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 do leaves fall off trees? - Emma, age 5.

Great question! The short answer is that leaves fall off trees when they aren’t doing their job any more.

A leaf’s job is to turn sunlight into food for the tree. To do this, the leaf needs water. This water comes from the soil, and is sucked up through pipes in the trunk and branches all the way to the leaves – this can be a very long way for tall trees!

If there isn’t enough water, the leaf can be damaged and stop working. The tree doesn’t want to waste all the good things in the leaf, so it takes the nutrients from the leaf back into the stems and roots. This way, they can be recycled.

When the leaf is empty, the tree stops holding onto it and it falls to the ground, or blows away in a gust of wind.

What are deciduous trees?

Some trees lose their leaves every year. These trees are called deciduous trees, and they lose their leaves in response to the seasons. Deciduous trees mostly come from places where winter gets cold and snowy.

When it is very cold, the water in the tree can freeze – the leaves stop working and can even be damaged by the ice crystals. These trees know to prepare for this, and start taking nutrients out of the leaves when the days get shorter in autumn – this is when we can see them changing colour.

But there are deciduous trees in tropical places where it never gets cold. Winter in these places is very dry. When the rainy season ends, the tree knows that it will not have very much water for a few months, so it lets go of its leaves.

Trees hibernate too

When the tree is leafless, it can’t make food. But it doesn’t get hungry. Instead, it rests.

Just like a bear goes into hibernation and snoozes all through winter, trees have a long sleep until the water in the pipes starts moving again. This can be in spring, or when it starts to rain again. Then, they wake up and put out new leaves, so they can start making food again.

Some trees hold onto their leaves all year long. These trees are called evergreens, because they stay “ever green”. But the leaves on these trees all die and fall off eventually. That happens when the leaves are old or damaged. Leaves don’t work very well after they’ve been munched on by an animal.

Leaves are really important for the tree, but sometimes it’s better for the tree to let them go. They can save all the good bits and when there is enough water, they can use them to grow brand new leaves.

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.

Matilda Brown, PhD, University of Tasmania

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 do tigers have whiskers? – Valentina, age 4, London.

A tiger’s whiskers are not just for decoration. They help it find its way around small spaces even when it is completely dark and can send important messages to the tiger’s brain.

Just like how the hairs on your arm can feel a soft breeze blowing or a spider crawling on you, whiskers on a tiger’s face and chin give it messages about what is going on around him or her.

But whiskers are not just ordinary hairs. They are thicker and go deeper into the tiger’s skin. In fact, they are connected to its muscles and to something we call the “nervous system.”

The nervous system

Most animals (including you and me) have a nervous system in their body which sends messages to the brain about the world they feel and sense around them.

Whether it is a small paper cut or a tickle, the nervous system can feel it all!

At the end of a tiger’s whiskers is a small but important body part. Its official name is a “proprioceptor”, but you can think of it as an alarm.

This alarm sends messages to the tiger’s brain about what is around it.

Whiskers are so sensitive they can even feel a small change in the air or wind around it. That could be important information for a tiger – it may be a clue that an animal it would like to eat is rushing past it. In other words, it could help them hunt in the dark.

If the whiskers tell the tiger it is moving into a small space where it could get stuck, or towards something prickly, that will help the tiger be more careful and decide where to put their next step.

Whiskers are handy helpers

Having whiskers can help a tiger guess the distance between two places. This is helpful to them when they need to jump, crouch or slide underneath a log or a cave. And did you know tigers even have whiskers on their legs?

As you can see, whiskers make life easier for tigers. They help them hunt, find their way in the dark and sense when danger or a tasty snack is nearby.

Over time, the tigers that had whiskers were more likely to live long enough to have babies (who also had whiskers). So the number of whiskery tigers grew and grew while the tigers with shorter or no whiskers may not have lived long enough to have babies, and their numbers fell.

That process – where certain features that help animals live longer get passed on to the next generation – is called evolution.

So I guess you could say a tiger has whiskers because of evolution!

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.

Alexander Richard Braczkowski, PhD Candidate - Wildlife Cameraman, The University of Queensland

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 are there waves? - Evie, age 5.

Thanks for a great question, Evie.

When you look at the waves breaking at the beach, those waves might be at the end of a long journey. The waves might have been created thousands of kilometres away, or they could have been created near you.

There are lots of types of waves in the ocean, but the waves you usually see at a beach are created by the wind. When the wind blows over a smooth ocean, it creates little waves or ripples on the surface. If the wind continues to blow, the waves grow bigger.

Faster, bigger, longer

The faster the wind blows (like in a strong storm out at sea), the bigger the waves will grow.

The further the wind blows (or the bigger the area of the storm), the bigger the waves will grow.

And the longer the wind blows (like in a storm that lasts a long time), the bigger the waves will grow.

If the wind stops, or changes direction, the waves will stop growing, but they won’t stop travelling.

They will keep travelling away from where they were created in a straight line, sometimes for days, until they run into something like a beach where they are stopped because they break. That’s why there are still waves at the beach, even when it is not windy.

Waves trip over themselves

Imagine you were running really quickly. But then suddenly, you ran into thick gloopy mud. Your feet would slow down, but the top half of your body would still be going fast. You’d trip over.

Waves do the same thing and that is when they break.

As waves approach the shore, the water is shallower, and the bottom of the wave starts to feel the sand and rocks and seaweed. The bottom of the wave slows down, and soon, the top of the wave is going faster than the bottom part of the wave, so the top spills forward and topples over in a big splash.

Waves can travel a long way

Scientists who study the ocean (called oceanographers) have measured waves created in the Southern Ocean, and seen them travel all the way across the Pacific Ocean and break on the beaches of North America more than a week later.

Try counting the seconds between waves breaking on the beach. If the time between waves is 10 seconds or more, the waves have come from a long way away. If the waves were created nearby, the time between waves will be short, perhaps five seconds or fewer.

Sometimes when we look at the sea we might see different waves (some big, some small) all happening at the same time. These waves were created at different places, perhaps by different storms, but ended up in the same spot at the same time.

Freak waves

During big storms, waves can get very big. If big waves from two different storms meet together, that can create enormous waves that we call “freak waves”. The largest waves measured are around 25 metres high (that’s five giraffes standing on top of each other!) and they can tip over ships.

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.

Mark Hemer, Senior Research Scientist, Oceans and Atmosphere, 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.

Can snails fart? Thank you. – Avalon, age 9, Scotts Head, NSW.

Lots of animals fart because of what they eat, but it was not easy for me to find a clear answer on whether snails really do. More research is needed to know exactly how the digestive system of a snail really works.

You might have heard about methane. It is a gas found in a lot of animal farts. I did find one study that said that scientists kept some snails in a glass container for one day and one night and checked if they would produce methane. And the snails did not.

(For the adults in the audience, the paper noted that, “In this aspect, the structure of the microbiota and in consequence the functioning of the digestive microbial ecosystem of the snails differs markedly from those of vertebrates, especially herbivores.”)

You may have seen reports that scientists built a database showing which animals do and don’t fart. Not every animal in the world is on there, but it does say that mussels and clams (which, like snails, are part of a group of animals called molluscs) do not fart. Moon snails, which live in the sea, were also listed as a no.

One thing I can tell you is that a snail’s bottom is right over its head. This is because snails are very different from other molluscs (which includes things like octopus and squid as well). Because they are squashed into a protective shell, their body is twisted round to fit in. As a result, their bottom is just above and to the side of where their head comes out.

Gassy molluscs

Water snails, mussels and other molluscs do produce a gas called nitrous oxide if they live in polluted water.

You might have heard of nitrous oxide. It’s also called “laughing gas”. But this can be a problem, as nitrous oxide is a greenhouse gas and lots of it will add to climate change.

These mussels, when they are not producing laughing gas, produce something called “pseudo-faeces” which literally means “false poo”. Because the food they eat (little plants and animals floating in the water which they suck in) can contain a lot of sand, they sometimes have to squirt it all out. This doesn’t come out of their bottom, but out of something called a siphon, through which they suck their food.

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.

Bill Bateman, Associate professor, Curtin University

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!

Why do tears come out of our eyes when we cry? – Grace, age 9, Melbourne

Hi Grace, thank you for a great question.

We cry, or make tears, for three reasons. First, we need tears to keep our eye healthy, so you can say that our eyes cry a little bit all through the day. These types of tears usually don’t come out of our eyes.

Tears do come out of our eyes when we are emotional – either very sad or happy – or when our eyes are irritated by something, like a bit of dust that gets into our eyes or when we cut an onion.

Tears are needed for our eyes to work properly. Your eye has special parts – called glands – that make tears all day. Normally they only produce a tiny amount of tears – less than half a teaspoon per day. Tears are mostly water and a little bit of salt, but they also have some oil, mucus and chemicals called enzymes that kill germs.

A small amount of oil in tears stops them from evaporating or leaking out of our eyes. If we didn’t have oil in our tears, it would make our eyes really dry and sore.

When you blink, the eyelid spreads the tears around your eye and mucus helps the tears stick to the eyeball. Any tears left over drain through a special drainage system that goes through to your nose.

When we cry – and I hope you don’t cry too often – we make more tears than the eye can hold. This is because the largest tear gland can switch on and produce a lot of tears at once, just like a little fountain.

Read more: Curious Kids: How can you tell if your cat is happy and likes you?

The part of the brain that switches on the “tear fountain” receives signals from the part of your brain that controls your emotions.

When this happens, the eye can produce more than half a cup of tears in minutes. This is way too much for the eye to hold and our drainage system goes to work. Remember that this drainage system goes to our noses? That’s why when you cry you may notice your nose starts running. These are these extra tears.

If you cry really hard, then there are far too many tears even for that drainage system to remove, so the tears start falling out of our eyes.

Psychologists believe that crying because of emotions is something only humans do. Most of us cry sometimes because we are really sad. Some of us also cry when we are happy.

We haven’t figured out exactly why we cry when we are emotional, but we do know that the chemicals found in emotional tears are different to normal tears. Some scientists believe that these chemicals may help us feel better after we cry.

Read more: Curious Kids: Do bees ever accidentally sting other bees?

There are also some strange conditions that can make people cry. Some people cry when they eat or even just think about food. This is called “crocodile tears syndrome”. It is named after a legend that said crocodiles pretend to cry to trick their prey into coming closer to them.

Crocodile tears syndrome may happen after someone has been in an accident and broken some bones in their face. As the face heals, some body parts called nerves repair themselves in the wrong way. Nerves that made your mouth water when you smell good food get mistakenly connected to the tear gland instead. Afterwards when that person eats or smells something delicious that makes their mouth water, they start to cry.

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Michelle Moscova, Senior Lecturer in Anatomy, UNSW Sydney

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 are zippers on different sides of male and female jackets? – Agrima, age 13, Delhi, India

Imagine you’re at a clothing store that stocks items for the whole family. You pick up a white buttoned shirt to try on. The style is pretty plain. Was it designed to be worn by a woman or man?

There may be a clue: Many women’s shirts have buttons on the left side, while men’s shirts usually button on the right. Even zippers in pants and jackets sometimes follow the same pattern.

But why does clothing fasten differently depending on whether it’s made for men or women? Fashion researchers and historians like us have wondered about this gender difference. The answer has a lot to do with tradition, history and the way clothes were made long ago. Even small details, like a zipper, can tell a story about the past.

Clothing is full of hidden history

When people look at clothes today, they often think about colors, comfort or style. But clothing is also part of what historians call material culture: all the objects people use every day. Examining the material culture of the past can reveal how people lived, worked and thought in earlier times.

Fasteners like buttons and zippers aren’t just practical. They also follow design traditions that became connected to gender over hundreds of years.

One of the most common explanations for why male and female garments have their buttons on opposite sides comes from European fashion history. A long time ago, wealthy women from the nobility often wore complicated dresses with buttons and fasteners – so complicated that they needed help getting dressed.

Some historians believe buttons were placed in a way that made it easier for a servant to fasten the clothing, reflecting class distinctions.

About 90% of people are right-handed. When a maid stood directly facing a noblewoman to dress her, buttons on the wearer’s left side were lined up perfectly for the maid to use her dominant right hand to fit them into the buttonholes. If you try buttoning a jacket onto a friend or a stuffed animal while facing them, you will see exactly why this layout made the maid’s job so much easier.

Men, on the other hand, usually dressed themselves. So shirts, trousers and uniforms were designed with fastenings that were easy for the wearer to manage himself – meaning buttons on the right side for a wearer to use his own right hand to fasten.

Men’s clothing was shaped by everyday practicality and function.

For example, some historians point to military traditions as a possible influence on button placement. Men often wore swords on their left side and drew them with their right hand. The direction jackets, shirts and trousers closed up may have helped prevent fabric from getting caught and in the way.

Fashion habits are hard to change

Once clothing started being made in factories in the early-19th century, brands needed consistent designs. Factories work best when patterns are standardized – so the button traditions stayed in place, even when people forgot how they started.

As zippers gained popularity in the early 1900s, clothing companies just stuck with the same customs about how men’s and women’s garments were supposed to close. Instead of creating brand-new rules, many manufacturers simply kept the same patterns they had used for buttons. So zippers often ended up following the same “direction” as older garment closures.

Today, more brands are making unisex and gender-neutral clothing meant for anyone, and many designers no longer follow the old left-side/right-side rule. It’s just a fashion tradition – there’s no reason zippers and buttons need to go on different sides for men versus women.

It is now more acceptable to break the old rules about which side buttons or zippers should go on. If you make your own clothes, you can put closures – whether buttons, zippers, snaps, ties, Velcro or even something new you invent yourself – wherever you want!

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.

JuYoung Lee, Associate Professor of Fashion Design and Merchandising, Mississippi State University and Caroline Kobia, Associate Professor of Fashion Design and Merchandising, Mississippi State University

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