Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to CuriousKidsUS@theconversation.com.

Why don’t humans have hair all over their bodies like other animals? – Murilo, age 5, Brazil

Have you ever wondered why you don’t have thick hair covering your whole body like a dog, cat or gorilla does?

Humans aren’t the only mammals with sparse hair. Elephants, rhinos and naked mole rats also have very little hair. It’s true for some marine mammals, such as whales and dolphins, too.

Scientists think the earliest mammals, which lived at the time of the dinosaurs, were quite hairy. But over hundreds of millions of years, a small handful of mammals, including humans, evolved to have less hair. What’s the advantage of not growing your own fur coat?

I’m a biologist who studies the genes that control hairiness in mammals. Why humans and a small number of other mammals are relatively hairless is an interesting question. It all comes down to whether certain genes are turned on or off.

Hair benefits

Hair and fur have many important jobs. They keep animals warm, protect their skin from the sun and injuries and help them blend into their surroundings.

They even assist animals in sensing their environment. Ever felt a tickle when something almost touches you? That’s your hair helping you detect things nearby.

Humans do have hair all over their bodies, but it is generally sparser and finer than that of our hairier relatives. A notable exception is the hair on our heads, which likely serves to protect the scalp from the sun. In human adults, the thicker hair that develops under the arms and between the legs likely reduces skin friction and aids in cooling by dispersing sweat.

So hair can be pretty beneficial. There must have been a strong evolutionary reason for people to lose so much of it.

Why humans lost their hair

The story begins about 7 million years ago, when humans and chimpanzees took different evolutionary paths. Although scientists can’t be sure why humans became less hairy, we have some strong theories that involve sweat.

Humans have far more sweat glands than chimps and other mammals do. Sweating keeps you cool. As sweat evaporates from your skin, heat energy is carried away from your body. This cooling system was likely crucial for early human ancestors, who lived in the hot African savanna.

Of course, there are plenty of mammals living in hot climates right now that are covered with fur. Early humans were able to hunt those kinds of animals by tiring them out over long chases in the heat – a strategy known as persistence hunting.

Humans didn’t need to be faster than the animals they hunted. They just needed to keep going until their prey got too hot and tired to flee. Being able to sweat a lot, without a thick coat of hair, made this endurance possible.

Genes that control hairiness

To better understand hairiness in mammals, my research team compared the genetic information of 62 different mammals, from humans to armadillos to dogs and squirrels. By lining up the DNA of all these different species, we were able to zero in on the genes linked to keeping or losing body hair.

Among the many discoveries we made, we learned humans still carry all the genes needed for a full coat of hair – they are just muted or switched off.

In the story of “Beauty and the Beast,” the Beast is covered in thick fur, which might seem like pure fantasy. But in real life some rare conditions can cause people to grow a lot of hair all over their bodies. This condition, called hypertrichosis, is very unusual and has been called “werewolf syndrome” because of how people who have it look.

In the 1500s, a Spanish man named Petrus Gonsalvus was born with hypertrichosis. As a child he was sent in an iron cage like an animal to Henry II of France as a gift. It wasn’t long before the king realized Petrus was like any other person and could be educated. In time, he married a lady, forming the inspiration for the “Beauty and the Beast” story.

While you will probably never meet someone with this rare trait, it shows how genes can lead to unique and surprising changes in hair growth.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Maria Chikina, Assistant Professor of Computational and Systems Biology, University of Pittsburgh

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to CuriousKidsUS@theconversation.com.

Why do baseball players put a black mark under their eyes? – Althea, age 9, Edmonton, Alberta

Bottom of the ninth. Two outs. Bases loaded. The winning run is standing on third base. The pitcher winds up and throws. The batter swings and sends a high fly ball into the air. The center fielder races back, looks up at the sky and then says the sentence no baseball fan wants to hear: “I lost it in the sun.”

For baseball players, seeing the ball clearly can be the difference between making a game-winning catch and watching the winning run score. That is one reason many athletes put black marks under their eyes before a game.

Baseball, football and other outdoor athletes apply black stripes under their eyes because they hope it might reduce the glare from the sun or bright stadium lights. But the use of eye black comes down to tradition as much as it does science.

As an athletic trainer and professor who studies sports medicine and performance, I spend a lot of time thinking about how details like vision, sunlight and confidence can affect the way athletes play.

Can eye black really help players see better?

Eye black is usually made from black grease or black stickers placed underneath the eyes. The idea is simple: Bright light from the sun or stadium lights can bounce off a player’s cheeks into their eyes. The black color absorbs some of that light instead of reflecting it, which may help reduce glare.

The practice of using eye black has been around for a long time. Some stories say Babe Ruth used burned cork under his eyes. Football players may have been experimenting with it more than 100 years ago. By the mid-1900s, those black marks had become a familiar part of outdoor sports.

Scientists have tested whether eye black actually works. In one study, black grease helped reduce glare a little and improved something called contrast sensitivity. That means it may help your eyes notice the difference between an object and its background, like a white baseball against a bright blue sky or a bank of stadium lights.

But the research is not totally settled. Another study found that the benefit may be small and can depend on how the test is done.

So eye black probably does not give players superhero vision. But in a sport where a hard-hit ball can travel more than 95 mph, even a potential tiny visual advantage can feel worth trying.

Eye black is not the only way athletes fight glare. Baseball hats help shade players’ eyes. Skiers wear goggles because snow can reflect sunlight like a mirror. Race car drivers use tinted helmet shields, and some athletes wear sunglasses, tinted visors or tinted contact lenses outdoors.

Why not just wear sunglasses?

If eye black helps only a little with glare, you might wonder why baseball players do not all wear sunglasses instead.

Some do wear sunglasses during games, especially outfielders. But not every player likes them.

In a fast game, players need to track the ball quickly and feel comfortable while they play. Sunglasses can fog, slide down, collect sweat or slightly change how the ball looks. Some players like sunglasses. Some would prefer not to have anything extra on their face. Others feel more comfortable relying on their own eyes, a baseball hat and a little eye black.

Eye black is not a secret weapon. It is more like one small tool from an athlete’s glare-fighting utility belt.

Why eye black became part of baseball culture

If science suggests eye black only helps a little, then why do so many players still wear it?

The answer is not just about eyeballs. It is also about routine.

Baseball is famous for routines and superstitions. Some players eat the same meal before every game. Others always put on their equipment in the same order or avoid stepping on the foul line.

Sports psychologists have researched how routines can help athletes prepare for performance. A 2021 study on preperformance routines found that routines before competition can help athletes improve focus, manage emotions, get ready to compete and perform better under pressure.

Eye black eventually became part of that routine for many athletes. Over time, it also became part of the look of baseball and football. Some players wear simple black lines. Others use stickers with messages, crosses, flags or team slogans.

The next time you see black marks under a player’s eyes, you’ll know that it’s not there just to look tough. They are trying to see the ball, block the glare and feel confident for the next big play.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Adam Annaccone, Clinical Associate Professor of Kinesiology, University of Texas at Arlington

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Erupting volcanoes spew molten lava, gas and rocks up into the air. But just how high can the lava go and how do eruptions work? That’s what eight-year-old Thomas from Leeds in the UK wanted to know.

Thomas joined our host Eloise to put his question to volcanologist Martin Mangler from the University of Southampton on The Conversation’s Curious Kids podcast.

In each episode of The Conversation’s Curious Kids, a curious kid joins host Eloise to ask a top researcher their burning question. If you’d like to join in with the experiments in this episode, you’ll need some bicarbonate of soda, some vinegar, honey, a bottle or mug and a straw, to hand.

To listen to season two, follow us wherever you get your podcasts, or listen on the Yoto Player via the Discover section on the Yoto interactive audio platform for kids.

You can also listen back to season one and read lots of answers to questions sent in by children around the world in our Curious Kids series.

Got a question? Pop it in an email, or record it and send us the audio to curiouskids@theconversation.com.

This season of The Conversation’s Curious Kids is supported by the University of Southampton in the UK, a world-leading research-intensive university with a global network of international students and campuses in Malaysia and Delhi.

Disclosure statement

Martin Mangler has received funding from UK Research and Innovation.

Credits

This episode of The Conversation’s Curious Kids was hosted and mixed by Eloise Stevens. The producer was Katie Flood and the executive producer was Gemma Ware. Volcano eruption sounds courtesy of Martin Mangler and Craig Smith via freesound.

Eloise Stevens, Host, The Conversation's Curious Kids podcast, The Conversation and Gemma Ware, Head of Audio, The Conversation UK, The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky! You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.

My name is Sanuki and I’m 8 years old. I live in Melbourne. My question is how do plastic bags harm our environment and sea life? – Sanuki, age 8, Melbourne.

Good question, Sanuki!

Plastic bags harm marine (and land) environments in a few ways.

Turtles (and other animals) may mistake plastic bags for food. Turtles like to eat jellyfish, and we think turtles eat the plastic bags because they resemble jellyfish.

When turtles eat plastic, it can block their intestinal system (their guts). Therefore, they can no longer eat properly, which can kill them. The plastics in their tummy may also leak chemicals into the turtle. We don’t know whether this causes long term problems for the turtle, but it’s probably not good for them.

How plastic impacts the ecosystems

Plastic bags can also smother corals and other seabed communities. When plastic bags end up in our oceans, animals (including seals, dolphins and seabirds) can get tangled up in them. An animal with a plastic bag around its neck will have trouble moving through the water, catching its prey or feeding, and escaping predators.

On land, plastic bags are an eyesore. They get stuck in trees, along fence lines, or as litter at our parks and beaches.

Many people don’t realise that plastic bags can also cause flooding. Previously in Ghana (in West Africa), plastic bags blocked storm water drains during a big rainstorm. This caused flooding so bad that people were killed.

Making plastic requires a lot of energy and work

Plastic bags can even be harmful before they are used. It takes a lot of resources and energy to create a plastic bag. A key ingredient is oil. As a fossil fuel, oil must be extracted from the ground. Do we want to use fossil fuel resources to make a product that is only used once (we call this a “single use plastic”)?

Many millions of barrels of oil are used to make plastic bags every year. A lot of energy is also used to make and transport plastic bags. It is better for the environment if we reduce our energy use.

The push towards plastic-free

Lately, lots of people recognise the impacts that plastic bags have, and they are working on alternatives. Many local and state governments have passed plastic bag bans here in Australia, which helps stop the use of single use plastic bags.

In fact, New South Wales is the only state in Australia where you can still get thin, single use plastic bags at the grocery store.

So, remind your parents to bring their reusable cloth bags whenever you go shopping. You just might save a turtle.

Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:

* Email your question to curiouskids@theconversation.edu.au
* Tell us on Twitter

Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.

Britta Denise Hardesty, Principal Research Scientist, Oceans and Atmosphere Flagship, CSIRO and Qamar Schuyler, Research Scientist, Oceans and Atmospheres, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Curious Kids is a series for children. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.

Why is the Sun orange when white stars are hottest? – Rain, age 6, Toowoomba.

Hi Rain. Thanks for sending in your excellent question.

The reason the Sun shines so bright is that it’s hot. And the colour it glows depends on how hot it is.

You are right that a star that glows white is hotter than one that glows orange.

And it’s true the Sun often looks orange. But it isn’t really orange. It is white. Well, it’s a bit on the yellow side but it’s mostly white.

But even white stars aren’t the hottest.

The blue giants that burn bright and briefly

The very hottest stars actually glow blue. We call them blue giant stars.

These blue giants are around 80 times larger than our Sun – so they are really, really big. They live and die very quickly. They are so hot and so big they burn through their fuel very quickly and last just a few million years.

That might sound like a long time but it’s not much compared to how long our Sun will live.

When our Sun was a million years old, it was still just a child. It’s about 5 billion years old now and will live to about 10 billion years. So you could say the Sun is now middle-aged. It’s about halfway through its life.

So blue giants are hottest, white stars are very hot, but there are also orange stars that burn less hot. There are even red stars, which are a bit cooler again. They are a half or even a quarter the size of our Sun and while they are still burning hot, they are nowhere near as hot as our lovely Sun.

So why does the Sun look orange, then?

A lot of the pictures we take of the Sun make it look orange because of special filters we use to take the photo. The Sun is putting out so much light that we would not be able to photograph the detail on its surface unless we cut some of the brightness out. That’s what the filters do.

At sunrise and sunset, the Sun can look especially orange to our eyes. That’s because, at those times of day, its light has to travel through a lot of the Earth’s atmosphere (the layer of swirling air that surrounds our planet). And all the dust and stuff in the atmosphere makes the light scatter and change so it looks less blue and more orangey-red.

Only Bored Astronomers Find Gratification Knowing Mnemonics

In the olden days, astronomers used letters to try to sort different types of stars. As we learned more about stars, the order changed, and labels became quite mixed up! Today we still use this naming system to remember the order of stars from hottest to least hot. It goes like this: O, B, A, F, G, K, M. (Some versions have more letters at the end).

The O-stars are the blue giants, while our Sun is a “G-class” star. That means it’s not the hottest but it’s not the coolest either.

Those letters are hard to remember, so astronomers came up with different tricks to remember it. One memory trick is called a “mnemonic” where you pretend each letter stands for a word. It’s easier to remember a sentence instead of a bunch of letters.

One student in my class came up with this mnemonic: “Only Bored Astronomers Find Gratification Knowing Mnemonics” (gratification means something like happiness).

Another one I like is: “Orange Butterflies And Frogs Get Knitted Mittens”.

Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.

Belinda Nicholson, Lecturer, University of Southern Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.