The Earth has seasons due to the inclination of its rotation axis compared to its orbital plane around the Sun. This inclination causes variations in sunlight at different times of the year, thus causing the changes in seasons.
The tilt of Earth's rotation axis is a key element explaining the phenomenon of seasons on our planet. The Earth's rotation axis is tilted relative to the plane of its orbit around the Sun. This tilt is about 23.5 degrees relative to the perpendicular to the plane of the ecliptic, the plane of Earth's orbit around the Sun. This characteristic remains constant throughout the year.
The tilt of Earth's axis is the reason why the Sun's rays hit the Earth differently at different times of the year. When the northern hemisphere is tilted towards the Sun, we have summer in that part of the Earth. Conversely, when the southern hemisphere is tilted towards the Sun, it is summer in the southern hemisphere and winter in the northern hemisphere.
This tilt of Earth's axis is responsible for changes in the length of day and night throughout the seasons, as well as temperature variations. It also creates differences in brightness and thermal intensity that are the origin of the seasons we observe on Earth.
The Earth revolves around the Sun in an elliptical trajectory. This revolution lasts about 365.25 days, which corresponds to one year. The distance between the Earth and the Sun varies during this revolution, with a point closest called perihelion and a point farthest called aphelion. The perihelion usually occurs around January 3, while the aphelion occurs around July 4. This variation in distance is not the main cause of seasons on Earth, but it has a slight influence.
Solstices and equinoxes are important celestial events that mark the changing of seasons on Earth. Solstices occur twice a year, in June and December. The summer solstice, which occurs in June in the northern hemisphere and in December in the southern hemisphere, marks the longest day of the year. The winter solstice, on the other hand, occurs in December in the northern hemisphere and in June in the southern hemisphere, marking the shortest day of the year.
Equinoxes also occur twice a year, in March and September. The spring equinox, which occurs in March, marks the beginning of spring in the northern hemisphere and fall in the southern hemisphere. The autumn equinox, which occurs in September, marks the beginning of fall in the northern hemisphere and spring in the southern hemisphere.
These phenomena are due to the tilt of Earth's axis in relation to its orbit around the Sun. When Earth reaches a solstice, one region of the planet is tilted towards the Sun, resulting in longer days and higher temperatures. On the other hand, when it reaches an equinox, the Sun's rays fall equally on both hemispheres, resulting in equal length days and nights.
These variations in Earth's tilt and position relative to the Sun are the cause of the seasons we observe on our planet.
The equator is the only region on Earth where seasons are virtually nonexistent. Days and nights last about 12 hours year-round, and sunlight exposure hardly varies throughout the year.
The Earth is closest to the Sun at the beginning of January (at perihelion) and farthest away at the beginning of July (at aphelion). Surprisingly, these variations have very little direct impact on the seasons, which mainly depend on the tilt of the Earth's axis.
Around the Arctic or Antarctic Circle, there are periods lasting several weeks during which the Sun never fully sets (the midnight sun) or never fully rises (polar night). These phenomena are directly caused by the tilt of the Earth's axis.
The tilt of the Earth's rotation axis is currently about 23.5°, but this figure is not constant: it slowly oscillates between 22.1° and 24.5° over a period of approximately 41,000 years. This influences the intensity of the seasons on Earth in the very long term!
The seasons are inverted between the two hemispheres because the Earth is tilted on its axis. When the northern hemisphere is tilted toward the Sun and receives more direct light, it is summer, while the southern hemisphere is tilted away, which corresponds to winter, and vice versa.
The equinox corresponds to the moment when the Sun is exactly above the Earth's equator. As a result, the duration of day and night is nearly equal everywhere on Earth. This occurs twice a year, at the beginning of spring and at the beginning of autumn.
Equatorial regions receive a relatively constant solar intensity throughout the year. The angle of the sun's rays varies little, which means that there are no significant fluctuations in seasonal temperatures as seen at higher latitudes.
The areas near the poles, known as polar regions, experience periods during which the Sun does not set (the midnight sun phenomenon) or does not rise (polar night), due to the tilt of the Earth and their very high latitude.
No, the distance from the Earth to the Sun has very little direct impact on the seasons. The main cause is actually the tilt of the Earth's axis, which causes a variation in light intensity depending on the regions and the times of the year.
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