Day/Night Earth Simulator
See the real-time boundary between day and night on Earth. Change the date and time to explore how axial tilt causes seasons and shifts the daylight pattern throughout the year.
Solar Information
Click on the globe to see
sunrise and sunset times
Drag to rotate the globe. Click any point to see sunrise/sunset times for that location.
Why Seasons Happen
Axial Tilt
Earth spins on an axis tilted 23.5 degrees from vertical. This tilt means different hemispheres receive more direct sunlight at different times of year, creating the seasons we experience.
Solstices
At the June solstice, the North Pole is tilted toward the Sun, giving the Northern Hemisphere its longest day. At the December solstice, the South Pole tilts toward the Sun instead.
Equinoxes
Twice a year, around March 20 and September 22, Earth's axis is perpendicular to the Sun. Day and night are nearly equal (12 hours each) everywhere on the planet.
Solar Declination
Declination is the angle between the Sun and Earth's equatorial plane. It ranges from +23.5 degrees at the June solstice (sun directly over the Tropic of Cancer) to -23.5 degrees at the December solstice (sun over the Tropic of Capricorn).
The Terminator
The curved line dividing day from night on Earth is called the terminator. Its tilt relative to the poles changes with the season, causing polar regions to experience continuous daylight or night for months at a time.
Key Concepts to Explore
Polar Day and Night
Jump to the June solstice and click near the poles. Notice that at high northern latitudes, there is no sunrise or sunset. The sun is above the horizon all day. The same happens at southern polar regions in December.
Daylight Duration at Different Latitudes
Click on different latitudes (near the equator vs. mid-latitudes vs. polar regions) on the same date. Compare how daylight hours vary with latitude and change throughout the year.
The Terminator at Equinoxes
Set the date to the spring or autumn equinox. The terminator runs straight through both poles, and every location on Earth has almost exactly 12 hours of daylight.
Earth's Rotation
Use the time slider to move through the hours of a day. Watch how the day/night boundary sweeps westward across Earth's surface as the planet rotates eastward at about 15 degrees per hour.
