Why Do We Have Seasons?

Earth’s 23.5° tilt is the secret — not distance from the Sun.

An interactive Three.js visualization showing how Earth’s axial tilt causes seasons. Watch how sunlight hits the Northern and Southern hemispheres differently as you switch between summer, autumn, winter, and spring.

Seasons aren’t caused by Earth’s distance from the Sun. The secret is Earth’s 23.5° axial tilt. As Earth orbits, different hemispheres tilt toward the Sun, receiving more direct sunlight — and that’s what makes it warm.

Use the buttons below to jump between seasons and see how the sun’s rays strike Earth differently. The golden rays show parallel sunlight beams; the markers on Earth’s surface show where light is concentrated (direct, small footprint = hot) versus spread out (angled, large footprint = cool).

SUMMER

Northern Hemisphere

Direct (hot) Angled (cool)

How It Works

Direct sunlight concentrates energy in a small area — that’s summer. Angled sunlight spreads the same energy over a larger area — that’s winter. It’s like a flashlight: shine it straight down and you get a bright spot; tilt it and the light spreads out and dims.

A mind-blowing fact: Earth is actually 3 million miles closer to the Sun during Northern Hemisphere winter! But 3 million out of 93 million is only ~3%. The angle of sunlight matters far more than distance.

For a deeper exploration with orbits, speed controls, and camera modes, see the full Earth & Sun Explorer.