As autumn deepens, many people wonder when the shorter days will begin to lengthen again. This common experience of changing daylight hours marks Earth’s annual journey around the Sun. Understanding this progression helps clarify the astronomical event that ushers in the return of more daylight.
The Winter Solstice: The Turning Point
The winter solstice marks the Northern Hemisphere’s shortest period of daylight. This astronomical event typically occurs around December 21st or 22nd. On this date, the Sun reaches its southernmost point in the sky, resulting in the fewest hours of sunlight.
Immediately following the winter solstice, the duration of daylight begins to gradually increase each day. This turning point signals the Northern Hemisphere’s return to longer days. For many cultures, the winter solstice has symbolized rebirth and the promise of returning light.
Why Days Get Longer After the Solstice
The changing length of days throughout the year is due to Earth’s axial tilt. Our planet is tilted on its axis by approximately 23.5 degrees relative to its orbital plane around the Sun. This consistent tilt means that as Earth revolves, different parts receive varying amounts of direct sunlight.
During the Northern Hemisphere’s winter, it is tilted away from the Sun, causing sunlight to strike at an oblique angle for fewer hours each day. After the winter solstice, as Earth continues its elliptical path, the Northern Hemisphere slowly begins to tilt back towards the Sun. This gradual shift results in sunlight hitting it more directly and for longer durations daily. While Earth’s elliptical orbit causes slight speed variations, the axial tilt is the predominant factor driving changes in daylight hours and seasons.
Understanding Earliest Sunset and Latest Sunrise
A common observation that can seem to contradict the winter solstice as the turning point for daylight is the timing of sunsets and sunrises. While the winter solstice marks the shortest day, the earliest sunset actually occurs a few weeks before the solstice for many Northern Hemisphere locations. Similarly, the latest sunrise typically takes place a few weeks after the solstice.
This phenomenon is due to the combined effects of Earth’s axial tilt and its elliptical orbit, which influence the apparent speed of the Sun across the sky. Earth’s orbital speed varies, moving faster when closer to the Sun and slower when farther away. This variation, coupled with the axial tilt, causes a slight discrepancy between mean solar time (what clocks show) and apparent solar time (the actual position of the Sun). Despite these shifts in the precise timing of sunrise and sunset, the total amount of daylight hours begins to increase immediately after the winter solstice.