eBook
Related collections and offers
Overview
From paintings and food to illness and icebergs, science is happening everywhere. Rather than follow the path of a syllabus or textbook, Andrew Morris takes examples from the science we see every day and uses them as entry points to explain a number of fundamental scientific concepts – from understanding colour to the nature of hormones – in ways that anyone can grasp. While each chapter offers a separate story, they are linked together by their fascinating relevance to our daily lives.
The topics explored in each chapter are based on hundreds of discussions the author has led with adult science learners over many years – people who came from all walks of life and had no scientific training, but had developed a burning curiosity to understand the world around them. This book encourages us to reflect on our own relationship with science and serves as an important reminder of why we should continue learning as adults.
Praise for Why Icebergs Float
'Asking questions is an important scientific skill and sometimes we can only understand something when we can find the language to ask the right questions; books like this can be really helpful in this respect....This book is one of UCL’s open access books. This means that it can be downloaded as a free PDF from the UCL Press website. The commitment to making scientific works such as this freely available is very welcome. This book is very accessible and deserves to reach a wide audience.'
School Science Review
'Morris says in the prologue: ‘If you come away from this book with a greater interest in science and enhanced confidence about tackling it, the book will have served its purpose.’ So, don’t be afraid of science and give Why Icebergs Float a chance. You will absolutely enjoy it.'
Chemistry World
'[Why Icebergs Float] draws on experiences and first-person narratives of adult learners who – out of genuine curiosity or embarrassment at their levels of scientific ignorance – have sought to catch-up on lost school science and get a better understanding of their surroundings as a result.'
Education Journal
'The approach illustrates beautifully the influence of language on understanding. The author makes clear how common language can be misleading when scientists have used everyday words but given them very specific meanings.’
Physics Education
‘I had fun reading this book. If it makes science more accessible to more people, that’s surely a good thing.‘Speculative Stories
Product Details
| ISBN-13: | 9781911307051 |
|---|---|
| Publisher: | U C L Press, Limited |
| Publication date: | 10/24/2016 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 220 |
| File size: | 16 MB |
| Note: | This product may take a few minutes to download. |
About the Author
Andrew Morris has been running science discussion groups since 2002. Originally a science teacher, he studied physics at University College London and completed a doctorate in molecular biophysics at the University of Leeds. His 2015 book is titled Getting to Grips with Science: A Fresh Approach for the Curious.
Read an Excerpt
Why Icebergs Float
Exploring Science in Everyday Life
By Andrew Morris
UCL Press
Copyright © 2016 Andrew MorrisAll rights reserved.
ISBN: 978-1-911307-05-1
CHAPTER 1
Foods We Love and Hate
Sally works in the lively office of a children's charity in central London. She had been chatting with her colleagues over lunch one day about which foods they liked and disliked. Her own pet hate was mushrooms, something she had always disliked, especially the musty old smell of the things. That evening Sally was due to meet up with her fellow enthusiasts in a science discussion group at a local wine bar. She decided to bring up this topic to see what others in the group felt and to discuss the underlying science together.
A fascinating exchange of experiences and thoughts ensued, leading to an exploration of the varied substances that flavour our food and the ways in which our bodies respond to them. Everyone seemed to have something to say about their food preferences. Dominic, a retired journalist, had disliked avocados until he was about 30, at which point he had unexpectedly developed a taste for them. Amy, a young woman in her mid-20s, had noticed that some foods you come to like as an adult, such as olives, may seem horribly bitter when you are young. Helen, who had had a lifelong aversion to cheese, had a personal theory about how this had come about: unhappy memories of having the ghastly stuff forced on her when she was a child.
This brief skirmish with likes and dislikes threw up some interesting ideas about how these preferences might have arisen – possible patterns and causes. Growing older seemed to play a part and this chimes with recent research. A lot of people do appear to become less fussy as they get older, perhaps because it can be socially awkward to reject certain foods as an adult. Another theory is that we tend to be cautious about foods that are new to us and, of course, for a young child many things are new. Talking of young children prompted Amy to comment on how unrestrained children tend to be in their demands for sweet things, often pestering their parents to the point of exhaustion for unhealthy kinds of snacks and fizzy drinks. Her suggestion was that perhaps there may have been some kind of evolutionary explanation for this. Hadn't she heard that it was in the interests of early humans to feast on sweet things as soon as they encountered them because there was no certainty about when they might next find any? Didn't sweet berries and fruits provide a highly valuable source of sugar in a time when it was scarce?
Evolution
Sugar is indeed one of the foods that yield plentiful energy when digested. In the time before agriculture, when chance played a major part in what foods you might stumble upon, sweet things would certainly have been very beneficial, though much scarcer than today. Darwin's idea of evolution through natural selection means that individuals best fitted to their environment would become more and more numerous in the population – not through any design intention, but simply by surviving longer and reproducing more. The high energy content of sweet foods may well have conferred an evolutionary advantage to those who sought them out.
So attraction to sweet things would have developed over millennia as a common human trait – a perfectly reasonable and successful feeding strategy, at a time when sugar remained in relatively short supply. For better or worse, the situation today is quite different. Sugar supplies are plentiful in highly processed forms, but we continue to express these ancient preferences, although they are no longer so advantageous for our survival – quite the reverse in many parts of the world. Evolution proceeds at a much slower pace than human cultural development. Celia summarised our modern predicament succinctly, based no doubt on personal experience: 'Isn't it odd,' she observed, 'that however full you feel after a hearty roast, you always have room for something sweet?'
Sarah wondered whether evolution might have played another role in the development of taste: signalling to the brain which kinds of food to avoid. As Amy had noted earlier, olives are not too popular with children; the love of their slightly bitter taste seems to develop later in life. Could this tendency also have evolved because bitter fruits may also be poisonous fruits? Has our sensitivity to what we perceive as bitterness evolved as a protection against accidentally eating poisons? Are poisons usually bitter in fact?
Bitterness
Fortunately there are places where tastes and smell are investigated scientifically. A study at one of them, the Monell Centre in Philadelphia, has investigated a long-held assumption among scientists that a bitter taste evolved as a defence mechanism to detect potentially harmful toxins in plants. Subjects in the study were genetically tested and then asked to rate various vegetables for taste. The evidence suggests that we are able to detect bitter toxins with our sense of taste, and genetic differences in our bitter taste receptors affect how we recognise foods containing a particular set of toxins.
This evidence bears out some of the speculative thoughts of the group: that the bitter sensation we associate with olives or broccoli appears to have developed over evolutionary time to help protect us from potential toxins. It also throws light on why individuals respond differently to a particular food, by linking taste to genetic differences. But as so often when we encounter scientific evidence, satisfying one inquiry, far from closing down a subject, seems to provoke even more questioning. If the molecules in our taste buds have evolved to detect molecules from toxic plants, what is it that gives us the actual sensation of bitterness? What is it that translates the presence of some particular chemicals in the taste buds into a subjective feeling – something that, at least when we are young, tends to turn us off such foods?
The chemistry of taste
With talk of bitterness and taste buds, the conversation turns naturally to what is actually happening in the mouth when we taste something. The idea that four principle tastes are associated with different regions of the tongue seems to be one of those pieces of information that actually stick from biology lessons at school, however long ago: salt, sweet, sour and bitter. Dominic, whose journalistic career had taken him around the world, raised the question of a fifth taste, umami. Well known in Chinese cuisine, this is associated with monosodium glutamate, an additive used to boost the meaty flavour in dishes. It occurs naturally in a wide range of foods that contain glutamate, including fish, cured meat, mushrooms and breast milk.
What those around the table did not know is what is happening chemically when each of the tastes is being experienced. It turns out that each of the five basic tastes is associated with an entirely distinct category of substance in the food. Different kinds of chemical trigger off different kinds of receptor molecule in the taste buds (explained later in the chapter). These receptors in turn send different kinds of signal to the brain. No prizes for guessing that it is sugar molecules that trigger the sensation of sweetness. No great surprise either to learn that sourness is felt when acids are detected in food. In fact the very word 'acid' derives from the Latin acidus, meaning sour.
More of a revelation is that the sensation of saltiness is simply the result of metal ions in food and drink hitting the palate. Ions are individual atoms, rather than the more complex molecules, which have gained a slight electric charge by losing or acquiring extra electrons in their internal structure (every electron carries a small negative charge). It is normal for the atoms in salts such as sodium chloride, for example, to separate out as ions in this way as they dissolve in water. Typical ions in food are sodium, potassium and iodine – all vital for the functioning of our nerves and other systems.
The bitter taste found in wine, beer and many vegetables corresponds to a class of chemicals called alkaloids which are present in many foods. Caffeine, nicotine, strychnine and morphine are examples of well-known alkaloids. It seems that these substances evolved as toxins in many plants precisely because they deterred herbivorous animals from eating them. Strangely this didn't seem to put us humans off coffee for long!
Finally we turn to umami, formally recognised in 1985 as a fifth distinct basic taste after it was found to be associated with a distinct receptor in the mouth. Umami is simply the taste buds' response to the naturally occurring substance glutamate, found in a very wide range of foods. It is frequently described as the 'meatiness' taste.
The psychology of taste
This introduction to the chemical basis of taste seemed interesting to people in the discussion group, if a little daunting. As often with chemistry, the number of unfamiliar terms can be off-putting. How do you get a feeling for a word such as 'alkaloid' if it has played no part in your life and doesn't connect with anything you know? The discussion took off from the basic chemistry of food and led to a more specific question: what is it in the tongue that actually picks up these various chemical sensations – the acids, the metal ions, the sugars? What are these so-called 'taste buds' we talk so loosely about?
Before a foray into the biology of the tongue could even begin, however, Helen – never one to let things hang – interrupted to bring us back to her earlier point about childhood experiences. 'Surely psychology has a crucial part to play in all this?' she rightly asked, reminding the group of her enduring memory of having been made to eat cheese as a youngster. Talk of childhood memories inspired others to chip in with recollections of a favourite children's story book. Hadn't Babar the Elephant sadly died after eating a poisonous mushroom? An interesting point for Dominic, who had spent much of his life abroad, was that the author of the Babar books was French. Given that hunting for wild fungi was a normal part of life in rural France, he wondered aloud whether the books had a hidden purpose: to warn children of the dangers of eating mushrooms indiscriminately? Talk of early years' reading reminded Amy of her lifelong antipathy to Turkish Delight, with its strange colours and wobbly texture. Could this have been linked subconsciously to its role in The Lion, the Witch and the Wardrobe, where the sweet is used maliciously to entice a young boy?
Our emotional responses to food do not seem to be limited to our memories of experiences in childhood. As the Turkish Delight discussion suggests, maybe other perceptions play a part too: the colour of food for example. As Helen realised, you don't see many blue foods – apart from a few kinds of berry. In fact she recalled sitting in a restaurant once under a blue light and feeling distinctly uneasy about tucking into her rice dish. Could it be that the colour blue is associated with mould, which is sometimes poisonous, she speculated?
This turn of discussion about the psychological aspects of food preferences led Julie to raise an even bigger question, particularly in relation to sugar: 'What about addiction? Is this a psychological matter or does biology play a part?' This is, as you might expect, an active area of neuroscience research. The Oregon Research Institute has used MRI scanning to conclude that sugar stimulates the same brain regions as drugs such as cocaine. Furthermore, heavy users of sugar develop tolerance (needing more and more to feel the same effect), which is a symptom of substance dependence.
It looks as though our current understanding of addiction is based on both psychological and biological research. Certain studies suggest that addiction is genetic, but environmental factors, such as being brought up by someone with an addiction, are also thought to increase the risk. As we find so often in trying to understand the science behind the way we behave, the nature versus nurture argument fails to get us very far. Our upbringing and other environmental factors play a part, but so do biological factors, including those we inherit. The balance will of course vary from individual to individual, as you might expect given the marked variation we see in our responses to sugar (or any other ingredient) in our diet.
Diabetes and hormones
Talk of sugar stirred Dominic to explain something of the nature of diabetes, a condition he had acquired later in life. In this type of diabetes (known as Type II) the level of glucose (a kind of sugar) in your blood is no longer properly regulated as a result of failings in your body's insulin system. Insulin is a naturally occurring substance manufactured in the pancreas, an organ 15 cm long that lies close to the stomach. It is a large molecule, one of many hormones in our bodies, whose particular job is to regulate the amount of glucose circulating in the blood.
Sugars are a class of substances that include fructose, lactose and sucrose (table sugar) as well as glucose. In the bonds that bind together the atoms in sugar molecules lies the energy that we need to keep our bodies ticking over. Too little glucose and our metabolism simply switches off: too much and damage ensues in organs such as the kidneys or retina, and to the cardiovascular system. For people such as Dominic, dealing with Type II diabetes means regulating the amount of sugar in their diet and taking other practical measures such as increasing physical exercise and losing weight. The other kind of diabetes, Type I, is the result of the cells that produce insulin in the pancreas actually being destroyed in an autoimmune response – that is, the body actually attacks itself. The ultimate cause of this is not known. People living with Type I have to inject insulin in order to regulate their sugar levels.
The crucial role of insulin in maintaining the right level of glucose in the blood sparked off serious discussion about the role of such chemicals in our bodies. 'OK, you've told us it's a hormone, but what does that mean?' was Helen's immediate response. By chance the answer to this question was ready to hand as the group had once organised a visit to a clinical endocrinologist at a local hospital (see chapter 8 on hormones). She had surprised the group by explaining that a hormone wasn't in fact a type of substance at all. It was simply a generic word applied to any kind of chemical in the body that is manufactured in one place but delivers its effect in a different one. So insulin is called a hormone because it is produced in the pancreas but acts in the bloodstream. Adrenalin is another example; it is produced in the adrenal glands, close to the kidneys, but acts on tissues throughout the body.
Talk of hormones and the earlier visit to an endocrinologist suddenly reminded Celia of something the endocrinologist had said. 'Hadn't she talked to us about hormones in the stomach? Wasn't she working on hormones connected with appetite?' she asked. The idea that there was more to appetite than the simple need to fill up set off new observations. 'It's not like filling up the tank of a motor car, is it?' said Sally, recalling a friend of hers who 'eats five Mars Bars a day and is still skinny. It all seems to depend on your metabolism, and this seems to change around the age of 30.' We needed to find out more about the role of hormones in stimulating appetite, and to find out why 'metabolism' differed from one individual to the next. Checking out the meaning of metabolism seemed a good starting point.
Metabolism
Metabolism describes the chemical processes that occur within a living organism in order to maintain life. It has two complementary aspects: a destructive one, in which substances that you take in are broken down to produce energy and waste, and a constructive one, in which the various chemical components of the body are built up. Metabolic rate simply means the speed at which your body burns energy. If it is fast, you burn up energy from food more quickly and remain thinner. The five Mars Bars a day person must clearly have had a high metabolic rate. Your rate is influenced by many things including the genes you inherit, your hormones, your gender, ethnicity and age – and of course we differ from one another in these respects.
The way in which hormones affect appetite is a lively area of research today. There appear to be many kinds of hormone that signal a state of either satiety (being full) or hunger to the brain. It is being discovered that some of these hormones circulate in the bloodstream and can directly influence nerve cells in a part of the brain (the hypothalamus). One hormone, called ghrelin, is secreted when the stomach is empty, signalling hunger, and ceases to be secreted when the stomach is full and stretched. It acts on brain cells, increasing the sensation of hunger and the release of gastric acid. Another hormone, leptin, has precisely the opposite effect, signalling the stomach is full. It interacts with the same cells in the brain as ghrelin.
There seem to be complementary systems in the body, one acting to promote, and one to inhibit, the same process. Like the systems that prevent sugar levels rising too high or falling too low, the body's regulation often acts like a thermostat in the home, switching on and off at the right moment to maintain steady conditions. The possibility that drugs might be designed to act directly on the hormones that regulate appetite is, as you might expect, an active area of research into obesity. By inhibiting the ghrelin hormone, appetite has been shown to be reduced. This leads in turn to lower food intake and reduced body weight, giving rise to speculation that this might be a possible way to treat or prevent obesity.
(Continues...)
Excerpted from Why Icebergs Float by Andrew Morris. Copyright © 2016 Andrew Morris. Excerpted by permission of UCL 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
List of Figures
Introduction
Getting the most from this book
1. Foods We Love and Hate
The chemistry and biology of taste
2. Why Old Masters Fade
Chemicals that give us colour
3. Cuts are Red, Veins are Blue . . .
How blood delivers our vital oxygen
4. The Dual Nature of Light
Particle or wave? That is the question
5. Models
Developing models or finding the truth?
6. How We See
From the eye to the brain
7. The Brain
What it’s made of, how it works
8. Hormones
What they are, what they do
9. Reflections on Molecules and the Body
Understanding the complexity of molecular mechanisms
10. Bacteria, Viruses and Antibiotics
Why you can’t take a pill for ’flu
11. Floating and Density
Why icebergs float
12. Tides and Gravity
Holding the universe together – from Newton to Einstein
13. Energy
The scientific angle on an everyday concept
14. Energy on the Move
How heat energy gets around
15. Energy for Life
Mitochondria and the ‘three- parent baby’
16. Electricity
Where does it come from, how does it work?
17. MRI and the Brain
Brain scanning and what it reveals: discussion with a cognitive neuroscientist
18. Animal Culture
Defining culture: discussion with an anthropologist
Epilogue
Reflections on what’s been learned and how to take it forward
Appendix: Atoms, Elements and Molecules
Briefing on the building blocks of matter
Further Resources
Index