Curious Kids is a series for children. You can send your question 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 spiders have hairy legs? - Audrey, age 5, Fitzroy, Melbourne.

Good question, Audrey! Believe it or not, I have studied the hairy legs of spiders for years and can give you some definitive answers on this.

But before we talk about the spider’s fur, think about your very own hairs.

Why do we have hair?

First, there is the hair on your head, which protects you from the sun and rain. Then, there is smaller hair above your eyes – your eyebrows and eye lashes. These prevent dust from entering your eye.

And then have a closer look – you have all that very fine hair on your arms and legs, you can hardly see. What happens when you very, very gently touch this hair or blow at it? It tickles! This very fine body hair helps humans to feel if something is touching you.

In spiders, it is quite similar. Their body hair helps them to feel if something is touching them. Say you took a paintbrush and gently touched a spider with it (don’t do this without an adult there, of course, because some spiders can be dangerous). This touch will make the spider’s hairs bend. The spider will feel that something big is touching it and probably think “Oh dear, there is something that wants to eat me!” and run off.

Like you, spiders have different types of hairs. But spiders can do much more cool things with their hair then we can with ours (except, maybe that we are superior in styling our hair in a cool fashion).

Spidey senses

Have you ever seen a spider with ears? Well, no (that would actually look funny!) That’s because spiders use hairs on their legs to listen! Sounds unbelievable, but that’s how it is.

Does a spider have a nose? I’ve never seen one, and I have seen lots and lots of spiders. To smell, spiders use hairs.

Does a spider have a tongue? Nope. They use – you guessed it – hairs!

So spiders can feel, listen, smell and taste with their hairy legs. Pretty cool, right?

Some spiders can also use their hairs to grip onto a very flat surface – this is why you see spiders walking happily across a window, a ceiling or high up on a wall. (This is also how Spiderman does it, by the way).

Actually, not all spiders than can do that. Only the ones that have special Spiderman-hairs on their feet can do it. These Spiderman-hairs are tiny and have even tinier hairs on them – hairs on hairs. Scientists are trying to learn from these spiders and create Spiderman gloves. With such gloves you could climb up a skyscraper like a spider!

Show-off spiders

Spiders can be quite colourful. Do you know peacock spiders? Here is a picture of one:

The peacock spider’s colours come from special hairs on its legs and body and they are used to impress other peacock spider mates and find a partner. The peacock spider boy waves his coloured hairy legs in a funky dance to tell the spider girl, “I am the best guy you’ll ever find”. Such a show-off! Here’s how they look when they dance:

So you see, spiders need hairs for quite a lot of things in their life – and that is why they have hairy legs.

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Jonas Wolff, Research Fellow in the Department of Biological Sciences, Macquarie 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! You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.

How do mountains get made? - Astrid, age 6, Marrickville

Hello Astrid. You may not believe this but when I was about your age my teacher (Mr Rouve) explained to the class how mountains get made.

He took a sheet of paper and put it flat on the table. Then, he put the tips of his right and left hands’ fingers on each side of the flat sheet and slowly moved his hands toward each other. Try to do it and you will see that the middle part of the paper will lift off the table to form a nice fold.

My teacher explained that mountains form in a similar way, when flat layers of rocks are pushed toward each other they move upward forming tall mountains.

My teacher was really excited by a discovery made by geologists at that time, when I was a kid. These geologists had figured out that the surface of the Earth was, like a giant jigsaw puzzle, made of pieces. Those pieces, called “tectonic plates”, move and bump into each other.

This bumping creates earthquakes, which slowly push the ground surface upward to make mountains. It happens so slowly that, in fact, you are getting taller faster than mountains do, except mountains keep growing and growing and growing for many millions of years until they are so heavy they can no longer grow taller, only wider.

In fact, Australia and New Zealand are sitting on two different “tectonic plates” that move towards each other at the speed of a few centimetres per year. Where they bump into each other, the ground gets lifted to form the stunning New Zealand Alps, the top of which stands close to 4,000 metres. Can you imagine about 4,000 people as tall as you, standing straight up on each other shoulders? That’s how tall these mountains are.

Mountains also form when the Earth’s crust is pushed upward from underneath. At the same time the New Zealand Alps started to form, a large hot bubble of rocks raising from deep in the Earth, like a giant air balloon, was pushing upward the surface of the eastern part of Africa forming a 4,000 metre high plateau. This plateau split to form what is known as the East African Rift, a valley twice as long as the New Zealands Alps.

There are many mountains at the surface of the Earth. Some we can see, some we can’t because they are under the sea. If you could take a submarine and dive under the sea, for instance in the ocean in between Australia and Antarctica, you could visit a long mountain where the Australian and Antarctica tectonic plates move away from each other.

Thank you again for your fantastic question.

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.

Patrice Rey, Associate Professor, School of Geosciences, University of Sydney

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.

Hi my name is Dean and I am 7 years old. My question is: How and why do magnets stick together? – Dean, age 7, Vermont Sth.

Hi Dean!

This is a good question and a bit tricky to answer, but I’ll try my best.

Every magnet has two sides: a north pole and a south pole. We use these names because if you hang a magnet from a thread, the magnet’s north pole points (almost) towards the north direction.

This is because the Earth’s core (its centre) is a large, weak magnet. Your little, strong magnet lines up with Earth’s magnetic core, so it points north. That’s how a magnetic compass works.

Magnets don’t always stick together.

If you hold two magnets the wrong way around, they push apart - they repel! In other words, if you hold two magnets together so that like-poles are close together (two norths OR two souths), they repel. Try it! It feels like the magnets are surrounded by an invisible rubber layer pushing them apart. That invisible layer is called a magnetic field.

It’s only when you hold unlike-poles together (a north pointing to a south) that magnets stick together (they are attracted). Now, the magnetic field acts like a stretched rubber band pulling the magnets together. (Be careful; two strong magnets can pinch your skin).

So, why do magnets attract or repel?

You have probably heard of energy. Energy is needed to create movement.

A car that’s sitting still will start to move when the petrol inside it burns. That’s because petrol contains stored-up energy which is released when it burns.

When this stored-up energy is released, some of it changes into movement energy. Scientists call this stored-up energy “potential energy” and call movement energy “kinetic energy”.

When you start running, it’s because energy stored in your food is released and some of it changes into movement energy.

What’s this got to do with magnets? Well, the magnetic field that surrounds all magnets contains stored-up energy. But there’s a way to change the amount of stored-up energy surrounding the magnet. And the way you change it will tell you which way the magnet will move.

A rule to remember

Everything in the universe follows a rule. I will tell you the rule in a moment, but first I have to say that it’s not easy to explain why the universe follows this rule without complicated mathematics. The best I can say is “that’s just how the universe behaves”. (I’m sorry. I don’t like answers like that either).

The rule is: wherever there is stored-up energy in an object (and the object is not tied down or stuck in place), then the object will be pushed in the direction that causes the stored-up energy to decrease. The stored-up energy will be reduced and replaced by movement energy.

So if two magnets are pointing with unlike-poles together (north pole to a south pole), then bringing them closer together decreases the energy stored up in the magnetic field. They will be pushed in the direction that decreases the amount of stored-up energy. That is, they are forced together (this is called attraction).

If two magnets are pointing with like-poles together (a south pole to a south pole OR north to north), then stored-up energy will decrease if they move apart.

So our rule says the magnets will be pushed in the direction that decreases the amount of stored-up energy. That is, they are forced apart (repelled).

I should also say that when dropped objects are attracted to Earth and fall down, it’s NOT because of magnetism. It’s because of gravity. Earth is also surrounded by a gravitational field which also contains stored up energy.

Unlike magnetism, gravity never repels because gravity only points one way. There are no north and south poles for gravity.

Can I keep taking stored-up energy from the magnetic field forever?

No.

Once two magnets stick together, you’ll need to put some stored-up energy back into the field by pulling the magnets apart again. You can’t get energy for nothing.

The energy needed to pull the magnets apart comes from you, and you get it from the food you eat. And the plants or animals you eat get their energy from other plants and animals, or from the Sun. All energy comes from somewhere.

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:

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Stephen G Bosi, Senior Lecturer in Physics, University of New England

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.

How does my tummy turn the food I eat into poo? – Luke, age 4.

Hi Luke. What a terrific question! The story of how your food ends up as poo is an amazing one.

The food that you eat is broken into small pieces by chewing and mashing it in your mouth. You make a little food ball with the help of your tongue.

Your body has a cool trick to get the food ball down to your tummy and not into your lungs. Just behind the tongue is a little gate called the epiglottis. It closes to stop food going down the wrong way and accidentally getting into your breathing pipe. If you have ever accidentally had some food or water go down the wrong way, you’ll know it makes you cough a lot.

When you swallow, the food ball is pushed back down to the start of a food tunnel called the oesophagus that leads to your stomach.

Getting food from your mouth to your stomach and beyond

Starting in the oesophagus (that food tunnel in your neck) an amazing action called peristalsis takes place. Peristalsis happens with the help of walls inside your gut. It gives your body the strength to send the food ball from the food tunnel to the stomach and all the way down to your bum.

The stomach is a J-shaped moving box full of stomach juices. When you start eating, the lower part of your stomach starts moving and mixing.

Did you know your stomach gets bigger when the food ball arrives? Your stretched stomach makes juices that can help to break the food ball into even tinier pieces no more than 3mm. That’s even smaller than your pinky nail!

A little help from your liver and pancreas

This mish-mash of small food pieces and stomach juices will now enter the very long windy tube known as the small intestine, which is labelled on this picture:

Now, two friends will start to help digest the food - a flat, pear-shaped thing called the pancreas and the liver. The pancreas makes juices of its own to break the food down and make it even smooshier. And the liver (among other things) makes bile.

Bile is a yellow-green, thick, sticky juice that acts like washing powder. It helps break big chunks of fat from oily foods into little pieces. The small intestine also has juices that help turn food such as bread into energy.

This smooth mush mixed with little fat pieces and energy can move from the small intestine into your blood. This part is called absorption and means that healthy things can get to different parts of the body where they are needed. The small intestine absorbs important parts of the food, such as iron, that help your body stay healthy.

Any food that is not taken in by the small intestine enters the large intestine (which we call the colon).

In the colon, a lot of water is taken away from the food, which makes it dry and hard. Many tiny bugs and germs live in the colon (that is normal and healthy, by the way). These germs also eat some of the food, and when they do, they produce gas. This is the gas that comes out when you fart.

The dry and hard food that cannot be used by your body now becomes waste. It is kept in the last part of the colon (known as the rectum) and is ready to leave the body when you do a poo.

And don’t forget to wash your hands!

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.

Vincent Ho, Senior Lecturer and clinical academic gastroenterologist, Western Sydney University

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

Curious Kids is a series for children, where we ask experts to answer questions from kids. All questions are welcome: find out how to enter at the bottom. You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.

Why is a magpie’s poo two different colours (black and white)? – Anjali, age 9, Melbourne.

Dear Anjali,

This is a very good question.

In humans and all mammals there are two exits for all the things the body does not need or cannot digest. We have a bladder (for the liquid) and an anus to get rid of solids. The fluid we call urine. It is fluid because we drink a good deal but the part that has to be expelled is called urea. It is toxic and that’s why it has to leave the body. Urea dissolves in water and it is in our urine.

The body has a clever way of separating out what is not good for us. All that work is done in the kidneys, which capture the toxins and then send these bad parts on their way out of the body.

In birds, it’s slightly different. Like reptiles, they do not have two separate exits from the body. They have one, and it is called the cloaca. It is quite similar to the human anus but expels both indigestible bits and toxins.

The solids (the indigestible and non-usable parts of what they eat) in birds are the black part of their poo. The toxins they expel, also filtered out in the kidneys, are white (called uric acids). Birds do not drink as much as humans so the toxins are also in solid form, not liquid as in human urine. Hence, the white solid uric acid gets expelled together with the indigestible solids (the black part).

As you can see, their bodies therefore do not need two separate channels to get the waste products expelled because both are solid. The composition of black and white differs between species. Some splatter more of the uric acid (white), some have more black (indigestible solids). It depends on their diet.

There is a third exit path for indigestibles, and quite a few bird species have this capacity. It is the ability to regurgitate “roughage” before it gets into the digestive system- in birds of prey this roughage may be feathers, bones, or hair from small animals they have eaten.

In birds, including magpies and currawongs, bits of hard wings of beetles for instance, also get expelled via the beak. These pellets look like small olive stones. Some seeds are also too hard to digest so they can get embedded in these pellets.

Nature has a clever trick here. Currawongs are very important for many native plants. As they also like eating lots of fruit, they ingest quite a few seeds. These seeds end up in the pellets which get expelled via the beak and are therefore unharmed by the process of digestion. The seeds get their own little seeding environment in these pellets and they can then develop and grow, often a long way away from the parent tree on which the fruit originally grew. So it is a good way for the tree to spread its offspring around.

To come back to poo: As in humans, one can often judge the state of health of an individual just by looking at the poo.

In birds, when the white part turns a slightly green or yellow colour, one knows immediately that something is very wrong: perhaps the bird has had too little in fluids, perhaps it is ill.

If the black solids turn very fluid, the bird may be suffering from diarrhoea. That is often a clear sign that the bird is very, very sick and needs to go to a vet immediately.

Best wishes,

Professor Gisela Kaplan.

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:

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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.

Gisela Kaplan, Emeritus Professor in Animal Behaviour, University of New England

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