Final answer:
Seasons are the phenomenon determined by Earth's 23.5° axial tilt and orbit, leading to varying sunlight intensity and duration at different times of the year, creating distinct climate variations such as summer and winter.
Step-by-step explanation:
The phenomenon that is determined by the tilt of Earth's axis and its orbit around the Sun, with different parts of the planet tilting towards the Sun at different times of the year, is known as seasons. Earth's axis is tilted at about 23.5°, and this tilt is responsible for the varying intensity of sunlight received at different latitudes throughout the year.
During the month of June, the Northern Hemisphere tilts towards the Sun, leading to longer days and more direct sunlight, which we recognize as summer. Conversely, in December, the Southern Hemisphere tilts towards the Sun, causing summer there while the Northern Hemisphere experiences winter with shorter days and less direct sunlight. This tilt also affects the angle and duration of sunlight during the equinoxes in March and September, when both hemispheres receive about equal amounts of sunlight.
Earth's tilt is not completely fixed; it wobbles slightly between 22.1 and 24.5 degrees over a 41,000-year cycle known as obliquity. This tilt affects the level of seasonality, which refers to the distinct differences between summer and winter temperatures. A greater tilt increases seasonality, leading to hotter summers and colder winters, while a smaller tilt decreases it, resulting in milder seasons.