Do Cats Have Belly Buttons?: And Answers to 244 Other Questions on the World of Science

by Paul Heiney (Editor)

Overview

Why do jellies wobble? Why don't the oceans overflow? Why do racing cars have fat tyres? How do widgets in beer cans work? How many bones does a giraffe have in that long neck? I've been told that dogs only see in black and white. Is that true? How do we know that no two snow crystals are the same? Why is the earth round? And how do we know it is? why do camels have such bad breath? What is a bruise? Are chemicals in my brain responsible for my falling in love? Will they fade as I grow older? How long can love last? Do Cats Have Belly Buttons? is a follow-up to the successful Can Cows Walk Down Stairs?.

Answering life's big questions, as well as the small, it unravels the science behind those things we take for granted, and explains just why the world and its contents are as they are. Informative, entertaining, humorous, it is the perfect present for quizaholics, science addicts, the insatiably questioning, and anyone curious about life on earth.

Product Details

ISBN-13:	9780752474182
Publisher:	The History Press
Publication date:	10/24/2011
Sold by:	INDEPENDENT PUB GROUP - EPUB - EBKS
Format:	eBook
Pages:	288
File size:	2 MB
Age Range:	18 Years

About the Author

PAUL HEINEY is a writer, broadcaster and journalist. Most recently he has been the presenter of ITV's Countrywise, and BBC's Watchdog. He has been an organic farmer, working his land with heavy horses, this experience forming the basis of his long-running column in The Times. He is also the author of several best-selling books, including Do Cats Have Belly Buttons? (The History Press, 2008).

Read an Excerpt

Do Cats Have Belly Buttons?

And Answers to 244 Other Questions on the World of Science

---

By Paul Heiney, Bill Ledger

The History Press

Copyright © 2011 Paul Heiney
All rights reserved.
ISBN: 978-0-7524-7418-2

---

CHAPTER 1

THE Human Body

BIG EARS TO BIG SNEEZES

Do people with sticky-out ears have better balance?

It's true that our ears allow us to keep our balance, but I think you have got hold of the wrong end of the stick about how they actually achieve that. It is nothing to do with the size of the external ear, the pinna.

A special part of the inner ear, called the vestibular apparatus, helps the body to cope with changes in position. This structure contains hair-like cells which wave about in the fluid inside the inner ear and connect to lots of tiny nerves. These all work together to tell the brain what position the body is in and whether it is moving or not. When the information from these hairs is at odds with messages going to the brain from our eyes, we can suffer from motion sickness such as car or sea-sickness.

However, these messages originate in the inner ear, not the outer ear, and so the size of your external ears make no difference to your balance at all. Unless, of course, they're so large that you trip over them.

Can sound hurt your ears?

Parents are always nagging their children to 'turn it down!' and not just because it is annoying. Sound can most certainly damage your ears. Hearing tests on gunners and people who have worked near jet engines show they can no longer hear high-frequency sounds, and have difficulty hearing normal speech. Even wearing headphones with the sound turned right up for long periods of time can cause some damage to hearing.

Sound travels in waves through the air but, unlike waves on water which we can see coming towards us and duck away from if we have to, there is no simple way to see a damaging sound wave coming at you. The only way to measure the power of a sound wave is to use a microphone to convert the sound waves into electrical waves, and measure the voltage produced by the microphone. The usual scale measures the loudness (sound pressure level) in decibels (dB), on a special sort of scale where 40 decibels is ten times louder than 20 decibels and 60 decibels is a hundred times louder than 20 decibels.

0dB, which is reckoned as being the threshold of hearing, represents the quietest sound we could ever hear – the sound of an empty building on a quiet night in the country. You would probably play music at about 40dB to keep you company while you do your homework. Traffic noise at rush hour in a busy city might reach 80dB, and the threshold of pain would be 120dB – roughly what you'd hear if you stood at the end of the runway when a jet aircraft took off.

Hearing loss occurs when there is severe damage to the structure of the highly sensitive inner ear, particularly the hair cells which transmit vibration to the brain for recognition. The first effects will be the loss of high frequencies which are important as they enable us to recognise the difference between similar words, such as thrill and sill. In severe cases, conversation begins to sound like a continuous mumble.

Remember, damage starts at about 80db – the roar of busy traffic. Rock concerts can hit 115, a passing ambulance 125 and a shotgun fired close to you 165.

What is the lowest intensity of light the human eye can detect?

All it takes is one single photon. A photon is complex to define, but you can think of it as being a particle of electromagnetic energy. Light consists of streams of photons, the smallest particles of light thought to exist.

Light is detected by cells in the retina at the back of the eye, called rods and cones. Rods are more sensitive than cones, and a single photon of light is enough to cause a rod in the human eye to fire up and send a message to the brain 'photon received!' How bright is a photon? Roughly equivalent to a single candle viewed from one mile away – not much.

Why do we need two eyes?

A pair of eyes produces binocular vision, which means that although our brains receive a different image from each eye, we only 'see' one image. Both in humans and animals, having two eyes is useful because it provides a larger field of view, and reduces the risk of becoming disabled following damage to one eye. It also allows stereoscopic vision so we can see things in three dimensions.

The placing of the eyes is important: in the animal world predators often have their two eyes placed on the front of their head to maximise this overlap of retinal images, giving excellent stereoscopic vision, allowing them to judge distances accurately and locate their prey. On the other hand, their prey tend to locate their eyes on the side of their head which reduces stereoscopic vision but gives a much improved all-round sight to help detect nearby predators.

Why do you get dizzy standing on top of a tall building?

Because your eyes are used to seeing the ground somewhere near your feet. If it suddenly spots them somewhere else, it starts to get confused. This mental confusion causes the sensation of dizziness. Because the perspectives are wrong, the confused brain starts to over-correct and, apart from the feeling of dizziness, it can also lead to a great feeling of anxiety.

If you swapped your eyes over so that your left eye was in your right socket and vice versa, would you see the world with two halves which didn't match up?

It's quite likely the brain could sort this out without you even noticing. After all, we're already seeing things upside down and back to front.

Images from our eyes are transmitted via the optic nerves to the brain through fibres which are divided into two bundles. One bundle contains fibres originating from cells on the temporal side of the eye – the same side as the ear – the other bundle contains fibres originating at the nasal side of the eye nearest the nose.

From here onwards you might want to draw a diagram of a head with two eyes, and a brain with two hemispheres – it helped me.

The fibres originating from the temporal side go back to the hemisphere of the brain on the same side of the head as the eye in which the fibres originated. The nasal fibres cross over and go to the opposite hemisphere.

Simple lenses produce images that are upside down, and the eye does the same. This means that if you imagine a human figure viewed by an eye, the image is inverted so that the head is at the bottom and the feet at the top. Also, the left side would be on the right, and the right side on the left. The inversion is actually a rotation of 180 degrees. This means that the image of the left side of the scene is formed towards the right side of the retina. So, in the case of the right eye, images formed from objects on the right side of the direction of gaze land on the left side of the retina – i.e. nasally. These nasal images would lead to neural signals that are transmitted to the left hemisphere. Points imaged on the left of the direction of gaze would be imaged in the right side of the retina, and signals produced would be transmitted to the right hemisphere.

So, images on the left side of either retina produce signals that are transmitted to the left brain hemisphere, and images on the right side of either retina are sent to the right hemisphere. The crossing of these signals to the two hemispheres is what allows us binocular depth perception.

About 70 per cent of the total number of fibres originating in one eye cross over, while 30 per cent remain uncrossed and go to the same side. So, if you put your right eye in your left socket, but attached it to the optic fibre originally in the left socket, and the same on the other side, then the brain would still receive images exactly as before and therefore nothing need be fixed.

However, if you put your right eye, plus the connecting optic fibre, in your left socket, then what you would find is that your peripheral vision would be in the middle of your vision, and your central line of vision on the outside. This would obviously take some fixing, but the brain can adjust to many things and it would be more than likely that your brain would eventually adapt to this without you even realising.

Don't try this at home.

How long do we spend in a lifetime with our eyes closed just by blinking?

A blink lasts about 0.3 to 0.4 seconds. We blink about 5 times a minute, every minute, for about 18 hours a day. This adds up to half an hour a day and about 5 years in a lifetime.

What are eyebrows for and why don't they grow?

Eyebrows are for protecting your eyes by deflecting water running down the forehead, and they're used in conveying facial expressions. They don't grow longer because the hair follicles are genetically programmed to stop after about a centimetre of growth which, I guess, is the reason you don't need your eyebrows trimmed every time you get your hair cut.

If your eyebrow is shaved, how long does it take to grow?

Human hair grows about 23cm a year and eyebrows tend to be about 1cm long. So, if you shaved your eyebrows, it would take about 17 days for them to grow back.

What are the black floaters you sometimes get in your eyes?

What you are seeing are small particles of debris swilling around in the vitreous fluid which fills your eye. Don't worry – in the vast majority of cases they are entirely harmless and most people will experience them to some degree if they stare hard enough and long enough at a blue sky or a blank wall.

The floaters might consist of very small quantities of blood or tissue which has become detached from the retina. But more usually they are part of the ageing process of the vitreous fluid, which is why floaters tend to be a problem for older people. They can also appear as streaks, clouds or spiders' webs. Incidentally, it is not the floater itself which you are seeing, it is its shadow as it passes across the retina.

Why do people sneeze?

We sneeze to clear irritating material from our upper air passages. This can be anything from dust, pollen or snuff, to excess mucus blocking the nose when we have a cold or hay fever. Pain receptors in the cells lining the upper respiratory tract are triggered by the dust or mucus and instruct the medulla (the base of your brain) to make you sneeze.

The sneeze itself is just a very powerful out-breath which propels the air at up to 100mph and can discharge 5,000 water droplets, all loaded with bacteria. A large number of muscles suddenly come into play just before a sneeze, including stomach muscles, the diaphragm, the muscles in your throat and, of course, your eyelids because it is almost impossible to sneeze with your eyes open.

A sneeze starts with a closing of the vocal cords until the pressure in the chest has risen, and then the air is suddenly allowed to escape upwards into the back of the nose by a soft palate. But the 100mph which the sneeze reaches is nothing compared to the 600mph at which a cough can travel.

When you sneeze, why do you see bright lights?

Remember how close your eyes are to your nose? As that blast of air is expelled at 100mph (see above) the eyeball is pressed hard against your eyelid, which always closes during a sneeze.

The eyeball is filled with a jelly-like substance, so any pressure on the front of the eyeball is transferred to the back where it falls on the retina. The retina cells are not only sensitive to light (they are what enable you to see) but they are also sensitive to pressure and will stimulate the nerves just as if light was falling on them. So, when you sneeze, the pressure on the retina presses on the nerves, which stimulates them, and the brain interprets the messages as being the result of light. This is quite reasonable since most of the time nerve messages from the eyes are the result of light falling on the retina.

By the way, you can also see lights which aren't there by closing your eyes and pressing gently on your eyeball. Migraine sufferers often complain of seeing bright lights when they get a migraine headache. This is because the blood vessels in the area of their head around the eye contract, so the blood is at higher pressure than normal, and presses on the eyeballs.

FUNNY BONES TO LAUGHING GAS

What's the funny bone?

Don't laugh when I tell you, but the funny bone is not a bone at all. It is a nerve which runs through a groove in a bone called the ulna, one of two bones of the lower arm. At the elbow, this bone and its nerve are very close to the surface and stick out, making it easily hurt by knocking or bumping. If you manage to hit your elbow in precisely the right spot, it sets off the tingling or prickly sensation which we describe as having hit your funny bone, although it's very rarely a laughing matter.

What you have actually struck is your ulnar nerve which controls feeling in your fourth and fifth fingers and plays a part in wrist movement. Because the nerve itself is being hit, you get a very painful physical reaction, making it hurt an awful lot more than you might expect. When things hurt a lot you get very emotional, which means you either laugh or cry. Quite often you can laugh and cry at the same time, and so people have come to call it the funny bone because it makes you laugh (or cry) when you hit it.

Don't confuse the funny bone with the humerus (not humorous) which can be found in the upper arm. As far as we know, it has no sense of humour at all.

How many bones are there in the human body?

The skeleton of an adult contains 206 distinct bones, and these are contained in two separate systems: the axial skeleton, which you can think of as the main trunk of your body, and the appendicular skeleton which is the arms and legs. There are 26 bones in the vertebral columns, 8 in the cranium, 14 in the face, 7 other skull bones, 25 in the sternum and ribs, 64 in the upper limbs and 62 in the lower limbs.

What is the smallest bone in the body?

The smallest bone is to be found in your ear and it is called the stirrup bone, so-called because it is shaped like a horse rider's stirrup. It is one of three little bones in the middle ear and measures from 2.6 to 3.4mm in length and weighs from 2.0 to 4.3mg, which makes it about the size of a grain of rice. Because of their shape, the other two middle ear bones are known as the hammer and anvil, and all three sit within the same cavity. When sound waves collide with the eardrum, it is these three small but vital bones which transmit the vibrations to the inner ear where sensitive nerves in the cochlea translate them into nerve impulses which are sent to the brain.

What am I made of?

Mostly you're a bag of water. Seventy per cent of the body is water. Since water consists of atoms of hydrogen and oxygen, you could say those are the two elements of which you are made. Of course, there are other elements such as carbon, nitrogen, phosphorous etc. Altogether there are 60 different elements found in the body. The most abundant is oxygen and a 70kg person would have 43kg of oxygen in their body, 16kg of carbon, 7kg of hydrogen, 1.8kg of nitrogen and 1.0kg of calcium. Those are the top five.

By the time you get to the bottom of the list the elements are becoming scarce. The least found is tungsten (20 micro-grammes) and vanadium, thorium, uranium, samarium and beryllium are present in only slightly larger quantities.

However, the atoms of these elements are made up of just three particles: protons, neutrons and electrons, so to say that you were made entirely of these three would be another equally valid answer. But if you want to get really serious, bear in mind that recent experiments have shown that protons and neutrons appear to be made up of smaller particles called quarks.

It's a bit like the old poem:

Big fleas have little fleas
which sit on 'em and bite 'em
but little fleas have smaller fleas
and so ad infinitum.

Perhaps one day we shall discover that quarks and electrons are made up of something smaller, and then there will be a new answer to the question. At the moment experiments suggest quarks are as small as things get. So, if you don't want to think of yourself as a bag of water, consider yourself to be a mountain of quarks.

Who was the first person in the world?

People, as we know them, evolved over thousands and thousands of years. Scientists think that people evolved from an ape-like animal. About 2 million years ago they started to walk upright, then their brains got bigger and eventually they became like us. But this all happened very gradually and there is no specific point at which a person appeared in the world. The general name which we give to the first group of people-type animals which looked a bit like us and walked on two legs not four, is Homo habilis.

Why does nitrous oxide make you laugh?

Nitrous oxide, famously used by dentists until better anaesthetics were introduced, does have a reputation for leaving some people feeling giggly. In fact, in the nineteenth century, it was used as a fairground attraction where people would pay money to inhale the gas in order to behave in a silly and uninhibited way. So intoxicating was it that the poet Robert Southey wrote: 'I am sure the air in heaven must be this wonder working gas of delight.'

It was first discovered in 1793 by Robert Priestley, the great discoverer of gases, who first isolated oxygen, carbon dioxide and ammonia. But it was another fifty years after Priestley's discovery before it was used in surgery to dull pain and the senses of sight, hearing and touch.

The precise mechanism which leads to laughter is unknown but a wide range of emotions can result from inhaling nitrous oxide, among them hysteria. It is dangerous to inhale nitrous oxide unless it is mixed in the correct proportions with oxygen.

(Continues...)

---

Excerpted from Do Cats Have Belly Buttons? by Paul Heiney, Bill Ledger. Copyright © 2011 Paul Heiney. Excerpted by permission of The History Press.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

---

Table of Contents

Contents

Title,
Introduction,
1. The Human Body,
2. Life in the Wild,
3. Science all Around,
4. How on Earth ...?,
5. Sky High and Beyond,
6. Can You Just Explain ...,
7. And Now the BIG ones,
Copyright,