Earth, Moon and Sun
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flagWhat you'll discover
- arrow_forwardExplain why we have day and night
- arrow_forwardConnect one orbit of the Sun to one year
- arrow_forwardShow how Earth’s 23.5° tilt creates the seasons
- arrow_forwardSpot the day–night line (terminator) on the 3D Earth
Day and night: Earth spins
The Sun never switches off — Earth just turns. Our planet spins once every 24 hours, so each place takes a turn facing the Sun (daytime) and facing away into space (night).
In the simulation you can see the terminator, the soft line between the bright day side and the dark night side. When it is midday in Nepal, it is the middle of the night in faraway places like Peru, on the opposite side of the globe.
A year: Earth orbits
While it spins, Earth is also racing around the Sun at about 107,000 km/h. One complete orbit takes 365.25 days — one year.
Watch the month badge in the simulation as Earth moves along its orbit. Notice that the orbit is almost a perfect circle, so our distance from the Sun barely changes during the year. That means distance is NOT the reason for summer and winter — the real reason is the tilt.
Seasons come from the tilt
Earth’s spin axis is tilted by 23.5 degrees, and it keeps pointing the same way in space all year, like a leaning spinning top. For part of the orbit the northern half leans toward the Sun — sunlight hits it more directly and days are longer, giving Nepal its hot summer.
Six months later the north leans away. Sunlight arrives at a low slant and spreads thin, days get short, and winter settles over the Himalaya. Turn on the axis line in the sim and watch this happen.
The Moon tags along
As Earth orbits the Sun, the Moon orbits Earth about once every 27.3 days, held by Earth’s gravity. It is our only natural satellite and our constant travelling companion.
Use the "Follow Earth" view to ride alongside our planet and watch the Moon loop around it while both of them sweep around the Sun. Three motions at once — spin, Moon orbit and Earth orbit — all happening right now while you read this.