Favorite – Intriguing Facts

7 Splashy Facts About Swimming Pools

Arvyn Braich — Tue, 28 Oct 2025 15:29:55 +0000

You might think swimming pools are just a simple mix of blue water & chlorine. But you’d be wrong. There’s a lot more going on with pools than meets the eye, including some strange chemistry and weird biology.

Here are seven interesting facts about swimming pools. Which one surprised you the most?

Urine really does react with chlorine

Pool smell doesn’t come solely from chlorine. It’s actually from when urine mixes with chlorine to create gases like cyanogen chloride & trichloramine, both of which irritate your eyes and nose.

Tiny amounts of uric acid trigger this chemical reaction. So yes, your eyes stinging after swimming is caused by chemistry, rather than cleanliness.

Scientists measured how much urine is actually in pools

Speaking of urine, scientists performed tests to see how much urine is in pool water. They checked for a sugar substitute known as acesulfame-K, which passes through the body unchanged. What did they find?

It was in every pool they tested. The scientists compared levels & found out that a public pool likely has around 30 to 75 liters of urine. How delightful.

Swimmers add sweat

Most people have no clue about how much they’re actually “contributing” to pool water. Each swimmer adds sweat & plenty of other organic material to the swimming pool, even when they don’t leave the lane.

The average person releases around 0.1 to 0.8 liters of sweat every hour. That’s not including other compounds like nitrogen & carbon. These all mix together in the pool, making for a shared experience in the worst way.

The water looks blue because red light gets absorbed

Physics is the reason why pools look blue, not dye or tiles. Water naturally absorbs red light better than blue. The light that bounces back to your eyes looks sky blue, and the deeper the pool, the more blue it appears to your eyes.

It’s the same reason a glass of water looks clearer than an Olympic pool.

Green hair from pools comes from copper, not chlorine

That’s not all for colors. Most people assume that when their hair goes green after swimming, it must mean there’s a high concentration of chlorine in the pool. But the real cause is copper.

Copper leaches from pipes & algaecides, then grabs onto your hair protein. The effect is especially noticeable with blond or color-treated hair.

Thankfully, you can avoid the effect by rinsing your hair first or using special shampoos to take the metal out.

Olympic pools are kept colder on purpose

Olympic swimming pools are cooler than you might expect. Officials keep the temperature around 77 to 82°F. Why?

Because it’s the perfect temperature for when you’re trying to move quickly, as cooler water helps your muscles work longer. The lower temperature also keeps your body temperature steady when you’re doing intense laps.

The world’s deepest pool could swallow a building

Poland is home to the world’s deepest swimming pool. It’s called Deepspot & it has a drop of approximately 148 feet. That’s rather impressive when you remember that the average building is only around 20 to 26 feet, including the roof.

Deepspot also holds a million gallons of water. But the pool isn’t made for a casual swim. It’s only for divers & film crews, as well as those who are training to deal with pressure under deep water.

The following sources were consulted in the preparation of this article:

10 interesting facts about the world’s population

Arvyn Braich — Tue, 07 Oct 2025 20:13:07 +0000

People talk about the world like it’s one big number. However, the statistics about population include some interesting details you don’t hear every day. These go beyond simply who’s living where. Here are ten interesting facts about the world’s population. Which of these surprised you most?

Featured Image Credit: Shutterstock.

The world hit 8 billion on November 15, 2022

Tuesday, November 15th, 2022, was a special date. It was when the UN’s official estimate finally reached over 8 billion people, although they didn’t count heads one by one. This number came from decades of birth & death records blended with census data. It’s more of a symbolic date than a “true” count. But it was still an important moment in history.

India is the most populous country

China had the most people for many years. But in 2023, India pulled ahead, with a gap of around two million people, which sounds small, but it was enough for the UN to call it. India had about 1.428 billion & China slightly less at 1.426 billion. It was a real passing of the crown. And it’s all thanks to the slowing birth rates in China and steady growth in India.

Global births peaked in 2012

More babies were born in 2012 than in any other year so far, at roughly 146 million. That number has decreased slightly since then. Demographers have tracked this figure with fertility rates, but the big picture is that the world’s “baby boom” year already came & went. Who knows when the next one will happen?

The growth rate fell below 1%

2020 sure was a record-breaking year. It was the first time since the 1950s that the global growth rate slipped under 1% a year. The headcount did rise afterwards, but it’s climbing more slowly than before. Fewer than one extra person per hundred has been added each year worldwide.

Eight countries drive over half of growth

Population growth isn’t spread evenly. According to the UN, just eight countries will account for more than half the world’s increase through 2050. These are Congo (DRC), Egypt, Ethiopia, India, Nigeria, Pakistan, the Philippines & Tanzania. The majority of other countries? They’re suffering from low birth rates.

Urban living will reach about 68% by 2050

Anyone who lives in a city will know how packed they feel now. But try imagining nearly 7 out of 10 people worldwide living in one. That’s the UN’s forecast for 2050, and in 2018, the number was closer to 55%. They used data from tracking settlements & standardizing to create this figure. Let’s hope it doesn’t get that bad.

Older adults surpassed under-fives in 2018

In 2018, the worldwide demographic flipped. The number of people aged 65+ outnumbered kids under five for the very first time in history. Looking forward, the UN projects that about one in six people will be 65 or older by 2050. This figure means that the age pyramid will look more like a rectangle in the future.

Japan has the highest share of people over 65

Almost three out of every ten people are now over 65 in Japan. That’s roughly 29% of the population in 2023. It’s a higher figure than anywhere else in the world, even in countries like Italy & Finland. These also have large older populations. But Japan has a high number of older people, yet also a low number of young people.

38% of people live close to coasts

A huge chunk of the world prefers to stay near the water. One 2018 study showed that about 38% of people live within 100 kilometers of a coast, for one reason or another. That’s nearly four out of every ten humans choosing spots that aren’t far from shorelines. It makes sense, though. Coastal zones often mean easier access to trade, food & transportation.

The world will have 43 megacities by 2030

A megacity is defined as 10 million people or more. And the UN expects there will be 43 of them by 2030, although back in 2018, there were only 33. The biggest growth is happening in Asia & Africa. Urban areas are expanding there faster than anywhere else, with cities like Lagos & Kinshasa being on track to join or climb higher on the list.

The following sources were consulted in the preparation of this article:

7 extraordinary animal abilities

Arvyn Braich — Sun, 05 Oct 2025 08:30:52 +0000

Animals are full of surprises. And some of the things they do may sound unbelievable, but they’re real. These include animals with bubble “guns” & little creatures that can shrug off space itself. Here are seven extraordinary animal abilities and the scientific studies behind them (see the end). Which one do you think is the weirdest?

Featured Image Credit: Shutterstock.

The pistol shrimp cavitation snap

A pistol shrimp is able to slam its claw shut, and it’s loud. Pretty loud. In fact, it blasts out a jet of water so fast that it makes a bubble collapse with a bang. That brief implosion is hotter than the surface of the sun & it also gives off a flash of light. It all comes from a shrimp under two inches long.

The peacock mantis shrimp’s punch

The peacock mantis shrimp uses more than simple muscles to punch. It has a biological “spring-loaded hammer,” which is a kind of joint that stores energy. The mantis then lets the punch fly in a move that’s faster than most bullets in water. In fact, high-speed cameras have clocked the strike at over 50 mph. That’s enough to crack crab shells & even aquarium glass.

The electric eel’s shock

An electric eel is essentially an eel with built-in tasers. It fires off rapid electrical pulses that are able to make the fish’s muscles contract without the fish needing to move. The shock freezes prey in place, leaving it utterly helpless, and the eel can use this ability when it’s threatened. The fish can leap up & deliver the jolt straight to whatever’s touching it.

The bombardier beetle’s boiling spray

This beetle has chemistry labs inside its body, and when threatened, it mixes stored chemicals. These instantly react & heat to boiling. The result? A scalding spray that comes out in bursts, almost like a tiny machine gun, with a temperature that reaches near 212°F. The beetle can swivel its nozzle to aim with surprising accuracy.

The wood frog’s deep freeze survival

Wood frogs do what sounds impossible every winter. They literally freeze. Their hearts stop & ice fills much of their bodies, but they aren’t dead. This is because of the amount of glucose & urea that they pump into their cells. It acts like natural antifreeze. Once the warmth of spring arrives, they thaw out and hop off as if nothing happened.

The hagfish’s rapid fiber-gel

The hagfish is a fish that defends itself with instant slime. Yes, really. It releases threads & mucus that mix with seawater to form a gooey net in seconds. The creature expands so much that it can choke the gills of predators trying to bite it, although that’s not the weirdest part. It’s the fact that it takes very little raw material to make gallons of the stuff.

The immortal jellyfish’s lifespan

Scientists found that Turritopsis dohrnii doesn’t age like other animals. Anytime something bad happens, like injury or stress, these jellyfish can literally de-age themselves. They roll back into their polyp stage. Essentially, they start fresh instead of breaking down with age, and they can do it again & again.

The following sources were consulted in the preparation of this article:

10 remarkable facts about the moon

Hasthi Wand — Thu, 02 Oct 2025 14:13:07 +0000

Everybody’s seen the Moon hanging up there. But it’s a lot stranger than a simple, pale ball of rock. The more scientists poke at it, the weirder it gets, and here are ten remarkable facts about the Moon, backed by science (see the end). Which one of these surprises you the most?

Featured Image Credit: Shutterstock.

The Moon’s core is shaped like Earth’s, but much smaller

To start with, the Moon isn’t simply a solid hunk of rock. It has a tiny inner core that’s made of dense iron-like material. It’s only a few hundred miles wide & is wrapped in a liquid layer. Essentially, you can think about it as being like Earth’s core. But it’s shrunk down by quite a bit. How cool is that?

Some lunar spots are colder than Pluto

Most people know that Pluto’s freezing. But it turns out that parts of the Moon are even colder, as the bottoms of certain lunar craters barely creep above minus 390°F. That’s colder than some parts of deep space. These holes trap ice, and they don’t get a single ray of sunlight. Ever.

The Moon has a 500,000-mile-long sodium tail

The Moon has its own faint orange tail made of sodium atoms, which stretches about half a million miles into space. We can’t see it with our eyes. However, astronomers have cameras that catch the glow around the same time of the new moon. It’s a pretty incredible sight to behold.

Moonquakes can last nearly an hour

You probably know that the Moon doesn’t have earthquakes because, well, it’s not Earth. It has moonquakes instead. The seismometers on Apollo spacecraft have measured these quakes, and some of have gone on for almost an hour. This is because the Moon’s dry crust doesn’t dampen vibrations like Earth’s. As such, the tremors just bounce around for a long time.

Gravity on the Moon is lumpy and weird

Gravity works differently on different parts of the Moon. That means that spacecraft flying over certain spots will be tugged down harder than expected, and those spots are called “mascons.” This is short for mass concentrations. Essentially, they’re hidden gravity potholes & they came from giant asteroid impacts. These left behind heavy, dense layers underground.

The far side is built like a fortress

The far side of the Moon is the one we never see from Earth. It has a crust that’s much thicker than the side we know, and the difference between the two is like the difference between a paper plate & a brick wall. This is one of the main reasons why that side has a lot of rugged mountains, instead of smooth lava plains.

Lava erupted just two billion years ago

Not all Moon lava is as ancient as you might think. In 2020, China’s Chang’e-5 mission scooped up volcanic rock that turned out to be only 1.96 billion years old. That’s practically yesterday from a geologic timeframe. Somehow, the Moon was spewing out lava while dinosaurs were just starting to stir on Earth. That really puts stuff into perspective, doesn’t it?

The Moon once had a magnetic field stronger than Earth’s

The Moon’s surface is relatively quiet today. But long ago, the Moon had a magnetic field that was even stronger than Earth’s. Rocks brought back from Apollo missions show that the field may have been twice as strong as Earth’s. That field lasted for billions of years. It’s quite surprising, given how small the Moon is.

We actually see 59% of the surface

The idea that we only ever see half the Moon isn’t strictly true. The Moon wobbles a little as it orbits, meaning that we get sneak peeks around the edges. Eventually, we see around 59% of the whole lunar surface. It’s not a lot more than half. But it’s enough.

The Moon is slowly moving away from Earth

Scientists have conducted numerous experiments & found out that the Moon isn’t staying put. It drifts a tiny bit farther from Earth each year. It’s not a lot, just over an inch, but it confirms that our lunar neighbor is slowly slipping out of reach. Astronauts left mirrors up on the Moon. On Earth, we bounce lasers off them to measure the distance.

The following sources were consulted in the preparation of this article:

6 interesting things to know about déjà vu

Arvyn Braich — Tue, 30 Sep 2025 13:48:53 +0000

That odd moment when you walk into a place & swear you’ve been there, even though you know you haven’t, isn’t just you. Scientists have studied déjà vu for years through some unusual experiments. It turns out that the brain has a lot of ways of tricking itself. Here are six interesting things scientists have actually found. Which one do you think is the strangest?

Featured Image Credit: Shutterstock.

Electrical stimulation in the temporal lobe can trigger déjà vu

Doctors discovered in neurosurgery labs that zapping certain parts of the brain can set off instant déjà vu. Patients reported feeling as though they were somewhere familiar or even that they had dream-like memories when the electrodes hit the temporal lobe. This is also true in epilepsy cases. Some people feel a sense of déjà vu right before a seizure.

People experience less déjà vu when they’re older

Questionnaires & surveys show déjà vu changes as you age. Teenagers & young adults say they get it a lot, but older adults report it far less, which could be due to stress and fatigue. In fact, one study estimated that around 60% of people have experienced déjà vu at least once. But how often that happens depends quite a lot on your age.

Your brain’s right-side experiences it more

Neurologists compared left vs. right brain stimulation and found something interesting. Déjà vu shows up a lot more often on the right. Patients with epilepsy had electrodes placed in both sides of the temporal lobe, and they reported stronger déjà vu when the right side was activated. That makes sense, since it’s where your hippocampus & rhinal cortex work together.

Some people suffer from “déjà vécu”

Experiencing déjà vu just once can be strange. Now imagine feeling it all the time. For some people, that’s a reality. They feel as though every single thing they do has already happened before. It happened to at least two dementia patients in an experiment, as well as someone with anxiety. Doctors called this “déjà vécu.” It means “already lived.”

Hypnosis can create déjà vu

In 2009, a group of researchers used hypnosis to see how it would affect people’s sense of déjà vu. Participants were told under hypnosis that certain new words would feel familiar later on. When those words actually appeared, the volunteers swore they’d seen them before. But they hadn’t. Clearly, hypnosis can make your brain play all sorts of tricks on you.

Some amnesia patients still experience déjà vu

Even memory loss can’t block déjà vu completely. In one case study, patients with serious amnesia (aka people who couldn’t recall events from just minutes before) still claimed to have feelings of déjà vu. The research found this could be connected to damage in the temporal lobe.

The following sources were consulted in the preparation of this article: