In summer, Earth is actually further from the Sun than in winter. So why is summer hot? The answer might surprise you.
Questions from Lessons 1, 2, and earlier topics — all mixed up. Let's see what's stuck.
Before we go any further — commit to your answer. No changing your mind after! Pick the reason you think is correct.
The most common wrong answer is "closer to the Sun" — and it's completely understandable. It seems logical! But here's the proof it's wrong: when it's summer in the Northern Hemisphere, it's winter in the Southern Hemisphere — and they're the same distance from the Sun.
The real cause is Earth's 23.5° axial tilt. This tilt means that during summer, your part of Earth is tilted towards the Sun. This does two things: sunlight hits the ground at a more direct angle (concentrating energy), and days are longer (more hours of heating). In winter, you're tilted away — sunlight hits at a shallow angle and days are shorter.
Fun fact: Earth is actually closest to the Sun in January (winter for the Northern Hemisphere)! Distance really doesn't cause seasons.
Use the controls to explore how Earth's tilt creates seasons as it orbits the Sun. Try turning the tilt to zero — what happens to the seasons?
When sunlight hits the ground straight-on (directly), the energy is concentrated in a small area — it gets hot. When it hits at a shallow angle, the same energy is spread over a larger area — it's weaker.
Tilt doesn't just change the angle — it also changes how many hours of daylight you get. In summer, the Sun is above the horizon for much longer, giving the ground more time to heat up.
You can model axial tilt right now with just a ball (or orange) and your phone torch. Follow the steps below.
Find a ball, orange, or any round object. This is Earth. Use your phone torch or a desk lamp as the Sun. Draw a line around the middle — that's the equator.
Hold the ball upright (no tilt) with the torch shining straight at it from about 30cm away. Notice how the light hits both hemispheres equally.
Now tilt the ball about 23° (roughly a quarter of the way to sideways). Keep the torch in the same position. The top half is now tilted towards the torch.
Without changing the tilt direction, move the ball to the other side of the torch. Now the top half is tilted away.
The tilt stays pointing the same direction in space as Earth orbits. It's not the tilt that changes — it's Earth's position in its orbit. Sometimes your hemisphere is tilted towards the Sun (summer), sometimes away (winter). The tilt itself never changes.
Thinking across all three lessons in this series — how does everything connect?