By Ethan Shaw
Updated Mar 24, 2022
The Sun is the central anchor of our solar system, holding nine planets, including Earth, in its gravitational embrace. Earth completes one orbit around the Sun in approximately 365.25 days. Our Moon, captured by Earth's gravity, orbits in 27.32 days and reflects sunlight in a predictable pattern that creates the familiar lunar phases.
During its orbital cycle, the Moon rotates once on its axis, presenting the same face to Earth. The appearance of the Moon changes depending on its position relative to Earth and the Sun. When the Earth lies between the Moon and the Sun, the Moon is fully illuminated—a full moon. When the Moon sits between Earth and the Sun, it is in shadow—a new moon. In the intervals between these extremes, the Moon shows a waxing crescent, first quarter, waxing gibbous, waning gibbous, third quarter, and waning crescent, completing a full cycle in about 29.5 days.
Earth orbits the Sun along the ecliptic plane, but its axis is tilted roughly 23.5° relative to the perpendicular of that plane. This tilt, which remains fixed in space (aligned with Polaris), causes one hemisphere to lean toward the Sun while the other leans away, resulting in varying solar radiation throughout the year.
At the equinoxes, the Sun’s rays strike the equator perpendicularly, giving all regions 12 hours of daylight and 12 hours of night. During the Northern Hemisphere’s summer, the hemisphere tilts toward the Sun, receiving more direct sunlight and higher temperatures, while the Southern Hemisphere experiences cooler, lower‑angle sunlight. The opposite occurs during Northern Hemisphere winter. This axial tilt explains the classic four‑season cycle—summer, winter, spring, and autumn—especially in higher latitudes.
Not all regions follow the four‑season model. In many tropical and subtropical areas, precipitation is the primary seasonal driver, creating distinct wet and dry seasons with substantial rainfall differences.
