# Day, Night and Seasons Simulation

> A free 3D simulation for class: see why we have day and night and why seasons come from the Earth's tilt, not its distance from the Sun. Real dates and cities.

Source: https://olyclass.com/simulations/day-night-and-seasons/ · Updated 2026-11-01

This simulation shows the Earth exactly where it is on any date and time in 2026, lit by the Sun, with its axis always pointing the same way in space. Switch between the whole orbit and a close-up of the Earth, pick a city, and the panel shows that day's sunrise, sunset, hours of daylight and how high the Sun climbs at noon. It answers the two big questions in one place: why do we have day and night, and why do we have seasons?

## How to use it

- **Two views:** Orbit shows the Sun, the Earth's orbit and four smaller Earths at the equinoxes and solstices, so the class can see the axis never changes direction. Earth shows the planet up close with the equator, tropics, polar circles, the line between day and night, and a pin on your city.
- **Date and time:** drag the Date slider through the year and the Time slider through the day (the Time slider shows night and daylight for that place). Press play to run time by hours (watch day and night sweep round) or by days (watch the Earth go round the Sun).
- **Equinoxes and solstices:** the four yellow buttons jump to the exact 2026 moments, shown in the city's own time.
- **Places:** pick Hanoi, Ho Chi Minh City, Singapore, Sydney, New York, London, Reykjavik or Tromsø, or tap the Earth in Earth view to put the pin anywhere.
- **On a projector or touch board:** use the full screen button. Text, sliders and buttons grow so the back row can read them. Drag with a finger to turn, pinch to zoom, and press Space to play or pause.

## Why do we have day and night?

The Earth is a ball, and the Sun can light only the half facing it. The Earth spins once on its axis about every 24 hours, from west to east, so each place is carried into the light (sunrise), across the middle of the lit half (noon) and back into the dark (sunset). The Sun is not moving across the sky: we are turning under it.

In Earth view, the orange ring is the line between day and night. Play time by hours and watch your pin cross it twice a day. The small glowing dot is the one place where the Sun is straight overhead at that moment.

## Why do we have seasons?

The Earth's axis is tilted 23.44° from upright, and it keeps pointing at the same spot in space, near the North Star (Polaris), all year. As the Earth goes round the Sun:

- around 21 June the northern half leans toward the Sun: long days, a high noon Sun, summer in the north and winter in the south;
- around 21 December the northern half leans away: short days, a low Sun, winter in the north and summer in the south;
- at the equinoxes in March and September neither half leans toward the Sun, and day and night are close to 12 hours everywhere.

Two things make summer warmer. Days are longer, so the ground has more hours to warm up. And the Sun is higher, so its light arrives more directly. The panel's sunlight picture shows this: the same beam of light spreads over a bigger patch of ground when the Sun is low, so each square metre gets less energy.

**It is not distance.** The Earth is closest to the Sun in early January (147.1 million km) and farthest in early July (152.1 million km). If distance caused seasons, the whole world would have summer in January. Instead Australia has summer while Europe has winter.

| On the solstice | 21 June: daylight | 21 June: noon Sun | 22 December: daylight | 22 December: noon Sun |
|---|---|---|---|---|
| Singapore (1° N) | 12 h 12 min | 68° | 12 h 03 min | 65° |
| New York (41° N) | 15 h 06 min | 73° | 9 h 15 min | 26° |
| London (52° N) | 16 h 38 min | 62° | 7 h 50 min | 15° |
| Sydney (34° S) | 9 h 54 min | 33° | 14 h 25 min | 80° |
| Tromsø (70° N) | 24 h (midnight Sun) | 44° | 0 h (polar night) | below the horizon |

Near the equator the day stays close to 12 hours all year. Beyond the polar circles (66.56°) the Sun does not set at all around midsummer and does not rise around midwinter.

## Try this

1. Choose **London** and press **Dec solstice**: 7 h 50 min of daylight and a noon Sun only 15° high. The sunlight picture says each square metre gets about a quarter of the light of an overhead Sun.
2. Press **Jun solstice**: 16 h 38 min, noon Sun 62°. More than twice the daylight, and over three times the light on each square metre at noon.
3. Now choose **Sydney** and press the same two buttons. Everything flips: June is Sydney's winter.
4. Switch to **Orbit** and look at the four Earths. The axes are parallel. Only the Earth's position changes, so the hemisphere that leans toward the Sun changes.
5. Choose **Tromsø**, press **Jun solstice**, switch to **Earth** and play by hours: the pin never leaves the light.

## Teaching ideas

The simulation supports NGSS 5-ESS1-2 (patterns of day and night, shadows and the Sun's position through the year) and MS-ESS1-1 (models of the Earth-Sun system that explain day and night and the seasons).

1. **Warm-up (3 minutes):** ask "Why is it warmer in summer?" Write down every answer. Many students say "the Earth is closer to the Sun".
2. **Day and night (5 minutes):** Earth view, play by hours. Ask: "Is the Sun moving or are we?" "When it is noon here, where is it midnight?"
3. **Test the distance idea (5 minutes):** Orbit view, read the closest and farthest labels. Ask: "When are we closest? Is that summer here?" Compare a northern and a southern city.
4. **The real reason (10 minutes):** step through the four yellow buttons with your city. Students fill in a table of daylight hours and noon Sun height, then explain the pattern using the tilt.
5. **Review (10 minutes):** make a review game from this topic: the whole class plays on the same screen in teams, with your phone as the remote.

## Questions teachers ask

### Are the times and positions real?

Yes. The Earth's position comes from NASA JPL's orbital elements and its turning from the International Astronomical Union's model, so the right side of the Earth faces the Sun at the right moment. Sunrise and sunset use the Astronomical Almanac's formulas and match published tables to within a minute or two, including summer time in New York, London, Sydney and Tromsø.

### Why is the day on the equator 12 hours 7 minutes, not 12 hours?

Air bends sunlight, so we see the Sun a little before it really rises and a little after it sets, and sunrise counts from the top edge of the Sun, not its centre. Together that adds about 3½ minutes at each end of the day.

### Why does the Earth look so big next to its orbit?

In Orbit view the Earth is drawn about 1,750 times larger than it should be, or it would be smaller than a pixel. The orbit's shape, the Sun's position in it and the direction of the axis are all to scale.

### Does the axis really always point the same way?

Very nearly. It points close to Polaris all year, which is why the North Star stays put in the sky while the others turn. Over about 26,000 years the axis slowly circles round (precession), far too slowly to see in a year.

### Do I need to install anything or sign up?

No. It runs in the browser on a computer, tablet, phone or interactive board, and it is free. It needs 3D graphics (WebGL); without them the numbers and charts still work.

[Make a review game](https://olyclass.com/create?subject=science&grade=6&topic=Day%20and%20night,%20the%20Earth's%20tilt%20and%20why%20we%20have%20seasons)

## Credits

Earth and Sun maps: [Solar System Scope](https://www.solarsystemscope.com/textures/), CC BY 4.0, based on NASA data. The Earth's orbit: NASA JPL Keplerian elements. The Earth's rotation: the International Astronomical Union's model. Sunrise, sunset and the Sun's position: the Astronomical Almanac's formulas, with the standard −0.833° for sunrise and sunset, as NOAA uses. 2026 equinox and solstice times: US Naval Observatory.