Understanding the Daily Variation in Sunrise and Sunset Differences
The time difference between sunrise and sunset varies throughout the year due to the Earth's tilt and its elliptical orbit around the Sun. This variation is not constant day-to-day. Instead, it follows a specific pattern that influences the length of daylight on different days.
What Affects Sunrise and Sunset Timing?
The daily variation in the time between sunrise and sunset is primarily influenced by two factors: the Earth's tilt and its elliptical orbit around the Sun. The tilt of the Earth's axis causes the Sun to appear at different positions in the sky throughout the year. Additionally, the elliptical nature of the Earth's orbit results in differences in the distance from the Earth to the Sun, further affecting sunlight and the length of daylight.
Day Length Variations Near the Equinoxes and Solstices
Near the equinoxes, which occur on or around March 21 and September 23, the length of day and night is approximately equal (about 12 hours each). However, the changes in daylight are relatively small, often varying by about 2-3 minutes per day.
During the solstices, which occur around June 21 and December 21, the changes in daylight can be more pronounced. Around the summer solstice, days can lengthen by about 3-4 minutes per day, while around the winter solstice, days can lengthen more slowly.
General Average for Day Length Variations
On a general average, the change in daylight over the course of the year averages around 1-2 minutes per day. This means that throughout the year, the total change in day length can be significant.
Calculating Exact Time Differences
To calculate the exact time difference for a specific location, you would typically need to refer to local sunrise and sunset tables or use astronomical software. These tools account for the specific latitude and longitude of a location, which significantly influence the sunrise and sunset times.
Examples and Observations
In England, the daily change in daylight can be observed more acutely. For example, after the shortest day of the year, in late December, the country gains three minutes of daylight per day. This change is evenly split between sunrise and sunset, resulting in sunrise getting 90 seconds earlier and sunset getting 90 seconds later each day.
During the lengthening days between December 22nd and June 21st (the Summer Solstice), there are 21 minutes more daylight each week. Conversely, between June 22nd and December 21st (the Winter Solstice), there is a reduction in daylight. Between these times, the Spring Equinox on March 21 and the Autumn Equinox on September 21 mark days with equal amounts of light and darkness.
While it may seem complex, there are websites and online tools that can provide the exact sunrise and sunset times for a given location, simplifying the process of calculating these variations.