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None of our senses is as frequently maligned as our sense of smell. Our noses, while convenient, often are portrayed as second-tier sniffers, behind the gifted olfactory senses of dogs, sharks, and other animals. It’s said our noses can’t even smell that many distinct odors. And after all, smell doesn’t help us navigate our world as much as our sight or touch does — supposedly. However, all of these purported “facts” are actually fictions. The seven (real) facts below explain just how amazing our sense of smell really is.

Olfaction Is the Oldest Sense

When complex life established a foothold on Earth 1.5 billion years ago, smell was the first sense that evolution developed. Chemoreception — detecting chemicals in the environment by scent — is a common trait among all animals, and even single-celled organisms. Smell is vital not only for finding food but also for finding a mate, a pretty key ingredient for furthering your particular limb on the tree of life. But although this sense is ubiquitous throughout the various phyla, kingdoms, and domains, not all organisms smell the same way. Single-celled organisms use a protein in the cell wall to detect chemicals, while plants use mechanisms baked in their genes to detect volatile organic compounds. Snakes, meanwhile, use their forked tongues to “grab” scents and then quickly return them to the olfactory bulb located at the roof of their mouths. This allows snakes to discern the direction of smells, which scientists describe as “smelling in stereo.” When it comes to life’s oldest sense, evolution has had more than enough time to create a variety of techniques.

Our Nose Can Sense 1 Trillion Odors

Humans are actually better than dogs when it comes to detecting certain smells, and our noses can actually sniff out a staggering 1 trillion (yes, with a “t”) odors. The impressive nature of our noses is a relatively recent discovery, however, which may explain why the human sense of smell long got a bad rap. Nearly a century ago, scientists pegged the human nose’s olfactory abilities at about 10,000 distinct smells — not bad, but far less impressive than our eye’s ability to glimpse 1 million colors (or more, for those lucky tetrachromats). In 2014, researchers from Rockefeller University in New York City decided to take a closer look at the nose’s true powers, and found that the human nose was much more capable than we imagined, giving the phrase “the nose knows” a whole new level of credibility.

Smell Is Closely Entwined With Memory

Sometimes smells like fresh-cut grass, a delicious baked pie, or a particular deodorant will bring back a long-forgotten recollection that sends you strolling wistfully down memory lane. Well, that’s by biological design, and it has to do with the way the human brain is wired. Unlike our four other best-known senses — which are first routed through the thalamus before reaching the hippocampus, the area of the brain associated with memory — smells are sent directly to the olfactory bulb located above the nasal cavity. While this bulb is directly tied into the hippocampus, it’s also connected with the emotion-processing amygdala, which is why smells can elicit such potent memories. Because smells can deliver these powerful whiffs of nostalgia, companies including Nike, Verizon, and many others have developed — and sometimes even trademarked — certain smells associated with their retail stores and products.

Some Women Don’t Have Olfactory Bulbs (But Smell Fine)

The olfactory bulb, as the name suggests, is central to our sense of smell. With millions of olfactory receptor cells, the bulb helps translate smells into signals the brain can interpret, so no olfactory bulb means no sense of smell — or so we thought. In 2019, scientists at the Weizmann Institute of Science in Israel were studying why some people have such a particularly strong sense of smell when they discovered in an MRI scan that one 29-year-old participant was completely missing her olfactory bulb. The woman was also left-handed — a factor that when combined with a missing olfactory bulb has a known effect on the organization of the brain. After poring over more data, the scientists estimated that 0.6% of women (and 4.25% of left-handed women) don’t have an olfactory bulb, but nevertheless can smell as well as — and in some cases even better than — those with one. Strangely, missing bulbs were not found in men.

How is this possible? Well, we don’t really know (yet). It’s possible that functions associated with the bulb were disorganized in these particular southpaws, meaning the necessary receptors are still there, just arranged in ways imperceptible to MRI scans. For now, the mystery remains.

Our Sense of Smell Is Strongest in the Evening

Although it’s imperceptible to the average person, smell actually fluctuates throughout the day. Research conducted by Brown University in 2017 studied 37 teenagers for a week and measured their sense of smell in relation to levels of melatonin, a hormone that helps induce sleep. The study found that our sense of smell is intimately entwined with our circadian rhythm — the natural cycle our bodies experience every day. When participants were approaching “biological night” around 9 p.m., their sense of smell was heightened, but strangely the opposite was true between 3 a.m. and 9 a.m. Although scientists don’t know the reason for this sniffing discrepancy, one theory harkens back to our evolution. In our hunter-gatherer days, the body might’ve ramped up our sense of smell right before sleep in an effort to hunt (or forage) for that last meal or to detect any nearby threats before bedding down for the night. An increased sense of smell might’ve also encouraged some pheromone-induced mating. Whatever the reason, humanity’s sense of smell appears to be a bit of a night owl.

Humans Are Wired To Smell Petrichor

You know that earthy smell that always accompanies rain after a long dry spell? That specific aroma has a name, “petrichor.” Coined in 1964 by Australian scientists (who would know a thing or two about dry spells), “petrichor” is a portmanteau of “petros” (stone) and “ichor,” which is a name for a bloodlike “ethereal fluid” of the gods in Greek mythology. The smell comes from actinobacteria that release organic compounds known as geosmin into the air when it rains. What’s strange is that humans are incredibly sensitive to the stuff — our ability to smell petrichor is far more sensitive than the ability of sharks to smell blood in the water. Many of humanity’s modern biological oddities can be explained by the hundreds of thousands of years spent living in hunter-gatherer tribes, and our keen sense for petrichor is another one to add to the list. Some scientists theorize our noses are so fine-tuned to sniff out this smell because finding water and rainy weather was often a matter of survival — and where there’s petrichor, there’s water. So the next time that telltale smell tickles your nostrils, sit back and marvel at the meticulous machinations of evolution that made such a moment possible.

You Can Smell Emotions

Most people are familiar with the power of pheromones, but research is hazy at best regarding what role they play in human behavior and sexual attraction. Bees, for example, possess a vomeronasal organ that detects pheromones and sends signals to the brain. While some humans possess the remnants of this organ, it’s vestigial and nonfunctional. However, scientists expect that other parts of the olfactory system might’ve picked up the slack, making chemoreception between humans possible. A study conducted in 2012 collected sweat from male participants as they watched fear- or disgust-inducing movies. When women participants were asked to do a visual task while exposed to the sweat samples, scientists monitored their facial expressions and discovered that women matched the emotion that originally elicited the sample — a sign that something in the sweat activated some form of chemoreception locked away in the human mind.

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Although radio is sandwiched between two revolutionary communication technologies — the telegraph and the television — the medium has remained remarkably resilient. First broadcast at the end of the 19th century, radio continues to provide the soundtrack to countless commutes. However, its importance goes far beyond local shock jocks and Top 40, and it still underpins the modern world. Here are six amazing facts about radio, from its remarkable discovery to its transformation into a world-changing communication system.

Radio Waves Were Theorized Before They Were Discovered

The scientific community knew about radio waves before anyone discovered actual evidence of them. In 1865, Scottish mathematician and physicist John Clerk Maxwell predicted the existence of radio waves in a paper titled “A Dynamical Theory of the Electromagnetic Field,” based on a presentation he gave before the Royal Society in December 1864. He also developed a set of electromagnetism equations known to history as “Maxwell’s equations.”

Although Maxwell gave due deference to his predecessor Michael Faraday, who had discovered electromagnetic induction among other principles of electromagnetism, many consider Maxwell’s work — which predicted various waves along the electromagnetic spectrum — a pivotal moment in the history of science and technology. These waves remained theoretical for more than 20 years, until German physicist Heinrich Hertz demonstrated radio waves for the first time in his laboratory in 1888 — forever transforming the history of communication.

The First Reported Transatlantic Radio Transmission Might Never Have Happened

Although Hertz got his own unit of frequency for his trouble, the undisputed giant of early radio is Italian inventor Guglielmo Marconi. After studying the work of Maxwell, Hertz, and other influential physicists while growing up, Marconi sent a radio signal more than a mile at his estate in Pontecchio, Italy, in 1895. Sensing both opportunity and celebrity, Marconi took out several patents and demonstrated his system throughout Europe. Then, on December 12, 1901, Marconi set out to prove that radio waves were not impacted by the curvature of the Earth. With a transmitter set up in Newfoundland, Canada, and another in Cornwall, England, some 2,100 miles away, Marconi waited for the three clicks (the letter “S” in Morse code) coming from Cornwall to prove that his invention — and the radio waves it produced — could work across long distances. Accompanied by his assistant George Kemp, Marconi believed he heard the expected three clicks, proving that his invention worked. Kemp also agreed that he heard the clicks.

Today, many experts are skeptical that the pair actually heard the clicks, since Marconi had many motives to act as if they did (and Kemp may have gone along). There were no independent witnesses, and it’s highly implausible the technology would have been capable of producing a transatlantic transmission at the time. It’s likely we’ll never know for sure what really happened that day.

The Most Powerful Radio Station Ever Was in Cincinnati, Ohio

In May 1934, President Franklin D. Roosevelt pushed a button in the White House, and the world’s first “super station,” WLW, came to life near Cincinnati, Ohio. The station used an 831-foot, 500-kilowatt tower capable of sending a signal halfway around the world. The project was designed as a temporary experiment to spread radio waves far and wide, but unfortunately, its immense power and operating costs proved to be too much. Stations far away from Cincinnati but still within range of the 700-hertz frequency complained of constant interference. People living close to the tower also reported hearing the broadcast vibrating along metal kitchen pans, barbed-wire fencing, or even bedsprings. After five years, Congress decided 500 kilowatts was simply too powerful, and limited broadcasts to 50 kilowatts — the current limit for AM clear-channel stations today.

The First Radio Commercial Was for a Real Estate Developer in NYC

In August 1922, New York radio station WEAF created something that would change the radio industry forever — it broadcast the very first radio commercial. The ad spot was for an apartment complex in Jackson Heights, Queens. Although radio ads are an obvious innovation now, one worry among early radio stations was how to make money from the service, since people weren’t charged for the endless stream of programming itself. Initially ads may not have seemed like a profitable strategy given the limited number of listeners, but economics changed as more radios began to find their way into American homes. Between 1923 and 1930, the number of Americans who owned at least one radio jumped to 60%, meaning that there were enough listeners for the radio ad business to be booming.

Radio Is an Extremely Important Tool for Astronomers

Because radio waves are part of the electromagnetic spectrum — one of the fundamental forces of nature — stars, quasars, planets, galaxies, and dust galaxies emit them. Some of the earliest attempts to use radio to investigate the stars came at the turn of the 20th century, when astronomers attempted to pick up radio emissions emanating from our sun. Today, radio astronomy is an entire field of dedicated scientists pointing massive radar arrays at the stars in an effort to glimpse things unseen by the naked eye. One of the most impressive radio telescopes in the U.S. is the National Radio Astronomy Observatory’s Robert C. Byrd Green Bank Telescope located in West Virginia. The telescope is the largest fully steerable radio telescope in the world, and the machine is so sensitive to radio waves that Wi-Fi is illegal in the 13,000-square-mile “National Radio Quiet Zone” surrounding the telescope.

The Eiffel Tower Avoided Destruction Because of Radio

It’s hard to imagine Paris without the Eiffel Tower, but the iconic tower wasn’t meant to stick around forever. Gustave Eiffel originally built his eponymous tower for the Exposition Universelle of 1889, and the city only leased the land to Eiffel for 20 years. After that, the land was to be returned to Paris and the tower demolished. Knowing the destruction in store for his precious monument, Eiffel set about finding some way to make the tower both useful and symbolic. On November 5, 1898, the Eiffel Tower participated in an early demonstration of radio when a signal was sent from the tower’s tip to the Pantheon some 2.5 miles away.

In the early 20th century, Eiffel doubled down on transforming his monument to progress into a full-fledged radio tower. By 1908, radio waves emanating from the Eiffel Tower could reach distances of more than 3,500 miles, and its creator had successfully proved its strategic worth. The Eiffel Tower then proved vital during World War I as it intercepted radio messages sent by the Central Powers. Today, the tip of the Eiffel Tower is still home to various radio antennas.

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It’s hard enough for your doctor to diagnose your mystery rash, but it’s leaps and bounds harder for historians to make sense of history’s weirdest and most mysterious maladies. Even with updated technology and research, it’s difficult to really know what really happened 500 or even 100 years ago. And that’s not to mention some afflictions that still stump us. These five cases — from explosive teeth to a dancing plague — have been the source of scientific speculation for decades or more. Do you have any theories?

The Dancing Plague of 1518

In July of 1518, a woman in Strasbourg — now part of France, then part of the Holy Roman Empire — stepped into the street and started to dance. She kept going until she collapsed from exhaustion, then started up again. More people started to join her, and a week later, there were more than 30 dancers, unable to stop even when overexertion set in and they started hurting themselves. Local leadership thought the solution might be more dancing, so they brought in dance halls, musicians, and even professional dancers. The issue, predictably, got worse, and eventually hundreds of people were afflicted. Some died of heart attacks and strokes. Strangely, this isn’t even the only time this happened — just the best-known case.

At the time, doctors and clergy thought the culprit was demonic possession or “hot blood.” Modern theories include stress-induced mass hysteria or a psychoactive mold called ergot that grows on rye (and which some have also blamed for contributing to the Salem witch trials).

The Mysterious 19th-Century Exploding Teeth

In the early 19th century, modern dentistry was basically in its infancy, which may be why nobody knows what caused several cases of exploding teeth. In 1817, a Pennsylvania reverend had a toothache so bad that he was, according to his dentist, “boring his head on the ground.” The next morning, his tooth burst apart with a sharp cracking sound and the pain was gone.

One exploding tooth is strange, but this wasn’t an isolated incident. Three more cases popped up in America in 1830, 1855, and 1871, and a few were recorded in England as late as the 1920s.

In 1860, one dentist theorized that gas from tooth decay was building up and causing the teeth to explode. Modern dentists have suggested that it was an issue with the varieties of metals used for fillings at the time. Both are pretty unlikely scenarios, and the cause remains a mystery.

What Plagued Ludwig van Beethoven?

Composer Ludwig van Beethoven famously started losing his hearing in his late 20s, and although he kept making music for another three decades, his affliction caused some severe depression. His lesser-known ailments certainly didn’t help, either; in his early 20s, he developed severe gastrointestinal symptoms that lasted the rest of his life. Overall, his symptoms were bad enough that he hoped his malady would be studied after his death. He died at the age of 56 with damage to his liver, kidneys, and pancreas after contracting pneumonia. Historians have spent the last 200 years trying to figure out his underlying illness, suggesting everything from lead poisoning to syphilis to celiac disease. DNA analysis from locks of his hair hasn’t turned up anything conclusive (and has just created some more mysteries), but it did reveal a genetic predisposition to liver disease.

The Sleeping Sickness of the 1920s

In 1915 or 1916, doctors in Europe started seeing patients with a mysterious set of symptoms. The condition would start out as a headache, fever, and sore throat before declining into a bevy of neurological symptoms such as double vision or tremors. Around 1 million people eventually developed encephalitis lethargica, or sleeping sickness — unrelated to African trypanosomiasis, which is also sometimes called sleeping sickness.

Eventually, many patients became catatonic or developed debilitating movement disorders that would keep them institutionalized for the rest of their lives. Some patients were revived briefly in 1969 with an experimental Parkinson’s drug, but eventually the symptoms returned. After killing hundreds of thousands of people, the disease all but disappeared in the late 1920s. Around 80 cases have been reported since 1940, but since the diagnostic criteria varies, the diagnoses may be unreliable.

Water Allergies

This affliction is more modern — it was first described in 1964. Technically known as aquagenic urticaria, it involves itchy, stinging welts that erupt within a couple of minutes after the sufferer’s skin touches water. (Drinking water usually seems to be fine). Only 37 cases have ever been reported. Scientists don’t understand what causes it: It might be a response to some kind of toxin in the water, a sensitivity to the ions in water, or some kind of histamine response. There’s no cure, only symptom management (like applying petroleum jelly before showering).