Most people are familiar with the saying, “the sun rises in the east and sets in the west.” While this is a common generalization, it’s not entirely accurate throughout the year. In reality, the sun only rises precisely due east and sets exactly due west on just two days annually: during the spring and fall equinoxes. On all other days, the sun’s rising and setting points shift, appearing either north or south of true east and west. This daily change in the sun’s path is a fascinating celestial phenomenon that has been observed and tracked for millennia.
The Shifting Points of Sunrise and Sunset
The familiar notion of the sun rising in the east and setting in the west holds true as a general direction, but the exact points on the horizon are dynamic. Only during the spring and fall equinoxes does the sun grace us with a sunrise directly in the east and a sunset directly in the west. As we move towards summer, the sunrise point gradually drifts northeastward, and the sunset point moves northwestward. Conversely, as we approach winter, the sunrise point shifts southeastward, and the sunset point trends southwestward. This daily subtle shift culminates in the solstices, marking the extremes of the sun’s journey.
Solstices and Equinoxes: Key Markers
The summer solstice marks the day when the sun rises furthest to the northeast and sets furthest to the northwest. This is also the longest day of the year in terms of daylight hours. Following the summer solstice, each day sees the sun rising and setting a little further south. By the time the fall equinox arrives, the sun is back to rising due east and setting due west, resulting in roughly equal hours of daylight and darkness. This southward journey continues until the winter solstice. At the winter solstice, the sun reaches its southernmost rising point in the southeast and setting point in the southwest. This marks the shortest day of the year.
Ancient cultures were keenly aware of these solar movements, understanding their profound impact on seasons and timekeeping. Many prehistoric societies meticulously tracked these sunrise and sunset points. In landscapes with jagged mountain horizons, these points were easily discernible and remembered. In flatter terrains, they ingeniously used standing stones, wooden poles, or rock cairns to precisely mark and align with the various sunrise and sunset positions throughout the year. These markers served as calendars, helping them anticipate seasonal changes and plan their activities accordingly.
Understanding with a Sun Track Diorama
To visualize how the sun’s path changes throughout the year, a sun track diorama is an excellent educational tool. These dioramas simulate the sun’s rising and setting points and its path across the sky during the summer solstice (longest path), winter solstice (shortest path), and the spring and fall equinoxes (medium path). Imagine yourself standing at the center of the diorama’s wooden disk, with the outer rim representing your horizon.
On the summer solstice, you would observe the sun rising on your eastern horizon at the northeasternmost point of the longest track. It would then trace a high arc across your sky, finally setting on the northwestern horizon. This long path signifies an extended period of daylight, characteristic of warm summer days. Conversely, during the winter solstice, the sun rises at the southeastern end of the shortest track. Its path across the sky is much lower and shorter, resulting in fewer daylight hours and colder winter days. During the spring and fall equinoxes, the sun rises at the eastern end of the medium track and sets at the western end, providing roughly equal day and night hours and the moderate climates of spring and fall.
Stars vs. Sun: Rising Points
While the sun’s rising points change noticeably throughout the year, the rising points of stars remain relatively constant. This is because stars are incredibly distant compared to the sun. Therefore, the horizon rising points of stars were not as crucial for ancient cultures in tracking the seasons as the sun’s were. However, the rising times of stars do change daily by about 4 minutes. This means that any particular star will rise at different times throughout the year. For approximately half of the year, a given star will rise during the daytime, making it invisible due to the sun’s brightness.
Ancient astronomers were particularly interested in what is known as the “heliacal” or dawn rising of a star. This special event occurs on only one day each year for each star, when it first becomes visible just before sunrise after a period of being hidden by the sun’s glare. These heliacal risings were invaluable for precise timekeeping and calendrical systems in ancient civilizations, allowing them to mark specific dates with remarkable accuracy.
In conclusion, while it’s commonly said that the sun rises in the east and sets in the west, this is a simplification. The precise points of sunrise and sunset shift throughout the year, tracing a path from northeast in summer to southeast in winter, crossing due east and west only during the equinoxes. Ancient cultures understood and meticulously tracked these solar movements, using this knowledge for timekeeping, seasonal awareness, and even cultural practices. Their observations highlight a deep connection to the celestial rhythms that continue to fascinate and inform us today.
