Clegg - Inflight science a guide to the world from your airplane window

Previously published in the UK in 2011 by

Icon Books Ltd, Omnibus Business Centre,

3941 North Road, London N7 9DP

email:

www.iconbooks.co.uk

This electronic edition published in the UK in 2011 by Icon Books Ltd

ISBN: 978-1-84831-280-7 (ePub format)

ISBN: 978-1-84831-281-4 (Adobe ebook format)

Printed edition (ISBN 978-184831-241-8)

sold in the UK, Europe, South Africa and Asia

by Faber & Faber Ltd, Bloomsbury House,

7477 Great Russell Street, London WC1B 3DA

or their agents

Printed edition distributed in the UK, Europe, South Africa and Asia

by TBS Ltd, TBS Distribution Centre, Colchester Road,

Frating Green, Colchester CO7 7DW

Printed edition published in the USA in 2011 by Totem Books

Inquiries to: Icon Books Ltd, Omnibus Business Centre,

3941 North Road, London N7 9DP, UK

Printed edition distributed to the trade in the USA

by Consortium Book Sales and Distribution

The Keg House, 34 Thirteenth Avenue NE, Suite 101

Minneapolis, Minnesota 55413-1007

Printed edition published in Australia in 2011 by Allen & Unwin Pty Ltd,

PO Box 8500, 83 Alexander Street,

Crows Nest, NSW 2065

Printed edition published in Canada by Penguin Books Canada,

90 Eglinton Avenue East, Suite 700,

Toronto, Ontario M4P 2YE

Text copyright 2011 Brian Clegg

The author has asserted his moral rights.

No part of this book may be reproduced in any form, or by any means, without prior permission in writing from the publisher.

Typeset by Marie Doherty

Contents

List of illustrations

About the author

Brian Clegg is a science writer (website: www.brianclegg.net). He runs www.popularscience.co.uk, and his most recent book was Armageddon Science (St Martins Press, 2010).

Disclaimer

The experiments in this book are designed to be safe, and many of them can be done on board an aircraft. Those that are better carried out at home are clearly indicated. When carrying out any experiments in the air, make sure that you dont disturb other passengers or distract the cabin crew. Any experiments that could cause damage, danger or disturbance are clearly marked as not to be performed and are theoretical examples only. The publisher accepts no responsibility for any damage, injury or loss arising from any of the experiments contained in this book, theoretical or otherwise.

For Gillian, Chelsea and Rebecca

At the Airport

Terminal boredom

Youre sitting in the terminal, waiting for the flight. A whole mix of conflicting emotions could be vying for attention: boredom, excitement and fear included. Boredom often wins. Flying may be the quickest way to get to a distant destination, but it includes a lot of waiting around.

Even if youre a seasoned traveller, though, theres something special about taking to the air, an excitement thats often triggered by the scent of kerosene on the tarmac, or the sound of an aircraft engine starting up. And theres an element of fear because however much you enjoy flying, theres something highly unnatural about being suspended in a metal and plastic tube seven miles up, with only science and technology to keep you alive.

If you dont like flying (and I dont), a little science might help by providing some very reassuring statistics. The risk of being killed in a plane crash in any particular year is 1 in 125 million passenger journeys. This makes it three times safer on any particular journey than travelling by train and when did you ever worry about that? The equivalent risk for a car is 1 in 10 million twelve times as dangerous. Youre more likely to have a fatal accident during six hours spent in the workplace than you are during six hours on a plane. Theres only so much reassurance you can get from statistics but flying is incredibly safe.

Our focus will be on what you see and experience on board an aircraft, but its quite possible that boredom will kick in as you wait in the terminal. You can only do so many trips round the duty-free shops, or drink so many coffees. So lets take a brief look at some of the extreme technology you might encounter on the ground before taking to the air.

An airport divided

Airports have a strict divide between groundside and airside. To get from one to the other, particularly when flying internationally, you will face a barrage of technology aimed at identifying you and checking that you arent carrying anything dangerous. If airlines were permitted, they would also weigh you as you pass through (this was done in the early days of flight). Plane loading is very sensitive to weight and airlines have to rely on average weights to know how much load the passengers are contributing.

Making such an estimate has, at least once, caused problems. The plane, taking off from a German airport, struggled to get away from the runway and only just managed to claw its way into the air. It later turned out that there was a coin fair on in the city, and many of the passengers were coin dealers with their pockets crammed with new acquisitions, because they didnt want to risk their new purchases being stolen from the hold baggage. All this unexpected spare change pushed the passengers weight well above the expected average. Added up over the entire aircraft, there was so much extra load that the plane didnt respond as the pilots expected it to, causing a few worrying moments on take-off.

Bag check

Your first encounter with interesting technology is likely to be the security scanners. Your hand baggage is put on a conveyor belt that carries it through a powerful X-ray machine. That name X-ray is not because of some special scientific naming convention, its just that when discoverer Wilhelm Roentgen first came across rays that would pass through solid objects he called them X-rays (or rather X-Strahlen ) to show that they were unknown and mysterious. They were officially renamed Roentgen rays, but everyone liked Roentgens original nickname for them, and it stuck.

In reality, X-rays arent particularly mysterious they are nothing more or less than light, but light of a colour that is far outside the spectrum that we can see. All light is electromagnetic radiation, a special interaction between electricity and magnetism that comes in a huge range of colours. As well as visible light there is radio, microwaves, infra-red, ultra-violet, X-rays and gamma rays all exactly the same kind of stuff but with varying amounts of energy (see illustration 1. below). We now know that light is made up of tiny particles called photons (more on these later). X-rays consist of much higher-energy photons than visible light. If you prefer to think of light as a wave, as it was probably described to you at school, then X-ray waves have a shorter wavelength (the distance in which the wave makes a complete wiggle) than visible light.

1. The electromagnetic spectrum: visible light forms a small segment near the middle.

When ordinary light hits an object like a suitcase that isnt transparent, the photons of light are absorbed. This happens because the energy in the photon is sucked up by one of the particles that make up the suitcase. Every object we see around us is made up of atoms, and each atom consists of a very small central part, the nucleus, which contains over 99 per cent of its weight, surrounded by a fuzz of tiny particles called electrons. When a photon of light meets an electron, the electron can consume the energy in the photon. This leaves the electron buzzing around with more energy than it started with.