[{"data":1,"prerenderedAt":908},["ShallowReactive",2],{"layer:phases-of-the-moon:discover":3},{"layer":4,"contentHash":890,"dependencyHashes":891,"approval":902,"releaseId":907},{"schemaVersion":5,"conceptId":6,"locale":7,"depth":8,"revision":5,"title":9,"subtitle":10,"summary":11,"objectives":12,"estimatedMinutes":18,"plate":19,"blocks":40,"sourceIds":885,"reviewStatus":886,"authoring":887},1,"phases-of-the-moon","en","discover","The shape that changes — except it never does","Why the Moon looks different every night, and what is really going on","Meet the Moon's monthly cycle: borrowed sunlight, a ball that is always half lit, and eight named phases. Learn to tell waxing from waning tonight, find out why the Moon is up in the daytime, and kill the biggest myth in astronomy — that the phases are Earth's shadow.",[13,14,15,16,17],"Explain that moonlight is reflected sunlight and that exactly half the Moon is always lit.","Name the eight phases in order and say what fraction of the disc is bright in each.","Tell a waxing Moon from a waning Moon using the bright edge, the D-O-C trick, or the time of night.","Explain why the Moon can be seen in daylight, and why a full moon cannot be.","Say why the phases are not caused by Earth's shadow, and what a lunar eclipse is instead.",30,{"title":20,"rows":21},"Lesson plate",[22,25,28,31,34,37],{"label":23,"value":24},"Depth","Discover",{"label":26,"value":27},"Reading time","about 30 minutes",{"label":29,"value":30},"Prior knowledge","None — bring an orange",{"label":32,"value":33},"Chapters","9",{"label":35,"value":36},"Labs","Moon phase lab, waxing\u002Fwaning sort, phase match",{"label":38,"value":39},"Project","A month-long moon diary",[41,45,51,56,62,65,86,91,96,99,104,110,113,118,135,140,143,147,152,169,187,192,195,240,244,292,317,336,341,344,348,384,445,466,471,474,503,507,511,524,529,533,536,540,572,593,598,601,641,646,651,665,670,673,704,708,711,715,720,724,858,875],{"id":42,"type":43,"markdown":44},"intro-look-up","prose","Go outside tonight and find the Moon. Draw its shape on a scrap of paper. Do it again tomorrow, and the night after that, and keep going for a month.\n\nYou will end up with a row of drawings that look like a slow, silent animation: a thin curved sliver, then a half-circle, then a fat lopsided blob, then a perfect bright disc — and then the whole thing shrinking again, back to nothing.\n\nAlmost every child who has ever lived has watched this happen. It is the oldest clock in the world. But it raises a strange question that most people never stop to ask:\n\n**Is the Moon actually changing shape?**",{"id":46,"type":47,"variant":48,"title":49,"markdown":50},"intro-answer-tease","callout","question","Hold that thought","The honest answer is: **no**. The Moon is a ball of rock 3,475 kilometres across, and it stays a ball of rock all month. It does not get thinner, it does not get eaten, and nothing bites pieces out of it.\n\nSo if the Moon never changes shape — why does it *look* as though it does? That is what this lesson is about, and the answer is beautiful once you see it.",{"id":52,"type":47,"variant":53,"title":54,"markdown":55},"how-to-read","try_it","How to use this lesson","Read it with something round in your hand if you can: an orange, a ball, a ripe tomato. Halfway through you will be asked to hold it up to a lamp, and the whole idea will click in about ten seconds.\n\nYou will also be asked to start a **moon diary**. It costs nothing, takes two minutes a night, and by the end of a month you will have proved every claim on this page with your own eyes.",{"id":57,"type":58,"title":59,"eyebrow":60,"navLabel":61},"ch1","chapter","A month of looking up","Chapter 01","1 A month of looking",{"id":63,"type":43,"markdown":64},"ch1-what-you-see","Here is what a month of Moon-watching looks like, written out in words.\n\nOn the first night you see **nothing at all**. The Moon is somewhere in the sky, but it is invisible.\n\nTwo evenings later, just after sunset, a **very thin bright curve** appears low in the western sky, like a fingernail clipping. It sets within an hour or two and is gone.\n\nEach following evening that curve is a little fatter and a little higher up when the Sun goes down. About a week in, it is a clean **half-circle**, high in the south at sunset, with its flat edge facing you.\n\nThen it swells past half into a **lopsided oval**, and about a fortnight after that first sighting, a **complete bright disc** rises in the east exactly as the Sun sets in the west. This is the night the whole village can read outdoors.\n\nAfter that, everything happens in reverse — but shifted later and later into the night — until the Moon is once again invisible, and the cycle starts over.",{"id":66,"type":67,"tone":68,"items":69},"ch1-cycle-spec","spec","blue",[70,74,78,82],{"label":71,"big":72,"value":73},"Full cycle","29.53 days","New moon back to new moon. Roughly a month — which is exactly where the word *month* comes from.",{"label":75,"big":76,"value":77},"Named phases","8","New, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter, waning crescent.",{"label":79,"big":80,"value":81},"Moon's width","3,475 km","About a quarter of Earth's width, and it never changes. Only our view of it changes.",{"label":83,"big":84,"value":85},"Distance","384,400 km","Far enough that light takes about 1.3 seconds to get here, close enough to see craters with cheap binoculars.",{"id":87,"type":47,"variant":88,"title":89,"markdown":90},"ch1-month-word","aha","Moon, month, Monday","The words are relatives. Old English *mona* (Moon) gave us *monath*, which became **month**, and *Monandaeg* — the Moon's day — became **Monday**. In Hindi, Sanskrit and many Indian languages the same relationship shows up: *chandra* (moon) and *maas* (month), *Somvaar* (Monday) from *Soma*, another name for the Moon.\n\nLanguages all over the world agree, because for most of human history a month simply *was* one full round of the Moon's shapes.",{"id":92,"type":58,"title":93,"eyebrow":94,"navLabel":95},"ch2","The Moon borrows all of its light","Chapter 02","2 Borrowed light",{"id":97,"type":43,"markdown":98},"ch2-not-a-lamp","Start with the most important fact on this page.\n\n**The Moon does not make light.** It is not a lamp, it is not on fire, and it is not glowing. It is a cold ball of grey rock, and grey rock in the dark is invisible.\n\nWhat the Moon *does* is reflect sunlight. The Sun pours light out in every direction. A tiny fraction of it hits the Moon, bounces off the dust and rock, and some of that bounced light happens to travel towards your eyes. That is moonlight: **second-hand sunlight**.\n\nOnce you accept that, the whole puzzle of the phases changes. The question is no longer \"what shape is the Moon tonight?\" It becomes: **\"how much of the sunlit part of the Moon can I see from here?\"**",{"id":100,"type":47,"variant":101,"title":102,"markdown":103},"ch2-dark-rock","observation","The Moon is darker than you think","Moonlight looks brilliantly white against a black sky, so people imagine the Moon is made of something pale, like chalk or snow.\n\nIt is not. Moon rock is about as reflective as an **old asphalt road** or a lump of charcoal — it bounces back only around a tenth of the light that lands on it. If you put a piece of Moon rock on a table in daylight, you would call it dark grey.\n\nIt looks dazzling for the same reason a dark-grey car looks dazzling at noon: there is an enormous amount of sunlight falling on it, and there is nothing brighter nearby to compare it with.",{"id":105,"type":106,"conceptId":107,"relation":108,"explanation":109},"ch2-link-light","connection","light","helps_understand","Everything about the phases follows from how light travels and bounces. Light only comes to your eye if something sends it there.",{"id":111,"type":43,"markdown":112},"ch2-sun-one-side","Now think about the Sun and a ball.\n\nLight travels in straight lines, and it cannot bend around corners. So when sunlight falls on any ball — a cricket ball, a laddoo, a planet, the Moon — it lights **exactly one half** of it. The half pointing at the Sun is in daylight. The half pointing away is in night.\n\nThis is true of Earth too, right now. As you read this, half of Earth is in daylight and half is in darkness. The line between them is sweeping across the world at hundreds of kilometres an hour, and we call it sunrise on one side and sunset on the other.\n\nThe Moon is no different. **Half of it is always lit, and half of it is always dark.** Always. Every single moment. Nothing about that ever changes.",{"id":114,"type":47,"variant":115,"title":116,"markdown":117},"ch2-def-phase","definition","Phase, in one line","A **phase** of the Moon is not a shape the Moon takes. It is *how much of the Moon's sunlit half happens to be facing Earth at the moment you look*.\n\nThe Moon is always half-lit. The phase tells you how much of that lit half is turned towards us.",{"id":119,"type":120,"component":121,"componentVersion":5,"config":122,"objective":128,"textAlternative":129,"help":130},"lab-moon-basic","interactive","moon-phase",{"startDay":123,"views":124,"showNames":126,"showTithi":127,"quizRounds":123},0,[125],"from-earth",true,false,"Step day by day through one full lunar month and watch the shape change as the Moon goes round Earth.","This lab shows the Moon as you would see it from the ground, with a slider for the day of the lunar month from 0 to 29.5 and the phase name printed underneath.\n\nAt **day 0** the disc is completely dark: **new moon**. Nothing is visible.\n\nBy **day 3.7** a thin bright crescent has appeared on the right-hand edge, about **15% lit**: a **waxing crescent**.\n\nAt **day 7.4** exactly the right half is bright and the left half is dark, a straight line down the middle: **first quarter**, **50% lit**.\n\nAt **day 11.1** the bright part has swollen past half, leaving a dark crescent on the left: a **waxing gibbous**, about **85% lit**.\n\nAt **day 14.8** the whole disc is bright: **full moon**, **100% lit**.\n\nAfter that the sequence runs backwards but with the dark side now on the right: waning gibbous at day 18.5, **last quarter** at day 22.1 with only the left half bright, waning crescent at day 25.8, and back to new moon at day 29.5.\n\nThe bright part always grows from the right and shrinks towards the left when you are watching from India.",{"simplerExplanation":131,"hints":132},"Drag the slider from day 0 to day 29.5 and the Moon fills up like a glass of milk, then empties again from the other side.",[133,134],"Find the day where exactly half is lit. There are two of them.","Notice which edge is bright while the Moon is growing, and which edge is bright while it is shrinking.",{"id":136,"type":58,"title":137,"eyebrow":138,"navLabel":139},"ch3","Half is always lit — so why the shapes?","Chapter 03","3 The orange and lamp",{"id":141,"type":43,"markdown":142},"ch3-geometry","If half the Moon is always lit, where do the shapes come from?\n\nThey come from **where you are standing**.\n\nThe Moon goes round Earth once a month. The Sun stays put, far away in one direction. So over the month, the angle between \"the way the Sun is\" and \"the way the Moon is\" keeps changing — and that angle decides how much of the Moon's lit half you get to see.\n\n- When the Moon is almost **in front of** the Sun, its lit half is pointing away from us. We see its night side. **New moon.**\n- When the Moon is **off to one side**, we see the lit half edge-on: half bright, half dark. **Quarter moon.**\n- When the Moon is **opposite** the Sun, with Earth in between, the lit half faces us squarely. **Full moon.**\n\nSame ball. Same lighting. Different viewing angle. That is the entire secret.",{"id":144,"type":47,"variant":53,"title":145,"markdown":146},"ch3-tryit-orange","The orange and the lamp (do this one)","You need: one orange (or any ball), one lamp, one dark-ish room.\n\n1. Put a bare lamp on a table and switch off the other lights. The lamp is the Sun.\n2. Hold the orange at arm's length. The orange is the Moon. **Your head is Earth.**\n3. Now slowly turn yourself around on the spot, keeping the orange at arm's length in front of your face all the way round.\n\nWatch the orange, not the lamp.\n\n- With the orange **between you and the lamp**, you see a dark orange with a glowing rim. That is new moon.\n- Turn a quarter turn: **half** the orange is lit. Quarter moon.\n- Turn until the lamp is **behind your head**: the whole face of the orange is lit. Full moon.\n\nHold your hand still and keep turning, and you will run the entire month in about ten seconds. Nothing about the orange changed. Only you moved.",{"id":148,"type":47,"variant":149,"title":150,"markdown":151},"ch3-shadow-not","misconception","\"My head made a shadow — is that the phase?\"","When you do the orange trick, hold the orange a bit above your head at full moon, or your own head really does cast a shadow on it and you get a mini eclipse instead.\n\nThat is exactly the mistake people make about the real Moon. **Phases are not a shadow falling on the Moon.** We come back to this properly in Chapter 7, because it is the single most common wrong idea about the Moon — and the fix is simple once you have done the orange test.",{"id":153,"type":154,"title":155,"items":156},"ch3-steps-three","steps","The three things that make a phase",[157,161,165],{"title":158,"tag":159,"text":160},"The Sun lights half","always","Sunlight travels in straight lines and lights exactly one half of the Moon, every moment of every day.",{"title":162,"tag":163,"text":164},"The Moon moves round us","29.5 days","In one lunar month the Moon travels all the way around Earth, so the angle between Sun and Moon keeps changing.",{"title":166,"tag":167,"text":168},"We see it from an angle","the phase","How much of the lit half we can see from Earth depends on that angle. That fraction is the phase.",{"id":170,"type":171,"prompt":172,"options":173,"explanation":186},"predict-half-lit","prediction","A friend says: \"At new moon the Sun must have stopped shining on the Moon, because there is no light coming from it.\" What is actually happening?\n\nPick the best answer.",[174,177,180,183],{"id":175,"label":176},"a","The Sun is blocked by Earth, so no sunlight reaches the Moon",{"id":178,"label":179},"b","Half the Moon is lit as always, but the lit half is facing away from us",{"id":181,"label":182},"c","The Moon has moved too far away to be seen",{"id":184,"label":185},"d","The Moon switches itself off for a night","**b.** Nothing happens to the sunlight at all. At new moon the Moon sits roughly between Earth and the Sun, so the half it turns towards *us* is the night half. Its day half is blazing away as brightly as ever — it is just pointing at the Sun, not at us.\n\nIf you could stand on the Moon at new moon and look back, you would see a brilliantly lit **full Earth** hanging in a black sky. Earth's phases and the Moon's phases are always opposites.",{"id":188,"type":58,"title":189,"eyebrow":190,"navLabel":191},"ch4","The eight shapes and their names","Chapter 04","4 The eight names",{"id":193,"type":43,"markdown":194},"ch4-names-intro","Astronomers give eight names to the cycle. Four of them are *moments* — instants when the geometry is exact — and four are the *stretches in between*.\n\nThe moments are **new moon**, **first quarter**, **full moon** and **last quarter**. Each lasts an instant, though of course the Moon looks nearly the same for a day or so either side.\n\nThe stretches are **crescent** (less than half lit) and **gibbous** (more than half lit), each of which happens twice: once while the Moon is growing and once while it is shrinking.\n\nTwo words are worth learning properly:\n\n- **Crescent** comes from a Latin word meaning *growing*. It is the thin curved sliver, less than half.\n- **Gibbous** comes from a Latin word for *humped* or *bulging*. It is the fat lopsided shape, more than half but not yet full.",{"id":196,"type":197,"caption":198,"columns":199,"rows":204},"ch4-phase-table","table","The eight phases: day of the cycle, how much of the disc is lit, and the Indian name",[200,201,202,203],"Phase","Day of the month","Disc lit","Indian name",[205,210,215,220,224,229,233,237],[206,207,208,209],"New moon","day 0.0","0%","Amavasya",[211,212,213,214],"Waxing crescent","day 3.7","15%","Shukla paksha",[216,217,218,219],"First quarter","day 7.4","50%","Shukla ashtami",[221,222,223,214],"Waxing gibbous","day 11.1","85%",[225,226,227,228],"Full moon","day 14.8","100%","Purnima",[230,231,223,232],"Waning gibbous","day 18.5","Krishna paksha",[234,235,218,236],"Last quarter","day 22.1","Krishna ashtami",[238,239,213,232],"Waning crescent","day 25.8",{"id":241,"type":47,"variant":149,"title":242,"markdown":243},"ch4-quarter-confusing","\"Quarter moon\" looks like a half. Why?","Every child notices this and nobody explains it. A **first quarter** moon looks like a half-circle, not a quarter. So why is it called a quarter?\n\nBecause the name counts **how far through the month the Moon has travelled**, not what fraction of the disc is bright. At first quarter the Moon has completed one quarter of its journey around Earth — about 7.4 days out of 29.5. At last quarter it has completed three quarters of the trip.\n\nThe shape is a half-disc. The name is about the calendar, not the picture. Both facts are true at once.",{"id":245,"type":246,"title":247,"terms":248},"ch4-glossary","glossary","Moon words worth owning",[249,252,255,259,262,266,269,272,276,280,284,288],{"term":200,"meaning":250,"example":251},"How much of the Moon's sunlit half is facing Earth right now. Not a shape the Moon takes, but a view we get.","\"Tonight's phase is waxing gibbous.\"",{"term":206,"meaning":253,"example":254},"The moment the Moon is most nearly between Earth and the Sun, so its lit half points away and we see nothing.","Amavasya in the Indian calendar.",{"term":256,"meaning":257,"example":258},"Crescent","Less than half the disc lit: a curved sliver. From Latin for 'growing'.","The thin Moon seen just after sunset a day or two after new moon.",{"term":216,"meaning":260,"example":261},"Exactly half the disc lit and growing, a quarter of the way through the cycle.","Rises around noon, sets around midnight.",{"term":263,"meaning":264,"example":265},"Gibbous","More than half lit but not yet full. From Latin for 'humped'.","The fat lopsided Moon a few nights before full.",{"term":225,"meaning":267,"example":268},"The whole disc lit, because the Moon is opposite the Sun as seen from Earth.","Purnima; rises at sunset.",{"term":234,"meaning":270,"example":271},"Exactly half lit and shrinking, three quarters of the way through the cycle. Also called third quarter.","Rises around midnight, sets around noon.",{"term":273,"meaning":274,"example":275},"Waxing","Getting bigger, night after night. From an old word meaning to grow.","New moon to full moon is the waxing half.",{"term":277,"meaning":278,"example":279},"Waning","Getting smaller, night after night.","Full moon to new moon is the waning half.",{"term":281,"meaning":282,"example":283},"Terminator","The line on the Moon between its day side and its night side, where the Sun is rising or setting.","The curved edge of the bright part.",{"term":285,"meaning":286,"example":287},"Earthshine","Faint light on the Moon's night side, bounced off Earth. Seen best near a thin crescent.","\"The old Moon in the new Moon's arms.\"",{"term":289,"meaning":290,"example":291},"Lunar month","One full round of the phases, about 29.5 days. Also called a synodic month.","New moon to the next new moon.",{"id":293,"type":120,"component":294,"componentVersion":5,"config":295,"objective":315,"textAlternative":316},"lab-match-names","match-pairs",{"prompt":296,"mode":297,"pairs":298},"Match each phase name to what you would actually see in the sky.","connect",[299,301,303,305,307,309,311,313],{"a":206,"b":300},"Nothing visible; the lit half faces away",{"a":211,"b":302},"Thin sliver low in the west just after sunset",{"a":216,"b":304},"Right half bright, high in the south at sunset",{"a":221,"b":306},"Fat and lopsided, with a dark sliver on the left",{"a":225,"b":308},"A complete bright disc rising as the Sun sets",{"a":230,"b":310},"Fat and lopsided, with a dark sliver on the right",{"a":234,"b":312},"Left half bright, high in the south at sunrise",{"a":238,"b":314},"Thin sliver low in the east just before sunrise","Connect each phase name to the sight it describes, including where in the sky and at what time you would see it.","Eight phase names on the left, eight descriptions on the right, to be joined up.\n\nNew moon goes with \"nothing visible; the lit half faces away\". Waxing crescent goes with \"thin sliver low in the west just after sunset\". First quarter goes with \"right half bright, high in the south at sunset\". Waxing gibbous goes with \"fat and lopsided, with a dark sliver on the left\". Full moon goes with \"a complete bright disc rising as the Sun sets\". Waning gibbous goes with \"fat and lopsided, with a dark sliver on the right\". Last quarter goes with \"left half bright, high in the south at sunrise\". Waning crescent goes with \"thin sliver low in the east just before sunrise\".\n\nThe pattern to notice: the **waxing** phases are all evening sights in the west, and the **waning** phases are all morning sights in the east.",{"id":318,"type":319,"itemId":320,"prompt":321,"check":322,"hints":330,"feedback":333},"practice-name-1","practice","phases-of-the-moon.discover-name-gibbous","Tonight the Moon is clearly more than half lit, but not quite a complete circle. The dark sliver is on the **left**. What phase is this?",{"kind":323,"options":324,"correct":329},"choice",[325,326,327,328],{"id":175,"label":211},{"id":178,"label":221},{"id":181,"label":230},{"id":184,"label":234},[178],[331,332],"More than half lit means gibbous, not crescent.","In India, a Moon that is growing has its bright side on the right, so the dark bit is on the left.",{"correct":334,"incorrect":335},"Right: more than half lit makes it **gibbous**, and dark-on-the-left means it is still growing, so **waxing gibbous**. Full moon is a few nights away.","More than half lit is always *gibbous*. Then ask which side is dark: dark on the left means the bright part is still spreading leftwards, so it is **waxing** gibbous.",{"id":337,"type":58,"title":338,"eyebrow":339,"navLabel":340},"ch5","Waxing or waning? How to tell tonight","Chapter 05","5 Waxing or waning",{"id":342,"type":43,"markdown":343},"ch5-waxing-waning","Look at tonight's Moon. It is a crescent. Is it on its way **up** to full, or on its way **down** to nothing?\n\nYou genuinely cannot tell from the shape alone, because a waxing crescent and a waning crescent are the same shape — just mirrored. But there are three completely reliable ways to tell, and each one works on its own.\n\n**1. Which edge is bright?** From India and everywhere else north of the equator, a **growing** Moon is bright on the **right**. A **shrinking** Moon is bright on the **left**. The bright part always advances from right to left across the disc, and then retreats the same way.\n\n**2. What time is it?** A waxing Moon is an **evening** Moon: it is already up when the Sun sets, and it sets a few hours later. A waning Moon is a **morning** Moon: it rises late at night and is still up at dawn. If you can see a crescent in the evening sky, it is waxing. Full stop.\n\n**3. Which way did it go?** If you kept a diary, you already know. Yesterday's Moon was either thinner or fatter than tonight's.",{"id":345,"type":47,"variant":88,"title":346,"markdown":347},"ch5-d-c-trick","The D-O-C trick (works in India)","Here is the memory trick used all over the northern hemisphere.\n\nAs the month goes on, the Moon draws three letters in the sky: **D**, then **O**, then **C**.\n\n- **D** — the bright part bulges to the right with a straight edge on the left. That is a **first quarter**, and the Moon is **waxing**. D for *developing*.\n- **O** — a complete circle. **Full moon**.\n- **C** — the bright part bulges to the left. That is a **last quarter**, and the Moon is **waning**. C for *closing*.\n\nSay it out loud once and you have it for life: **D, O, C — grow, full, go.**\n\nCareful: this is upside down in Australia or South Africa, and the Moon looks sideways from near the equator. Trick 2 (the time of night) works everywhere.",{"id":349,"type":197,"caption":350,"columns":351,"rows":355},"ch5-waxing-table","Telling a waxing Moon from a waning Moon from India",[352,353,354],"Clue","Waxing (growing)","Waning (shrinking)",[356,360,364,368,372,376,380],[357,358,359],"Bright edge","Right-hand side","Left-hand side",[361,362,363],"Letter shape at quarter","Like a **D**","Like a **C**",[365,366,367],"When it is up","Afternoon and evening","Late night and morning",[369,370,371],"Where you see it at sunset","Already high in the sky, in the south or west","Not yet risen; still below the eastern horizon",[373,374,375],"Where you see it at sunrise","Already set","High in the sky, in the south or west",[377,378,379],"Indian fortnight","Shukla paksha (bright fortnight)","Krishna paksha (dark fortnight)",[381,382,383],"Tomorrow it will be","Fatter and set later","Thinner and rise later",{"id":385,"type":120,"component":386,"componentVersion":5,"config":387,"objective":443,"textAlternative":444},"lab-sort-waxing","sort-game",{"prompt":388,"bins":389,"seconds":123,"items":394},"Sort each sighting into the growing half or the shrinking half of the month.",[390,392],{"id":391,"label":353},"waxing",{"id":393,"label":354},"waning",[395,399,403,407,411,415,419,423,427,431,435,439],{"id":396,"label":397,"bin":391,"why":398},"i1","A thin crescent low in the west just after sunset","Evening sighting in the west, bright side on the right: a young waxing crescent, a day or two after new moon.",{"id":400,"label":401,"bin":393,"why":402},"i2","A thin crescent low in the east just before sunrise","The old Moon of the month, seen in the morning sky a day or two before new moon.",{"id":404,"label":405,"bin":391,"why":406},"i3","A Moon shaped like the letter D","Bright on the right with a straight left edge: first quarter, halfway to full.",{"id":408,"label":409,"bin":393,"why":410},"i4","A Moon shaped like the letter C","Bright on the left: last quarter, halfway from full back to new.",{"id":412,"label":413,"bin":391,"why":414},"i5","A fat Moon high in the sky at 9 pm, dark sliver on the left","Gibbous with the dark part on the left, and up in the evening: waxing gibbous.",{"id":416,"label":417,"bin":393,"why":418},"i6","A fat Moon still up at 8 am, dark sliver on the right","Gibbous with the dark part on the right, and up in the morning: waning gibbous.",{"id":420,"label":421,"bin":391,"why":422},"i7","Shukla paksha, tithi 5","Shukla paksha is the bright fortnight, running from Amavasya up to Purnima.",{"id":424,"label":425,"bin":393,"why":426},"i8","Krishna paksha, tithi 11","Krishna paksha is the dark fortnight, running from Purnima down to Amavasya.",{"id":428,"label":429,"bin":393,"why":430},"i9","Three days after Purnima","Purnima is full moon; everything after it until Amavasya is shrinking.",{"id":432,"label":433,"bin":391,"why":434},"i10","Moonrise at 3 pm, moonset at 2 am","Rising in the afternoon means the Moon is well ahead of the Sun in the sky: it is between first quarter and full.",{"id":436,"label":437,"bin":393,"why":438},"i11","Moonrise at 11 pm, moonset at 11 am","A Moon that rises near midnight is at last quarter, on its way down to new.",{"id":440,"label":441,"bin":391,"why":442},"i12","Tomorrow night it will look fatter","Getting fatter is the definition of waxing.","Decide for each clue whether the Moon is in the growing half or the shrinking half of the lunar month.","Twelve cards are sorted into two bins: **Waxing (growing)** and **Waning (shrinking)**.\n\nWaxing: a thin crescent low in the west just after sunset; a Moon shaped like the letter D; a fat Moon high at 9 pm with the dark sliver on the left; shukla paksha tithi 5; moonrise at 3 pm with moonset at 2 am; \"tomorrow night it will look fatter\".\n\nWaning: a thin crescent low in the east just before sunrise; a Moon shaped like the letter C; a fat Moon still up at 8 am with the dark sliver on the right; krishna paksha tithi 11; three days after Purnima; moonrise at 11 pm with moonset at 11 am.\n\nThe rule behind every card: **evening Moons are waxing, morning Moons are waning.**",{"id":446,"type":319,"itemId":447,"prompt":448,"check":449,"hints":460,"feedback":463},"practice-waxwane","phases-of-the-moon.discover-evening-crescent","You spot a thin crescent Moon in the **west**, just after sunset, on your way home from the market. Which is it?",{"kind":323,"options":450,"correct":459},[451,453,455,457],{"id":175,"label":452},"A waxing crescent, a day or two after new moon",{"id":178,"label":454},"A waning crescent, a day or two before new moon",{"id":181,"label":456},"It is impossible to say without knowing the date",{"id":184,"label":458},"A first quarter moon seen from the side",[175],[461,462],"Where is the Sun at that moment? Just below the western horizon.","A waning crescent is a morning object — it rises only shortly before the Sun.",{"correct":464,"incorrect":465},"Correct. A crescent visible **in the evening** must be close behind the Sun in the sky, which only happens just *after* new moon. It is **waxing**, and tomorrow it will be fatter and set later.","Think about when each crescent is up. A waning crescent rises shortly before dawn and is washed out by the time the Sun is up; you can never see it in the evening. An evening crescent is always waxing.",{"id":467,"type":58,"title":468,"eyebrow":469,"navLabel":470},"ch6","Why you can see the Moon in the daytime","Chapter 06","6 Daytime Moon",{"id":472,"type":43,"markdown":473},"ch6-daytime","Ask most people when you can see the Moon and they will say \"at night\". Then point at the pale half-Moon sitting in a blue afternoon sky and watch them be surprised.\n\nThe Moon is up in the daytime for **about half of every month**. It is not rare, not special and not a sign of anything. It is just that nobody looks up during the day.\n\nHere is why it happens. The Moon does not rise at sunset and set at sunrise, like a well-behaved night light. It rises at a **different time every day**, drifting about fifty minutes later each night as it works its way round Earth. Over a month it rises at every hour of the clock, including the middle of the morning and the middle of the afternoon.\n\nSo:\n\n- A **waxing crescent** rises in the middle of the morning and sets in mid-evening. It is up all afternoon, riding high in a blue sky.\n- A **first quarter** Moon rises around noon. If you look south-east at 3 pm you will often catch it.\n- A **waning gibbous** is still up well into the morning, sometimes past breakfast.\n- A **full moon** is the exception. It rises as the Sun sets and sets as the Sun rises, so it really is a night-only Moon.\n\nWhether you can *notice* it is a different matter: near new moon the Moon is close to the Sun in the sky and lost in the glare, and a thin crescent is faint. The daytime Moon is easiest to spot between first quarter and gibbous, when it is bright and far from the Sun.",{"id":475,"type":197,"caption":476,"columns":477,"rows":482},"ch6-rise-set","When each phase is up (approximate times for an observer near the equator)",[200,478,479,480,481],"Rises","Highest","Sets","Easy to see in daylight?",[483,488,493,495,497,499,501,502],[206,484,485,486,487],"06:00","12:00","18:00","No — too close to the Sun",[211,489,490,491,492],"09:00","15:00","21:00","Yes, in the afternoon",[216,485,486,494,492],"00:00",[221,490,491,496,492],"03:00",[225,486,494,484,498],"No — it is a night Moon",[230,491,496,489,500],"Yes, in the morning",[234,494,484,485,500],[238,496,489,490,500],{"id":504,"type":47,"variant":53,"title":505,"markdown":506},"ch6-check-table","Check this table against the real sky","This table is a *prediction*, and predictions are there to be tested.\n\nFind out tonight's phase (a calendar, a phone, or just look). Then use the table: it tells you roughly when the Moon should rise, when it should be highest, and when it should set.\n\nGo outside at the predicted time and see whether the Moon is where the table says.\n\nThe times are approximate — they shift by an hour or two depending on where you live and the time of year — but the **pattern** is rock solid. A full moon really does rise at sunset. A last quarter really is high in the south at breakfast time.",{"id":508,"type":47,"variant":101,"title":509,"markdown":510},"ch6-why-blue","Why the daytime Moon looks pale","In the daytime you are looking at the Moon through a sky full of scattered sunlight. The blue haze is *in front of* the Moon, washing it out, exactly as a torch looks feeble in bright sunshine.\n\nThe Moon is exactly as bright as it ever was. The background got brighter. That is also why a daytime Moon looks whitish-grey and slightly transparent, as though someone had drawn it in chalk.",{"id":512,"type":171,"prompt":513,"options":514,"explanation":523},"predict-full-daytime","Could you ever see a **full moon** high in the sky at noon?",[515,517,519,521],{"id":175,"label":516},"Yes, on any day of the month",{"id":178,"label":518},"Yes, but only in winter",{"id":181,"label":520},"No — at full moon the Moon is opposite the Sun, so when the Sun is highest the Moon is below the horizon",{"id":184,"label":522},"No, because the Moon is not lit at midday","**c.** \"Full\" means the Moon is on the opposite side of the sky from the Sun. When the Sun is at its highest, the Moon must be at its lowest — which means below your feet, on the far side of Earth.\n\nThe same reasoning run backwards is why a full moon rises exactly as the Sun sets: the two are always on opposite sides of you. This is one of the neatest consequences of understanding phases, and you can check it on the next full moon night.",{"id":525,"type":58,"title":526,"eyebrow":527,"navLabel":528},"ch7","The big mistake: phases are not a shadow","Chapter 07","7 Not a shadow",{"id":530,"type":47,"variant":149,"title":531,"markdown":532},"ch7-misconception","\"The dark part is Earth's shadow on the Moon\"","This is the single most common wrong idea in all of astronomy, and adults believe it as often as children do. It sounds sensible: something dark is covering part of the Moon, and Earth is big and dark, so it must be Earth's shadow.\n\nIt is wrong. Three pieces of evidence kill it straight away:\n\n1. **The timing is impossible.** Earth's shadow points directly away from the Sun. So it can only ever fall on the Moon when the Moon is *opposite* the Sun — that is, at full moon. Yet the Moon looks half-lit at first quarter, when the Moon is off to the side and Earth's shadow is pointing nowhere near it.\n2. **It would happen every month, and identically.** A shadow explanation predicts the same event once per orbit. Phases change smoothly every single night.\n3. **The shadow is the wrong shape.** Earth's shadow is round, and always round. The edge of a gibbous Moon curves the *other* way from the edge of a crescent Moon. No single round shadow can do both.\n\nThe dark part of the Moon is not in shadow at all. It is simply **night** — the half of the Moon that is turned away from the Sun.",{"id":534,"type":43,"markdown":535},"ch7-eclipse-is-real","Here is the honest part: Earth's shadow **does** sometimes fall on the Moon. That event is real, and it has a name — a **lunar eclipse**.\n\nBut notice how different it is from a phase:\n\n- A lunar eclipse only happens at **full moon**, and not even every full moon — only two or three times a year at most.\n- It is over in a couple of hours, not a couple of weeks.\n- The shadowed part is not black. Sunlight bending through Earth's atmosphere leaks into the shadow and paints the Moon a dim coppery red, which is why people call it a *blood moon*.\n- Everyone on the night side of Earth sees it at the same instant.\n\nPhases are a **viewing angle**. An eclipse is a **shadow**. Two completely different things that happen to involve the same three objects.",{"id":537,"type":106,"conceptId":538,"relation":108,"explanation":539},"ch7-link-eclipses","eclipses","Eclipses only happen at new moon or full moon, when Sun, Earth and Moon line up. Knowing the phases tells you when an eclipse is even possible.",{"id":541,"type":197,"caption":542,"columns":543,"rows":547},"ch7-phase-vs-eclipse","Phase or eclipse? Two things that are often muddled",[544,545,546],"Question","A phase","A lunar eclipse",[548,552,556,560,564,568],[549,550,551],"What causes it?","Our changing view of the Moon's sunlit half","Earth's shadow genuinely falling on the Moon",[553,554,555],"How often?","Every night; a full cycle every 29.5 days","A few times a year at most, and not every full moon",[557,558,559],"How long does it last?","Weeks of slow change","A couple of hours from start to finish",[561,562,563],"What colour is the dark part?","Black — it is simply lunar night","Dim coppery red, lit by sunlight bent through Earth's air",[565,566,567],"Which phase is it seen at?","All of them; that is the point","Only at full moon",[569,570,571],"Is the Moon's shape changing?","No. Neither event changes the Moon.","No.",{"id":573,"type":319,"itemId":574,"prompt":575,"check":576,"hints":587,"feedback":590},"practice-not-shadow","phases-of-the-moon.discover-not-shadow","A classmate argues that the phases must be Earth's shadow, because \"the dark bit is exactly the shape a shadow would make\". What is the strongest single piece of evidence against this?",{"kind":323,"options":577,"correct":586},[578,580,582,584],{"id":175,"label":579},"Earth's shadow is much too small to reach the Moon",{"id":178,"label":581},"Earth's shadow always points away from the Sun, so it could only ever touch the Moon at full moon — yet the Moon is half-lit at first quarter",{"id":181,"label":583},"The Moon is too far away for any shadow to reach it",{"id":184,"label":585},"Shadows are always black, and the Moon's dark part is grey",[178],[588,589],"Think about which way a shadow points, and where the Moon is at first quarter.","Earth's shadow does reach the Moon sometimes — that is a lunar eclipse — so the answer is not about distance.",{"correct":591,"incorrect":592},"Exactly. The geometry is the killer argument: at first quarter the Moon is off to the side of Earth, nowhere near the shadow, and yet it is neatly half-lit. Only the viewing-angle explanation fits.","The shadow *does* reach the Moon sometimes — that is what a lunar eclipse is — so size and distance are not the problem. The problem is direction: a shadow points straight away from the Sun, so it can only touch the Moon at full moon.",{"id":594,"type":58,"title":595,"eyebrow":596,"navLabel":597},"ch8","Purnima, Amavasya and your own calendar","Chapter 08","8 Purnima, Amavasya",{"id":599,"type":43,"markdown":600},"ch8-indian-calendar","If you live in India you have been using the Moon's phases your whole life, whether or not anyone told you so.\n\nThe traditional Indian calendar is a **lunar** calendar: its months are built out of the Moon's cycle, not out of numbered squares on a wall chart.\n\n- **Purnima** is the full moon day. The Moon is a complete bright disc.\n- **Amavasya** is the new moon day. The Moon is invisible.\n- The fortnight of growing Moon between Amavasya and Purnima is **shukla paksha** — the bright fortnight.\n- The fortnight of shrinking Moon between Purnima and Amavasya is **krishna paksha** — the dark fortnight.\n\nOnce you know that, festival dates stop being random. **Buddha Purnima** is a full moon, by definition. **Guru Purnima**, **Sharad Purnima** and **Kartik Purnima** likewise. **Diwali** falls on the Amavasya of the month of Kartik, which is exactly why Diwali nights are so dark — and why the lamps matter so much. **Holi** is lit on a Purnima.\n\nThe Moon is not decorating these festivals. It is *scheduling* them.",{"id":602,"type":197,"caption":603,"columns":604,"rows":608},"ch8-festivals","Some Indian festivals and the Moon phase that fixes their date",[605,606,607],"Festival","Moon phase","What that means in the sky",[609,613,617,621,625,629,633,637],[610,611,612],"Diwali (Lakshmi Puja)","Amavasya of Kartik","New moon: the darkest night of the month, so the lamps stand out",[614,615,616],"Holi (Holika Dahan)","Purnima of Phalguna","Full moon rising at sunset as the bonfire is lit",[618,619,620],"Buddha Purnima","Purnima of Vaishakha","Full moon; marks the Buddha's birth, awakening and passing",[622,623,624],"Guru Purnima","Purnima of Ashadha","Full moon in the monsoon month",[626,627,628],"Karva Chauth","Chaturthi of krishna paksha","A fat waning gibbous, about 87% lit, rising several hours after sunset",[630,631,632],"Eid al-Fitr","First sighting of the new crescent","A very thin waxing crescent, low in the west just after sunset",[634,635,636],"Ganesh Chaturthi","Chaturthi of shukla paksha","A young waxing crescent, up in the evening sky",[638,639,640],"Maha Shivaratri","Chaturdashi of krishna paksha","The night before Amavasya: a razor-thin old crescent, or none at all",{"id":642,"type":47,"variant":643,"title":644,"markdown":645},"ch8-eid-crescent","example","Why Eid is announced, not printed","The Islamic calendar counts each month from the **first sighting of the new crescent** after new moon. That crescent is thin, faint, low, and visible for only twenty or thirty minutes after sunset — and whether anyone actually sees it depends on haze, cloud, the exact angle of the Moon's path and how sharp your eyes are.\n\nThat is why the date of Eid is often confirmed only the evening before, and why it can differ by a day between two cities. People are not guessing. They are waiting on a genuinely difficult observation.\n\nIf you want to know how hard it is, try it yourself: find the date of the next new moon, then go out the following evening and hunt for the crescent in the western twilight. Most people fail on their first attempt.",{"id":647,"type":47,"variant":648,"title":649,"markdown":650},"ch8-moon-not-eaten","nuance","Stories and observations can live side by side","Many cultures have stories that explain the Moon's changing shape — that it is being swallowed, or drunk, or that it wastes away and is reborn. In India you will hear the story of Chandra being cursed to wane and blessed to wax again.\n\nThese stories are part of how people have felt about the sky for thousands of years, and they are worth knowing. What this lesson adds is a *different* kind of answer: one you can test with an orange and a lamp tonight, and one that lets you predict exactly what the Moon will look like next Tuesday.\n\nKnowing the physics does not take the beauty away. Standing under a Purnima moon knowing precisely why it is full is, if anything, better.",{"id":652,"type":120,"component":121,"componentVersion":5,"config":653,"objective":658,"textAlternative":659,"help":660},"lab-moon-quiz",{"startDay":654,"views":655,"showNames":126,"showTithi":127,"quizRounds":657},14.8,[656],"both",6,"See the same moment from two places at once — from space and from the ground — and then test yourself on naming phases.","This lab shows two panels side by side. The left panel is the view **from space**, looking down on Earth's orbit: the Sun off to one side, Earth in the middle, and the Moon on its circular path, with the sunlit half of both Earth and Moon shaded bright and the other half dark. The right panel is the view **from the ground**: what the Moon actually looks like in the sky at that moment.\n\nIt opens at **day 14.8, full moon**. In the space view, the Moon is on the opposite side of Earth from the Sun, and the whole of its lit face is turned towards Earth. In the ground view, the disc is completely bright.\n\nDrag the Moon round the space view and the ground view changes in step. Put the Moon between Earth and the Sun and the ground view goes dark: new moon. Put it a quarter of the way round and exactly half the disc lights up.\n\nSix quiz rounds then show a Moon in the ground view and ask you to name the phase, or show a position in the space view and ask what you would see from Earth.",{"simplerExplanation":661,"hints":662},"The left picture shows where the Moon is. The right picture shows what you would see. Move one and the other follows.",[663,664],"Find the two positions where exactly half the disc is lit. They are on opposite sides of Earth.","At every moment, check that exactly half of the Moon-ball is bright in the space view. It never changes.",{"id":666,"type":58,"title":667,"eyebrow":668,"navLabel":669},"ch9","Start a moon diary tonight","Chapter 09","9 Your moon diary",{"id":671,"type":43,"markdown":672},"ch9-diary","Everything on this page can be checked by one person with a pencil. Here is the project.\n\nEvery evening for one month, at roughly the same time, go outside and:\n\n1. **Look** for the Moon. If you cannot find it, write \"not visible\" — that is real data, not a failure.\n2. **Draw** what you see, as a circle with the bright part shaded in. Do not draw what you think it should look like.\n3. **Note the time**, and roughly where it was: east, south, west, and low or high.\n4. **Note the date.**\n\nTwenty-nine drawings later, lay them out in order. You will see the full cycle, in your own handwriting, and you will be able to answer questions that no book can answer for you — such as exactly how many days *your* Moon took to go from one full moon to the next.",{"id":674,"type":154,"title":675,"items":676},"ch9-diary-steps","What to look for as the month goes on",[677,681,685,689,693,696,700],{"title":678,"tag":679,"text":680},"Nights 1-3","hunting","Just after new moon the Moon is a thin crescent very low in the west at dusk. Find a spot with a clear western horizon. This is the hardest sighting of the month.",{"title":682,"tag":683,"text":684},"Nights 4-7","earthshine","The crescent is fatter and higher. Look for the faint grey glow filling in the unlit part: earthshine, sunlight bounced off Earth.",{"title":686,"tag":687,"text":688},"Night 7 or 8","the D","First quarter. A clean straight edge down the middle, bright on the right. High in the south at sunset.",{"title":690,"tag":691,"text":692},"Nights 9-14","craters","Waxing gibbous. If you have binoculars, look along the curved edge of the bright part, where the shadows are longest and craters stand out best.",{"title":694,"tag":228,"text":695},"Night 15","Full moon, rising in the east exactly as the Sun sets in the west. Flat and featureless in binoculars, because nothing is casting a shadow.",{"title":697,"tag":698,"text":699},"Nights 16-22","late nights","Waning gibbous, rising later and later. You may have to look in the early morning instead, or before bed.",{"title":701,"tag":702,"text":703},"Nights 23-29","mornings","Last quarter and waning crescent are morning objects. Look east before breakfast. The last old crescent before Amavasya is very hard to catch.",{"id":705,"type":47,"variant":53,"title":706,"markdown":707},"ch9-diary-tip","Two tricks that make the diary work","**Draw the bright part, not the outline.** Start by drawing a full circle faintly, then shade the part that is actually glowing. If you sketch only the bright shape you will keep drawing the same banana every night without noticing it has changed.\n\n**Use a fixed landmark.** Stand in the same place each evening — the same step, the same corner of the terrace — and note where the Moon is compared with a tree, a water tank or a rooftop. After a week you will spot something surprising: the Moon has shifted a long way east against your landmark, and it arrives later and later each night.",{"id":709,"type":43,"markdown":710},"ch9-what-youll-find","Two discoveries are waiting for you in the data, and they are the doorway into the next layer of this topic.\n\n**First, the Moon is late every day.** Whatever time it rose last night, tonight it rises roughly **fifty minutes later**. Over a fortnight that adds up to a full twelve hours, which is why an evening Moon slowly becomes a morning Moon.\n\n**Second, the shapes are not symmetrical in time.** The Moon spends about a fortnight growing and about a fortnight shrinking, and the whole round trip takes about twenty-nine and a half days — not thirty, not twenty-eight. That awkward half-day is the reason lunar calendars and solar calendars drift apart, and the reason an extra month, **adhik maas**, has to be slotted in every few years.\n\nBoth of these have sharp, satisfying explanations. They are waiting in the Understand and Go-deeper layers.",{"id":712,"type":713,"prompt":714},"reflect-diary","reflection","Before you start your diary, write down two predictions: what phase you expect to see one week from tonight, and what time you expect the Moon to rise on that night. Seal them in an envelope. Open it in a week and see how you did — and if you were wrong, work out which part of your reasoning went astray.",{"id":716,"type":106,"conceptId":717,"relation":718,"explanation":719},"connect-tides","tides","related_to","The biggest tides of the month arrive at new moon and full moon, when Sun and Moon pull along the same line. The tide table follows the phase calendar.",{"id":721,"type":106,"conceptId":722,"relation":108,"explanation":723},"connect-gravity","gravity","Gravity is what holds the Moon in the orbit that produces the whole monthly cycle of phases.",{"id":725,"type":726,"title":727,"questions":728},"quiz-discover","quiz","Check yourself",[729,742,755,768,781,794,807,820,833,845],{"itemId":730,"prompt":731,"options":732,"correct":178,"why":741},"phases-of-the-moon.discover-q-lit-half","How much of the Moon is lit by the Sun at this exact moment?",[733,735,737,739],{"id":175,"label":734},"It depends on the phase",{"id":178,"label":736},"Exactly half, always",{"id":181,"label":738},"All of it",{"id":184,"label":740},"None of it at new moon","Exactly half, always. Sunlight travels in straight lines and lights one half of any ball. The **phase** tells you how much of that lit half is turned towards Earth.",{"itemId":743,"prompt":744,"options":745,"correct":178,"why":754},"phases-of-the-moon.discover-q-source","Where does moonlight come from?",[746,748,750,752],{"id":175,"label":747},"The Moon glows with its own heat",{"id":178,"label":749},"Sunlight reflected off the Moon's rock",{"id":181,"label":751},"Light from Earth's cities",{"id":184,"label":753},"Starlight collected by the Moon","Moonlight is second-hand sunlight. Moon rock is actually dark grey, about as reflective as old asphalt; it looks brilliant only because so much sunlight falls on it.",{"itemId":756,"prompt":757,"options":758,"correct":178,"why":767},"phases-of-the-moon.discover-q-cycle-length","About how long does one full cycle of phases take, from new moon to the next new moon?",[759,761,763,765],{"id":175,"label":760},"7 days",{"id":178,"label":762},"About 29.5 days",{"id":181,"label":764},"Exactly 30 days",{"id":184,"label":766},"365 days","About 29.53 days — roughly a month, which is where the word *month* comes from. The awkward half-day is why lunar calendars need adjusting.",{"itemId":769,"prompt":770,"options":771,"correct":181,"why":780},"phases-of-the-moon.discover-q-gibbous","What does *gibbous* mean?",[772,774,776,778],{"id":175,"label":773},"Less than half lit",{"id":178,"label":775},"Exactly half lit",{"id":181,"label":777},"More than half lit but not full",{"id":184,"label":779},"Completely dark","Gibbous comes from a Latin word for *humped*. It is the fat, lopsided Moon between a quarter and a full moon, in either direction.",{"itemId":782,"prompt":783,"options":784,"correct":178,"why":793},"phases-of-the-moon.discover-q-evening-crescent","You see a crescent Moon in the west just after sunset. Tomorrow night it will be:",[785,787,789,791],{"id":175,"label":786},"Thinner and lower",{"id":178,"label":788},"Fatter and higher",{"id":181,"label":790},"Exactly the same",{"id":184,"label":792},"On the other side of the sky","An evening crescent is a **waxing** crescent, growing towards first quarter. Each night it is fatter, higher at sunset, and sets later.",{"itemId":795,"prompt":796,"options":797,"correct":181,"why":806},"phases-of-the-moon.discover-q-full-rise","At what time does a full moon rise?",[798,800,802,804],{"id":175,"label":799},"Around midnight",{"id":178,"label":801},"Around noon",{"id":181,"label":803},"At sunset",{"id":184,"label":805},"At sunrise","A full moon is opposite the Sun in the sky, so it climbs above the eastern horizon just as the Sun drops below the western one. It then sets at sunrise.",{"itemId":808,"prompt":809,"options":810,"correct":181,"why":819},"phases-of-the-moon.discover-q-daytime","Can the Moon be seen during the day?",[811,813,815,817],{"id":175,"label":812},"Never",{"id":178,"label":814},"Only during an eclipse",{"id":181,"label":816},"Yes, for about half of every month",{"id":184,"label":818},"Only from high mountains","The Moon is above the horizon in daylight for roughly half the month. A first quarter Moon rises around noon; a waning gibbous is often still up at breakfast.",{"itemId":821,"prompt":822,"options":823,"correct":178,"why":832},"phases-of-the-moon.discover-q-shadow","Are the phases caused by Earth's shadow falling on the Moon?",[824,826,828,830],{"id":175,"label":825},"Yes, that is exactly what they are",{"id":178,"label":827},"No — that is a lunar eclipse, which is a different and much rarer event",{"id":181,"label":829},"Yes, but only the crescent phases",{"id":184,"label":831},"No, they are caused by clouds","Earth's shadow points away from the Sun, so it can only reach the Moon at full moon — and even then only a few times a year. Phases are about our viewing angle, not a shadow.",{"itemId":834,"prompt":835,"options":836,"correct":181,"why":844},"phases-of-the-moon.discover-q-purnima","Diwali (Lakshmi Puja) falls on Amavasya. What does the Moon look like that night?",[837,839,840,842],{"id":175,"label":838},"A full bright disc",{"id":178,"label":775},{"id":181,"label":841},"Invisible — it is new moon",{"id":184,"label":843},"A fat gibbous","Amavasya is new moon: the lit half faces away from Earth and nothing is visible. That is why Diwali nights are the darkest of the month, and why the lamps are the whole point.",{"itemId":846,"prompt":847,"options":848,"correct":178,"why":857},"phases-of-the-moon.discover-q-doc","In India, a Moon shaped like the letter **C** is:",[849,851,853,855],{"id":175,"label":850},"Waxing, and will be full in a week",{"id":178,"label":852},"Waning, and will be new in a week",{"id":181,"label":854},"Always a new moon",{"id":184,"label":856},"Only visible in winter","D-O-C: **D** for growing, **O** for full, **C** for closing. A C-shaped Moon is bright on the left, at last quarter, and heading for new moon. (This is reversed in the southern hemisphere.)",{"id":859,"type":860,"title":861,"points":862},"cheat-sheet-discover","summary","Cheat sheet",[863,864,865,866,867,868,869,870,871,872,873,874],"**The Moon makes no light of its own.** Moonlight is sunlight bounced off grey rock — about as reflective as old asphalt.","**Half the Moon is always lit.** Every moment, sunlight lights exactly one half. Nothing about that ever changes.","**A phase is a viewing angle**, not a shape: how much of the lit half happens to face Earth.","**The cycle takes about 29.53 days**, new moon to new moon. That is where the word *month* comes from.","**Eight names:** new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter, waning crescent.","**Crescent** = less than half. **Gibbous** = more than half. **Quarter** counts the journey, not the shape — which is why a quarter moon looks like a half.","**Waxing** = growing, bright on the right (in India), up in the evening. **Waning** = shrinking, bright on the left, up in the morning. Remember **D-O-C**.","**Phases are not Earth's shadow.** A shadow can only fall on the Moon at full moon, and that rare event is a *lunar eclipse*.","**The Moon is up in the daytime** for about half of every month; a full moon is the one phase that is strictly a night object.","**A full moon rises at sunset** and sets at sunrise, because it is opposite the Sun in the sky.","**Purnima** = full moon, **Amavasya** = new moon. **Shukla paksha** is the bright fortnight, **krishna paksha** the dark one.","**Moonrise slips about 50 minutes later each night**, which is why an evening Moon slowly turns into a morning Moon.",{"id":876,"type":877,"sourceIds":878},"sources-discover","sources",[879,880,881,882,883,884],"phases-of-the-moon-nasa-moon-phases","phases-of-the-moon-nasa-moon-facts","phases-of-the-moon-wikipedia-lunar-phase","phases-of-the-moon-wikipedia-hindu-calendar","phases-of-the-moon-britannica-moon","phases-of-the-moon-timeanddate-moon",[879,880,881,882,883,884],"needs_review",{"generatedBy":888,"notes":889},"claude-code","Draft generated locally; pending owner review. Every phase fraction, rise\u002Fset time and cycle length computed in numbers.py.","cd0b16180206ce2d957fa41fba48a387a8be986cceb14e50e032d8c3632e67bf",{"component:moon-phase@1":892,"component:match-pairs@1":893,"logic:practice":894,"component:sort-game@1":895,"source:phases-of-the-moon-britannica-moon":896,"source:phases-of-the-moon-nasa-moon-facts":897,"source:phases-of-the-moon-nasa-moon-phases":898,"source:phases-of-the-moon-timeanddate-moon":899,"source:phases-of-the-moon-wikipedia-hindu-calendar":900,"source:phases-of-the-moon-wikipedia-lunar-phase":901},"39afeb0bba7518b8118317655457b27214a4a2a315d236762bf1d6a6a40e18f3","2a8ee4ac87460b4e1175a4bb13c96b03d577db06dde95670eb7fcfe4ad787899","3d6b0fe1b15255975a32b0fcd94e8019bc959ad45cbf12e136e86149549c6878","b164f45a2c8ca08f26c450768ff0231e113e9fe45381eddb34dc6d0548596c38","7851afcfed44e83c91e1cd033e5a51b31ed72915a7f12ac117b6c8076cf99a8a","42fce1fa13db44246876ac36bd3506964da8f7fa12ecfcb17813905e4161b696","a204a49fd1f0bcc99b9c71da877e71b83931eba1bf4e931d4af08d83cabb175c","bae89711f5182b93b0801064bc61ce6f84a72c54016f6369f629d9fbf2be2d7f","8e594d900f52500015a6a6a8a85532f2a10b743592b6ba41ad92d43adb5fb040","7d0371e53bbaa01b158d9a8d193e8b907f2089d4cb08a73f37d1328b6add3ef9",{"state":903,"reviewer":904,"selfReview":126,"reviewedAt":905,"method":906},"approved","The library owner","2026-09-20T10:18:37.581Z","owner_bulk","preview-7e1cbbcc4f",1789899598750]