The changing of seasons on Earth is primarily caused by two key factors: the tilt of the Earth’s axis and its orbit around the Sun. The tilt of the Earth’s axis plays a significant role in determining the intensity and duration of sunlight received in different regions throughout the year.
Here’s a simplified explanation of how the seasons occur:
- Earth’s Tilt: The Earth is tilted on its axis by about 23.5 degrees relative to its orbit around the Sun. This tilt remains relatively constant throughout the year. It means that as the Earth orbits the Sun, different parts of the planet receive varying amounts of sunlight at different times.
- Summer Solstice: During the summer solstice, which occurs around June 21 in the Northern Hemisphere, the North Pole is tilted towards the Sun. This tilt results in the Northern Hemisphere receiving more direct sunlight, causing longer daylight hours, more intense solar radiation, and warmer temperatures. It marks the beginning of summer in the Northern Hemisphere.
- Winter Solstice: Conversely, during the winter solstice, which occurs around December 21 in the Northern Hemisphere, the North Pole is tilted away from the Sun. This tilt leads to the Northern Hemisphere receiving less direct sunlight, resulting in shorter daylight hours, less intense solar radiation, and cooler temperatures. It marks the beginning of winter in the Northern Hemisphere.
- Equinoxes: In between the solstices, there are two equinoxes. The vernal equinox occurs around March 21, and the autumnal equinox occurs around September 21. During these times, neither pole is tilted directly towards or away from the Sun. As a result, the daylight hours and the intensity of sunlight are relatively equal in both the Northern and Southern Hemispheres. These points mark the transitions from winter to spring and from summer to fall.
It’s important to note that the timing of the seasons is reversed in the Southern Hemisphere. When it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere, and vice versa. The tilt of the Earth’s axis causes the Sun’s rays to strike different parts of the planet at varying angles, resulting in the changing seasons throughout the year.