Day, Night and Seasons: Discover Earth’s Tilt
Understand that Earth spins to give day and night while its tilted axis, always pointing the same way, changes the angle of sunlight and the length of day through the year, producing the seasons.
Before you try
What if Earth had no tilt at all? Would we still get summer and winter?
Try it out
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What happened?
Move a control to see what changes and why.
The orbit is drawn as a circle and the air is ignored. Real daylight lasts a little longer than the geometry suggests, because the atmosphere bends sunlight.
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Try these ideas
- Set the tilt to 0 degrees and watch the daylight graph flatten to twelve hours.
- Set latitude to 70 north and find a date with 24 hours of daylight.
- Jump to the June solstice and compare the north and south seasons.
Why it works
Earth spins once a day, so half of it faces the Sun and half is in darkness. That gives day and night. The seasons come from something else: the axis Earth spins around is tilted by about 23.5 degrees, and it keeps pointing the same way all year. For half the year the northern half leans toward the Sun, which means longer days and sunlight arriving at a steeper, stronger angle. Six months later the same is true in the south.
Distance is not the reason. Earth is actually closest to the Sun in early January, in the middle of northern winter. In this simulator you can change the tilt, the day of the year and your latitude, and see the lit half, the daylight hours and the season. Set the tilt to zero and the seasons vanish completely. The declination formula used here is a simplified one, with a circular orbit.
Check your understanding
Question 1 of 4
What causes the seasons?
When it is summer in India, what season is it in Australia?
What happens at an equinox?
Why does the Sun not set for weeks at the North Pole in June?
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Look up sunrise and sunset times in June and December and compare.
- Use a torch and a tilted globe or ball to model the seasons at home.
- Ask why the hottest month is not the one with the longest day.