We know that lots of animals, maybe all animals, sleep. Cats, dogs, even worms and jellyfish sleep. But we still don’t know exactly why they started sleeping.
Marcella Cheng/The Conversation
Pond snails use things like rocks or the side of their aquarium as their bed, attaching themselves while they sleep. This might not seem very relaxing but their shells do hang away from their body.
The time of moonrise and moonset and the shape of the Moon change throughout the month.
Marcella Cheng/The Conversation
The world is made of tiny building blocks called ‘elements’. Scientists have worked out how fast some elements change into other elements. That gives us a very big clue about how old the Earth is.
Glasses help people to see by focusing light onto the retina.
Marcella Cheng/The Conversation
You might be trying to catch up on sleep. Sleep scientists say some children need only nine hours of sleep at night, while others need as much as 11 hours. It depends on the person.
The leaves of most plants are green because the leaves are full of green chemicals.
Marcella Cheng/The Conversation
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…
The short answer is that it depends on the material the cups and plates are made of, and even what shape they are.
Marcella Cheng/The Conversation
X-rays are like light rays, but they can pass through more stuff. Some of the x-ray’s energy is blocked by bone, which is why you can see bones so clearly on x-ray scans.
Ferns are a very old group of plants that came along more than 200 million years before the dinosaurs walked the earth.
Marcella Cheng/The Conversation
Ferns came along more than 200 million years before the dinosaurs walked the Earth. They were food for plant-eating dinosaurs and they’re really great survivors. Heather, age 8, wants to know more.
Volcanologists often visit active volcanoes in order to observe eruptions and collect samples of lava and ash.
Flickr/MONUSCO Photos
Volcanologists study the formation and eruptions of volcanoes - surely one of the most interesting jobs around. However, it can also be very dangerous.
Scientists aren’t sure exactly why we cry when we are sad.
Thomas Stromberg/Flickr
Maeve, age 8, has a question that has stumped many scientists over the years. And that’s because it’s a surprisingly tricky question to answer. It depends a bit on what you mean by ‘person’.
Animals that evolved in cold parts of the world usually have lighter skin. If a light-skinned animal has blood vessels close to the surface of their ear skin, this will make the ears look pink.
Flight Engineer Peggy Whitson suits up ahead of a spacewalk. Vomiting inside a spacesuit during a spacewalk could be fatal for astronauts.
NASA