Put simply, it's the outcome of a chemical reaction, which humans learned how to make some 400,000 years ago.
Sea turtle eating a plastic bag.
Plastic bags are commonly mistaken for food by sea animals. They require a lot of energy and resources to be made, and have caused floods in some countries.
Have you seen a mermaid?
Even if mermaids aren't real, they'll likely feature in human stories for many years to come. Very few mythical creatures are found in so many diverse cultures, across so many years without changing.
Ministry of Defence.
You have to be smart and fast to be a fighter pilot – but perhaps the most surprising challenge is the clothes you have to wear.
SIM cards contain a computer chip that can do some simple mathematics and store some data.
SIM cards link accounts to handsets. They keep communications private. They store messages. Although small and simple, they are a big part of modern mobile phone systems.
Some explosive volcanoes can send ash high up into the sky and it can travel around the world over different countries.
When magma rises towards the surface gas bubbles start to form. Whether or not they can escape as the magma is rising affects how explosive the eruption will be.
Even a small cloud can weigh as much as four tonnes – but gravity, chemistry and temperature keep them floating in the sky.
Once the car is at steady speed, the insect doesn’t need to be pulled along anymore and it won’t be able to tell that the car is moving.
If the insect wants to stay right in front of your nose, it must fly forwards just a little bit when the car is speeding up. But when the car is at constant speed, it only needs to hover.
Both male and female birds sing to impress other birds, but as well as that, they do it for pleasure!
Both humans and animals experience these reflex responses.
The loud noise might be a warning that there is something falling nearby, or flying towards you. Our brain tells our eyes to quickly shut, to help protect them from any damage.
Many people think green snot means you are really sick, or that you need antibiotics. Not true. Green snot is actually a sign that our immune system is working and that we are getting better.
Nobody knows for sure where black holes lead to.
The pull created by a black hole is so strong that if you get too close to one – even if you are travelling away from it at the fastest speed it is possible to go – you will never be able escape.
Imagine This is a co-production between ABC KIDS listen and The Conversation, based on our Curious Kids articles.
If you're looking for ways to keep kids occupied on road trips or at home, we'd love you to check out a podcast called Imagine This, a co-production between ABC KIDS listen and The Conversation.
The existence of wormholes is not forbidden by our current theories of the universe. So we can say that they do exist in theory.
Marcella Cheng/The Conversation NY-BD-CC
A wormhole is like a tunnel connecting two places in space. They would be incredibly useful and are great for science-fiction stories.
The problem is we haven't found any evidence of them existing.
Where all the water in the ocean came from is a very good question. Scientists have been wondering about it for a long time.
The Big Bang created a cloud of dust and rocks that included a lot of rocks that were made of ice, like giant snowballs. That's where some of the water came from.
Most of the time you won’t be able to tell if a puppy or kitten’s tooth falls out. Often they fall out in food, or the animal might even swallow them.
Puppies and kittens are born without teeth, but by around two months of age they have a full set of baby teeth.
In fact, some things are slowing the Earth down or could change its spinning in the future.
To answer this tricky question, we have to look back in time to when the Earth was born, 4.5 billion years ago.
You may need to pop your ears by yawning when you go up in a plane.
Listen up. Today we're hearing all about why your ears pop when you go up, up, up and away.
Australia and New Zealand are neighbours but our accents are quite different. We even have different words for things.
The short answer is that the accent you have depends on the people you grew up with and the history of the place that you live in.
About a century ago, we didn’t even know that galaxies existed.
Mai Lam/The Conversation NY-BD-CC
Pretty much as soon as we understood what galaxies were, we realised they are all moving away from each other. And the ones that are further away are moving faster. In short, the universe is expanding.