Sunday marks the longest day of the year in the Northern Hemisphere. This day is known as the solstice, signifying the start of astronomical summer north of the equator. Conversely, in the Southern Hemisphere, it is the shortest day, indicating the beginning of winter.
The word ‘solstice’ originates from the Latin words ‘sol’ meaning sun and ‘stitium,’ which implies pause or stop. The summer solstice occurs when the sun reaches its highest point in the sky, creating the longest arc. After this, the sun begins its retreat, leading to shorter days until late December.
Solstices have been significant for centuries, celebrated with festivals and monuments. In Sweden, midsummer eve celebrations are held, while Stonehenge aligns with the sun’s paths during these events.
Understanding Earth’s Orbit:
As Earth orbits the sun, it does so at an angle. This tilt causes sunlight and warmth to distribute unevenly across the northern and southern hemispheres throughout the year.
Solstices occur when Earth tilts most markedly toward or away from the sun, resulting in vastly different levels of sunlight across hemispheres. This causes the longest and shortest days of the year, with the Northern Hemisphere enjoying its longest day during the summer solstice, which can fall between June 20 and 22. In 2023, it happens on June 21. The opposite takes place during the winter solstice, between December 20 and 23, characterized by the shortest day and longest night.
Exploring the Equinox:
During an equinox, Earth’s tilt does not favor either hemisphere, allowing both to receive equal sunlight. The sun rises due east and sets due west. The term ‘equinox’ is derived from Latin words meaning equal and night, because day and night durations are nearly the same globally, although slight variations exist based on location.
The fall, or autumnal, equinox in the Northern Hemisphere occurs between September 21 and 24, while the spring, or vernal, equinox occurs between March 19 and 21. The equinox occurs when the sun is directly above the equator.
Difference Between Meteorological and Astronomical Seasons:
Astronomical seasons depend on Earth’s position relative to the sun. Meteorological seasons, however, are defined by weather patterns and temperatures. Meteorologists divide the year into three-month segments where spring starts on March 1, summer on June 1, fall on September 1, and winter on December 1.
The Associated Press Health and Science Department acknowledges support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP independently manages all content.