Why We Have Seasons Experiment: A Globe and a Lamp

Here is the fact that makes this a why we have seasons experiment worth running carefully: Earth is closest to the Sun in early January, in the depth of the northern winter. On 3 January 2027 it will be 147.1 million kilometres away; on 5 July it will be 152.1 million. If distance caused seasons, January would be July. It does not, because seasons come from the 23.4-degree tilt of Earth’s axis and what that tilt does to the angle of incoming sunlight. The usual globe-and-lamp demo can accidentally teach the opposite, so this version includes the fix.

Key Takeaways

• You carry a tilted globe around a lamp to four positions while keeping the axis pointing the same absolute direction, then shine a torch on graph paper at different angles to measure what tilt actually does.
• The mechanism is the angle of sunlight, not the distance, and the graph paper makes that numerical rather than verbal.
• Best for ages 7 to 13. The arithmetic of the cosine effect suits 11 and up.
• The classic mistake, built into most versions of this demo: the tilted hemisphere looks nearer the bulb, which quietly confirms the wrong answer.
• Seasons are reversed in the southern hemisphere, and near the equator they are mostly wet and dry rather than hot and cold.

What You’ll Need for the Why We Have Seasons Experiment

Item	How much	Where to get it	If you don’t have it
Globe on a tilted axis	1	A school globe, ideally with the standard 23.4° mount	An orange with a skewer through it, marked with a felt pen
Bare bulb lamp	1, no shade	Desk lamp with the shade removed	A single candle is not a substitute; use any bare bulb
Torch with a defined beam	1	Home	A phone torch, taped into a card tube to narrow the beam
Graph paper	3 sheets, 5 mm squares	Stationery shop	Any paper with a ruled grid drawn on it
Protractor	1	Stationery drawer	A folded paper angle gauge at 30° and 60°
Stickers or a marker	2 small stickers	Home	Blobs of poster putty
Tape measure or ruler	1	Home	A piece of string with knots
A room you can darken	1	Home	Evening, curtains closed

Time: prep 10 min, experiment 30 min, cleanup 5 min Cost: everything is probably in your kitchen, assuming you can borrow a globe Mess level: low

Do the Experiment

Step 1 — Mark two cities at the same latitude, opposite hemispheres

Stick one marker on your own city, and a second on a city at a similar latitude in the other hemisphere. Buenos Aires at 34° south pairs neatly with Los Angeles or Casablanca at 34° north. These two stickers carry the whole lesson, because whatever happens to one will be happening in reverse to the other.

Step 2 — Fix the axis direction and keep it fixed

Put the lamp in the middle of a table and stand the globe a metre away. Now the critical instruction: as you carry the globe around the lamp, the axis must keep pointing at the same wall of the room the whole time. Earth’s axis does not swivel to follow the Sun. If you let the tilt rotate to always lean toward the bulb, you have built a model of nothing.

Step 3 — Visit the four positions

Move the globe a quarter turn at a time around the lamp, stopping at four stations. At one, the northern tip leans toward the lamp. A quarter turn later neither pole leans toward it. Then the southern tip leans toward it, then neutral again. These are the June solstice, September equinox, December solstice and March equinox.

Step 4 — At each station, measure the distance and read the daylight

Use the tape measure to check the distance from the bulb to each sticker. The difference is a couple of centimetres on a 1 metre baseline, or about 2%, which is close to the real 3.3% annual variation. Then spin the globe on its axis and watch how much of each sticker’s daily circle is in light versus shadow. That fraction is day length.

Step 5 — Now do the graph paper measurement

This is the step that fixes the demo. Hold the torch so its beam hits graph paper straight on, trace the lit patch and count the squares. Then tilt the paper to 30° and trace again, then 60°. Same torch, same power, bigger patch each time. At 60° the patch covers about twice the area, so each square receives half the energy.

Step 6 — Compare the two findings out loud

Distance changed by about 2%. The energy arriving per square centimetre changed by 50% or more just from angle. Ask your kid which of those could explain summer and winter. The answer is now theirs rather than yours.

What you should see: At the June station the whole Arctic region stays lit as you spin the globe, while the Antarctic stays dark; in December it reverses. Your northern sticker gets more than half its circle in light in June and less than half in December, and the southern sticker does the exact opposite on the same day. On the graph paper, expect the 60° patch to be roughly double the area of the straight-on patch.

What’s Actually Going On

Earth’s rotation axis is tilted 23.4 degrees from the perpendicular to its orbital plane, and that axis holds its direction in space as Earth goes round the Sun. NASA’s planetary fact sheet lists that obliquity, and it is the single number the whole phenomenon rests on. Because the axis holds still while Earth moves, there are six months when the northern hemisphere leans sunward and six when the southern does.

Leaning sunward does two things. First, the Sun climbs higher in the sky at midday, so sunlight strikes the ground closer to head-on. A beam of fixed width spreads over a smaller patch of ground when it arrives steeply, so each square metre receives more energy. That is the cosine effect your graph paper measured: light arriving at 60 degrees from vertical spreads over 1/cos(60°), which is exactly twice the area, halving the intensity. Second, the day is longer, so the heating lasts more hours. Both effects point the same way and they compound.

Now the distance question, properly. Earth’s orbit is slightly elliptical. The US Naval Observatory’s own explainer says it plainly: the distance variation “is too weak to cause the seasons, but it might have some influence over their severity.” The numbers back that up. Perihelion is 147.1 million km and aphelion 152.1 million, a 3.3% range in distance, which translates to roughly a 7% variation in the sunlight intensity reaching Earth. Compare that with the local change from angle and day length, which in temperate latitudes alters the energy received by a factor of two or three across the year. And the timing is simply wrong for the distance story: perihelion in 2027 falls on 3 January, twelve days after the December solstice.

Two more things worth saying, because most explanations leave them out. The seasons are reversed in the southern hemisphere: when Santiago and Buenos Aires are in high summer in January, Madrid and Chicago are in winter. And near the equator the tilt barely changes the midday Sun’s height or the day length at all, so there is no thermal summer and winter. Equatorial regions instead have wet and dry seasons, driven by the annual migration of the tropical rain belt. Telling a child that “December is winter” is wrong for most of the planet’s people.

How to Explain It to Your Kid

Ages 5–8: the torch on the floor

Give them a torch and let them shine it straight down on the carpet, then from a low angle. Ask which bright patch is smaller and brighter. Then tell them that in summer the Sun shines on them from high up, like the first one, and in winter from low down, like the second. No mention of distance at all.

Ages 9–12: same light, bigger patch

Use the graph paper result. Same torch, same amount of light, but spread over twice as many squares. Then give them the two numbers side by side: distance varies by 3%, energy per square metre varies by much more than that from angle alone. Let them conclude which wins.

Ages 13+: cosine, insolation and the eccentricity question

Give them the actual relationship: the energy per unit area goes as the cosine of the angle from vertical, so solar elevation controls intensity. Then set the real question: given that Earth is 3.3% closer to the Sun in January, why is the southern summer not noticeably hotter than the northern one? The answer involves land and ocean distribution and the heat capacity of water, and it is a genuinely open-ended discussion.

The question to ask: “It is the middle of July. Is Earth close to the Sun or far from it right now, and what season is it in Chile?”

Why Teaching This Early Pays Off

The distance explanation for the seasons is one of the most durable wrong ideas in all of science education. Ronald and Virginia Atwood surveyed trainee primary teachers and found that a substantial share held it, which tells you it survives school, survives a degree, and survives teaching the topic. It is not a child’s error; it is an everyone error.

Vosniadou and Brewer’s research on children’s mental models of the Earth explains why it is so sticky. Children build internally consistent models and then patch them when challenged rather than rebuilding, so being told “it’s the tilt” once simply gets absorbed into the old picture as a detail. What dislodges a model is evidence it cannot accommodate, which is exactly what the graph paper and the tape measure provide: two numbers, side by side, where the wrong explanation predicts the wrong one is bigger.

The honest limit: one afternoon will not inoculate anyone permanently, and nothing here claims an effect on grades. But a child who has physically measured the cosine effect has something better than a remembered sentence. They have a reason.

Before You Start: What Parents Should Know

Best age	7 and up. The globe walk works from about 7; the graph-paper measurement and the cosine idea land properly from about 11.
Supervision	Adult handles the lamp. An unshaded bulb is hot, and a bare bulb on a table near a moving globe is the one practical risk.
Real hazards	Hot bulb; a trailing lamp cable in a darkened room. Tape the cable down before you turn the lights off.
Don’t	Do not simplify by letting the globe’s tilt swing toward the lamp to “make it clearer.” That change teaches the distance misconception, which is the thing this experiment exists to destroy.

When It Doesn’t Work

• The tilt keeps rotating as you walk. The commonest failure, and fatal to the model. Pick a fixed object on one wall and insist the North Pole points at it at all four stations. Say it out loud each time.
• You cannot see any difference in the lit area on the globe. The lamp is too far away or the room is not dark enough. Bring the lamp to within a metre, remove the shade, and turn off everything else.
• The graph paper result is unconvincing. The beam is too wide or too fuzzy. Tape the torch inside a cardboard tube so the beam edge is sharp, and trace the patch before you move anything.
• Your kid still says “but it’s closer in summer.” Expected, and not a failure of the lesson. Go back to the tape measure and have them write down both numbers themselves. A number they recorded is harder to argue with than one you quoted.
• The globe has no tilt, or a wonky one. Many cheap globes are mounted at odd angles. Check with a protractor against the table, and if it is wrong, build the orange-and-skewer version where you set 23.4° yourself.

Take It Further

Measure your own Sun angle across months. Stand a vertical stick in the ground and measure its shadow length at local noon once a fortnight. The ratio of stick height to shadow length gives the Sun’s elevation by trigonometry. Over a few months you will see the angle swing, which is the same effect the torch demonstrated, measured on the real Sun. It pairs directly with building a sundial that actually keeps time.

Track day length instead. Record sunrise and sunset times weekly and plot daylight hours against date. The curve is a sinusoid, steepest at the equinoxes and flat near the solstices, and understanding why it flattens is the next concept up. Carry that into tracking sunrise for a month to find the solstice, and connect the energy-absorption half of the story through the black cup and white cup albedo experiment.

What to Watch For Over the Next 3 Months

• Week 4: They correct someone, politely or otherwise, who says Earth is closer to the Sun in summer. Correcting an adult means the model has replaced the old one rather than sitting beside it.
• Month 2: They notice their own shadow is shorter at midday than it was months ago, and connect it to the torch on the carpet.
• Month 3: They ask what happens at the poles, or why Australia has Christmas in summer. Both are the right next questions and both have satisfying answers.

Frequently Asked Questions

So the distance to the Sun has no effect at all?

It has a small one. The 3.3% variation in distance produces roughly a 7% variation in the sunlight reaching the top of the atmosphere, which may slightly affect how severe seasons are in each hemisphere. It cannot cause them, because both hemispheres are at the same distance at the same time and they have opposite seasons.

Why is the hottest weather weeks after the summer solstice?

Thermal lag. The solstice is the peak of incoming energy, but land and especially ocean take weeks to warm up, so peak temperature trails peak sunlight by roughly four to six weeks in most places. The same lag puts the coldest weather after the winter solstice.

What about countries on the equator?

They get very little thermal seasonality, because the midday Sun stays high and the day stays close to twelve hours all year. What they do have is a wet and a dry season, set by the annual north-south migration of the tropical rain belt rather than by temperature.

Do we need a proper globe?

No. An orange with a bamboo skewer through it works well, and has one advantage: you set the tilt yourself with a protractor, which makes the 23.4 degrees a deliberate choice rather than an invisible feature of the toy.

Why is the southern hemisphere summer not hotter, given the closer Sun?

Because the southern hemisphere is mostly ocean, and water has a very high heat capacity, so it warms and cools far less than land for the same energy input. Earth’s unequal land distribution offsets the orbital effect. This is a real research-grade answer and worth giving honestly.

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About the author

Ricky Flores is the founder of HiWave Makers and an electrical engineer with 15+ years of experience building consumer technology at Apple, Samsung, and Texas Instruments. He writes about how kids learn to build, think, and create in a tech-saturated world. Read more at hiwavemakers.com.

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Sources

1. NASA Space Place. “What Causes the Seasons?” NASA Science. https://spaceplace.nasa.gov/seasons/en/
2. US Naval Observatory, Astronomical Applications Department. “The Seasons and the Earth’s Orbit.” https://aa.usno.navy.mil/faq/seasons_orbit
3. US Naval Observatory. “Earth’s Seasons and Apsides: Equinoxes, Solstices, Perihelion, and Aphelion.” https://aa.usno.navy.mil/data/Earth_Seasons
4. NASA Space Science Data Coordinated Archive. “Planetary Fact Sheet (Metric).” https://nssdc.gsfc.nasa.gov/planetary/factsheet/
5. Atwood, R. K., & Atwood, V. A. (1996). “Preservice elementary teachers’ conceptions of the causes of seasons.” Journal of Research in Science Teaching, 33(5), 553–563. https://doi.org/10.1002/(SICI)1098-2736(199605)33:5<553::AID-TEA6>3.0.CO;2-Q
6. Vosniadou, S., & Brewer, W. F. (1992). “Mental models of the earth: A study of conceptual change in childhood.” Cognitive Psychology, 24(4), 535–585. https://doi.org/10.1016/0010-0285(92)90018-W
7. National Research Council. (2012). A Framework for K-12 Science Education. National Academies Press. https://doi.org/10.17226/13165