Using a diagram, explain why the tilt of the Earth's axis relative to the Earth's orbit causes the seasons as we orbit the Sun.

The journey that our planet takes around the Sun is what we refer to as Earth's orbit. It's an established fact that Earth's path is not a perfect circle but an ellipse, slightly elongated. This elliptical shape means that at different times during its year-long orbit, Earth is various distances from the Sun. However, the distance from the Sun does not cause seasons; it's actually Earth's constant axial tilt of about 23.5 degrees in relation to the plane of its orbit that's the key player.

As Earth travels on its circumnavigation of the Sun, the orientation of its tilt remains fixed in space, pointing towards the North Star, Polaris. This means that throughout the year, as Earth orbits, different parts of the planet are tilted towards or away from the Sun at different times. When the Northern Hemisphere is angled towards the Sun, it experiences more direct sunlight and thus, warmer temperatures, which we characterize as summer. Conversely, when it's angled away, this hemisphere experiences winter due to the indirect and sparse solar energy.

Sunlight distribution is integral to understanding why different parts of Earth experience varying climates and weather patterns. Essentially, it's all about how the Sun's rays hit the Earth. Because the Earth is a three-dimensional sphere, sunlight doesn't fall evenly across its surface. This uneven distribution of sunlight is largely due to Earth's axial tilt.

Imagine the Sun as a lamp and Earth as a tilted basketball undergoing a spin; the area of the basketball that's inclined towards the lamp gets bathed in concentrated light, while the area tilted away receives a more diffuse, spread-out light. The same goes for Earth: when the Northern Hemisphere tilts towards the Sun, sunlight strikes this region more directly, delivering energy intensely over a smaller area, resulting in warmer conditions. In contrast, the Southern Hemisphere, being tilted away, gets the sunlight at a slimmer angle, dispersing the energy over a larger area, which leads to cooler temperatures.

Thus, the tilt causes varying angles at which sunlight hits Earth, creating the change in intensity of light and, correspondingly, the seasons. Notably, on a global scale, the difference in sunlight distribution is why we have tropical regions that receive nearly vertical sunlight year-round and polar regions that get low-angle sunlight, leading to colder climates.

Solstices and equinoxes are the significant milestones in Earth's orbit that mark the change of seasons. They correspond to specific positions in its orbit regarding the degree of Earth's axial tilt toward or away from the Sun.

At the solstices, the tilt of Earth's axis is at its maximum toward or away from the Sun. The summer solstice occurs when one hemisphere is tilted the most towards the Sun and experiences the longest day of the year, followed by the onset of summer. Contrastingly, the winter solstice takes place when the same hemisphere is tilted farthest away from the Sun, bringing about the shortest day, followed by winter.

The equinoxes, on the other hand, occur when the tilt of Earth's axis is neither towards nor away from the Sun, resulting in nearly equal day and night lengths across the globe. During these times, both hemispheres receive roughly equal amounts of sunlight. The vernal equinox, marking the start of spring in the Northern Hemisphere, and the autumnal equinox, signaling the beginning of autumn, are transitional periods between the extremes of the solstices.

Understanding the solstices and equinoxes, and their relationship with Earth's axial tilt, clarifies the timing of seasons and contributes to our chronology of the year. Moreover, these events have historically helped societies structure calendars and organize agricultural activities.