When humans are happy, they may smile, or laugh, or dance - but what do animals do? Melissa, age 12, wants to know how she can tell if her cat is happy and likes you.
Imagine the Earth pulling everything it is made up of, all of its mass, towards its centre. This happens evenly all over the Earth, causing it to take on a round shape.
If one venomous snake bites a mouse and injects venom into it, you can then feed that same dead mouse to another snake. The second snake won't die.
Ada, 7, wants to know why things close to the train windows zoom by really fast, while things further away seem to go by much slower.
Bees sting other animals, including humans, when they think there might be a threat to their hive. But Evie, age 8, wonders if bees ever accidentally sting other bees.
Niamh, age 7, wants to know why we have scary dreams. But after 200 years of study, dreams are still very much a mystery.
How exactly do the stars twinkle in the night sky? As it turns out, the answer is full of hot air... and cold air.
Georgina, age 5, wants to know why rainbows are round.
Breathing in through your nose has many medical benefits over mouth breathing. As usual, be wary of misinformation and bias when looking up health on the internet.
You flush the toilet. Down it goes. What happens after that? Clancy, age four, wants to know.
Why are there 60 minutes in an hour, and not 10? Why do we count up to 10, anyway? Quentin, age five, wants to know.
The planets closer to the Sun are indeed hotter than the Earth is. But they are still not hot enough to melt the rocks they are made from.
The way humans make an 'ssss' noise is different to the way a snake does it. We put our tongue behind our teeth when we hiss, but for a snake the tongue isn't involved at all in making sounds.
In five or seven billion years time, the Sun's life will come to an end. And it will be really spectacular - if you're watching from far enough away.
Some people think the sky is blue because of sunlight reflected off the ocean and back into the sky. But that's not the real reason.
What caused the Big Bang is still a mystery. And that's just one of the many unanswered questions, in spite of everything we do know about the birth of the Universe.
James, aged 8, of Sydney wants to know: are zombies real?
Taste dictates most food choices, but there's more to it than just the taste buds on your tongue.
Nicholas, aged 6, was watching TV one day when his tooth fell out. He noticed that the bottom edge of the tooth was very spiky. Now he wants to know why.
A seed contains nearly everything a tree needs to get growing. Just add a dash of water, a bit of warmth and the right location, and you'll be seeing green in no time.