Final answer:
The seasons on Earth are primarily caused by the 23.5° tilt of Earth's axis and Earth's revolution around the Sun. These factors lead to varying amounts of sunlight hitting different parts of Earth during the year. The common belief that Earth's distance from the Sun causes seasons is incorrect, as this distance only varies slightly and does not significantly affect temperature.
Step-by-step explanation:
What Causes the Seasons?
The two primary factors most directly responsible for causing the seasons on Earth as observed from your backyard are the 23.5° tilt of Earth's axis and the revolution of Earth around the Sun. Throughout the year, the tilt of Earth's axis remains constant, pointing in the same direction.
This axial tilt causes different parts of Earth to receive different amounts of sunlight at different times of the year. When the Northern Hemisphere is tilted toward the Sun during June, it receives more direct sunlight, leading to longer days and warmer temperatures, which is why we experience summer. Conversely, when it is tilted away from the Sun during December, the Southern Hemisphere receives more direct sunlight, while the Northern Hemisphere experiences winter.
The idea that the varying distance from the Sun causes seasons is countered by the fact that Earth's orbit only changes our distance from the Sun by about 3%, which is insufficient to cause significant temperature variations. Moreover, when Earth is closest to the Sun in January, the Northern Hemisphere is in winter, not summer.
Observable evidence from the surface of Earth, such as the varying altitude of the Sun in the sky and changing lengths of day and night over the year, also support the understanding that the tilt of Earth's axis and its orbit cause the seasons, rather than the distance from the Sun.