This year’s summer solstice takes place a day earlier than it’s been for the past three years, due to the fact that 2012 is a leap year—this February got an extra day, to keep our calendar year of 365 days in sync with the astronomical year, which is about 365.24 days. In general, the exact timing of the summer solstice changes from year to year, “but there’s a bigger jump when you have a leap year,” explained Mark Hammergren, an astronomer at the Adler Planetarium inChicago. “But it’s still always going to be around June 20 or 21.”
What is the Summer Solstice?
The solstices are the results of Earth’s north-south axis being tilted 23.4 degrees relative to the ecliptic, the plane of our solar system. This tilt causes different amounts of sunlight to reach different regions of the planet during Earth’s year-long orbit around the sun.
Today the North Pole is tipped more toward the sun than on any other day of 2012. (The opposite holds true for the Southern Hemisphere, where today is the winter solstice, the shortest day of the year.) As a result of Earth’s tilt, the path of the sun across the sky rises in the lead-up to the summer solstice and then begins descending for the rest of the summer.
At high noon on the summer solstice, the sun appears at its highest point in the sky—it’s most directly overhead position—in the Northern Hemisphere. That doesn’t mean the sun will be exactly overhead at noon for everyone, saidCornellUniversityastronomer James Bell. It depends on the viewer’s latitude—the sun will shine down directly overhead at noon only along the Tropic of Cancer, a line that circles the planet at about the latitude ofCuba. “It’s still at a low angle if you’re up inAlaska,”Bellexplained.
The summer solstice, also referred to as ‘midsummer,’ has been a time of celebration for centuries.
The ancient Egyptians built the Great Pyramids so that the sun, when viewed from the Sphinx, sets precisely between two of the Pyramids on the summer solstice.
The Inca of South America celebrated the corresponding winter solstice with a ceremony called Inti Raymi, in the city ofCuzco. The festival included food offerings and sacrifices of animals, and sometimes even people.
Recently, archaeologists discovered the remains of an astronomical observatory in a long-buried Maya city inGuatemalain which the buildings were designed to align with the sun during the solstices. During such times, the city’s populace gathered at the observatory to watch as their king appeared to command the heavens.
Stonehenge in theUnited Kingdomhas been associated with the winter and summer solstices for about 5,000 years. Observers in the center of the standing stones can still watch the summer solstice sun rise over the Heel Stone, which stands just outside the main ring ofStonehenge.
Modern Day Festivities
The summer celebrations continue all over the globe. Last year, modern-day Druids gathered at Stonehenge to celebrate the solstice for the first time as members of an officially recognized religion in theU.K., following a controversial vote by the national Charity Commission forEnglandandWalesin the fall of 2011.
Traditionally, Scandinavians celebrated midsummer on the solstice itself—the longest day of the year. Today, they observe it on a weekend around the solstice, so merrymakers can take an extra day off work. InScandinavia, the solstice celebrations consist of decorating homes with birch leaves, dancing around maypoles, and lighting bonfires. Also, during the summer solstice, Scandinavians enjoy the ‘midnight sun.’ During that time of the year, the sun is out all day (and night) long, allowing people to enjoy nature and the outdoors even at midnight.