r/didyouknow

On August 7, 1994, residents of Oakville, Washington, woke up to find that instead of normal rain, an area of about 20 square miles was covered in strange, rice-sized gelatinous blobs. The substance fell from the sky six distinct times over a three-week period.

SOURCE : What were the ‘Oakville blobs’? - BBC Science Focus Magazine

In 1697, Peter left Russia on the Grand Embassy, an 18-month tour of Western Europe meant to gather naval and technical expertise. He traveled under a fake name, Peter Mikhailov, posing as a low-ranking sergeant rather than the ruler of Russia. His plan fell apart almost immediately, since Peter stood well over six feet tall and had a distinctive twitch, making him nearly impossible to miss in a crowd.

He still went to work. In the Dutch shipbuilding town of Zaandam, Peter rented a tiny one-room wooden cottage and signed on as an apprentice carpenter at a local shipyard. Word of his identity spread within days and crowds began following him through the streets, so he left after about a week and moved to Amsterdam, where the Dutch East India Company gave him a fenced-off shipyard to work in privately. He spent four months there building an East Indiaman alongside professional shipwrights and walked away with an actual carpentry certificate.

He brought that hands-on training home and used it to build Russia's first navy from scratch, a project that helped transform Russia into a European power within his lifetime.

Source: https://en.wikipedia.org/wiki/Peter_the_Great

Charles II ruled Spain from 1665 until his death in 1700, the last of the Spanish Habsburgs after generations of the family marrying close relatives to keep power concentrated. A 2009 genetic study tracing 16 generations and over 3,000 family members calculated his inbreeding coefficient at 0.254, roughly equivalent to a child born to a brother and sister, even though his actual parents were uncle and niece.

The physical toll showed up directly in his face. Charles carried an extreme version of the "Habsburg jaw," a protruding lower jaw so pronounced that his upper and lower teeth never met, making it nearly impossible to chew. He swallowed his food whole and suffered chronic digestive problems as a result, alongside a tongue so large it was often hard to understand his speech.

He was also left impotent and unable to produce an heir, ending the Habsburg dynasty in Spain and triggering the War of the Spanish Succession.

Source: https://en.wikipedia.org/wiki/Charles_II_of_Spain

The Janissaries were the Ottoman Sultan's elite infantry, built from a system called the devshirme, or "blood tax," in which officials swept through Christian villages in the Balkans every few years and took boys as young as eight to be converted to Islam and trained for state service. The goal was total loyalty: cut off from family, homeland, and birth religion, a Janissary's only remaining bond was to the Sultan himself.

The system worked almost too well. Stripped of the normal ties that pulled soldiers elsewhere, the Janissaries became some of the earliest full-time, professional, salaried soldiers in the world, and among the first infantry anywhere to adopt firearms on a large scale. Some devshirme boys rose even higher than the battlefield, becoming provincial governors or Grand Viziers, the most powerful office in the empire below the Sultan, a level of social mobility almost unheard of for peasant children anywhere else in that era.

The ban on marriage eventually collapsed in the 16th century, and with it went the discipline that made the corps so effective. By the 19th century the Janissaries had become a hereditary, privileged class that blocked reform and repeatedly turned on the very sultans they were created to protect. In 1826, Sultan Mahmud II finally had the four-century-old corps destroyed in an event the Ottomans called the Auspicious Incident.

Source: en.wikipedia.org/wiki/Devshirme

The Agojie were the royal military of the West African Kingdom of Dahomey (in modern Benin), and the only standing all-female army in modern history. At their peak in the 1840s, they numbered up to 6,000 women, roughly a third of Dahomey's entire military, and European accounts consistently rated them as more effective and more fearless in combat than their male counterparts.

Training accounts describe recruits traversing walls of acacia thorns to build up their tolerance to pain, alongside drills in swordsmanship, musket handling, and hand-to-hand combat. Once training was complete they were issued uniforms and organized to mirror the structure of the male army, with a central royal guard flanked by two wings under separate commanders.

At the peak of their power in the 1840s, the roughly 6,000-strong Agojie force struck such fear into their enemies that reports of the era described their "prodigious bravery." They fought their last battles defending Dahomey against French colonial forces in 1892, and the last known Agojie veteran, a woman named Nawi, is believed to have died in 1979 at well over 100 years old.

Source: https://en.wikipedia.org/wiki/Dahomey_Amazons

The toxins in a poison dart frog's skin are not produced by the frog itself. They come entirely from its diet: wild frogs eat specific ants, mites, and beetles that contain alkaloid compounds, which the frogs absorb and store unchanged in skin glands as a defense against predators. The frogs have unique genetic mutations that prevent those same toxins from harming them while they accumulate in the skin.

Remove the diet and the poison disappears. Frogs raised in captivity on crickets and fruit flies, which contain none of the relevant alkaloids, develop no toxicity at all. Their offspring are born harmless and stay that way. The most dangerous species in the wild, the golden poison frog Phyllobates terribilis, carries enough batrachotoxin to kill around 20 adult humans, but zoo-bred individuals of the same species can be handled safely with bare hands. When researchers at the Smithsonian's National Zoo fed captive frogs alkaloid-spiked insects, the toxins reappeared in the frogs' skin, confirming the mechanism. Scientists still don't fully understand how the frogs transport the alkaloids from their gut to their skin without poisoning themselves in the process.

Source: https://en.wikipedia.org/wiki/Poison_dart_frog

The popular story, a single catastrophic blaze that wiped out the ancient world's greatest collection of knowledge in one stroke, traces largely back to 18th century historian Edward Gibbon, who blamed a Christian mob for sacking the library in 391 CE. A separate, even later legend claims Arab conquerors burned it in 642 CE because they believed the Quran was the only book worth keeping. Neither version holds up well: the surviving contemporary accounts of the 391 CE temple destruction don't even mention a library being burned, and the Arab conquest story doesn't appear in writing until centuries after it supposedly happened, while early Muslim scholars were actually translating and preserving Greek texts at the time.

What the evidence does show is a library in decline for hundreds of years before it disappeared. The trouble started as early as 145 BCE, when the ruling Ptolemy VIII purged intellectuals from Alexandria, prompting the head librarian to resign and flee the city along with other scholars. Julius Caesar's troops did accidentally damage part of the collection during fighting in 48 BCE, but it survived that. From there, shrinking institutional support, political instability, and the simple fact that papyrus scrolls degrade without constant, expensive recopying did the rest. No single villain, no single fire, just centuries of neglect that left no dramatic story behind, which may be exactly why a tidier legend took its place.

Source: https://www.worldhistory.org/article/207/what-happened-to-the-great-library-at-alexandria/

For most of the samurai's early history, from roughly the 10th through the 14th century, the bow was the primary weapon, not the blade. Samurai were trained foremost as mounted archers, and swords were treated as backup weapons drawn only after arrows ran out or a rider was knocked from his horse. A 12th century account in the chronicle Azuma Kagami describes a group of warriors whose bowstrings had been gnawed through by rats overnight, forcing them to fight with swords alone, and notes that even skilled swordsmen could not hold their own against incoming arrows and thrown stones.

The pattern continued as warfare evolved. Princeton historian Thomas Conlan analyzed surviving Japanese battle reports, official petitions samurai filed to document wounds they suffered in combat, and found that pikes caused more recorded injuries than swords once pike formations became widespread after 1500. Firearms, introduced to Japan in the mid-1500s, eventually displaced both. The katana held enormous cultural and symbolic weight throughout this history, but the historical record shows it was rarely a samurai's first choice on an actual battlefield.

Source: https://www.way-of-the-samurai.com/The-Samurai-Sword-Reality-vs-Myth.html

After 24 years away, Marco Polo returned to Venice in 1295, then was quickly captured during a naval battle in Venice's ongoing war with Genoa and thrown into a Genoese prison. There he met Rustichello da Pisa, a fellow inmate best known for writing chivalric romances, including one of the earliest Arthurian legend compilations by an Italian author. Over several months, Polo dictated his account of two decades in Asia and Rustichello wrote it down, and it began circulating around 1300 as Il Milione.

Scholars have since found that Rustichello didn't simply transcribe; some passages, including the book's opening lines addressed to "emperors and kings, dukes and marquises," are lifted almost word for word from one of his own earlier Arthurian romances. Historians still debate how much of the book's most fantastical material came from Polo's memory versus his cellmate's professional instinct for what readers of romance literature expected. According to one early Dominican friar's account, Polo himself maintained on his deathbed that he had only told half of what he'd actually seen.

Source: https://en.wikipedia.org/wiki/The_Travels_of_Marco_Polo

At Racetrack Playa, certain rocks weighing as much as 700 pounds leave trails stretching for hundreds of yards across the dry lake's surface, and visitors and scientists have been documenting the phenomenon since the early 1900s without ever seeing it happen. Theories ranged from Earth's magnetic field to gale-force winds to slippery algae.

In 2011, paleobiologist Richard Norris and his cousin, engineer James Norris, set up motion-activated GPS units on 15 rocks along with a high-resolution weather station and time-lapse cameras, expecting nothing for years since the rocks can sit still for a decade at a time. During a rare sequence of wet winter storms from December 2013 through February 2014, hundreds of rocks scooted across the playa five separate times in just ten weeks. The footage revealed that thin, jagged plates of ice, formed when a shallow flood on the playa froze overnight, were cracking apart in the sun and getting pushed by light winds, bulldozing the rocks across the soft, wet mud beneath them. The full study and footage were published in PLOS ONE in 2014.

Source: https://www.sciencedaily.com/releases/2014/08/140828141902.htm

Australian geologist Thomas Griffith Taylor found the reddish flow in 1911 while exploring the Antarctic valley that now bears his name. He and other early explorers first attributed the color to red algae, but it was later proven to be iron oxide instead, rust forming as iron-rich saltwater hits the air after seeping out of the glacier.

What stayed a mystery for over a century was where that saltwater was coming from and how it moved. A team led by the University of Alaska Fairbanks and Colorado College finally mapped its path in 2017, using radar to trace a 300-foot route of brine running from beneath Taylor Glacier to the falls. The evidence suggests the source is a body of salty water that may have been sealed under the glacier for more than a million years. Because saltwater has a lower freezing point and releases heat as it freezes, it stays liquid even though the glacier sits at around 1.4 degrees Fahrenheit, making it the coldest known glacier on Earth with water that still flows.

Source: https://en.wikipedia.org/wiki/Blood_Falls

Beethoven asked his doctor before his death in 1827 to study his body and publish the cause of his ailments. Researchers finally attempted this in 2023, sequencing his genome from locks of hair clipped after his death. They tested eight locks attributed to him, and found that one of the most famous, the Hiller Lock, had actually come from a woman, not Beethoven at all.

Five other locks, all dating to the last seven years of his life, did genetically match a single individual consistent with Beethoven's documented ancestry. Comparing that DNA to living descendants, researchers found a discrepancy between Beethoven's legal and biological family line, evidence of an "extra-pair paternity event," meaning at some point in his direct paternal ancestry, a child was fathered outside the marriage. The break in the bloodline happened sometime between 1572 and Beethoven's birth in 1770, but researchers couldn't pin down exactly which generation. On the medical side, the real hair confirmed a strong genetic risk for liver disease and a hepatitis B infection, but found no genetic explanation for his deafness, leaving that part of the mystery unsolved.

https://www.cam.ac.uk/stories/beethovens-dna-reveals-health-and-family-history-clues

Hi everyone — I work with Dementia Society of America®, a nonprofit focused on Dementia awareness, enrichment programs and funding Dementia-related research. This month is Dementia Awareness Month so I wanted to share some commonly asked questions we receive!

What is Dementia? The simple answer is it's an umbrella term, like "cancer." Cancer is found in different forms, such as breast cancer, leukemia, testicular cancer, melanoma, etc. It's no different with Dementia, there are many forms and types.  In addition, Dementias are considered severe forms of cognitive impairment that affect at least two functions of the brain. Examples include memory, decision-making, behavior, motor skills, etc. Memory loss alone does not mean Dementia.

What is the difference between Dementia and Alzheimer's Disease? Alzheimer's Disease (often shortened to just "AD"), is simply one very common form of Dementia. There are many types of Dementia besides Alzheimer's. Moreover, not all Dementias are diseases or conditions related to Alzheimer's.

Can an Alzheimer's diagnosis be confirmed 100% while someone is alive? Well, the most recent answer used to be "no." But that is changing rapidly. Today, still, only a post-mortem autopsy of the brain tissue can reveal with complete 100% certainty the types of pathology that Dr. Alois Alzheimer discovered over 100 years ago. Yet, within just the past few years, new brain imaging and bodily fluids (blood or cerebrospinal fluid) tests are giving medical professionals more than 90% certainty before death. The science of brain imaging, DNA testing, and other state-of-the-art methods is improving the ability to detect certain telltale signs of all causes of Dementia. But still, not everyone has easy access to the testing advancements available. The best thing to do is not to assume or rubber-stamp a diagnosis. Instead, the Dementia Society of America strongly urges anyone thought to have a cognitive impairment to get the best possible diagnostic workup by a board-certified geriatric or cognitive neurologist and his or her team.

What questions do you wish more people understood about Dementia, either from personal experience, caregiving, or supporting a loved one?

Stay strong! You are not alone in this journey<3

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The Answers above are from www.dementiasociety.org

Important Notice: Dementia Society of America (DSA) does not provide medical advice. The contents are for informational purposes only and are not intended to substitute for professional medical advice, diagnosis or treatment.