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KS3 · 15 minutes · no login
Solar altitude and sun path
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Why this lesson, and why the 3D
Solar altitude and sun path 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: A dome over a marked horizon. Date and latitude write the path. Noon altitude and day length fall out. By the end of the slot a pupil should be able to read noon altitude and day length from a sun-path dome for London, Nairobi, New York. Curriculum tags in the header (KS3; NGSS MS-ESS1-1; GCSE) are filters, not a flag. The room is worldwide; SI first; International English. Ages on the card (KS3, GCSE, NGSS MS, APES) are a suggested band, not a gate.
London in December is a low noon and a short day. Miami still has a useful beam. Same dome idea. Different latitude. Leeds glasshouses plot hours above a height that plants can use. Florida growers plot the same curve with a different φ. Snowdonia fieldwork in June is a long arc; the same slope in December is a brief, low Sun. New York sits between London and Miami on that ladder. The skill is to read noon altitude and day length from a path, not from a weather app. Pairs with the calculator tool. A magnetic compass is not true south. Overhead Sun is not a global noon habit. If you cannot move latitude in your head from 51.5° to 0°, you cannot compare a UK playground with Nairobi, and you will keep saying the Sun is overhead everywhere at lunch.
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
Leave Latitude near 51.5°. That is London. Play. Watch the path on the dome. Read noon altitude and day length. The Sun is overhead at noon only between the tropics, and not every day. That is the misconception: overhead everywhere. Scrub Latitude toward the equator, near Nairobi. Day length sits nearer 12 h. Noon Sun stays high. Raising latitude in winter lowers noon Sun and shortens the day. Noon altitude is 90° minus the absolute difference of latitude and declination. A magnetic compass is not true south. Say that once. Finish in Check.
Open the lab full screen (F). Labels on (L). Speak the first step before you touch a slider: Dome. Today’s path. London marker. Then the second: Scrub date. Change latitude toward Nairobi. Then the third: Noon altitude = 90° − |φ − δ|.
The sliders that earn their keep are Latitude (°). Space plays; arrows nudge time; R resets. Parameters the URL can remember: latitude. 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.
Leave Latitude near 51.5°. That is London. Play. Space toggles play. Arrows nudge the Sun along the path. Speed 1×, 2×, 4×. Drag Latitude toward 0° for Nairobi, or toward Miami’s band, or south. Read noon altitude and day length from the readout. L labels. R reset. P projector. No explode, no slice in the bar. Reset if the dome has walked off a useful latitude. True south is not a magnetic compass. The Latitude slider is the extra. The time slider walks the Sun on the dome. Read the gnomon shadow as well as the numbers.
The in-site film is “Why we have seasons” (Khan Academy, about 8 min, Khan Academy on YouTube. CC BY-NC-SA. 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.
“The Sun is overhead at noon everywhere.” — no. Only between the tropics, and not every day.
“Day length is 12 hours everywhere, every day.” — no. Near 12 h at the equator. London swings from a short December to a long June.
“Raising latitude always makes the Sun higher.” — no. In winter it lowers noon Sun and shortens the day. Geometry, not a hill.
Pitfalls to keep in your pocket: Magnetic compass vs true south. Overhead Sun as a global noon habit. Forgetting that day length and noon altitude both move with latitude. 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 latitude, plus the time slider that walks the Sun along the dome. Default latitude is 51.5°, London. The path is the day’s arc on a sky hemisphere over a marked horizon. Noon altitude is 90° minus the absolute difference of latitude and declination: 90° − |φ − δ|. Day length falls out of whether the path clears the horizon, and for how long. What moves: the Sun along the arc, the length of that arc when you change φ, the gnomon’s shadow. What does not: the formula, the fact of a horizon, the fact that overhead Sun only happens between the tropics, and not every day. What is conserved: spherical geometry. Raise latitude in winter: noon Sun drops, day shortens. Toward the equator: noon stays high, day length sits near 12 h. Polar extremes are a longer day or a night that will not end, depending on season, but this slider caps short of the pole. The lie the model tells: a small dome, a fat Sun, a toy gnomon, a teaching plinth instead of a real playground. The path is the lesson. The numbers on the readout are the lesson. Seasons still come from tilt; this lab aims the beam for one place.
The first place to land is London day length. The second is New York / Miami. 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 sundial: altitude as a shadow length. Noon height is 90° minus |φ − δ|. Credit: Wikimedia Commons, CC BY.
Mechanism photograph: Field or official figure for teaching Solar altitude. A second photograph for the projector script — not the lab cover. Credit: Wikimedia Commons / NASA / USGS.
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.
Solar altitude: Angle of the Sun above the horizon. Noon altitude is the day’s peak. Exam language also accepts “Elevation angle”. Sun path: The day’s arc on the sky dome. Date and latitude write it. Declination: The latitude where the Sun is overhead at noon. It travels between 23.44°N and 23.44°S. Noon altitude: 90° − |φ − δ|. School formula. φ is latitude, δ is declination. Day length: Hours the Sun is above the horizon. Near 12 h at the equator. A wide swing at London. Gnomon: A stick that casts a shadow. Shadow length is a readout of solar altitude. Tropics: 23.44°N to 23.44°S. Overhead Sun lives only in this belt, and not every day. Latitude: Angle from the equator. This lab’s slider. Default 51.5° is London. Exam language also accepts “φ”.
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 dome will not spin, keep the formula and the places. Noon altitude = 90° − |φ − δ|. London winter: low noon, short day. Equator: day length near 12 h, noon Sun high. Overhead at noon only between the tropics, and not every day. Raising latitude in winter lowers the Sun and shortens the day. Miami is not London. Snowdonia in June is not Snowdonia in December. That is enough for Check on paper, and enough to kill ‘the Sun is overhead everywhere at noon’.
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. NOAA solar calculator.
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; GCSE) are filters, not a flag. A class in Nairobi, London, or Shanghai can use the same 3D. Ages (KS3, GCSE, NGSS MS, APES) 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: A dome over a marked horizon. Date and latitude write the path. Noon altitude and day length fall out. Two: the misconception “The Sun is overhead at noon everywhere.”. 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 latitude. Send them home with the same link; there is no login.
London in December is a low noon and a short day. Miami still has a useful beam. Same dome idea. Different latitude. Leeds glasshouses plot hours above a height that plants can use. Florida growers plot the same curve with a different φ. Snowdonia fieldwork in June is a long arc; the same slope in December is a brief, low Sun. New York sits between London and Miami on that ladder. The skill is to read noon altitude and day length from a path, not from a weather app. Pairs with the calculator tool. A magnetic compass is not true south. Overhead Sun is not a global noon habit. If you cannot move latitude in your head from 51.5° to 0°, you cannot compare a UK playground with Nairobi, and you will keep saying the Sun is overhead everywhere at lunch.
In-site film
Why we have seasons. Khan Academy. Khan Academy on YouTube. CC BY-NC-SA. Educational embed, autoplay off. Autoplay off.