Why Earth has seasons — Earth science, 7–10 years
Earth’s axis is tilted as Earth travels around the Sun. That tilt changes how directly sunlight reaches each half of Earth and how long daylight lasts, creating the seasons.
Tilt makes seasons
Earth spins around an imaginary line from pole to pole, called its axis. This axis leans about 23.5 degrees instead of standing straight up. As Earth travels around the Sun, each hemisphere takes turns leaning towards the Sun, bringing stronger sunlight and longer days, or away from it, bringing weaker sunlight and shorter days.
What problem does this solve?
A tempting explanation is that summer happens when Earth is closer to the Sun. That cannot be the main cause, because northern and southern summers happen at opposite times. Earth’s tilt explains both the opposite seasons and the changing length of daylight, which helps us understand why temperatures follow a yearly pattern.
Comparing two days
Imagine a place in the Northern Hemisphere where daylight lasts 8 hours in winter and 16 hours in summer. In winter, sunlight arrives at a lower angle and is spread over more ground, while the night is longer. In summer, the higher Sun and 16 hours of light warm the ground for longer, so the average temperature is usually higher.
The distance mistake
It feels sensible that summer must mean Earth is nearer the hot Sun, like standing closer to a heater. But Earth’s orbit is nearly circular, and the two hemispheres have opposite seasons at the same time. The tilt and the angle and length of sunlight matter much more than the small change in distance.
Planning with seasons
Farmers choose crops and planting times partly by the amount of sunlight and warmth each season brings. Architects and households plan for summer shade, winter heating, and changing daylight. Remember that seasons are not identical everywhere: when it is summer north of the equator, it is winter south of it.
Keep exploring
Other languages
Loading MyLeoNes™…