This Saturday marks the winter solstice, bringing the shortest day and longest night of the year to the Northern Hemisphere—perfect for holiday lights and cozy blankets.
For those preferring more sunlight, the Southern Hemisphere currently enjoys summer. Alternatively, those in the Northern Hemisphere can look forward to slightly longer days starting Sunday, continuing until late June.
These annual variations in sunlight, caused by Earth’s orbit around the sun, have been understood for centuries. Ancient structures like Stonehenge in England and the Torreon at Machu Picchu in Peru were partly built to align with solstices.
Here’s an explanation of Earth’s yearly journey around the sun.
What is the solstice?
Earth orbits the sun at an angle. For most of the year, the Earth’s tilt directs varying amounts of sunlight to the northern and southern hemispheres.
Solstices occur when Earth’s tilt is most extreme relative to the sun. This results in significantly different sunlight durations in each hemisphere, creating unequal day and night lengths.
The Northern Hemisphere’s winter solstice, featuring the shortest day and longest night, falls between December 20 and 23.
Conversely, the summer solstice, with the longest day and shortest night in the Northern Hemisphere, occurs between June 20 and 22.
What is the equinox?
During the spring and autumn equinoxes, Earth’s axis and orbital plane align, resulting in roughly equal sunlight for both hemispheres.
The term “equinox” derives from Latin words meaning “equal” and “night,” referencing the nearly equal day and night lengths on these dates, though minor variations exist depending on location.
The Northern Hemisphere’s spring equinox falls between March 19 and 21, while the autumn equinox occurs between September 21 and 24.
What’s the difference between meteorological and astronomical seasons?
These are simply two different ways of dividing the year.
Meteorological seasons are weather-based, dividing the year into three-month periods according to annual temperature patterns. This calendar assigns spring to March 1, summer to June 1, autumn to September 1, and winter to December 1.
Astronomical seasons, in contrast, are determined by Earth’s movement around the sun.
Solstices initiate summer and winter, while equinoxes mark the start of spring and autumn.