By SARAH CHALMERS

Last updated at 17:55 25 September 2007

What holds the sky up? Why do some people get bitten by midges while others appear immune? And do cats have belly buttons?

A new book tries to answer 300 of these niggling questions about the world around us. Here, SARAH CHALMERS presents a selection of the most puzzling - and their answers...

Why do we get dizzy when we stand on top of a tall building?

Our eyes are used to seeing the ground somewhere near our feet. So if the ground suddenly appears to be much further away from our head than normal, our brains get thoroughly confused. This means it tries to correct the different perspective back to what our eyes are used to seeing. This over-correction by the brain makes us feel dizzy and can also lead to a feeling of anxiety.

What causes the feeling of butterflies in the stomach?

These are actually small muscle contractions in the digestive tract. The gut's muscles are normally well co-ordinated - but when disrupted by stress, the body's priority is no longer digestion.

So, rather than wasting vital blood and oxygen supplies on processing food, the body diverts them to the legs where they can be better used - for example, to help us run out of the way of danger.

The gut is therefore shut down by the brain, leaving it with irregular rhythmic contractions.

Do babies dream?

With their limited vision and understanding of the world, it is often impossible to imagine a newborn baby can dream. But we all dream every night - and babies, in fact, dream more than adults. This is because most dreaming occurs during the lighter phases of sleep which babies, with their regular naps, have a lot of. And although their sense of sight and language skills are not developed, they will dream of bright lights and colours, fuzzy images, noises and smells - in fact, any of the physical stimuli they experience while awake.

Why do some people get bitten by midges, while others are immune?

Everyone has a different smell, and insects can detect these differences and express their preference by feeding on some people and not others.

The difference in our smell is due to the amount of carbon dioxide we expel. We all expel different quantities in our breath, and it is this gas which attracts insects such as mosquitoes and midges. Insect repellents work by masking these odours or creating smells insects find repulsive - lemon or garlic usually work well.

Why does a drink fizz up when you drop an ice cube in?

In a liquid, gas bubbles are formed when they attach to a solid surface. They form especially well when placed against something rough. So, in a liquid drink there are thousands of tiny potential bubbles in the dissolved carbon dioxide jostling for position against the wall of the glass, hoping to take shape. When a rough ice cube is placed in the drink, the carbon dioxide fights to attach itself to the cube so it can shape itself as lots of gassy bubbles. It prefers the ice cube to the glass because of the roughness of the cube.

If you cut a worm in half will both halves live?

The end with the head will survive if the cut is made behind the fatty part of the worm, where the major organs are located. While the worm cannot grow a new head and organs, the nonessential body fat in the lower half of its body can easily be renewed and replaced.

Do cats have belly buttons?

Indeed they do, and it is located just below the rib cage - similar to humans. However, the cat's navel is nothing like ours.

It is hidden under its fur and resembles a scar, rather than the typical human's round or oval-shaped navel. This is because it is the remnants of the umbilical cord which the mother cat cuts with her teeth just after the kitten is born.

Why do we never see baby pigeons?

Ducklings, infant starlings and sparrows are all common sights, yet we never see a baby pigeon. This is because they don't leave the nest until they are 35 days old and have fully-formed feathers to allow them to fly. So by the time we see them leave the nest, they look no different from fully-grown pigeons.

Why don't birds get electric shocks from standing on high-voltage wires?

Electricity always prefers to flow through the easiest route. Metals are the easiest materials for electricity to travel through. This is because the tiny atoms which make up metals contain even tinier electrons that can move from atom to atom. So the electrons bounce from atom to atom, taking electricity along with them.

But when birds stand on high-voltage wires, the electrons cannot move to the atoms which make up their feet. The bird's feet are highly resistant to electricity. So when faced with these two routes, the electricity always chooses the wire with its much lower resistance.

What holds the sky up?

This question isn't as daft as it sounds. After all, the atmosphere is exclusively made up of gases. These can be squashed as their molecules have very loose bonds connecting them (as opposed to any solid material's molecules, which have very firm bonds holding them together).

So if the air is so squashy and flexible, why doesn't gravity just act on those loosely attached molecules, pulling them all down nearer the ground?

Instead of being miles thick, why can't the atmosphere be just a few metres thick? In fact, it is these same flexible molecules which keep the air right where it is.

The movement of gases' molecules is so great that they are never still enough for gravity to act upon them.

But while they bounce around just enough to stop gravity pulling them towards Earth, they don't move around so much that they become detached from the atmosphere and zip off into space.

Can chewing gum get tangled up in your intestine?

Many parents have warned their children this might happen - but it simply isn't true. Although gum can stick to shoes, bus seats, hair and pavements, it makes its way unhindered through the digestive system - passing straight through the stomach and on to the intestines. It cannot adhere to the moist and slippery walls of the gut.

Why do we always see the same side of the Moon?

Our Moon always keeps the same face turned towards the Earth because the time it takes to orbit us happens to be the exact same time it takes to rotate on its own axis.

The Moon takes 27 days to revolve once around the Earth and 27 days to turn once on its own axis.

Do astronauts grow in space?

Yes! In space, the body does not experience the same downward pull of gravity that it does on Earth. As a result, the gaps between the vertebrae in the spine expand and astronauts do get slightly taller.

When they return to Earth, the gravity quickly squashes them back to normal height, however.

Why are bananas curved?

Bananas grow on tall trees in big bunches around the top of the trunk. Their curving shows how efficient nature is. Their shape means they can fit very closely together, which allows more bananas to grow around the tree - as many as 50 in a bunch.

Why do razor blades become blunt - after all, hair is soft?

A blade is very thin - the thinner the blade, the sharper the cut. And the thinner the blade, the fewer atoms there are at the cutting edge.

As the blade passes over the stubble on a chin, the hair knocks individual atoms off the steel blade. Since there are many thousands of hairs it doesn't take long to slightly dull the blade.

Why doesn't blood rush to a bat's head when it hangs upside down?

All animals are designed to make sure that enough blood circulates round their body regardless of what position they are in.

In this way, bats are no different from humans. The process involves the force of the heartbeat ensuring that blood is pushed around the relevant parts of the body, through the system of the arteries, capillaries and veins and back to the heart again, without being affected by gravity or the direction of the body.

The fact that bats have proportionately larger hearts than many mammals means the blood is even more efficiently pumped around their bodies and doesn't drain to the head just because they are hanging upside down.

If a car travels at 1,000mph with its headlights turned on, does the light travel faster?

If a man in a car fired a bullet forward at 500mph, and the car was doing 1,000mph, then the bullet would travel at 1,500mph. But if he switched on the headlights, the light would travel at its usual speed of 186,000 miles per second, not 186,000 miles per second plus 1,000mph.

It is one of those quirks of science that light travels at the same speed for everyone in the universe - no matter how fast the actual light source is travelling.

• Do Cats Have Belly Buttons, edited by Paul Heiney. Published by Sutton Publishing on October 31.