Axis stays parallel
The dotted rotation axis keeps the same direction as Earth moves around the Sun. That fixed tilt is the key.
Learning Mission
Interactive Seasons Simulator
Drag Earth around the Sun and watch how a fixed tilted axis changes sunlight, day length, solstices, equinoxes, and seasons.
Big idea: Seasons happen because Earth stays tilted as it orbits the Sun. Distance from the Sun is not the main cause of seasons.
June solstice
JuneSeptemberDecemberMarch
You can also drag Earth directly around the Sun.
23.5 deg
Try 0 deg. Without tilt, both hemispheres receive similar seasonal sunlight.
0 deg
This spins the continents and the rotation arrow. It does not change the season.
Jump to a key date
Show or hide layers
NorthSummer
SouthWinter
Sun angleHigh in north
Day lengthLonger north
Northern summerThe north end of Earth's axis leans toward the Sun, so the Northern Hemisphere gets more direct light and longer days.
Fixed tilt + orbit = changing sunlightEarth's axis stays pointed in nearly the same direction in space while Earth travels around the Sun.
What to notice
Direct light changes
The hemisphere leaning toward the Sun receives more direct rays and usually has longer daylight.
Equinox balance
Near an equinox, neither hemisphere leans strongly toward the Sun, so day and night are more balanced.