15 Facts About the Summer Solstice

iStock/JayKay57
iStock/JayKay57

It's the longest day of the year in the Northern Hemisphere, so soak up some of those direct sunrays (safely, of course) and celebrate the start of summer with these solstice facts.

1. This year the summer solstice falls on June 21.

June 21 date against a yellow background
iStock/Bychykhin_Olexandr

The summer solstice always occurs between June 20 and June 22, but because the calendar doesn't exactly reflect the Earth's rotation, the precise time shifts slightly each year. For 2019, the Sun will reach its greatest height in the sky for the Northern Hemisphere on June 21 at 11:54 a.m. Eastern Time.

2. The Sun will be directly overhead at the Tropic of Cancer.

A vintage mapped globe showing the Tropic of Cancer
iStock/Valerie Loiseleux

While the entire Northern Hemisphere will see its longest day of the year on the summer solstice, the Sun is only directly overhead at the Tropic of Cancer (23 degrees 27 minutes north latitude).

3. The name comes from the fact that the Sun appears to stand still.

Stonehenge at sunrise.
CARL DE SOUZA, AFP/Getty Images

The term "solstice" is derived from the Latin words sol (sun) and sistere (to stand still), because the Sun's relative position in the sky at noon does not appear to change much during the solstice and its surrounding days. The rest of the year, the Earth's tilt on its axis—roughly 23.5 degrees—causes the Sun's path in the sky to rise and fall from one day to the next.

4. The world's biggest bonfire was part of a solstice celebration.

A large bonfire
iStock/Ralf Menache

Celebrations have been held in conjunction with the solstice in cultures around the world for hundreds of years. Among these is Sankthans, or "Midsummer," which is celebrated on June 24 in Scandinavian countries. In 2016, the people of Ålesund, Norway, set a world record for the tallest bonfire with their 155.5-foot celebratory bonfire.

5. The hot weather follows the Sun by a few weeks.

Colorful picture of the sun hitting ocean waves.
iStock/kaisorn

You may wonder why, if the solstice is the longest day of the year—and thus gets the most sunlight—the temperature usually doesn't reach its annual peak until a month or two later. It's because water, which makes up most of the Earth's surface, has a high specific heat, meaning it takes a while to both heat up and cool down. Because of this, the Earth's temperature takes about six weeks to catch up to the Sun.

6. Thousands of people gather at Stonehenge to celebrate the summer solstice.

Rollo Maughfling, the Archdruid of Glastonbury and Stonehenge, conducts a Solstice celebration service for revelers as they wait for the midsummer sunrise at Stonehenge on June 21, 2012, near Salisbury, England.
Rollo Maughfling, the Archdruid of Glastonbury and Stonehenge, conducts a Solstice celebration service for revelers as they wait for the midsummer sunrise at Stonehenge on June 21, 2012, near Salisbury, England.
Matt Cardy, Getty Images

People have long believed that Stonehenge was the site of ancient druid solstice celebrations because of the way the Sun lines up with the stones on the winter and summer solstices. While there's no proven connection between Celtic solstice celebrations and Stonehenge, these days, thousands of modern pagans gather at the landmark to watch the sunrise on the solstice.

7. Pagans celebrate the solstice with symbols of fire and water.

Arty image of fire and water colliding.
iStock/Jag_cz

In Paganism and Wicca, Midsummer is celebrated with a festival known as Litha. In ancient Europe, the festival involved rolling giant wheels lit on fire into bodies of water to symbolize the balance between fire and water.

8. In ancient Egypt, the solstice heralded the new year.

Stars in the night sky.
iStock/GM Stock Films

In Ancient Egypt, the summer solstice preceded the appearance of the Sirius star, which the Egyptians believed was responsible for the annual flooding of the Nile that they relied upon for agriculture. Because of this, the Egyptian calendar was set so that the start of the year coincided with the appearance of Sirius, just after the solstice.

9. The ancient Chinese honored the yin on the summer solstice.

Yin and yang symbol on textured sand.
iStock/filmfoto

In ancient China, the summer solstice was the yin to the winter solstice's yang—literally. Throughout the year, the Chinese believed, the powers of yin and yang waxed and waned in reverse proportion to each other. At the summer solstice, the influence of yang was at its height, but the celebration centered on the impending switch to yin. At the winter solstice, the opposite switch was honored.

10. In Alaska, the summer solstice is celebrated with a midnight baseball game.

Silhouette of a baseball player.
iStock/Kameleon007

Each year on the summer solstice, the Alaska Goldpanners of Fairbanks celebrate their status as the most northerly baseball team on the planet with a game that starts at 10:00 p.m. and stretches well into the following morning—without the need for artificial light—known as the Midnight Sun Game. The tradition originated in 1906 and was taken over by the Goldpanners in their first year of existence, 1960.

11. The Earth is actually at its farthest from the Sun during the solstice.

The Earth tilted on its axis.
iStock/Volodymyr Goinyk

You might think that because the solstice occurs in summer that it means the Earth is closest to the Sun in its elliptical revolution. However, the Earth is actually closest to the Sun when the Northern Hemisphere experiences winter and is farthest away during the summer solstice. The warmth of summer comes exclusively from the tilt of the Earth's axis, and not from how close it is to the sun at any given time. 

12. Ironically, the solstice marks a dark time in science history.

Galileo working on a book.
Hulton Archive, Getty Images

Legend has it that it was on the summer solstice in 1633 that Galileo was forced to recant his declaration that the Earth revolves around the Sun; even with doing so, he still spent the rest of his life under house arrest.

13. An alternative calendar had an extra month named after the solstice.

Pages of a calendar
iStock/Gam1983

In 1902, a British railway system employee named Moses B. Cotsworth attempted to institute a new calendar system that would standardize the months into even four-week segments. To do so, he needed to add an extra month to the year. The additional month was inserted between June and July and named Sol because the summer solstice would always fall during this time. Despite Cotsworth's traveling campaign to promote his new calendar, it failed to catch on.

14. In ancient Greece, the solstice festival marked a time of social equality.

Ancient Greek sculpture in stone.
iStock/imagestock

The Greek festival of Kronia, which honored Cronus, the god of agriculture, coincided with the solstice. The festival was distinguished from other annual feasts and celebrations in that slaves and freemen participated in the festivities as equals.

15. Ancient Rome honored the goddess Vesta on the solstice.

Roman statue of a vestal virgin
iStock/bpperry

In Rome, midsummer coincided with the festival of Vestalia, which honored Vesta, the Roman goddess who guarded virginity and was considered the patron of the domestic sphere. On the first day of this festival, married women were allowed to enter the temple of the Vestal virgins, from which they were barred the rest of the year.

A version of this list originally ran in 2015, and was updated in 2019.

10 Juicy Facts About Leeches

Ian Cook
Ian Cook

Leeches get a bad rap, but they’re actually pretty cool once you get to know them—and we're finding out more about them, even today. Recently, a team led by Anna Phillips, curator of parasitic worms at the Smithsonian National Museum of Natural History, discovered a new species of medicinal leech (pictured above) in a Maryland swamp. We asked parasite expert and curator at the American Museum of Natural History Mark E. Siddall to share some surprising facts about the worms we love to hate. 

1. Not all leeches suck blood.

Hematophagous, or blood-feeding, species are only one type of leech. “The vast majority of species are [hematophagous],” Siddall tells Mental Floss, “but it depends on the environment. In North America, there are probably more freshwater leeches that don’t feed on blood than there are blood-feeders.” And even among the hematophagous species, there are not too many who are after you. “Very few of them are interested in feeding on human blood,” Siddall says. “Certainly they’ll do it, if they’re given the opportunity, but they’re not what they’re spending most of their time feeding on.” 

2. Leeches are everywhere.

Japanese leech on a log
Pieria, Wikimedia Commons // Public Domain

“Every continent on the planet has leeches, with the exception of Antarctica,” Siddall says. “And even then there are marine leeches in Antarctic waters.” Humans have co-existed with leeches for so long, according to Siddall, that just about every language has a word for leech. 

3. Leeches have made a comeback in medicine.

Bloodletting for bloodletting’s sake has fallen out of favor with Western physicians, but that doesn’t mean medicinal leeches are enjoying a cushy retirement. Today, surgeons keep them on hand in the operating room and use them as mini-vacuums to clean up blood. “That is a perfectly sensible use of leeches,” Siddall says. Other uses, though, are less sensible: “The more naturopathic application of leeches in order to get rid of bad blood or to cure, I don’t know, whatever happens to ail you, is complete hooey,” he says. How on Earth would leeches take away bad blood and leave good blood? It’s silly.” 

4. Novelist Amy Tan has her own species of leeches.

Land-based leeches made an appearance in Tan’s 2005 book Saving Fish from Drowning, a fact that instantly put the author in leech researchers’ good graces. “There are not a lot of novels out there with terrestrial leeches in them,” Siddall says. So when he and his colleagues identified a new species of tiny terrestrial leeches, they gave the leech Tan’s name. The author loved it. “I am thrilled to be immortalized as Chtonobdella tanae,” Tan said in a press statement. “I am now planning my trip to Queensland, Australia, where I hope to take leisurely walks through the jungle, accompanied by a dozen or so of my namesake feeding on my ankles.”

5. Leeches can get pretty big.

The giant Amazon leech (Haementeria ghilianii) can grow up to 18 inches and live up to 20 years. And yes, this one’s a blood-feeder. Like all hematophagous species, H. ghilianii sticks its proboscis (which can be up to 6 inches long) into a host, drinks its fill, and falls off. Scientists thought the species was extinct until a zoologist found two specimens in the 1970s, one of whom he named Grandma Moses. We are not making this up.

6. Leeches make good bait.

Many walleye anglers swear by leeches. “A leech on any presentation moves more than other types of live bait," pro fisher Jerry Hein told Fishing League Worldwide. "I grew up fishing them, and I think they're the most effective live bait around no matter where you go." There’s an entire leech industry to provide fishers with their bait. One year, weather conditions kept the leeches from showing up in their typical habitats, which prevented their collection and sale. Speaking to CBS news, one tackle shop owner called the absence of leeches “the worst nightmare in the bait industry.”

7. Leech scientists use themselves as bait.

Siddall and his colleagues collect and study wild leeches. That means hours of trekking through leech territory, looking for specimens. “Whether we’re wandering in water or traipsing through a bamboo forest,” Siddall says, “we are relying on the fact that leeches are attracted to us.” Do the leeches feed on them? “Oh my god, yes. We try to get them before they feed on us … but sometimes, obviously, you can’t help it.”

8. Leech sex is mesmerizing.

Like many worms, leeches are all hermaphroditic. The specifics of mating vary by species, but most twine themselves together and trade sperm packets. (The two leeches in the video above are both named Norbert.)

9. Some leech species make surprisingly caring parents. 

“There’s a whole family of leeches that, when they lay their eggs, will cover them with their own bodies,” Siddall says. “They’ll lay the eggs, cover them with their bodies, and fan the eggs to prevent fungus or bacteria from getting on them, and then when the eggs hatch, they will attach to the parent. They’re not feeding on the parent, just hanging on, and then when the parent leech goes to its next blood meal it’s carrying its offspring to its next blood meal. That’s pretty profound parental care, especially for invertebrates.”

10. You might be the next to discover a new leech species. 

Despite living side-by-side with leeches for thousands of years, we’ve still got a lot to learn about them. Scientists are aware of about 700 different species, but they know there are many more out there. “I’ll tell you what I wish for,” Siddall says. “If you ever get fed on by a leech, rather than tearing off and burning it and throwing it in the trash, maybe observe it and see if you can see any color patterns. Understand that there’s a real possibility that it could be a new species. So watch them, let them finish. They’re not gonna take much blood. And who knows? It could be scientifically useful.”

22 Weird Jobs From 100 Years Ago

Metal Floss via YouTube
Metal Floss via YouTube

Before everyone started working in tech, people actually had their choice of eclectic and strange vocations that put food on their old-timey tables. Discover what lamplighters, lectores, and knocker-uppers did back in the day as Mental Floss editor-in-chief Erin McCarthy runs down 22 Weird Old Jobs from 100 Years Ago.

For more episodes like this one, be sure to subscribe here.

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