It is sometimes said that there are two types of tickling: knismesis and gargalesis. The former is the “light, featherlike” kind, which doesn’t induce laughter, while the latter is more high-pressure and does cause laughter. And while you may think of humans as the only creatures susceptible to gargalesis, one of our much smaller counterparts is as well: the humble rat. Rats actually love being tickled, especially on their back and belly, and there’s even a specific term for the frolicking they do in between tickles: freudensprünge, or “joy jumps.” Sadly, rat giggles are too high for us to hear without special microphones that can reproduce the sound in a lower register. (That doesn’t make videos of rats being tickled any less adorable, however.)

You can tickle yourself.

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Because your brain knows that you’re using your own fingers to do it, it’s impossible to be surprised by a self-tickle. The mind “dials down the sensory response” in such situations, and much of the joy (or displeasure!) of being tickled apparently comes from the lack of control.

All of the great apes (gorillas, chimpanzees, bonobos, and orangutans) let out a “remarkably humanlike laugh” when tickled, while animals ranging from dogs to penguins appear to enjoy it as well. That said, many humans do not — some find the sensation deeply uncomfortable, and laugh out of discomfort rather than joy. One study in which participants rated how much they like being tickled on a 10-point scale (from very unpleasant to very pleasant) produced an average of only 5. Perhaps surprisingly, people rated tickling others at only 5.9.

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Most rock formations found in nature are revered for their stoic appearance — think snow-capped mountains or monoliths like the Rock of Gibraltar. But some more active landscapes, like ever-shifting sand dunes, have a livelier presence: They can “sing.” An estimated 35 sand dunes around the world, including some in the United Arab Emirates, Chile, and the U.S., are known to produce eerie, vibrational hums in a variety of tones. Some even produce booms or croaking sounds. Marco Polo noted the phenomenon during his travels, and many communities surrounding dunes have developed their own superstitions about the songs. Yet for centuries, no one really understood why or how these sounds happened. 

NASA tests its space rovers on sand dunes.

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Mars has more than 4,000 sand dune fields, so navigating the rugged off-Earth territory takes some preparation. That’s why NASA has tested two Viking spacecraft at Colorado’s Great Sand Dunes National Park, where the robots experience extreme terrain and high temps.

Today, scientists believe sand dunes produce their songs in part because of avalanches. By nature, sand dunes shift as wind whips sand into new locations, and it’s likely the humming sound occurs when air pushes through millions of sand grains as they tumble into new positions. Even then, it takes a combination of weather conditions to create the silty harmonies; generally, sand must be extremely dry to emit sound.

Some of the world’s loudest sand dunes are found in China in the Badain Jaran Desert, reaching more than 1,600 feet tall and emitting sounds that peak at 105 decibels — the same volume as a music concert. In North America, the largest sand dunes are all found within Great Sand Dunes National Park in southern Colorado, reaching 741 feet at the base of the Sangre de Cristo Mountains, where scientists believe they have been singing their tune for nearly 12,000 years.

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Watermelon snow may sound like something from the Candy Land board game, but the phenomenon is very real — Aristotle even wrote about a “reddish” snowbank he found on Mount Parnassus in the fourth century BCE. Visitors to Antarctica, the Himalayas, the Rockies, the French Alps, and Yosemite National Park have also glimpsed this colorful occurrence. In the 1800s, Scottish botanist Robert Brown finally determined the culprit: a species of algae called Chlamydomonas nivalis. Under a microscope, single-celled C. nivalis appear green, but they also feature a secondary red pigment, astaxanthin, which is a carotenoid, part of the chemical family that can make carrots orange. This astaxanthin is dormant for much of the year, but when winter ice and snow start to thaw and the algae surface to divide and photosynthesize, they trigger their astaxanthin as a barrier against the sun’s harsh UV rays, turning red in the process. Some say this rosy snow smells sweet and fruity, although experts warn that eating large amounts can cause digestive problems. 

The visiting locker room at the University of Iowa's Kinnick Stadium is painted pink.

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Former Iowa football coach Hayden Fry requested the paint job upon joining the staff in 1979. Fry, who had a master's degree in psychology, felt the color calmed opponents. After Fry's 20-year tenure, pink toilets, showers, and lockers were added to complement the walls.

Algae is responsible for creating much of the world’s oxygen and forming the basis for most food webs; thousands of species exist. Algae is also often a factor associated with major color changes: Dunaliella algae are believed to be one origin for the pink lakes that draw shutterbugs to places such as Australia, Senegal, and Spain, and many experts hypothesize that Trentepohlia algae led to the red rains that fell in Kerala, India, between July and September 2001. Recently, cold climates on different continents have witnessed an increase in clusters (or blooms) of C. nivalis algae, and scientists are working to understand why. Besides red, the blooms can appear green, gray, or yellow. 

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In the last 15 years or so, 10 Downing Street in London has welcomed six different British prime ministers — and one tenant has lived and served alongside all of them. Larry the Cat is the latest in a long line of pets at the U.K. prime minister’s residence, but the first to be awarded the official title of chief mouser to the Cabinet Office (though others have performed similar functions).

Mice love to eat cheese.

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While a hungry mouse may sink its teeth into an available hunk of cheese, it’s far more likely to enjoy fruits and grains.

Like his predecessors, Larry has been treated with largely playful coverage by the U.K. tabloids. Adopted from the Battersea Dogs & Cats Home for his alleged hunting abilities, the domestic shorthair was “roasted” by the press when a rodent surfaced at a Cabinet dinner early in his tenure, and he later drew attention for his tussles with fellow mouser Palmerston from the Foreign Office. The government’s media arm has even gotten in on the fun with an official profile that lists such feline responsibilities as “testing antique furniture for napping quality” and “contemplating a solution to the mouse occupancy of the house.” Meanwhile, Larry’s unofficial X account has racked up more than 800,000 followers thanks to a steady stream of reliably cheeky quips.

Reportedly tolerant of the family dog that accompanied the previous PM Rishi Sunak into office, Larry showed his predatory instincts remained sharp by chasing away a fox that wandered too close to 10 Downing in October 2022. While U.K. residents may have their hands full with the usual complement of domestic and international issues, they can feel comfortable knowing that Larry is doing his part to keep government operations running smoothly.

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