92046 · The Sun and the Earth-Moon system

• Spin relative to the Sun gives day and night

  Earth turns west to east on its axis once a day. The half of the globe facing the Sun is in daylight; the half turned away is in night. As Aotearoa rotates toward the Sun we see sunrise in the east; as it rotates away we see sunset in the west. Tilt is not required for this cycle. A globe held upright in a torch beam still has a lit side and a dark side. The spin is the interaction; day and night are the effect on Earth.

• Through one day the Sun angle, shadows and temperature change

  The same spin that makes day and night also changes how high the Sun stands while a place is on the lit side. Near sunrise the Sun is low in the eastern sky, so a stick throws a long shadow toward the west. At noon the Sun is highest, the shadow is shortest, and in New Zealand that noon shadow falls south because the Sun is in the northern sky. Near sunset the Sun is low in the west and the shadow stretches east again. Surface temperature usually climbs after sunrise and is often warmest after noon, then falls once the Sun is low or gone. You read those patterns from a shadow record or a temperature graph. You do not calculate a solar altitude.

• Tilt stays fixed; orbit decides which hemisphere leans in

  Earth's axis is tilted at about 23.5 degrees from the perpendicular to the orbital plane, and that direction does not swing around as the year goes on. What changes is Earth's place on the orbit. In December the southern end of the axis leans toward the Sun, so the Southern Hemisphere is presented more face-on. In June the same fixed lean presents the Southern Hemisphere more edge-on. March and September sit between those two positions. If you label a Southern Hemisphere orbit, December at the “Sun-facing” southern position is summer in Aotearoa, not winter.

• A season is tilt plus orbital position at a named latitude

  To describe a season you name a place, the orbital position, and which way the axis is leaning. Wellington in December is in southern summer: the South Pole end of the axis leans toward the Sun, noon Sun angle is high, days are long, and typical temperatures are the warmest of the year. Wellington in June is the reverse. In Aotearoa the reappearance of Matariki — te Mātahi o te Tau — is a midwinter seasonal marker, not a change in the tilt. A cold week in December is weather. The season is the months-long pattern of solar radiation and daylength at that latitude.

• Summer is warmer because of solar radiation, not distance

  When the noon Sun stands higher, the same bundle of solar radiation is spread over a smaller patch of ground, so each square metre receives more energy. The day is also longer, so that energy arrives for more hours. Those two together are why southern summer is warmer than southern winter. Earth is nearest the Sun in early January, about 147.1 million kilometres, and farthest in early July, about 152.1 million kilometres. That is the wrong way around for a distance story in the south, and it cannot explain why the north is in the opposite season on the same date. Both hemispheres are the same distance from the Sun at any moment. “Increased sunlight” is not the link; solar radiation, heat or insolation is.

• Daylength changes between solstice and equinox

  Daylength is the interval from sunrise to sunset. At a solstice one hemisphere is tilted most toward the Sun, so that hemisphere has its longest day and the other its shortest. At an equinox neither hemisphere is tilted toward the Sun, so day and night are close to equal everywhere. On the real Earth, refraction and the Sun's disc make daylight a little longer than a labelled model of “exactly 12 hours”. Through the year the rising and setting points also appear to shift: in southern summer the Sun rises south of east and sets south of west, on a high arc; in southern winter it rises north of east and sets north of west, on a low arc. Moving the clock for daylight saving does not change the interval from sunrise to sunset.

• The same links explain how the effect varies on Earth

  Temporal variation is the change at one place through the year: Wellington's monthly temperature and daylength rise toward December and fall toward June because orbital position changes how the Southern Hemisphere is presented to the Sun. Latitudinal variation is the difference between places at the same moment: Invercargill at 46°S has a longer December day and a shorter June day than Auckland at 37°S, while at equinox the two daylengths are similar. On the same spring-equinox noon, a resource may show the Sun at 90° at the equator and at 43° at Dunedin, so the Dunedin noon shadow is longer and the energy is less concentrated. Opposite hemispheres have opposite seasons on the same date. Polar day and night at the Antarctic and Arctic Circles are the extreme of the same daylength swing, not a separate mechanism.

• A diagram or table carries an observation or a science idea

  92046 expects you to use the resource in front of you plus what you know. Annotating the lit and dark sides of a globe, labelling December as southern summer on an orbit, or marking the high Sun-arc as the summer solstice can itself be a description. A modelled sunrise table is read for the pattern: which day is longer, which town swings more. A classroom demonstration supports a science idea; it does not prove the mechanism, and writing up the practical is not what this standard assesses. Do not turn a printed 43° into an angle you compute. The number is already the observation.

• Half the Moon is always lit

  The Moon does not make its own visible light. Sunlight hits the lunar surface and some of it bounces toward Earth — that is reflected sunlight. At any moment about half the sphere is in sunshine and about half is in the Moon's own night, just as half of Earth is in daylight. We do not see the whole lit hemisphere. We see only the part of that lit half that is turned toward us. People talk about a “dark side” as if it were never lit; that is a different claim mixed in. The face we never see from Earth is still sunlit every lunar day. Half is always lit. What changes is which slice of that half we are looking at.

• A phase is the Earth-facing slice of that lit half

  A moon phase is the shape of the sunlit part of the Moon that is facing Earth at that point in the month. Draw the Sun, then Earth, then the Moon, and shade the Moon's sunward half. The outline we actually photograph is whatever of that shading sits on the Earth-facing side. That is why the shape changes as the Moon moves, and why the same night looks like a crescent from a backyard and like a half-disc a week later. Earth's shadow is not doing this work. Earth's shadow can fall on the Moon only near full, and only when the alignment is unusually close — that event is a lunar eclipse, taught on the next page. Ordinary months have no such crossing.

External · grade-score marked.

This is an external achievement standard. Whetū offers original exam-style questions marked on the NCEA grade-score scale. Grades are estimates, not official results.

A mock paper is available in Whetū: Mock paper · The Sun and the Earth-Moon system.

4 authored Learn units for this standard.

• Day, night and the seasons

  On any clear evening in Aotearoa you can watch the Sun drop in the west and the sky go dark. That daily switch is not the Sun circling us. Earth's rotation is a west-to-east spin on an axis through the poles, and it is that spin relative to the Sun that puts one half of the globe in sunlight while the other half is turned away. The lit side has day; the dark side has night. A classroom globe and a torch can show the same split, but the model only supports the idea — it does not prove it.

• Moon phases and orbit

  From a backyard in Ōtautahi the Moon is a thin left-lit crescent one evening and a bright disc two weeks later. This page is about that changing appearance: why we see the Moon at all, how the shape changes as the Moon orbits Earth, and why the same full Moon can look larger in some months than in others. Earth's shadow sliding across the disc is not the cause. The cause is geometry: sunlight, orbital position, and the fraction of the lit half that faces us.

• Eclipses and variation across the Earth

  On a winter afternoon in July 2028, a narrow strip of the southern South Island — Queenstown, then Dunedin — is due to sit inside the Moon’s darkest shadow. Daylight will drop to a few minutes of twilight while the rest of Aotearoa sees only a bite taken out of the Sun. Same interaction; a different effect on Earth. That difference is what this page is for.

• Tides

  A tide is not a storm, a flood, or the season called spring. Around Aotearoa New Zealand the sea rises and falls twice on most days, in a regular pattern you can read on a harbour board or a tide table. That pattern is one of seven closed observations in this standard, sitting beside day and night, seasons, Moon phases and eclipses. Your first job is to describe what the table, graph or labelled sketch actually shows: a high, a low, a larger range, or a smaller one.

34 Practise questions in “The Sun and the Earth-Moon system”. Feedback here is formative and is not an official NCEA grade.

• Day and night

  Spin relative to the Sun. Sun angle, shadows, temperature through one day.

• Seasons

  Tilt stays fixed; orbit decides which hemisphere leans in. Not distance.

• Latitude and daylength

  How the same links vary with latitude, solstice and equinox.

• Moon phases

  Half the Moon is always lit. A phase is the Earth-facing slice.

• Two clocks

  Lunar month versus perigee/apogee (size, not phase). Super full moon needs both.

• Eclipse type

  Solar at new Moon, lunar at full Moon. Umbra / penumbra / annular.

• Why most months miss

  Orbital tilt. From one town a lunar eclipse is the more likely sight.

• Variation across Earth

  Latitudinal and temporal variation.

• Two tidal bulges

  Two bulges, not one. Earth’s spin carries a coast through both.

• Spring, neap, perigean

  Alignment at new and full; neap at quarters; perigean is alignment plus closest approach.

Sample questions

1. From a backyard in Rotorua the Sun rises in the east and sets in the west. Which interaction produces that daily switch between day and night?
2. Which statement correctly describes the noon record in New Zealand?
3. Put these observations from one clear day in Taupō into the order they happen.
4. Earth's axis is tilted at about 23.5 degrees. What stays the same, and what changes, as Earth travels once around the Sun?
5. This uses the wrong link. Which changes would fix it? Select all that apply.
6. Explain why January is warmer in Timaru. Use tilt and orbit, and say why distance is the wrong link.
7. Which prediction follows from the same tilt-and-orbit idea, without inventing a new mechanism?
8. What is the table actually evidence for?

Practise 92046 in Whetū

352 original exam-style questions in Whetū. These are practice papers, not official NZQA assessments.

• Day and night cycle · Day, night and the seasons
• Sunrise and sunset · Day, night and the seasons
• Globe tilt model · Day, night and the seasons
• Torch beam demonstration · Day, night and the seasons
• Shortest and longest day · Day, night and the seasons
• What an equinox means · Day, night and the seasons
• Hamilton daylight hours · Day, night and the seasons
• Wellington summer warmth · Day, night and the seasons
• Paddock warmth by season · Day, night and the seasons
• Fixed tilt, changing orbit · Day, night and the seasons
• Earth-Sun distance · Day, night and the seasons
• Distance claim debate · Day, night and the seasons