Final answer:
The diurnal cycle of insolation changes is caused by the Earth's rotation on its axis, which exposes different parts of the Earth to sunlight throughout the 24-hour day.
Step-by-step explanation:
The changes in insolation over the course of the diurnal cycle are caused by the Earth's rotation on its axis. As Earth rotates every 24 hours, different parts of the world are alternately exposed to sunlight, leading to day and night. This rotation of the Earth accounts for the daily variation in sunlight that any particular location on the planet experiences.
The idea that the Earth's tilt and its revolution around the Sun cause the seasons is also valid. However, that process influences the annual cycle of the seasons, not the diurnal (daily) cycle of insolation. Because the Earth is tilted at an angle of 23.5°, as it orbits the Sun, different latitudes receive varying amounts of solar energy at different times of the year, leading to seasonal changes, which is more relevant to the varying angle and duration of insolation over the course of a year rather than the diurnal cycle.