Pictures show summer solstice 2024 at Stonehenge

O Summer Solstice on Thursday signals the end of spring in the Northern Hemisphere and the beginning of a new season, which promises more heat and more sunlight. To mark the transition to the summer of 2024, the astronomical event serves as a grand opening of sorts: everywhere above the equator, it will be the longest day of the year.

At the StonehengeA prehistoric monument of massive stones that is now a protected heritage site in southern England, historians believe that ancient people built a ceremonial circular structure from enormous sarsen stones with the specific intention of honoring and celebrating the solstice.

Mysteriously erected around 2,500 BC, Stonehenge is thought to be some kind of spiritual or ritual ground, although the real reasons why people came up with the idea to build it, and what they used it for, are still unknown. The stones were erected and meticulously arranged in the late Neolithic period, or Stone Age — a time when the creation of such a monument would have been a brilliant feat of advanced construction and engineering.

For those in the center of Stonehenge, the layout is oriented so that the stones accurately frame the sunrise on the summer solstice and the sunset on the summer solstice. Winter Solstice. Thousands of people visit the site every year on both solstices to witness the phenomenon for themselves.

Just one day before this year’s summer solstice, climate protesters sprayed Stonehenge with orange paint to make a statement against fossil fuels. The organization that manages the Stonehenge site, English Heritage, told CBS News that the incident was “extremely disturbing and our curators are investigating the extent of the damage,” but that the monument remained open to the public.

What is the summer solstice?

The solstice is technically the beginning of summer in the Northern Hemisphere, with its converse, the winter solstice, simultaneously ushering in winter throughout the Southern Hemisphere.

It occurs when the Earth, which is tilted 23.5 degrees on its axis, reaches the maximum point at which the northern half of the planet is oriented towards the sun since the last time the summer solstice occurred. As the Earth constantly rotates on its axis and simultaneously orbits the Sun, this tilt offers each hemisphere the opportunity to bathe in its greatest extent of daylight, just once a year.

Seasons exist on Earth because of the 23.5 degree tilt. As the planet rotates and travels its orbital path approximately 365 days, Earth’s tilted axis means the angles at which different parts of its surface facing the sun change throughout the year. During the Northern Hemisphere’s summer solstice, which usually falls on June 20 or 21 — this year it’s June 20 — these cosmic mechanics push the top of the planet toward the sun. At the North Pole, six months of daylight begin, while at the South Pole, this means six months of darkness.

Conditions are reversed six months later, when the Earth reaches a point in its orbit where the axis tilts it backwards, so that the South Pole is closest to the Sun. On that day, usually December 21 or 22, the Winter solstice in the Northern Hemisphere brings the shortest period of daylight, while the Southern Hemisphere begins summer.

Crowds gathered at Stonehenge in December to also mark the winter solstice.

Why is June 20th the longest day in 2024?

The North Pole is never tilted more towards the Sun than during the summer solstice. This pronounced tilt exposes a larger section of the Northern Hemisphere to sunlight at any given time than at any other point in the Earth’s revolution. From the perspective of a person on the ground, this exposure creates the longest period of 24-hour daylight throughout the year.

This year, the North Pole reaches its most extreme tilt at 4:51 pm EDT on June 20, according to to the National Oceanic and Atmospheric Administration. The Sun is then directly over the Tropic of Cancer, a longitudinal line that horizontally wraps around the Earth’s circumference at 23.5 degrees above the equator. The line passes through Mexico, Bahamas, Egypt, Saudi Arabia, India and southern China.

At the other end of the cycle, when the North Pole is tilted as far from the Sun as possible, the section of the Northern Hemisphere that sunlight can reach is as small as possible. This is why the winter solstice is the shortest day of the year for people above the equator and the longest day of the year for people below.

How the summer solstice has been celebrated throughout history

The summer solstice is an occasion that civilizations have observed and celebrated for millennia. Historians believe that the Neolithic people who built Stonehenge were part of a broader ancient culture in northern and central Europe that, experts say, seemed to recognize the solstice and the changing of the seasons as it related to agriculture and, potentially, with the calendar of harvest cycles.

British non-profit organization National Trust writes in an overview of ancient solstice traditions that the event “was typically marked by Celtic, Slavic and Germanic peoples by the lighting of bonfires, intended to increase the strength of the sun for the rest of the harvest season and ensure a healthy harvest.” Other Neolithic stone circles, such as Stonehenge, also appear to have been built with the solstices in mind, according to the organization.

Nowadays, people mark the solstice with their own take on traditional ceremonies from ancient times. Festivals and bonfires are common in communities around the world. But there are countless ways that modern people recognize Earth’s seasonal transit. Depending on where it takes place, a summer solstice celebration may seem a midnight baseball game in Fairbanks, Alaska, or a full day mass yoga meeting in Times Square.