCK CYCLE over reg_cycle]
15To predict what a rock becomes next, ask what happens to it.[one arrow of reg_cycle pulses]
16To trace a path through the rock cycle, start at the first rock, follow one arrow at a time, and name each rock you reach.[a two-arrow path on reg_cycle highlights]
17And the rock cycle has more than one path.[a second path highlights beside the first; closing screen: three bullets — • Sort a rock by its grains: igneous, sedimentary or metamorphic. • Melted rock cools into igneous rock; pressed and cemented sediment becomes sedimentary rock; heat and pressure without melting make metamorphic rock. • Any rock can become any other kind of rock, by more than one path.]
18Okay, now your turn.[the three attached questions follow on the page]

Attached questions

1. A pale rock is made of small pieces of shell stuck together in flat layers. Which family is it in?

  1. igneous
  2. sedimentary ✓
  3. metamorphic

2. A layer of limestone is buried deep underground, where heat and pressure change it while it stays solid. Which kind of rock forms?

  1. igneous
  2. sedimentary
  3. metamorphic ✓

3. Rock deep under the ground melts and stays under the ground. What is the melted rock called?

  1. magma ✓
  2. lava
  3. sediment

A: Fine / B: Change this

Topic 9 — weather or climate, and what sets a climate

T09 intro video

119 spoken words, about 60 s.

1Here is Jaxon stepping off a plane in Phoenix, Arizona, one January afternoon.[Jaxon's labeled figure at the top of the plane steps; bright sun, a clear sky, palm trees beyond the runway; no title card]
2He left Seattle this morning in rain and a thick coat; here the sky is clear and warm.[a small inset: the same morning in Seattle, gray rain on a wet runway; then back to the Phoenix sun]
3He wonders whether Phoenix is like this every January, or whether he just got lucky.[Jaxon takes off the coat and squints at the sun]
4Both cities sit under the same Sun, but one is gray and wet and the other is warm and dry.[a map of the United States with Seattle and Phoenix marked, a rain icon over one and a sun icon over the other]
5So what makes one place's weather, year after year, so different from another's?[the map holds; a question mark between the two cities]
6To find out, we will look at what a climate is, what counts as evidence about it, what sets it, and how to read it off a graph.[the map holds]
7Okay, so are you ready to find out what sets a climate?[the three replies appear]

A: Fine / B: Change this

T09 L01 — Weather, season or climate?

EAR-070 · Decide whether a statement is describing weather or climate.

176 spoken words, about 88 s.

1Here is Gia reading about Chicago, because her family is moving there in January.[Gia's labeled figure at a kitchen table; a phone, a text message and an open guidebook on the table; no title slide]
2Her weather app says snow this morning.[the phone enlarges: a snow icon, SNOW THIS MORNING]
3Her cousin's text says it is freezing now, but hot and sticky by July.[the text message enlarges: 'Freezing now, but hot and sticky by July!']
4And her guidebook says Chicago has cold, snowy winters, year after year.[the guidebook enlarges: 'Chicago has cold, snowy winters, year after year.']
5The weather is what the sky and the air are like at a place on one day.[the three items in a row; a clock appears under the phone; chip ONE DAY]
6So the app is telling Gia the weather: snow, this morning, one day.[chip THE WEATHER on the phone]
7Through the year, the weather changes from season to season.[a calendar appears under the text and flips from January snow to July sun; chip THROUGH THE YEAR]
8So her cousin is telling her about the seasons: the weather's pattern over one year.[chip THE SEASON on the text]
9The weather a place usually has at a particular time of year, year after year, is called its climate.[a stack of calendars appears under the guidebook; chip YEAR AFTER YEAR]
10So the guidebook is telling her Chicago's climate: cold, snowy winters, year after year.[chip THE CLIMATE on the guidebook]
11Snow this morning is the weather, and snow every winter is the climate.[the phone and the guidebook side by side, chips THE WEATHER and THE CLIMATE under them]
12So, here's what we've seen: the weather is one day; the season is the pattern over the year; the climate is year after year.[closing screen: three bullets — • The weather is what the sky and the air are like at a place on one day. • Through the year, the weather changes from season to season. • The climate is the weather a place usually has at a particular time of year, year after year.]
13Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. Every October, for as long as anyone remembers, a town has been cool and rainy. Which word names the weather a place usually has like that, year after year?

  1. the weather
  2. the season
  3. the climate ✓

Essential questions after the lesson (7)

1. A forecast for Denver, Colorado, says there will be hail this afternoon. Is this sentence about the weather, the season, or the climate?

  1. the weather ✓
  2. the season
  3. the climate

2. A book about Phoenix, Arizona, says its summers are very hot and dry, year after year. Is this sentence about the weather, the season, or the climate?

  1. the weather
  2. the season
  3. the climate ✓

3. A girl in Minneapolis, Minnesota, says it is cold now, but it warms up in spring and gets hot by July. Is this sentence about the weather, the season, or the climate?

  1. the weather
  2. the season ✓
  3. the climate

4. A lifeguard in Miami, Florida, tells swimmers there is a strong wind and high waves today. Is this sentence about the weather, the season, or the climate?

  1. the weather ✓
  2. the season
  3. the climate

5. A farmer near Houston, Texas, says every winter there is mild, and it hardly ever freezes. Is this sentence about the weather, the season, or the climate?

  1. the weather
  2. the season
  3. the climate ✓

6. A boy in Seattle, Washington, says it rained all winter this year, and now the summer has turned dry. Is this sentence about the weather, the season, or the climate?

  1. the weather
  2. the season ✓
  3. the climate

7. A student says a town's climate is just another word for the weather it has today. Is the student correct?

  1. yes
  2. no ✓

A: Fine / B: Change this

T09 L02 — One cold morning against thirty years of records

SR-005 · Decide which of two pieces of evidence gives better support for the same claim.

170 spoken words, about 85 s.

1Here is Hugo on his porch in Houston, Texas, one January morning, and the thermometer reads minus 2 degrees Celsius.[Hugo's labeled figure in a coat on a porch; frost on the grass; a digital porch thermometer reading −2 °C; no title slide]
2Hugo says Houston has a cold winter climate.[a speech bubble: 'Houston has a cold winter climate.']
3His claim is about the climate: the weather Houston usually has in January, year after year.[chip YEAR AFTER YEAR under the speech bubble]
4He has two pieces of evidence: this morning's reading, and 30 Januaries of records.[reg_evidence draws in: the ONE MORNING card showing −2 °C, the THIRTY JANUARIES card showing the average 12 °C]
5Evidence supports a claim better when it covers the stretch of time the claim is about.[chip THE SAME STRETCH OF TIME between the cards and the speech bubble]
6The weather changes from day to day.[the ONE MORNING card; a small calendar flips a day and the reading changes]
7This morning's reading covers one day, so it is weak evidence about a climate.[chip WEAK EVIDENCE on the ONE MORNING card]
8Thirty years of records cover January year after year, so they are strong evidence about a climate.[the THIRTY JANUARIES card; thirty small January pages fan out behind it; chip STRONG EVIDENCE]
9In those records, the January average is 12 degrees Celsius.[the average 12 °C pulses on the card]
10So, when Hugo said Houston has a cold winter climate, he was not right: Houston does not have a cold winter climate; this was one cold morning.[the speech bubble's words are struck through; the ONE MORNING card sits beside it with the chip ONE DAY]
11Here's the pattern: to judge a claim about a climate, use years of records, never one day.[closing screen: one line — "To judge a claim about a climate, use years of records, never one day."]
12Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. A town's thirty years of records show mild Januaries. One January morning there is below freezing. Does that one morning change the town's climate?

  1. yes
  2. no ✓

Essential questions after the lesson (4)

1. A student claims Phoenix, Arizona, has a hot summer climate. Which evidence supports the claim better?

  1. thirty years of Phoenix July records ✓
  2. one afternoon in Phoenix at 45 °C

2. A student claims Seattle, Washington, has wet winters. Which evidence supports the claim better?

  1. the rainfall records for Seattle's last twenty winters ✓
  2. one rainy Tuesday afternoon in downtown Seattle

3. One July morning in Denver, Colorado, is cool, at 9 °C. A student says this one morning shows that Denver has a cool summer climate. Is the student correct?

  1. yes
  2. no ✓

4. A student claims it is raining in Miami, Florida, right now. Which evidence supports that claim better?

  1. the rainfall records for Miami over thirty years
  2. a live webcam picture of a Miami street right now ✓

A: Fine / B: Change this

T09 L03 — Three things set a place's climate

EAR-071 · Identify the factors that set a region's climate, such as latitude, altitude, and nearness to water.

173 spoken words, about 86 s.

1Here is Isla comparing the climates of pairs of places on a map.[Isla's labeled figure at a desk; a map of the United States with six dots: Chicago, Houston, Denver, Pikes Peak, Seattle, Minneapolis; no title slide]
2Three things set a place's climate: latitude, elevation, and how near it is to a large body of water.[three chips in a row: LATITUDE · ELEVATION · NEAR A LARGE BODY OF WATER]
3How far north or south of the equator a place is, is called its latitude.[the map: a dashed line far to the south labeled equator; an arrow from the equator up to Chicago]
4How high up a place is, is called its elevation, or its altitude.[a side view: a low city and a mountain top, with a height arrow up to the mountain top; chip ELEVATION]
5Chicago and Houston are both low and both beside large water, but Chicago is much farther north.[pair_latitude: the table; the latitude row highlights, the other two rows match]
6Chicago's winters are much colder, so latitude makes the difference.[a snow icon over Chicago, a sun icon over Houston; chip LATITUDE on the pair]
7Denver and the top of Pikes Peak share a latitude and are both far from the sea, but Pikes Peak is far higher.[pair_elevation: the table; the elevation row highlights]
8Its summers are cold while Denver's are warm, so elevation makes the difference.[a side view: Denver low, snow on the top of Pikes Peak in July; chip ELEVATION on the pair]
9Seattle and Minneapolis share a latitude and are both low, but Seattle sits beside the Pacific Ocean.[pair_water: the table; the water row highlights]
10Seattle has cooler summers and warmer winters, so nearness to a large body of water makes the difference.[the map: the ocean beside Seattle shaded; Minneapolis far from any shading; chip NEAR A LARGE BODY OF WATER on the pair]
11So, here's what we've seen: three things set a place's climate.[closing screen: one line — "Three things set a place's climate: its latitude, its elevation, and how near it is to a large body of water."]
12Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. A city sits right beside the ocean. Which of the three things that set a place's climate is this about?

  1. latitude
  2. elevation
  3. nearness to a large body of water ✓

Essential questions after the lesson (4)

1. Flagstaff, Arizona, sits high in the mountains, and Phoenix, Arizona, sits low in the desert nearby; both are far from the sea and at nearly the same latitude. Flagstaff has much colder winters. Which difference between them sets the difference in their climates?

  1. latitude
  2. elevation ✓
  3. nearness to a large body of water

2. Miami, Florida, and New York City are both low down and both on the Atlantic coast, but Miami is much farther south. Miami has warm winters, and New York City has cold winters. Which difference between them sets the difference in their climates?

  1. latitude ✓
  2. elevation
  3. nearness to a large body of water

3. San Francisco, California, sits on the Pacific Ocean, and Sacramento, California, is a city far inland; both are low down and at nearly the same latitude. San Francisco has much cooler summers. Which difference between them sets the difference in their climates?

  1. latitude
  2. elevation
  3. nearness to a large body of water ✓

4. Minneapolis, Minnesota, and Kansas City, Missouri, are both low down and both far from the sea, but Minneapolis is much farther north. Minneapolis has colder winters. Which difference between them sets the difference in their climates?

  1. latitude ✓
  2. elevation
  3. nearness to a large body of water

A: Fine / B: Change this

T09 L04 — Why those three things set a climate

EAR-072 · Explain why a given region has its climate, using those factors.

176 spoken words, about 88 s.

1Here is Isla with her three pairs, asking why each difference matters.[Isla's labeled figure at her desk; the three pair tables small on the wall behind her; no title slide]
2Why is Houston's winter warmer than Chicago's?[pair_latitude enlarges; a question mark]
3Earth is a sphere, so sunlight lands straight on near the equator and at a slant far from it.[reg_sun_spread draws in: the sphere, the equator, parallel rays from the left]
4Far from the equator, the same sunlight lands more spread out, so each patch of ground gets less and stays colder.[the two equal beams shade in; the small patch at the equator and the larger patch near the top pulse in turn; chip MORE SPREAD OUT on the larger patch]
5The whole Earth is about the same distance from the Sun, so distance is not the reason.[a tiny Sun far to the left; a long arrow from it reaches the whole sphere; chip THE SAME DISTANCE]
6Why is the top of Pikes Peak colder than Denver?[pair_elevation enlarges; a question mark]
7The air up high is thin and holds little warmth, so places high up are colder.[reg_mountain_air draws in: the dots crowded low down, sparse near the top; chip THIN AIR near the top]
8Why does Seattle have cooler summers and warmer winters than Minneapolis?[pair_water enlarges; a question mark]
9Water warms up and cools down more slowly than land.[a beach in summer sun: a thermometer in the sand climbs fast, a thermometer in the sea climbs slowly]
10So in summer the ocean is cooler than the land and cools Seattle's air; in winter it is warmer and warms it.[the map: a cool-air arrow in the AIR FLOW color from the ocean onto Seattle under a July label, then a warm-air arrow under a January label]
11So, here's what we've seen: spread-out sunlight far from the equator, thin air high up, and water that warms up and cools down more slowly than land.[closing screen: three bullets — • Far from the equator, the sunlight lands more spread out, so it is colder. • High up, the air is thin and holds little warmth, so it is colder. • Near a large body of water, summers are cooler and winters are warmer, because water warms up and cools down more slowly than land.]
12Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. A town far from the equator is colder than a town near the equator, year after year. What is the reason?

  1. The sunlight lands more spread out far from the equator. ✓
  2. The town far from the equator is farther from the Sun.
  3. The air far from the equator is thinner.

Essential questions after the lesson (5)

1. Sunlight reaches the ground near the equator and far from the equator. Where does the same amount of sunlight land more spread out?

  1. near the equator
  2. far from the equator ✓

2. Miami, Florida, is much warmer than Minneapolis, Minnesota, year after year. What is the reason?

  1. Sunlight lands more spread out in Minneapolis. ✓
  2. Miami is closer to the Sun.
  3. The air in Minneapolis is thinner.

3. San Diego, California, sits on the Pacific Ocean, and its summers are cooler than the summers of a town far inland at the same latitude. What is the reason?

  1. Water warms up more slowly than land. ✓
  2. The ocean is higher up than the land.
  3. Sunlight lands more spread out on the ocean.

4. A town sits 3 000 m up a mountain, above a valley. A student says the town is warmer than the valley, because the town is nearer the Sun. Is the student correct?

  1. yes
  2. no ✓

5. Two towns in Colorado are at the same latitude and both far from the sea. One sits at 200 m and the other at 2 500 m. Which town has the colder climate?

  1. the town at 200 m
  2. the town at 2 500 m ✓

A: Fine / B: Change this

T09 L05 — Read a climate graph

EAR-073 · Read temperature and rainfall off a climate graph and describe the pattern.

172 spoken words, about 86 s.

1Here is Jaxon planning a July trip to Phoenix, Arizona, with a graph of Phoenix's climate on screen.[Jaxon's labeled figure at a laptop; cg_phoenix fills the screen beside him; no title slide]
2The line shows each month's temperature, read on the left in degrees Celsius; the bars show each month's rainfall, on the right in millimeters.[the line pulses and the left axis title Temperature (°C) highlights; then the bars pulse and the right axis title Rainfall (mm) highlights]
3A graph like this is called a climate graph.[chip CLIMATE GRAPH above the graph]
4To read July's temperature, find July along the bottom, go up to the line, and across to the left: 35 degrees Celsius.[cg_phoenix_read_temp: the dashed route climbs from J for July to the dot and runs across to the left axis; the number 35 is written beside the axis]
5To read January's rainfall, find January, go up to the top of its bar, and across to the right: 20 millimeters.[cg_phoenix_read_rain: the dashed route climbs from J for January to the bar top and runs across to the right axis; the number 20 is written beside the axis]
6The pattern comes next: the line is highest in July and August and lowest in winter, so Phoenix has hot summers and mild winters.[the July and August dots and the December and January dots ring in turn; chip HOT SUMMERS, MILD WINTERS]
7Every bar is short, and May and June have almost none, so Phoenix is dry all year.[the twelve bars pulse together; the May and June positions ring; chip DRY ALL YEAR]
8So, here's what we've seen: find the month along the bottom, go up to the line for the temperature and to the top of the bar for the rainfall; then describe the pattern.[closing screen: two bullets — • To read a climate graph, find the month along the bottom, go up to the line for the temperature, and go up to the top of the bar for the rainfall. • To describe the climate, say how warm the warmest and coldest months are, and which months have the most and the least rain.]
9Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. A climate graph has a line and a set of bars, one bar for each month. Which part shows each month's rainfall?

  1. the line
  2. the bars ✓

Essential questions after the lesson (5)

1. The graph is the climate graph for Anchorage, Alaska. What is its temperature in July? Type the number of degrees Celsius; answers within 2 degrees are accepted. (typed number)

Accepted: 13 · 13 C · 13 celsius · 13 degrees

2. The graph is the climate graph for Miami, Florida. About how much rain falls in Miami in June?

  1. 70 mm
  2. 170 mm
  3. 270 mm ✓

3. The graph is the climate graph for Chicago, Illinois. Which month has the highest temperature?

  1. January
  2. July ✓
  3. October

4. The graph is the climate graph for Seattle, Washington. In which months does the most rain fall?

  1. June to August
  2. November to January ✓

5. The graph is the climate graph for Minneapolis, Minnesota. Which sentence describes its climate?

  1. It has cold winters and warm summers, with the most rain in summer. ✓
  2. It has warm winters and hot summers, with the most rain in winter.
  3. It has cold winters and cool summers, with little rain in any month.

A: Fine / B: Change this

T09 summary video

231 spoken words, about 116 s.

1Here is everything we found out about weather or climate, and what sets a climate.[a still: the register climate graph cg_phoenix; no title chip]
2The weather is what the sky and the air are like at a place on one day.[chip ONE DAY]
3Through the year, the weather changes from season to season.[chip THROUGH THE YEAR]
4The weather a place usually has at a particular time of year, year after year, is called its climate.[chip YEAR AFTER YEAR; chip CLIMATE]
5To judge a claim about a climate, use years of records, never one day.[the two evidence cards reg_evidence as a still; chip YEARS OF RECORDS]
6Three things set a place's climate: its latitude, its elevation, and how near it is to a large body of water.[three chips: LATITUDE · ELEVATION · NEAR A LARGE BODY OF WATER]
7Places far from the equator are colder, because the sunlight lands more spread out there.[the still reg_sun_spread; chip MORE SPREAD OUT]
8Places high up are colder, because the air up high is thin and holds little warmth.[the still reg_mountain_air; chip THIN AIR]
9And places near a large body of water have cooler summers and warmer winters, because water warms up and cools down more slowly than land.[a still: the map with the ocean beside Seattle shaded; chip WATER CHANGES SLOWLY]
10On a climate graph, the line shows each month's temperature and the bars show each month's rainfall.[the still cg_phoenix; the line pulses, then the bars]
11To read a climate graph, find the month along the bottom, go up to the line for the temperature, and go up to the top of the bar for the rainfall.[the still cg_phoenix_read_temp, then cg_phoenix_read_rain]
12Finally, to describe a climate from its graph, say how warm the warmest and coldest months are, and which months have the most and the least rain.[the still cg_phoenix; closing screen: three bullets — • The weather is one day; the season is the pattern over the year; the climate is year after year. • A claim about a climate is judged on years of records, never one day. • Latitude, elevation and nearness to a large body of water set a place's climate.]
13Okay, now your turn.[the three attached questions follow on the page]

Attached questions

1. A weather report for Houston, Texas, says fog this morning, clearing by noon. Is this sentence about the weather, the season, or the climate?

  1. the weather ✓
  2. the season
  3. the climate

2. Two towns are at the same latitude and both far from the sea, but one sits 2 000 m higher than the other. Which of the three things that set a climate differs between them?

  1. latitude
  2. elevation ✓
  3. nearness to a large body of water

3. A student claims Denver, Colorado, has snowy winters. Which evidence supports the claim better?

  1. one snowy Friday in Denver
  2. a photo of snow in Denver taken this morning
  3. thirty years of Denver's winter snowfall records ✓

A: Fine / B: Change this

Topic 13 — Earth's spin and Earth's tilt: day, night and the seasons

T13 intro video

119 spoken words, about 60 s.

1Here is Ximena at a pool in Houston on a July evening.[Ximena's labeled dot at the edge of a pool, the Sun low but up, a long shadow; no title slide, no topic title on screen]
2It's eight o'clock, and the Sun is still up.[a clock on the pool wall reads 8:00]
3In December at this pool, the Sun set before half past five, and the water was too cold to swim.[the scene dims to the same pool in December: dark sky, the pool covered, the clock reading 5:30]
4The Sun rises and sets every day.[a quick sweep of the Sun across the sky over the pool]
5But the days stretch in summer and shrink in winter, and so does the warmth.[the July and December pools side by side]
6What makes the Sun rise and set, and why do the warm days come back every summer?[a question mark over the two pools]
7To find out, we will look at how Earth spins, how it leans, and how to pick the explanation that fits every clue.[the two pools hold]
8Okay, so are you ready to find out why we have day, night and the seasons?[the three replies appear]

A: Fine / B: Change this

T13 L01 — Day and night come from Earth rotating on its axis

EAR-090 · Explain that day and night happen because Earth turns on its axis.

178 spoken words, about 89 s.

1Ximena in Austin is video-calling her cousin in Mumbai.[a split screen: Ximena's labeled dot at a window in Austin, her cousin's labeled dot at a window in Mumbai; no title slide]
2The Sun is setting behind Ximena and rising behind her cousin.[the Austin window shows the Sun low and sinking; the Mumbai window shows the Sun low and climbing]
3How can one Sun set in Austin and rise in Mumbai at the same moment?[a question mark between the two windows]
4Earth is too big to see at once, so we look at a globe instead.[the windows fade; reg_lamp_globe draws in: a desk lamp at the left, a globe on its stand at the right]
5To show day and night, shine a lamp on a globe, mark your town with a sticker, and turn the globe slowly from west to east.[the lamp lights the globe's near half; a sticker appears on the lit half; the globe turns slowly, the sticker moving from the lit half into the dark half]
6Earth spins around an imaginary line through its center, from pole to pole.[the globe's dashed rod pulses; beside it, Earth as a sphere with the same dashed line through it from pole to pole]
7This line is called Earth's axis.[chip AXIS beside the dashed line]
8This spin is called rotation, and one rotation takes about 24 hours.[chip ROTATION; a small clock face runs once round; on screen: 1 rotation = about 24 hours]
9It is daytime on the side of Earth facing the Sun, and night on the side facing away from the Sun.[reg_earth_above draws in: Earth seen from above the North Pole, the Sun at the left, parallel sunlight arrows, the lit half pale and the dark half grey]
10The Sun never stops shining.[the sunlight arrows pulse]
11Austin is turning away from the Sun, and Mumbai toward it.[Austin's dot at the bottom just inside the dark half and Mumbai's dot at the top just inside the lit half; the rotation arrow over the top from right to left pulses; the dots creep along with the turn]
12The Sun seems to cross our sky because Earth turns, not because the Sun moves.[the Sun holds still; Earth turns a little further; the Austin window shows the Sun gone, the Mumbai window shows it higher]
13So, here's what we've seen: day and night happen because Earth rotates on its axis.[closing screen: one line — "Day and night happen because Earth rotates on its axis."]
14Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. The drawing shows Earth from above the North Pole, with Cairo marked. Is it daytime or night in Cairo?

  1. daytime ✓
  2. night

Essential questions after the lesson (4)

1. A student in Denver watches the Sun set in the evening and rise again the next morning. What causes this?

  1. Earth rotates on its axis. ✓
  2. Earth travels around the Sun.
  3. The Sun moves around Earth.

2. The drawing shows Earth from above the North Pole, with Lima marked. Is it morning or evening in Lima?

  1. morning
  2. evening ✓

3. How long does Earth take to make one rotation on its axis?

  1. about 24 hours ✓
  2. about one month
  3. about one year

4. It is midnight in Phoenix. Is the Sun still shining anywhere on Earth at that moment?

  1. yes ✓
  2. no

A: Fine / B: Change this

T13 L02 — The seasons come from Earth's tilted axis, not from its distance to the Sun

EAR-094 · Explain that seasons come from Earth's tilted axis, not from its distance to the Sun.

179 spoken words, about 90 s.

1In June, Yosef in Chicago has summer, while his aunt in Buenos Aires has winter.[a split screen: Yosef's labeled dot in shorts on a sunny Chicago sidewalk; his aunt's labeled dot in a coat on a grey Buenos Aires street; no title slide]
2Why is it summer in one place and winter in the other?[a question mark between the windows]
3The equator around Earth's middle divides Earth into the Northern Hemisphere and the Southern Hemisphere.[reg_side_june draws in without its axis: Earth as a sphere from the side, the Sun at the left, parallel sunlight arrows, the equator line; chips NORTHERN HEMISPHERE above it and SOUTHERN HEMISPHERE below]
4Earth's axis leans over by about 23 degrees, so we say it is tilted.[the dashed axis draws in from S to N, leaning; the grey upright reference line and the arc labeled 23° appear; chip TILTED]
5In June the north end of the axis leans toward the Sun.[the N end pulses; the figure is now reg_side_june in full]
6Sunlight lands more directly on the Northern Hemisphere, for more hours each day: that hemisphere has summer.[the sunlight arrows striking the upper half pulse; Chicago's daily path shows more than half its length in the lit half; chip SUMMER on the Northern Hemisphere]
7Sunlight lands more spread out on the Southern Hemisphere, for fewer hours each day: that hemisphere has winter.[the arrows striking the lower half pulse; chip WINTER on the Southern Hemisphere]
8Earth's trip around the Sun is called revolution, and one revolution takes one year.[reg_orbit_above draws in: the Sun at the center, the circle, the four Earths; chip REVOLUTION; on screen: 1 revolution = 1 year]
9The axis points the same way all year, so in December the south end leans toward the Sun: the seasons swap.[the N ticks on all four Earths pulse together; the December Earth highlights; a small reg_side_december beside it with chips WINTER above and SUMMER below]
10In March and September, neither end leans toward the Sun, so both hemispheres get about equal sunlight.[the March and September Earths highlight; a small reg_side_march beside them, the axis upright]
11So, here's what we've seen: seasons happen because Earth's axis is tilted, not because its distance from the Sun changes.[closing screen: one line — "Seasons happen because Earth's axis is tilted, not because Earth's distance from the Sun changes."]
12Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. Earth travels once around the Sun along its orbit. How long does one revolution take?

  1. about 24 hours
  2. about one month
  3. about one year ✓

Essential questions after the lesson (7)

1. The drawing shows Earth from the side, with the Sun at the left. Which hemisphere has summer at this time?

  1. the Northern Hemisphere ✓
  2. the Southern Hemisphere

2. The drawing shows Earth from the side, with the Sun at the left. Sydney, Australia, is in the Southern Hemisphere. Which season does Sydney have at this time?

  1. spring
  2. summer ✓
  3. fall
  4. winter

3. In December, which end of Earth's axis leans toward the Sun?

  1. the north end
  2. the south end ✓
  3. neither end

4. The drawing shows Earth in March, with the Sun at the left. Which sentence is true about the sunlight on the two hemispheres?

  1. Both hemispheres get about the same sunlight. ✓
  2. The Northern Hemisphere gets more direct sunlight.
  3. The Southern Hemisphere gets more direct sunlight.

5. The drawing shows Denver's daily path as Earth turns, with the Sun at the left. Does Denver have more hours of daylight or more hours of night at this time?

  1. more hours of daylight
  2. more hours of night ✓

6. Earth is nearest the Sun in early January. Which season does Chicago, north of the equator, have in early January?

  1. spring
  2. summer
  3. fall
  4. winter ✓

7. Which of the following causes the seasons?

  1. Earth's axis is tilted. ✓
  2. Earth's distance from the Sun changes through the year.
  3. Earth rotates on its axis once every 24 hours.

A: Fine / B: Change this

T13 L03 — Choose the explanation that accounts for every clue

SR-043 · Choose the explanation that best accounts for a set of observations.

178 spoken words, about 89 s.

1Here is Zuri's class, with three clues on the board.[a whiteboard with three numbered lines, blank until spoken; Zuri's and Adrian's labeled dots at desks; no title slide]
2In June, Chicago has summer while Buenos Aires has winter.[clue 1 appears on the board: Chicago summer, Buenos Aires winter, same June day]
3In Chicago the midday Sun is higher and the days longer in June than in December.[clue 2 appears: Sun higher and days longer in June]
4And Earth is nearest the Sun in early January.[clue 3 appears: nearest the Sun in early January]
5Adrian says Earth is nearer the Sun in summer; Zuri says the axis is tilted.[two cards beside the board: ADRIAN: nearer the Sun in summer; ZURI: the axis is tilted]
6To choose, we ask of each: does it account for every clue?[the frame question appears above reg_clues, its cells still empty]
7Adrian's explanation fails the first clue, because the whole Earth is at one distance from the Sun, yet the cities have opposite seasons.[a cross appears in the Distance column, row 1]
8It fails the third clue too, because Earth is nearest the Sun in Chicago's winter.[a cross in the Distance column, row 3; row 2 gets a cross as the narration moves on]
9Zuri's explanation passes the first clue, because one hemisphere leans toward the Sun while the other leans away.[a tick in the Tilt column, row 1]
10It passes the second clue, because that hemisphere sees the Sun higher, for more hours.[a tick in the Tilt column, row 2]
11And it passes the third clue, because the tilt sets the seasons, not the distance.[a tick in the Tilt column, row 3; the figure is now reg_clues in full]
12So, here's what we've seen: the best explanation is the one that accounts for every clue.[closing screen: one line — "The best explanation is the one that accounts for every clue."]
13Okay, now your turn.[the attached question appears]

Attached question (after “Okay, now your turn.”)

1. A student tests an explanation for a frozen pond against four clues. It can account for three but not the fourth. Is it the best explanation?

  1. yes
  2. no ✓

Essential questions after the lesson (5)

1. A puddle on a playground is gone by the afternoon. The clues: the day was hot and sunny, the ground around the puddle is dry, and there is no drain nearby. Which explanation can account for every clue?

  1. The water evaporated into the air. ✓
  2. The water ran down a drain.

2. A bike's front tire is flat in the morning. The clues: both tires were full last night, there is a nail in the front tire, and the back tire is still full. Which explanation can account for every clue?

  1. The cold night air made the air in the tire shrink.
  2. The nail let the air out of the tire. ✓

3. A houseplant has wilted. The clues: its soil is dry, the room is warm, and a plant with wet soil by the same window is healthy. A student explains that the plant got too cold. Does this explanation account for every clue?

  1. yes
  2. no ✓

4. Paw prints in fresh snow lead to a shed and none lead away. The shed door stands open, and a dog is barking inside. A student explains that the dog walked into the shed and is still there. Does this explanation account for every clue?

  1. yes ✓
  2. no

5. A student explains that summer happens because the Sun gives out more heat in June than in December. The clue: in June, Miami has summer while Cape Town, in the Southern Hemisphere, has winter. Does this explanation account for the clue?

  1. yes
  2. no ✓

A: Fine / B: Change this

T13 summary video

239 spoken words, about 120 s.

1Here is everything we found out about Earth's spin and Earth's tilt: day, night and the seasons.[a still: reg_side_june; no chips yet]
2Earth spins around an imaginary line through its center, from pole to pole.[the dashed axis pulses]
3This line is called Earth's axis.[chip AXIS]
4This spin is called rotation, and one rotation takes about 24 hours.[chip ROTATION; on screen: 1 rotation = about 24 hours]
5It is daytime on the side of Earth facing the Sun, and night on the side facing away from the Sun.[a still: reg_earth_above; the lit half and the dark half pulse in turn]
6The Sun never stops shining.[the sunlight arrows pulse]
7Day and night happen because Earth rotates on its axis.[chip DAY AND NIGHT: ROTATION]
8The equator around Earth's middle divides Earth into the Northern Hemisphere and the Southern Hemisphere.[a still: reg_side_june; the equator and the two hemisphere labels pulse]
9Earth's axis leans over by about 23 degrees, so we say it is tilted.[the 23° arc pulses; chip TILTED]
10Sunlight lands more directly on the hemisphere leaning toward the Sun, for more hours each day: that hemisphere has summer.[chip SUMMER on the Northern Hemisphere]
11Sunlight lands more spread out on the hemisphere leaning away from the Sun, for fewer hours each day: that hemisphere has winter.[chip WINTER on the Southern Hemisphere]
12Earth's trip around the Sun is called revolution, and one revolution takes one year.[a still: reg_orbit_above; chip REVOLUTION; on screen: 1 revolution = 1 year]
13The axis points the same way all year, so in December the south end leans toward the Sun: the seasons swap.[the four N ticks pulse together; the December Earth highlights]
14In March and September, neither end leans toward the Sun, so both hemispheres get about equal sunlight.[the March and September Earths highlight]
15So seasons happen because Earth's axis is tilted, not because its distance from the Sun changes.[chip SEASONS: THE TILT, NOT DISTANCE]
16Finally, the best explanation is the one that accounts for every clue.[a still: reg_clues; closing screen: three bullets — • Day and night: Earth rotates on its axis once every 24 hours. • Seasons: Earth's axis is tilted; the hemisphere leaning toward the Sun has summer. • The best explanation accounts for every clue.]
17Okay, now your turn.[the three attached questions follow on the page]

Attached questions

1. It is noon in Dallas. Which sentence is true at that moment?

  1. Dallas is on the side of Earth facing the Sun. ✓
  2. Dallas is on the side of Earth facing away from the Sun.
  3. The Sun has traveled around Earth to reach Dallas.

2. In Melbourne, Australia, in the Southern Hemisphere, December is one of the warmest months. Which of the following is the reason?

  1. Earth is nearer the Sun in December than in June.
  2. The Southern Hemisphere leans toward the Sun in December. ✓
  3. Earth rotates on its axis more slowly in December.

3. Two explanations are tested against five clues. One can account for four of the clues; the other can account for all five. Which is the better explanation?

  1. They are equally good.
  2. the explanation that accounts for four clues
  3. the explanation that accounts for all five clues ✓

A: Fine / B: Change this