The December 21 solstice will mark the shortest day in the Northern Hemisphere (Credit: National Park Service/ Facebook/ Public Domain)

As days grow shorter and temperatures drop, it might seem like winter has already arrived. However, the astronomical start of winter in the Northern Hemisphere will not occur until December 21, 2024. This date, known as the winter solstice, marks the shortest day and longest night of the year. Meanwhile, residents of the Southern Hemisphere will celebrate the summer solstice on the same day. They will enjoy the longest day and shortest night of 2024.

Earth's seasons result from its orbit around the Sun and the tilt of its axis at a 23.5-degree angle. During the December solstice, the Northern Hemisphere tilts farthest from the Sun, receiving much less sunlight. On the other end, the Southern Hemisphere leans toward the Sun, basking in its warmth.

A winter sunrise at Stonehenge (Credit: English-heritage.org.UK/ CC-BY-SA-2.0)

For ancient cultures, the winter solstice held great significance. Though many cold months lay ahead, the longer days that followed signaled that the Sun had not left them. The people marked the Sun's "rebirth" with elaborate rituals.

Stonehenge in Wiltshire, England, is believed to have been built specifically for solstice ceremonies. Its modest circle of stones is designed to perfectly align with the Sun's movement during the solstices. Every year, hundreds of people gather here on winter solstice to commemorate Yule. It is one of the oldest known solstice celebrations.

Newgrange in Boyne Valley, Ireland, is also very popular. The 5,200-year-old stone structure is designed to receive a beam of light into its central chamber at sunrise during the five days surrounding the winter solstice. The light illuminates the intricate carvings inside the structure for about 17 minutes. Due to its popularity, dawn admission to the chamber from December 19th to 23rd each year is limited to a few dozen people selected by lottery. Once they are done, visitors without tickets are allowed to enter in groups of 20.

Many cities in the United States have started their own winter solstice traditions. In San Francisco, California, residents celebrate the occasion with a bonfire on Ocean Beach. Meanwhile, those in Anchorage, Alaska, enjoy the over-18-hour-long night with fun activities. These include sleigh riding, hiking along paths lit with ice lanterns, and admiring the shimmering northern lights, which often make an appearance during this time.

Happy Winter Solstice!

Resources: NASA.gov, Wikipedia.org, rmg.co.uk