Winter is the coldest season of the year. The Northern Hemisphere, the northern half of Earth, has winter weather from December to early March. Winter storms produce large snowfalls in some areas, shown here. In the Southern Hemisphere, winter weather begins in late June and lasts until early September.
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Tuesday, Dec. 21, 2021 is the winter solstice for the Northern Hemisphere. On the winter solstice, the sun is at its most southerly position. It marks the day in the year with the least amount of sunlight and the beginning of winter. After the winter solstice, days begin growing longer and nights shorter approaching spring. The winter solstice in the Southern Hemisphere happens in June because the seasons are reversed. December 21 in the Southern Hemisphere is the summer solstice, the longest day of the year.

During the winter solstice, the sun is directly overhead at the Tropic of Capricorn. The Tropic of Capricorn is an imaginary line that traces the southern boundary of the earth’s Tropical Zone. It marks the farthest limit south of the equator where the sun can appear directly overhead. The change results from the tilt of Earth’s axis of rotation. The winter solstice in the Northern Hemisphere happens on December 21 or 22.

Earth spins around its axis once every 24 hours. This motion creates day and night. Earth also travels around the sun once every 365 days. This motion creates the year. The entire solar system revolves around the center of the Milky Way Galaxy.

On the winter solstice which occurs in December in the Northern Hemisphere and June in the Southern Hemisphere, people celebrate the rebirth of the sun and the beginning of winter. For a long time, cultures around the world have celebrated holidays and feasted around the winter solstice. Most of the celebrations feature light since it occurs on the darkest day of the year.

Stonehenge may have been a place where people celebrated the winter solstice. Stonehenge is an ancient ruin in southwestern England. It consists of huge, rough-cut stones set in a circle. The stones are aligned toward the winter solstice sunset. There is archeological evidence the people who lived there held a large feast on the winter solstice.

Ancient Roman holidays were planned around the winter solstice. People have also celebrated specific holidays on the winter solstice in China, Iran, Japan, and Scandinavia. The Incas and some Native American tribes celebrated the winter solstice by fasting, dancing, and then feasting.

June 21, 2016

When the North Pole has its greatest slant toward the sun, left, summer begins in the Northern Hemisphere and winter begins in the Southern Hemisphere. Credit: WORLD BOOK map

Have you noticed that the days have been getting longer and longer (or the reverse, if you live in the Southern Hemisphere)? The increasing difference between day and night reached its peak yesterday at 22:34 Coordinated Universal Time. This moment is called the June solstice.

A solstice is one of the two moments each year when the sun is at either its northernmost or southernmost position in Earth’s sky. Earth’s axis of rotation is tilted at an angle of 23 degrees 27 minutes in relation to the plane of Earth’s orbit around the sun. As Earth orbits the sun, the angle of tilt points toward the same direction in space. Thus, the direction of this angle in relation to the sun changes throughout the year, causing seasons on Earth.

Solstices mark the beginnings of astronomical summer and winter. In the Northern Hemisphere, the June solstice marks the longest day of the year. In the Southern Hemisphere, yesterday was the shortest day of the year and signaled the arrival of astronomical winter. Now, the day and night will get closer to the same length until the next equinox in September. During an equinox, the tilt of Earth’s axis lies such that neither hemisphere is angled toward the sun. This means that each part of Earth receives the same amount of daylight, so day and night are roughly the same length.

Cultures around the world, but especially those in higher latitudes in the Northern Hemisphere, celebrate the June Solstice. For example, the people of Sweden celebrate Midsummer’s Eve and Midsummer’s Day around the time of the June Solstice. Solstices were also important to ancient people. Thousands of years ago, people living in what is now southwestern England built Stonehenge, a circle of large carved stones. Several features of Stonehenge align with the sun on solstices, suggesting that they were important to its builders.

June 20, 2014

The sounds of celebrations welcoming the summer solstice at Stonehenge in England thousands of years ago might have included rock music. If so, the music made from striking the huge stones used to construct the monument might explain why ancient Britons went so far afield to find the stones. People who gather at the valued World Heritage site for the arrival of the summer solstice tomorrow, however, will almost certainly have to content themselves with beating drums and singing.

The ancient ruin of Stonehenge, which lies on the Salisbury Plain in Wiltshire, consists of huge, rough-cut stones set in a circle. Archaeologists think that ancient Britons constructed the site as a gathering place and religious center, particularly for ceremonies linked to the solstices, the times of the year that mark the beginning of summer and winter. In fact, the paved avenue at Stonehenge lines up with the sunrise on the summer solstice. Thousands of people continue to gather at the site twice a year to celebrate the solstices.

Stonehenge was probably used as a tribal gathering place and a religious center by ancient inhabitants of England. It was built between about 2800 and 1500 B.C. The drawing shows what scholars believe was the original arrangement of the monument's huge stones. (Aerofilms)

One of the many mysteries of Stonehenge is why its ancient builders used rocks from hundreds of miles away for the inner ring–despite the presence of rock deposits much closer. Stonehenge’s inner stones, called bluestones, were quarried some 245 miles (395 kilometers) away in the Preseli Mountains of Pembrokeshire in southern Wales. After quarrying, the stones were dragged to the sea, loaded onto barges, and floated up Hampshire’s River Avon to near Stonehenge. For the ancient Britons, this was no small effort. The bluestones are massive, with some weighing up to 4 tons (3.6 metric tons).

Now researchers from the Royal College of Art in London have suggested an answer: The rocks were chosen for the bell-like sounds they produce when struck. Such sounding stones, also called lithophones, are often associated with healing rituals and can be found throughout the world. In the United States, Ringing Rock State Park in Pennsylvania is known for the chime-like qualities of its ancient boulders. Stonehenge’s bluestones, like the Pennsyvania boulders, are diabase rocks, dense, fine-grained igneous rocks with deposits of iron and magnesium. The volcanic rocks spent some 170 million years cooling below ground, explained geologist Lawrence L. Makinconico of Lafayette College in Pennsylvania. “When they cool, it’s something like forging a cast-iron bell,” he told The New York Times.

Additonal World Book articles:

• Avebury
• Megalithic monuments
• History of the United Kingdom (Prehistoric Britain)
• Archaeology (1966) (a Back in Time article)
• Cahokia: Mysteries in the Mounds (a Special Report)
• Reading the Sky: Early Places of Astronomy (a Special Report)

To hear sounds made by rocks in the Preseli Mountains, where Stonehenge’s bluestones were quarried, go to:

http://www.landscape-perception.com/acoustic_mapping/

Dec. 22, 2011

The arrival of the December solstice has marked the official start of winter in the Northern Hemisphere and of summer in the Southern Hemisphere. At the December solstice, the sun reaches its southernmost position on the horizon. At that point, Earth is tilted on its axis as far away from the sun as possible. The axis, the imaginary line around which Earth rotates, is not straight up and down but is tilted by about 23 degrees 7 minutes in relation to the plane of the planet’s orbit around the sun. In the Northern Hemisphere, the December solstice, also known there as the winter solstice, is the shortest day and longest night of the year. In the Southern Hemisphere, the December solstice, also known there as the summer solstice, is the longest day and shortest night of the year.

The solstice officially occurred at 5:30 Coordinated Universal Time (UTC) on Thursday, December 22, at the prime meridian at the Royal Greenwich Observatory in Greenwich, England. In the United States, 5:30 UTC was 12:30 a.m. in New York City (Eastern Standard Time) on Thursday and 9:30 p.m. in Los Angeles (Pacific Standard Time) on Wednesday, December 21. In Sydney, Australia, the December solstice began at 4:30 p.m. (Australian Eastern Daylight Time) on December 22.

The seasons change because the tilt of Earth's axis causes places on the planet to receive different amounts of sunlight during the year. Winter begins in the North Hemisphere when the North Pole has its greatest tilt away from the sun (right). At the same time, summer begins in the Southern Hemisphere, which has its greatest slant toward the sun. World Book illustration by Amie Zorn, Artisan-Chicago

The December solstice is one of two solstices that take place as Earth completes a full orbit of the sun. The June solstice occurs on June 20, 21, or 22, when the sun reaches its northernmost point on the horizon. It marks the start of summer in the Northern Hemisphere and the start of winter in the Southern Hemisphere.

As they have since prehistoric times, solstice celebrations were held in many places around the world. In the Northern Hemisphere, the December solstice has had particular significance as the day on which the sun is reborn and days begin to grow longer.

Additional World Book articles:

• Cahokia: Mysteries in the Mounds (a Special Report)
• Inca (Religion)
• Newgrange
• Reading the Sky: Early Places of Astronomy (a Special Report)
• Stonehenge