Ah, summer. The season of swimming, relaxing, and lazy days in the sun arrives June 20, the summer solstice for the Northern Hemisphere.
So what is a solstice, exactly? It's the result 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.
On the June solstice, the North Pole is tipped more toward the sun than on any other day of the year. (The opposite holds true for the Southern Hemisphere, where it will be the winter solstice, the shortest day of the year.)
Read on for some more intriguing facts about the summer solstice.
More Sunlight Doesn't Mean More Heat
On the summer solstice, the Northern Hemisphere receives more sunlight than on any other day of the year—but that doesn't mean the first day of summer is also the hottest.
Earth's oceans and atmosphere act like heat sinks, absorbing and reradiating the sun's rays over time.
Even though the planet absorbs a lot of sunlight on the summer solstice, it takes several weeks to release it. As a result, the hottest days usually occur in July or August.
"If you think about turning up an oven, it takes it a long time to heat up," explains Robert Howell, an astronomer at the University of Wyoming.
"And after you turn it off, it takes awhile for it to cool down. It's the same with the Earth."
The Earth Isn't Any Closer to the Sun
Another popular misconception is that during the summer—and especially during the summer solstice—Earth is closer to the sun than at other times of the year, says Mark Hammergren, an astronomer at the Adler Planetarium in Chicago.
In reality, the tilt of the Earth has more influence on the seasons than does our planet's distance to the sun.
"During the Northern Hemisphere summer, we're actually farthest from the sun," Hammergren says. (Related: "Despite Heat, Earth Is Farthest From Sun on Friday.")
Solstice Sparked Ancient Celebrations
The summer solstice—also called midsummer—has long been recognized and often celebrated by many cultures. 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. (See "Summer Solstice Pictures: From Stonehenge to Carhenge.")
The Inca of South America celebrated the corresponding winter solstice with a ceremony called Inti Raymi, which included food offerings and sacrifices of animals, and maybe even people.
Archaeologists have also discovered the remains of an astronomical observatory in a long-buried Maya city in Guatemala, in 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.
Observers in the center of the standing stones can still watch the summer solstice sunrise over the Heel Stone, which stands just outside the main ring of Stonehenge. (Read about pagans' campaign to enter Stonehenge on the summer solstice and other sacred days.)
Some Keep the Tradition Alive
But for many modern cultures—and Americans in particular—the solstices and equinoxes are no longer as important.
Most people who "really pay attention to what's going on outside on a regular basis are the neo-pagans in America and farmers, because it's important for their growing and harvest seasons," says Jarita Holbrook, formerly a cultural astronomer at the University of Arizona in Tucson.
Not so for the city of Fairbanks, Alaska, which has been commemorating the summer solstice with a late-night baseball game for 109 years. (See "Pictures: Summer Solstice Marked With Fire, Magic.")
The first Midnight Sun Game, held in 1906, began as a bet between two local bars shortly after a building fire gutted downtown Fairbanks, according to Tom Dennis, the general manager of the Alaska Goldpanners baseball team, which has been hosting the game since 1960.
Every year, a different team—usually from out of state—is invited to participate in the symbolic event.
The game typically begins around 10:30 p.m., continues straight through midnight, and often lasts as late as 2 a.m. Fairbanks, which is located only 160 miles (250 kilometers) south of the Arctic Circle, gets up to 22.5 hours of summer daylight, Dennis says.
"We don't need caffeine," he says, "because we have sunlight."
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