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 bats sleep upside down? - Questions from Year 5 at Brandon Park Primary School, Victoria. The class has been studying animal adaptation.

Evolution allows animals to adapt to their environments by favouring those who have an advantage that helps them survive. If they survive long enough to have babies they pass that advantage onto their children through their genes. That process is what we call adaptation.

Animals have adapted to live in different environments and eat different foods, so they don’t have to compete with each other.

Around 530 million years ago, all animals lived in the ocean. They were rapidly evolving and adapting to live in different places to minimise competition.

Some animals have evolved to live at great depths, like the anglerfish. It has a bioluminescent light it uses to attract prey in the dark water. Other sea creatures evolved amazing camouflage skills, which helps them stay safe from predators.

Eventually, sea animals developed adaptations that allowed them to live on land. More adaptations occurred over millions of years, leading to the amazing and complex range of animals we have today.

Sometimes, two different animals will evolve to have a similar adaptation, even when they are not closely related. Flight is an excellent example.

The four flights

Flight has evolved four times: in insects, bats, birds and pterosaurs (the flying creatures from the time of dinosaurs).

These four groups don’t have a common ancestor who could fly. In fact, they all evolved to fly from ancestors who could not. This is what we call “convergent evolution”.

However, birds and bats have some major differences. Bats still have the five digits, or fingers, that their mammalian ancestors had (mammalian means they are mammals, which are animals who have a mammary gland, that produces milk to feed their babies; they also typically have hair or fur).

Birds, however, have lost the digits that their ancestors had. The bones in a bird wing have fused.

Hunt, but don’t be hunted

The bat ancestor (or pre-bat) lived in trees, hunting small insects as they moved along the bark. Since it’s much harder to run up a tree chasing an insect, the pre-bat would wait, facing downwards for prey to come up the tree trunk. That way they could easily run downwards if they saw something tasty.

They used their hands and mouth to grab the prey and hung from their back legs. This led to an adaptation in their claws which allowed their tendons to lock into place when they hang. That’s why bats can hang upside down without using muscles, and barely any energy. Gravity does all of the work for them.

Since it uses the least amount of energy, it’s the best way for a bat to sleep. But on the trunk of a tree, they are visible to predators who hunt during the day while bats are sleeping. Some bats moved to sleep under the horizontal branches, which provided protection.

As with all evolution, the adaptations that help a species to survive is the one that will persist. Most bats now sleep in protected areas and only a few species still sleep on tree trunks.

Make light work

To save energy while flying, you want to make yourself as light as possible. Birds have hollow processes in their bones but bats do not. One way in which bats evolved to save weight was to make their back leg bones shorter and thinner.

However, this means that the bats can no longer stand on their back legs. The pressure is too much for the small bones. As a result, they have lost the ability to run on their back legs as well.

The drop and fly theory

When you watch a bird take off from the ground, you will notice they need a run-up. In order to get off the ground, flying animals needs to achieve what scientists call “lift” to overcome gravity. Many big birds, and bats, do not have strong enough wing muscles to generate the lift required to take off from a standing position (like a helicopter can).

Bats cannot run so it would be almost impossible for them to take off from the ground. A major advantage to hanging upside down is that bats do not need to generate lift to begin flight. They just drop out of their bed, open their wings and off they go.

Did you know there are seven species of bats that do not sleep upside down? They sleep in curled-up leaves! Six of these species live in Central and South America, while the other one lives only in Madagascar.

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

Amy Edwards, Post Doctoral Researcher, La Trobe 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 remote controls work? – Ethan, 10, Sydney.

Thanks, Ethan. I was younger, I wondered the same. I was completely mesmerised with how a lump of plastic could possibly change channels on a TV without any physical connection.

Very early TV remote controls worked with wires. Then we created battery-powered remotes and we didn’t need the wires any more.

Now remotes are everywhere. In fact, the planet-watching Voyager spacecraft are controlled remotely and they are presently 20 billion kilometres away. It takes 20 hours for instructions to travel from Earth to the spacecraft but we can do it – using a remote.

A remote control has three things, what engineers would call a “communications channel”, a “procotol”, and an “interface”. I will explain what those words mean.

The communications channel

The communications channel is what connects the remote to the device you want to control (like a TV).

It could be light (such as infra-red light), sound or radio waves (sometimes called electromagnetic waves). The human eye cannot see infra-red light or radio waves.

TVs tend to use infrared light as it is low cost, easy to build, and suitable for a short distance like in a lounge room. However, it does require a direct “line of sight” so that the light beam is not blocked. How many times have you heard “get out of the way!” when someone is trying to change the channel?

Radio waves are usually used for long distance situations, or for outdoors, and can even travel through objects.

Many game consoles like the XBox and PlayStation use low power radio waves (like Bluetooth, which is a type of radio wave system). This is great for games as it does not need line of sight. It will still work even if you bounce around the room, or dive behind the couch with your controller.

Protocol

You can think of the protocol as the “language” the remote uses to communicate with the TV, XBox or whatever the device may be.

TVs, for instance, use a long list of “binary codes” (on and off, or one and zero bit sequences) that tell the TV what to do. Some codes tell the TV volume to go up, others tell it to go down, or change channel.

These patterns have been predetermined so that the TV will understand the remote. It can “speak” the language of the remote. The remote will package the message up in a little packet of data that the TV can understand.

Some remotes are able to send messages and receive them. For instance, a game console control will send commands to the console (eg “move the character forward”) and can receive them (for example, “make the controller rumble and vibrate”).

User interface

“User interface” is just a fancy way of saying how the remote looks and is used.

TV remotes just have a rather boring array of buttons. Some remotes have a screen and look like a mobile phone.

Pump up the volume

Say you want to turn up the volume on your TV. You press a button on the remote. The little microcontroller (which is just a tiny computer) in the remote wakes up, and reads which button you have pressed (“volume turned up, please”). It then creates a packet of data – a message – in a language the TV can understand.

It sends the message via an infrared light to the TV, assuming you aimed the remote correctly.

That message is then picked up by the infrared TV receiver, which decodes it (“ahh, he wants the volume turned up, ok.”). Then the small microcontroller (a tiny computer) in the TV makes the necessary changes to the volume.

All remotes all are designed to:

1. take your request
2. apply the protocol (translate it into a language the device can understand)
3. create a packet of data (a message) and
4. send the message via the communications channel to the device.

You then put these things together and you have a remote control.

Even the remote used to control the Voyager Spacecraft follows the same method. It’s no more complicated than controlling a TV, it just has more steps to it.

Thank you for this question, and I hope I have helped you understand the fascinating world of remote controls.

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Andrew Maxwell, Senior Lecturer, University of Southern 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.

When I swipe the matchstick how does it make fire? Thank you. – Laura, aged 5, Brisbane.

I’m glad you asked this, Laura. I have been interested in the science of fire and fireworks for a long time, and can tell you there is a lot happening in the very short time it takes to light a match.

But first I want to give an important warning: matches are dangerous and they shouldn’t be used without supervision. You can hurt yourself, your friends and family, destroy your home, or damage the environment.

Now, let’s get back to the science.

Friction

To learn how the match can catch fire, we first need to understand something called “friction”. Friction is when you rub two things together and it creates heat or warmth. Have you ever rubbed your hands together on a cold morning to warm them up? That’s friction.

(For the adults reading, friction converts kinetic energy into thermal energy.)

Friction is important for the first part of lighting a match. You rub the match head against the red strip on the side of the matchbox.

This strip on the box contains a bit of powdered glass to make it extra rough. Scratching the rough match head against the rough strip leads to friction. That creates just enough heat to start a series of chemical reactions.

Chemical reactions

You probably know about chemical reactions. That’s when one chemical interacts with another chemical, and a change occurs. Maybe you’ve added vinegar to bicarb soda to create a mini volcano. That’s a chemical reaction. Heat can help kick off some chemical reactions or make them happen faster.

There are a lot of chemical reactions involved in the lighting of a match.

Surprisingly, the first chemical to react is not on the match, it is on the box!

This chemical is called “red phosphorus”. To our eyes it just looks like a red powder. But if you zoomed right in to see how all its atoms are arranged, it would look like a bunch of triangles and other shapes stuck together into a long chain.

When you rub the match on the box, you get friction, which means you get heat. This heat causes a small amount of the red phosphorus chain to be broken apart.

When that happens, some of the red phosphorous changes into another chemical called “white phosphorus”. It reacts immediately with a gas in the air called oxygen. This will create a lot more heat.

So the story so far: the friction breaks the red phosphorous chain, which allows the white phosphorous to react with oxygen and the match starts to get hot.

But that’s not the end of the story.

Fuel + heat + oxygen = fire

You need three ingredients for a fire: fuel, heat, and oxygen.

Friction and white phosphorus have provided the starting heat, and now the match needs fuel and oxygen to continue to burn.

The fuel comes from the sulphur (that’s another chemical) and wax in the head of the match. It also comes from the wood in the matchstick.

When it comes to oxygen, the match has a secret supply. Stored inside the match head is another chemical called “potassium chlorate”. When it gets hot, it releases a lot of extra oxygen and heat. This makes the match head burn quickly and strongly.

When you put it all together – the heat, the fuel, and the oxygen – you get a flame! And amazingly, all this chemistry happens in a fraction of a second.

‘Strike anywhere’ matches

What I’ve described are safety matches, which are the kind you probably have at home.

But maybe you’ve seen an old cowboy movie, or a cartoon, where a character has lit a match with their boot, a wall, or something else that’s not a matchbox.

These matches are known as “strike anywhere” matches, and they work very similarly to safety matches.

The difference is that the phosphorus component is in the match head rather than on the box.

While this is convenient, it is also much more dangerous!

So please remember — any kind of match can be very, very dangerous, so never use them without adult supervision.

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.

Nathan Kilah, Senior Lecturer in Chemistry, 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 eggs have orange stuff inside? – Rafael, age 7.

This is a very interesting question. That orange stuff is called a yolk. It’s a great source of vitamins, minerals, fats and proteins packaged up by the female animal for an embryo (the developing cells that turn into a baby).

You probably know that the yellow bit inside a chicken’s egg is the yolk, but in fact a lot of animals lay eggs that have yolks in them. However, not all animal eggs have a yolk!

A contest called evolution

To understand why different animal species have different types of eggs, you need to know that all living things change slowly over time, through a process called evolution.

When a living thing is born with a special difference – what we would call a “trait” – sometimes this trait helps them live and survive better than someone who doesn’t have that trait. This trait may help them live longer and have more babies.

Because of these differences in survival, eventually, the trait that lets one individual living thing live and prosper will become quite common and be found all throughout a species.

Back to eggs

Imagine you are a worm living millions of years ago. You produce heaps and heaps of eggs that develop quickly into little worms. But most of the babies die because they are small and have to find food straight after hatching. They can’t go far because they are very little and so most starve to death (or are eaten by bigger creatures).

But what if some of those eggs happened to contain a little bit of fat from the mother? Compared to its brothers and sisters, the fat will allow the worm to spend just a little bit more time growing inside the egg and less time looking for food after hatching.

The worms that were lucky enough to have that fat inside the egg are more likely to survive long enough to have their own babies. And they pass on the fatty-egg trait to their own worm kids. Soon this fatty-egg trait becomes quite common.

So the worm who was able to feed its babies when they’re still inside the egg had more babies survive, and a yolk evolved.

Which eggs have a yolk and why?

Eggs with tiny bits of yolk are found in animals such as earthworms, leeches, clams, mussels, starfish, sea urchins, and marine arthropods (shrimp, lobsters, crabs) and some insects. These animals produce huge numbers of eggs.

Most of the babies that grow in these sorts of eggs have to go through a lot of steps before they reach the adult stage. First they have to grow into a larvae (which is what we call a junior body, and often looks a bit like worm).

The babies have to change into a larvae so they can eat, and after having eaten a bit they develop into an adult (think of caterpillars that eventually turn into butterflies).

Animals that produce eggs with a bit more yolk have babies that can fully develop and skip the larvae step, such as in hagfish and snails.

Big yolks for big babies

Eggs with really large yolks are found in animals that produce very few eggs, and the offspring can use the yolk to develop completely. These sorts of eggs are found only in cephalopods (squid, octopus and nautilus) and some vertebrates (animals with backbones).

Vertebrates that produce eggs with large yolks include bony fish, cartilaginous fish (sharks and rays), reptiles, birds and egg-laying mammals (platypus and echidnas).

The rest of the mammals (animals that don’t lay eggs) have found a different system. They have a placenta, which is a kind of a feeding sack linking mother to embryo inside the mother’s body. This system allows the developing embryo or fetus to get nutrients straight from the mother. That’s how you were grown!

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.

Maggie J. Watson, Lecturer in Ornithology, Ecology, Conservation and Parasitology, Charles Sturt 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 are leaves green? – Indigo, age 6, Elwood.

The leaves of most plants are green, because the leaves are full of chemicals that are green.

The most important of these chemicals is called “chlorophyll” and it allows plants to make food so they can grow using water, air and light from the sun.

This way that a plant makes food for itself is called “photosynthesis” and it is one of the most important processes taking place on the whole planet.

Without photosynthesis there would be no plants or people on Earth. Dinosaurs would not have been able to breathe and the air and oceans would be very different from those we have today. So the green chemical chlorophyll is really important.

All leaves contain chlorophyll, but sometimes not all of the leaf has chlorophyll in it. Some leaves have green and white or green and yellow stripes or spots. Only the green bits have chlorophyll and only those bits can make food by photosynthesis.

If you’re really good at noticing things, you might have seen plants and trees with red or purple leaves – and the leaves are that colour all year round, not just in autumn.

These leaves are still full of our important green chemical, chlorophyll, just like any other ordinary green leaf. However, they also have lots of other chemicals that are red or purple – so much of them that they no longer look green. But deep down inside the leaves the chlorophyll is still there and it’s still green.

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

Gregory Moore, Doctor of Botany, The University of Melbourne

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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 we see snow on mountaintops that are closer to the Sun but not near the ground? – Ms. Drews’ third grade class, Beechview Elementary School, Farmington Hills, Michigan

There’s not much better than a bluebird day in the mountains – a crisp, sunny day accompanied by a fresh blanket of snow. But why doesn’t the Sun quickly melt all that high altitude snow away?

It all boils down to our atmosphere, which is what I research as a scientist in Colorado. Let’s dive in!

Our atmosphere: Earth’s armor

Earth’s atmosphere begins right at its surface and extends to outer space, and it is filled with a mixture of many different gases. Gases in the atmosphere include the oxygen we breathe and the water vapor that makes it rain and snow. They are essential to supporting life on Earth in several ways.

One of the most important jobs those gases have is to protect us from harmful things in space, including our closest star: the Sun.

The Sun’s radiation provides heat to our planet, but too much of it can be a problem. If you’ve ever gotten a sunburn, then you’re already familiar with this idea.

Some of our atmospheric gases limit the amount of radiation from the Sun that can reach the Earth’s surface by absorbing some of it, which prevents temperatures from being way too warm in the daytime. At night, certain atmospheric gases also trap some of the heat that the Earth’s surface releases as it cools down, protecting us from unsurvivable cold.

The way the atmosphere regulates Earth’s temperatures is known as the greenhouse effect. You’ll often hear this term used alongside climate change or global warming. That is because global warming is caused by enhancing the greenhouse effect: As people burn fossil fuels in cars and factories, the amount of greenhouse gases in the atmosphere increases. These extra gases allow the Earth’s atmosphere to trap more heat, causing an increase in temperatures.

The atmosphere likes to stay grounded

If you were to compare the Earth’s atmosphere along a Caribbean beach to that surrounding the top of Mount Everest, it would look quite different.

That is because as you go higher up in the atmosphere, it gets “thinner,” meaning that there are less gases present at higher elevations and altitudes.

Why? Blame it on gravity.

In the same way that gravity keeps people and objects from flying away to outer space, Earth’s gravitational force pulls on the gases in our atmosphere, trying to keep them as close to Earth as possible.

As a result, there are fewer gas molecules in the atmosphere as you go higher up in altitude, making the air thinner, or less dense. Humans can sometimes experience altitude sickness at high elevations because there is less oxygen present in the air as a result of this phenomenon.

Closer to the Sun, but still cold and snowy?

Our high-elevation mountains protrude into higher altitudes of the atmosphere, where the air has fewer gas molecules. While this thinner air allows more of the Sun’s radiation to pass through compared with the atmosphere at sea level, thinner air tends to be colder for two reasons:

First, collisions between gas molecules generate heat, and if you have fewer molecules available to run into each other, that heat generation is lower.

Second, a thinner atmosphere is less effective at maintaining heat because there are fewer molecules available to trap and hold on to heat.

Colder temperatures can create more opportunities for precipitation to fall in the form of snow rather than rain, which is why some mountains can be so snowy.

And if the ground is habitually covered in snow, as is the case in many mountain ranges, it can be even easier to maintain cooler temperatures. That’s because snow-covered surfaces are very reflective, making them highly effective at causing the Sun’s incoming rays to bounce back toward space instead of getting absorbed by the ground.

So if you visit the mountains to have fun in the snow, be sure to pack your jacket, but don’t forget that sunscreen too.

Allie Mazurek, Engagement Climatologist and Researcher, Colorado Climate Center, Colorado State University

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