Photo: Yvonne Höpfl - Dornberg, Germany
Though school is out and the weather is warming up, it hasn’t been summer just yet—at least, not from an astronomical standpoint. Today (June 20, 2024), those of us in the Northern Hemisphere will experience the longest day of the year. This astronomical event, called the June Solstice, marks the official beginning of the summer in the Northern Hemisphere and the winter in the Southern Hemisphere.
What is the June Solstice?
The Earth is divided into two halves called hemispheres, which are separated by an imaginary line called the equator. As the Earth orbits around the Sun, its Northern and Southern Hemispheres receive different amounts of sunlight. Because the Earth is tilted on its axis at about a 23.5 degree angle, one hemisphere is always receiving more sunlight than the other. As we orbit, the Sun appears to rise and set at different points on the horizon. This changes the length of the Sun’s path across the sky and determines the amount of daylight hours we have in our hemisphere.
In the summer, we experience long days and hot weather—a result of the hemisphere being tilted toward the Sun and receiving its light directly. Winter is marked by short days and cold weather, meaning the hemisphere is tilted away from the Sun and receiving less direct sunlight. When one hemisphere experiences summer, the other experiences winter. This is also true of spring and fall.
On the June Solstice, the Sun will rise and set as far north as it can as seen from the Northern Hemisphere, and it will rise and set as far south as it can as seen from the Southern Hemisphere. In the Northern Hemisphere, the Sun will take the longest possible path across the sky, resulting in the longest day of the year. At noon on this day, the Sun will also reach its highest possible point in the sky. The December Solstice is the exact opposite of this process. After the solstice ends, the days will get shorter by about a minute every day. Eventually, we will transition into fall—the full arrival of which will be marked by an equinox.
An animation demonstrating the position of the Sun and Earth during the June solstice. | NASA’s Goddard Space Flight Center
How can I celebrate the June Solstice?
Throughout history, the June Solstice has been celebrated and recognized in countless ways around the world. In ancient China, the June Solstice was observed with a ceremony honoring femininity. Northern European countries like Sweden, Denmark, Norway, and Finland celebrate with joyful Midsummer festivals that venerate the Earth’s fertility. Stonehenge, a prehistoric monument once shrouded in mystery, is now thought by historians to be an early solar calendar organized around the date of the solstice.
Today, be sure to make the most of your extra daylight hours by getting outside and doing something you enjoy!