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'Does my goldfish know who I am?' and other kids' questions answered

A NEW book invites some of Britain's most eminent brains to answer questions about science and nature posed by primary school children.

Fish are actually much smarter than people realise Fish are actually much smarter than people realise [GETTY]

Does the universe have an edge? Asked by Josh, age 10 Professor Brian Cox, particle physicist, says: That's a great question. The answer is that we don't even know how big the universe is. We can only see a small part of our universe - the part that light has had the time to travel across to reach us during the 13.8 billion years since the Big Bang. Anything further away can't be seen simply because the light from these distant places hasn't reached us yet.

The part that we can see is pretty large, however. It contains around 350 billion large galaxies, each containing anything up to a trillion suns. This part, which is known as the observable universe, is just over 90 billion light years across. But we are sure that the universe extends far beyond this. It may even be infinitely big which is impossible to imagine.

Do spiders speak? Asked by Eleanor, age 7 Dr George McGavin, entomologist, says: Spiders do not speak like you and I but they do communicate with each other.

Some spiders make visual signals that other spiders can understand. Jumping spiders for example, have two particularly large eyes at the front of their head. They use these eyes to stalk insect prey but also when male and female spiders meet. If a male wants to be accepted as a mate by a female of the same species he must give the correct signals, such as dancing in front of the female in a particular way. Each species has a special dance, which the female watches very carefully. If the male gets it wrong or fails to impress her she will lose interest and walk away.

In many spiders however communication is based on what they can feel. The bodies of spiders are covered with many touchsensitive hairs, which respond to all kinds of vibrations carried through their silk or the air so they can sense the presence of other animals, including other spiders.

When I yawn, why do people near me yawn too? Asked by Alex, age 7 Dr Jack Lewis, neuroscientist and broadcaster says: You yawn when your brain becomes a little bit hotter than it needs to be to work well. Yawning helps cool down the blood on its way up into your brain. This helps you to feel more alert and to focus your attention better when you're feeling sleepy. It fights the tiredness.

It often happens after you have been sitting around not doing very much at the moment that you realise it is time to do something more active.

For instance paratroopers often yawn before they jump out of an aeroplane into enemy territory.

The reason that yawning is "catching" or "contagious" is to get everyone in the group ready to be more active. When other people "catch" your yawn their brain gets cooled down as well. This gets everyone more alert and focused at the same time.

science, nature, children, schoolkids, spiders, space, universe, brian cox, yawn, yawning, onions, cry, counting, maths, mosquitoesYawning is a way of cooling the brain [GETTY - PIC POSED BY MODEL]

Paratroopers often yawn before they jump out of an aeroplane into enemy territory

Why do onions make us cry? Asked by Matthew, age 9, and Eleanor, age 5 Greg Foot, daredevil scientist says: Slicing through an onion with a knife rips through its cells, releasing various chemicals that react together. After about 30 seconds a sulphur-carrying gas is produced that wafts up to your eye. It mixes with the water in your eye, producing a burning sulphuric acid.

But what about the tears? Well, your cornea is packed with nerve endings to detect any physical or chemical irritants. They sense that tear-provoking chemical and send a signal to your tear glands to boost the production of tears to flush it away.

So how can you stop yourself from blubbing? Cut the onion under water to soak up that irritating chemical, chill it in the fridge first to slow down those reactions or wear goggles.

Where does counting come from? Asked by Tommy, age 7 Alex Bellos, maths author says: Probably from gazing at the Moon. Our ancient ancestors will have noticed that the Moon follows a cycle from Full Moon to New Moon and then back again.

In order to track the position of the Moon on its cycle, our ancestors would have made notches on pieces of wood or bone or painted splashes on rock walls to mark the days as they passed. Each notch or splash represented a day, a bit like the way a prisoner in a film marks a line on the wall of his cell every day in order to remember how long he has been there.

The purpose of counting therefore stemmed from the human desire to track time, which thousands of years later led to the invention of numbers.

Why do mosquitoes only bite some people? Asked by Charlotte, age 8 Dr Rob Hicks, GP, medical journalist and television presenter says: Mosquitoes have a really powerful sense of smell and are attracted to chemicals that we all release from our bodies. One of these is carbon dioxide which is in the air we breathe out and mosquitoes use it like a signpost to help them find a possible meal.

Women and large people tend to breathe out more carbon dioxide, and the more carbon dioxide breathed out, the easier it is for the mosquito to find you.

As the mosquito gets closer to someone it detects whether the combination of chemicals from the person's body means they will be a tasty snack or not.

science, nature, children, schoolkids, spiders, space, universe, brian cox, yawn, yawning, onions, cry, counting, maths, mosquitoesMosquitoes can detect people by the amount of carbon dioxide they breathe out [GETTY]

Does my goldfish know who I am? Asked by Shauna, age 10 Dr Mike Webster, biologist says: First of all fish are much smarter than people give them credit for. People often talk of goldfish having three-second memories but actually they can learn all kinds of things and remember them for quite a long time.

Just like other animals they have evolved to find enough to eat and to know when it is safe to be out in the open. Being able to learn and remember things helps them to do this.

Many kinds of fish can tell each other apart too. They recognise other fish from their shoal, their relatives and even their own eggs.

However we do know that fish live in a very different world from us and for many kinds of fish, although seeing is important, other senses such as smell and touch are even more important.

Why don't humans have tails? Asked by Ben, age 8 Dr Louise Leakey, palaeontologist says: None of the great apes have tails and we are one of the seven species of great ape that are alive today on planet Earth.

The main function of a primate's tail is for balance, which is particularly helpful when swinging through tree branches. Great apes are large and mostly live on the ground.

Through our evolutionary journey we have lost the need for our long tails.

But do you know that you still have the remnants of your tail? You have a little tailbone that is called the coccyx and if you fall down hard and land on it you can in fact break it.

Extracted from Does My Goldfish Know Who I Am? by Gemma Elwin Harris (published by Faber and Faber, price £12.99 for hardback)