... like I'm 5 years old
Seasons on Earth occur because our planet doesn't stand straight up and down as it orbits the Sun. Instead, it tilts to one side, at an angle of about 23.5 degrees. This means that as the Earth goes around the Sun, sometimes the North Pole is pointing towards the Sun (which is summer in the Northern Hemisphere) and sometimes it's pointing away (which is winter). In between, we have spring and autumn, when the tilt is neither towards nor away from the Sun. This tilt and the resulting sunlight distribution are what cause the seasons.
Imagine you're holding a flashlight directly above a basketball. The light is spread evenly over the ball. Now tilt the basketball - some parts get more light, while others get less. That's how Earth's tilt affects the seasons.
... like I'm in College
Let's delve deeper into the science behind seasons. The Earth's tilt, or axial tilt, plays a crucial role in the change of seasons. As stated earlier, the Earth is tilted at approximately 23.5 degrees relative to its orbit around the Sun. This tilt remains constant as the Earth orbits the Sun, meaning that throughout the year, different parts of the Earth receive varying amounts of sunlight.
In addition, the Earth's elliptical orbit means that it is not always the same distance from the Sun. However, contrary to common belief, the Earth is actually closer to the Sun during the Northern Hemisphere's winter, and farther during the summer. But this distance has less effect on the seasons than the axial tilt. The angle at which sunlight hits the Earth is the major factor that influences the seasons.
Imagine your Lego set. Let's use a Lego sun at the center, and a Lego Earth on a circular track around it. The Lego Earth is a rectangle standing on one of its narrow sides, and it's tilted. As you move the Lego Earth around the Lego Sun, keep it tilted in the same direction.
When the top of your Lego Earth is leaning towards the Lego Sun, that's like the Northern Hemisphere's summer because it gets a lot of sunlight. When it leans away, it's like winter, with less sunlight. The times in between, when the Lego Earth isn't leaning towards or away from the Lego Sun, represent spring and autumn.
By using the Lego Earth and Sun, you can visually represent how the Earth's tilt on its axis as it orbits the Sun results in varying amounts of sunlight on different parts of the world, creating the seasons.
... like I'm an expert
The axial tilt and its relationship with the Earth's orbit around the Sun is the basic principle behind the change in seasons. But there are more factors that influence this phenomenon. The Earth's axial precession, a slow, top-like wobble that takes about 26,000 years to complete, also contributes to seasonal shifts over long periods.
Moreover, the orbital eccentricity of Earth varies over time, which means the shape of our orbit changes from being less to more elliptical in a cycle of about 100,000 years. This variation, known as Milankovitch cycles, can affect the severity of seasons and is considered a key factor in the Earth's long-term climate change.