It's a question children ask as often as they ask why the sky is blue. Why is pee yellow? Any answer outside of "I don't know" was most likely more entertaining than the truth, which scientists have revealed to us. A previously unknown enzyme called bilirubin reductase is behind it. Bilirubin reductase is not yellow, but it factors into the process.

Our bodies are always producing new red blood cells and eliminating old ones. Old red blood cells release an orange pigment called bilirubin as they die. Several species of gut microbes in our bodies use the enzyme bilirubin reductase to break down the bilirubin into urobilinogen, which turns yellow as it degrades. Biochemists who've been studying the question for more than a century (not the same scientists) knew about bilirubin and urobilinogen, but the step in between them is the discovery that makes it all work. Those microbes producing bilirubin reductase are doing us a great favor, because too much bilirubin causes jaundice. You can read up on the experiments that revealed the new enzyme at Ars Technica.

But what if your urine isn't yellow? You might need to see a doctor.

(Image credit: Turbotorque)

The tschäggättä are villagers who roam the narrow streets of the valley, clanging bells and making mischief dressed as Sasquatch-like creatures. https://t.co/WqyozsgJti

— Smithsonian Magazine (@SmithsonianMag) January 30, 2024

Name a holiday celebrated anywhere, and there will be some kind of legendary monster associated with it. Carnival is the season of gluttony before the Christian fasting time of Lent leading up to Easter. In most places, Carnival involves parties, parades, masquerade balls, eating, drinking, and various debaucheries that will be forbidden beginning on Ash Wednesday. In Switzerland's Lötschental Valley, they have the added festivity of monsters roaming the streets.

These creatures are called tschäggättä. Villagers dress in fur with padding to make them look taller and wooden masks carved with scary human faces. They ring cowbells and make mischief that once included fights, theft, and assaults, but now involve mainly harmless teasing to folks who come out to see them. We have evidence of the tschäggättä going back more than 200 years, but the tradition could be much older. How did it start? No one, not even those who participate every year, knows. Read what we do know about the tschäggättä of the Lötschental Valley at Smithsonian.

From an individual point of view, time moves in a line from your past to the present and then into the future. All we experience is the present, but we remember the past, and anticipate the future -although we cannot know it until it is the present. But the theory of relativity states that time moves differently for beings moving through space at different speeds, so is their "present" different from ours? And how would different "presents" work? The idea of multiple presents warps the idea of an unknowable future that can be affected by the choices we make in the present. If that's too mind-blowing, maybe we should look at time in a different way to make it mesh with our lived experience. Then there's always the possibility that we are wrong, but how would we ever know? Some scientists have even weirder ideas about how time works. Kurzgesagt takes us through these ideas in ten minutes with a video full of more or less obscure cultural references you may not catch the first time around; the rest of this video is an ad. -via Digg

British novelist Wilkie Collins met Charles Dickens when they were both doing amateur theater. They became good friends, which was sometimes a drawback when critics pointed out that Collins' novels weren't as good as Dickens. Collins' may not have been as gifted as his friend, but he left a lasting legacy in his works. Collins wrote melodramatic stories in what were called "sensation novels" at the time, that were written to play to the emotions and stir a physical reaction in the reader. Many of them used supernatural elements to elicit a response, but Collins never did. His horrors were real and based on the laws of the time.

See, Collins had a law degree, even though he never practiced law. But he understood the laws of the day, and his novels incorporated them into "the worst that could happen" scenarios for women. Married women had no rights at all, even to their own property. They were at the mercy of their husbands, who, in Collins' stories, could control their autonomy and their very lives. He also explored the themes of poverty, adultery, abuse, inheritance, illegitimacy, divorce, power, and murder. His years of writing coincided with a push for reform in women's rights (which his sensation novels no doubt contributed to), and each story was carefully vetted for contemporary legal accuracy in consultation with Collins' own lawyer. Read about Collins, his works, and the changing laws involving women's rights in Victorian England at Smithsonian.

Could there be a more perfect or hilarious crossover than the Muppets doing Mad Max: Fury Road? There isn't a movie (yet), but the idea is looking pretty good in a series of 20 images by redditor InkSlinger1983 using the artificial intelligence program Midjourney. He's been working on this for some time- this is version 6.

AI still isn't all that great at recreating images of humans, which honestly is a good thing, but putting Muppets into the vehicles works because they come with their own permanent expressions that lend a certain levity to the two-hour chase scene we know as Fury Road. Muppets fit into the roles of the War Boys, the Doof Warrior, Immortan Joe, and the other drivers. InkSlinger1983 tells us he tried, but couldn't recreate Mad Max or Furiosa because Midjourney kept wanting to render them as humans.

   

See all 20 images in a slideshow at reddit, or in a one-page gallery at Geeks Are Sexy.

Some pretty high-profile crimes have been solved by examining how the perpetrators, or accused innocents, use language. The way a person uses words, grammar, and puctuation creates a personal style and vocabulary that's somewhat like a fingerprint. Linguists know how individual these styles can be, and forensic linguists detect these patterns as clues to uncovering the truth in crimes.

When I listened to this video, I was deeply impressed by what forensic linguists can do, but I could also see how we all can learn these skills with time and effort. I'm no linguist, but having dealt with the written word for so long (and the spoken word before that), I know my own writing habits and try to correct for their overuse, not always successfully. I also recognize the styles and habits of writers whose words I proofread and edit. Avid readers recognize the style of their favorite author even when the byline is different. And everyone knows when someone close to them is drunk when they are texting. Language is something we all learn as children, but the way we use it eventually gains its own personal stamp.

Some countries, like Denmark and Iceland, have a list of approved names you can give your baby. Some countries keep a list of names you can't give your baby. New Zealand has no such lists, but each name is judged on a case-by-case basis, and must be approved by the Department of Internal Affairs. The department has released a list of the rejected names of 2023, led by Prince. That named supplanted last year's top rejected name, King, but further down the list is Kiing and Kingkillah. New Zealand has a rule for rejecting titles for names, like Major, Bishop, Princess, Messiah, Judge, Captain, and Sovereign. See the list of names rejected by New Zealand authorities at Today. You have to wonder how they got two requests to name a child III3. Kiwi names used to be much more imaginative, as seen in this article from 2008.

Americans would laugh at such tame attempts. For evidence of the things we name our children, all you have to do is take a peek at the subreddit r/tragedeigh. Be warned that it's a serious time sink. -via Fark

(Image credit: jimieye)

Butterflies are light and delicate and catch our eyes with an amazing variety of vivid colors as they flutter about. This is all due to some insanely complex and intricate systems that they've evolved. The way they fly through the air involves astonishing physics tricks. Their colors have different purposes, and come about through different schemes. Add those tricks to the weird way they transform from a caterpillar to something completely different, and you have to wonder why they didn't just take over the world while they're at it. The physiology of a butterfly is mind-blowing, but for some reason, we don't have as much respect for moths. Maybe that's because butterflies won't eat our winter coats. Moths are a lot like butterflies, but they fly at night, so we don't pay as much attention because we just don't see them as much. Anyway, you'll learn a lot from the latest episode of Ze Frank's True Facts series. There's a one-minute skippable ad at 7:14.

During NASA's Space Shuttle program, highly-trained NASA astronauts were supplemented by payload specialists, who were sent up to conduct experiments in microgravity. Their priority was the task they were assigned to do, and their space training was not as long nor as rigorous as that of career astronauts. In 1985, this presented a problem.

Physicist Taylor G. Wang was a payload specialist on the Challenger shuttle, mission STS-51-B. He designed the Drop Dynamics Module experiment, meant to study the physics of liquid drops in microgravity. Wang had been preparing for this experiment for years. But on the shuttle, the module did not activate. It was a serious setback, but Wang thought he could repair the module. He asked NASA for more time in orbit to fix the experiment. They said no. Growing despondent, Wang told Mission Control,

"Hey, if you guys don't give me a chance to repair my instrument, I'm not going back,"

That was quite a statement, and one situation NASA had never encountered before. What do you do? The mission commander and Ground Control spent hours talking to Wang, but to learn how the situation was resolved, you'll need to read the whole story at Ars Technica. You'll also learn about the steps NASA took in case that sort of situation were to come up again, which was rarely talked about at the space agency. -via Nag on the Lake

(Image credit: NASA)

pic.twitter.com/uIy4dqZlUv

— cat with confusing auras (@CatsIX) January 20, 2024

You look like you could use a laugh. Here's a video that will make everything all better. And now I've discovered a genre of internet video I can really get behind- a supercut of cats being goofballs, here set to Jacques Offenbach's "Can-Can"! Make sure the sound is on. This was posted by cat with confusing auras, and you might have to watch it twice as you'll surely miss something the first time around, because you're laughing. -via Everlasting Blort

In the 1960s, McDonald's began their quest to initiate children into a life of fast food when they introduced Ronald McDonald. In the '70s, they went all in by adding playgrounds to their outlets that they called PlayLand. The kids loved it, but the metal playground equipment wasn't all that safe. But McDonald's wasn't giving upon kids. The playgrounds moved inside gradually through the 1980s and '90s, when metal equipment was replaced by plastic that included tall tunnels, spiral slides, and ball pits. The new indoor playgrounds were called PlayPlaces. Parents loved the PlayPlaces, where they could eat in peace while their children burned off energy on the safe and modern playground equipment, away from stranger danger.

But the PlayPlaces had their own problems. If you've ever taken a good look at the structures, they were very hard to access for adults. My youngest once laughed at me from the top tube for twenty minutes because she didn't want to leave. McDonald's employees didn't want to climb up there to clean, either, and you can imagine what little children can leave behind in those small spaces. That was just one of the factors that rang the death knell for PlayPlaces, which you can read about at Mental Floss.

(Image credit: Sikalar)

Actor Dev Patel, who you know from Slumdog Millionaire and The Green Knight, is both director and star of Monkey Man. The film has been described as "John Wicke in Mumbai." If the trailer is at all representative, Monkey Man offers gun fights and street fights and fighting in the ring as well, Hindu deities and superheroes, social justice and revenge, sin and redemption, over-the-top yet realistic set pieces, and even a touch of comedy. Oh yeah, and some bangin' music. If I had to describe the trailer in one word, it would be "intense."   

If you need it, a bit of the plot is explained at the YouTube page. Monkey Man was originally supposed to premiere on Netflix, but after seeing it, producer Jordan Peele pushed for a theatrical release. I can understand that; this is going to be epic on the big screen. Monkey Man will hit theaters on April 5.

A couple of years ago, we told you about the Perth Museum, which, despite its name, is in Scotland. Perth, Scotland, to be exact. The museum will open on March 30 with an exhibit on Scotland's national animal, the unicorn.

This raises the question: why does Scotland have a national animal that doesn't live there and never has? Or anywhere else, for that matter? They could have chosen the Scottish wildcat, the Scottish terrier, or the wild haggis. But the designation wasn't put to a vote. King William I, or William the Lion, put the unicorn on his royal coat of arms in the 12th century. It was kept by later monarchs as a symbol of "purity and power." Today, the unicorn has many connotations, which the museum exhibit addresses. Read up on what the unicorn means to Scotland and see a preview of some of the museum exhibits at Smithsonian.   

(Image credit: Thomas Nugent)

Twenty years ago, we started playing Six Degrees of Kevin Bacon, to see how everyone in Hollywood is connected to actor Kevin Bacon by either appearing in a movie with him, or appearing in a movie with someone who did. But it was not a new idea. The phenomenon of the Erdős number was first mentioned in print in 1969! Paul Erdős, who died in 1996, was the world's most prolific mathematician, publishing more than 1500 papers on mathematics. Collaborators whose name appears on those papers have an Erdős number of one, and anyone who produces a science paper with those people gain an Erdős number of two. Thousands of mathematicians have an Erdős number of two or lower, but a quarter million mathematicians have numbers. And you don't even have to be a mathematician to have this number. Elon Musk has an Erdős number of four, and Natalie Portman has a five.

Paul Erdős could publish so many math papers because he constantly thought about math and never did anything else. He never married or had children, had no hobbies, never learned to drive, and had no permanent residence. Erdős would move in with another mathematician to collaborate, but was a horrid houseguest with his singular drive to do math. Read about the brilliant but strange mathematician at Scientific American.  -via Strange Company

(Image credit: Kmhkmh)

Earlier this month, we looked at the relative number of victims of various pandemics in history. Now let's find out more about those diseases. What illnesses were people most afraid of during different historical eras? There was leprosy, influenza, bubonic plague, syphilis, smallpox, cholera, tuberculosis, and COVID-19, but none of those existed by themselves, and even these diseases were sometimes misdiagnosed because there was always something else out there that wanted to kill you. And these deadly illnesses became epidemics because of close living conditions and poor sanitation in crowded cities. Our own sociability became a mass transit system for bacteria and viruses. Enhanced travel took diseases to other communities all around the world. If you worry about getting sick, just be thankful for modern science. Back when we couldn't figure out what was causing these diseases, much less prevent or treat them, your odds for surviving them were downright dismal.