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Eclipses

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Why this lesson, and why the 3D

Eclipses is a fifteen-minute projector lesson, not a homework packet and not a film with a quiz bolted on. Put this hook on the board before you dim the lights: Umbra and penumbra are cones. The Moon’s 5° tilt is why most months miss. By the end of the slot a pupil should be able to show umbra/penumbra and why a 5° lunar-orbit tilt makes eclipses rare. Curriculum tags in the header (KS3; NGSS MS-ESS1-1) are filters, not a flag. The room is worldwide; SI first; International English. Ages on the card (KS3, GCSE, NGSS MS) are a suggested band, not a gate.

Snowdonia and Yosemite see the same phase on the same night. Eclipses are pickier. A full Moon over Eryri is geometry, not a promise of Earth’s shadow. A full Moon over Yosemite is the same triangle. Eclipse chasers wait for a node, not for every full. UK school trips still miss most months. US park night walks still miss most months. The skill is to split phase from eclipse. Phases are how much of the sunlit half faces us. Eclipses are alignment plus the 5° lunar-orbit tilt being near zero. Clouds are weather. Time zones are clocks. Neither is the cone. If you cannot say umbra versus penumbra, you cannot say why a total is a tunnel and a partial is a graze. Holderness does not get a private Moon. Miami does not get a different shadow. Same machine, rare hit.

The 3D is a named, inspectable object. Click the part, not a caption. If the model will not spin, the Why panel still carries the mechanism, the two photographs, and the film. Do not apologise for the model. Drive it. A silent spin teaches a screensaver. A named mesh that changes under a slider teaches the process.

Fifteen minutes on the projector

Play the month. Sun, Earth, Moon: umbra dark, penumbra pale. The umbra is the dark core of the shadow. A total eclipse sits there. Leave Eclipse alignment off. The Moon’s orbit is tilted about 5°. New and full happen every month. An eclipse needs a node. Ask why next month’s full Moon fails. It usually misses the cone. Toggle Eclipse alignment on once so the cones line up. Then off again. Rarity is the lesson, not the special effect. Every full Moon is not an eclipse. That is the misconception. A lunar eclipse needs full Moon plus a node. A solar eclipse needs new Moon plus a node. Finish in Check.

Open the lab full screen (F). Labels on (L). Speak the first step before you touch a slider: Sun, Earth, Moon. Umbra dark, penumbra pale. Then the second: Toggle 5° vs aligned. Then the third: New/full every month. Eclipse only near a node.

The sliders that earn their keep are Eclipse alignment. Space plays; arrows nudge time; R resets. Parameters the URL can remember: align. If you only have eight minutes, skip the last step and finish in Check. Projector layout (P) is for the back row: one idea, large type, the model still live.

Play the month. Space toggles play. Arrows nudge time. Speed 1×, 2×, 4×. Toggle Eclipse alignment off for the 5° miss, on once so the cones line up, then off again. L labels. R reset. P projector. No explode, no slice in the bar. Pause at new. Pause at full. Ask why next month fails before you toggle. Rarity is the lesson, not the special effect. The toggle is labelled Eclipse alignment. Off is the real 5°. On is the special-effect month. Use it once, not as the default.

The in-site film is “NASA Now: Reasons for the Seasons” (NASA, about 8 min, NASA / NASA Goddard on YouTube. Public domain US government work. Educational embed, autoplay off.). Autoplay is off. Play one minute if you need a second voice; do not let the film eat the slot. The 3D still has to move under your hand.

What the third row will get wrong

You will hear the misconception before you have finished the first sentence. Write the false claim on the board and leave it there until the model has contradicted it. Do not skip this. A fluent pupil can recite the hook and still believe the false sentence.

“Every full Moon is an eclipse.” — no. Need a node.

“A crescent is Earth’s shadow on the Moon.” — no. A crescent is the Moon’s night side. Earth’s shadow is a lunar eclipse, and it is rare.

“The Moon is too small to ever cover the Sun.” — no. Angular size can match. The reason most months miss is the 5° tilt, not a tiny Moon.

Pitfalls to keep in your pocket: Crescent as Earth’s shadow. Teaching every full Moon as an eclipse. Saying the Moon is too small to ever hit, instead of naming the 5° tilt. Do not let a pupil leave thinking the 3D is a photograph. It is a teaching model. Where vertical exaggeration exists, T collapses it and the caption says so. A labelled lie of scale is honest. An unlabelled one is a cartoon.

Two places, not a slogan

Input is a month on the slider, plus the Eclipse alignment toggle. Sun, Earth, Moon. The Moon runs a ring. Leave alignment off and the ring is tilted about 5° to the ecliptic. What moves: the Moon’s place, the cones if you are looking, whether a new or full sits near a node. What does not: the 5° unless you toggle it to zero, the fact of two cones, the fact that new and full happen every synodic month. What is conserved: half the Moon is always sunlit; umbra is the dark core; penumbra is the pale outer shadow. A solar eclipse needs new Moon plus a node — Moon between Sun and Earth. A lunar eclipse needs full Moon plus a node — Earth between Sun and Moon. The lie the model tells: Moon and Earth are huge beside their true gap; cones are fat enough to read from the back row; the orbit is a tidy hoop. Size is exaggerated on purpose. The tilt is the mechanism. Most months the Moon misses the cone. Every full Moon is not an eclipse. A crescent is not Earth’s shadow — that is a different lab’s trap, and it is still wrong here.

The first place to land is Snowdonia Moon. The second is Yosemite Moon. Same process, different rock or climate. If a pupil can only name one place, they have a postcard, not a mechanism. Atlas entries for those names are a click from the case list; send them back to the lab with one sentence they can say in Check.

Do not flatten the comparison into “this country versus that country.” Name the landform. Holderness is till, not chalk. Hawaii is a hotspot, not an island arc. Yosemite is a glacial trough, not a river canyon. The 3D is allowed to be schematic; the place names are not allowed to be sloppy.

Figures and the film

Field photograph: A solar eclipse: the Moon’s shadow on Earth-view. A shadow geometry, not weather. Credit: Wikimedia Commons, CC BY.

Mechanism photograph: Field photograph or official scientific figure for teaching eclipses. Field photograph or official scientific figure for teaching eclipses. A second photograph for the projector script — not the lab cover. Source: Wikimedia Commons / NASA / USGS / NOAA, public domain or CC. Credit: Wikimedia Commons / NASA / USGS / NOAA, public domain or CC.

Two photographs, two jobs. The field picture is the place. The mechanism picture is the process. Do not run the lesson on a single Apollo Earth disc. A carbon-cycle class is a forest and a seam, not a blue marble. An ENSO class is a Pacific temperature map, not Africa from Apollo 17.

Words they must be able to say

Say these out loud once while you click the matching mesh. If a word has no mesh, it still has a photograph in Terms.

Umbra: Dark core of a shadow. A total eclipse sits here. Penumbra: Partial, paler shadow around the umbra. A graze, not the tunnel. Node: Where the Moon’s tilted orbit crosses the ecliptic. Eclipses need the Moon near a node. Ecliptic: The plane of Earth’s orbit around the Sun. The Moon’s orbit is tilted about 5° to it. Orbital inclination: The Moon’s ~5° tilt to the ecliptic. That is why eclipses are rare. Solar eclipse: New Moon plus a node. Moon between Sun and Earth. Umbra on the ground is a small track. Lunar eclipse: Full Moon plus a node. Earth between Sun and Moon. The Moon rides through Earth’s umbra. Synodic month: New to new, about 29.5 days. Phase clock. Not the eclipse clock.

Exam-language toggle (the Teacher tab) swaps UK/US pairs where they exist — levée/levee, arête/arete — so a mixed room is not punished for spelling.

Close the slot

If the cones will not spin, keep the sentences. Umbra is the dark core. Penumbra is the partial shadow. The Moon’s orbit is tilted about 5°, so most months miss. New and full happen every month. An eclipse needs a node. Solar: new plus node. Lunar: full plus node. Snowdonia and Yosemite share the phase; they do not share an eclipse every month. Size in the kit is fat on purpose. That is enough for Check on paper. Without the 3D view, a student should still split phase from eclipse and still name the 5° tilt as the miss.

Finish in Check — ten questions, not a mood. The bank mixes definition, process, the misconception you just killed, a named place, and a read-the-model item (click the part; T). If a pupil can only recite the hook, they have not used the geometry. Wrong answers still show the one-line explain. Do not skip the explain.

Sources on the Teacher tab are the trail, not a bibliography to copy. NASA eclipses.

Link back to the live lab and keep the same slug. Do not invent a parallel worksheet that contradicts T, SI, or the named parts.

This note is worldwide. Curriculum tags (KS3; NGSS MS-ESS1-1) are filters, not a flag. A class in Nairobi, London, or Shanghai can use the same 3D. Ages (KS3, GCSE, NGSS MS) are a suggested band. If a sentence only works in one exam board, rewrite it before you project it.

Write these three lines on the board before you dim the lights. One: Umbra and penumbra are cones. The Moon’s 5° tilt is why most months miss. Two: the misconception “Every full Moon is an eclipse.”. Three: the named parts they must click. Then drive the model. Check is ten questions covering definition, process, the misconception, a place, and a read-the-model item. Do not skip the explain on a wrong answer.

Board, units, and what not to say

SI first. Metres, kilometres, degrees Celsius, metres per second. A conversion in brackets is courtesy, not a second system. Do not let a pupil leave thinking the 3D is a photograph. It is a teaching model. Where vertical exaggeration exists, T collapses it and the caption says so.

Do not say “teaching mesh”, “sprinkle”, or “thin free surface not a fat pipe” out loud. Say the landform. Seasons are ~23.44° of axial tilt, not Earth–Sun distance. The outer core is liquid; S-waves do not pass. Yosemite is a glacial U-trough. San Andreas is a transform. Hawaiʻi and Yellowstone are hotspots. Florida is not a glacial trough.

If the room is noisy, projector layout (P) is the back-row setting: one idea, large type, the model still live. Full screen (F). Labels (L). Space plays. Arrows nudge time. R resets. The URL can remember align. Send them home with the same link; there is no login.

In-site film

NASA Now: Reasons for the Seasons. NASA. NASA / NASA Goddard on YouTube. Public domain US government work. Educational embed, autoplay off. Autoplay off.