Can Cows Walk Down Stairs? E-Book

Paul Heiney

• Herausgeber: The History Press
• Kategorie: Lebensstil
• Sprache: Englisch

Seitenzahl: 271

Veröffentlichungsjahr: 2011

Beschreibung

What is ear wax for? Do bacteria have sex? How do they put stripes in toothpaste? Does your nose run in space? What are stars made of? This book answers those tantalising or perplexing questions for which you thought you'd never find an answer. A book for the naturally curious, as well as those seekers after scientific truths, it unravels both those things we take for granted, such as when you boil an egg, why does the yolk stay in the middle, or why is the sky blue, as well as questions which probe deeply, such as, what does an atom look like, or what was there before the beginning of time? if you were to write in the dust on the moon, how big would the letters have to be so you could see them from earth without a telescope? Drawing on the expertise of a team of enthusiastic scientists around the world, authoritative, entertaining, and often a touch humorous, it will appeal to anyone who's ever been curious about life on earth.

Leseprobe

Contents

Title

Introduction

1. Where it All Began: Secrets of the Universe

Atoms to Big Bangs

2. Cats, Dogs and Animals in the Wild

The Chicken, the Egg and Swimming Kangaroos

3. Birds, Bees and Creepy Crawlies

Sneezing Birds and Spiders’ Webs

4. Down to Earth

Autumn Leaves, Ripe Tomatoes and Germs

5. Seeing isn’t Always Believing

Mirror, Mirror on the Wall …

6. Body Works

Curly Hair, Belly Buttons and Hangovers

7. Kitchen and Home

Jelly, Diamonds and Custard Powder

8. Got that Feeling?

Curries, Sherbet and Falling in Love

9. Number Crunching

Starting at Zero

10. Can You Just Explain … ?

11. Brainstorms

From Grey Matter to Bread Crusts

Copyright

Introduction

The French philosopher and anthropologist Claude Lévi-Strauss (not the inventor of denim jeans), whose complex theories of structuralism are as far removed from my understanding as the small print of an insurance policy, once said, ‘The scientific mind does not so much provide the right answers as ask the right questions.’ This view, from one of such intellectual authority, comes as a great relief for I’ve always been able to come up with the killer questions: it’s the answers that have eluded me.

I know no more science than I learnt at school, and this was just enough to oblige me to spend the rest of my life frustrated that I did not know more. Somehow, my knowledge of science always stopped two photons short of a good answer to all the fundamental and fascinating questions raised by the business of living. There is a neatness and satisfaction in a convincing answer to a scientific question, but only frustration when a too-slender grasp of the principles involved leaves you unable to produce one. For example, if you ask me why satellites orbit the Earth, I know that it is something to do with Newton’s Law of Motion, isn’t it? Does angular momentum come into it? Could I define angular momentum? No, of course I couldn’t. That’s the problem: it’s always easier, and much more fun, to come up with the questions than it is to provide full and proper answers.

So I am grateful to Mr Lévi-Strauss for allowing me some credit for only ever wanting to ask why, and expecting someone else to do the hard graft of coming up with the reply. If you are in a similar position, don’t worry – Lévi-Strauss puts us at the very heart of scientific thinking.

We occasional seekers after scientific truth are joined by a large body of enquiring people who, in frustration, picked up their phone or connected their computer to the Internet to quiz the brains behind a London-based question-answering service called ‘Science Line’ – a product of a concerned government which became worried that young people were turning increasingly to the study of media, humanities and sport, and shunning the sciences. This raised the prospect that there might be, a generation hence, no one left in Britain who understood that pi was not part of the food technology syllabus.

The government decided to do something about it. The aim was to provide a telephone and Internet service, available freely to all, which would answer any scientific question anyone, young and old, cared to throw at it. There were a few rules: complexity alone did not rule out any question, so an explanation of why light cannot emerge from Black Holes was fine; but strictly non-scientific questions, such as, ‘in the expression, “what’s up?”, what does the “up” refer to?’ was banned. Also ruled out were calls from cheats who were attempting to use the service to do their homework for them.

Behind the scenes at this all-knowing super-brain was a small team of enthusiasts, mostly young scientists from across a wide field of knowledge, who could deal with the recurring questions which were well within the understanding of anyone with a reasonable scientific education, such as ‘why is the sky blue?’ (Brief answer: blue light gets scattered much more than all the other colours in the light from the sun because of its short wavelength, causing the sky to appear blue.) Of course, very often one question leads inevitably to another, if sometimes out of a natural desire to prove yourself smarter at asking questions than the other person is at answering them. Such a clever-clogs might now ask, ‘if the sky’s blue because of scattering, why is a sunset red?’ (Brief answer: because the light from the sun, as seen at sunset, is coming to you through a thicker atmosphere, which absorbs the blue light. But the blue light of the sky doesn’t come directly from the sun – it’s scattered light.) And from a fertile mind a hundred further questions can probably emerge, but we’ll draw the line there.

Some questions asked of Science Line, however, were harder for them to deal with than the blue sky theory. ‘What is the exact difference between Henkin’s proof for the Completeness Theorem for First Order Logic and Godel’s proof?’ Eh? I’m sorry; I would need someone to explain the question before I could begin to understand any answer. But Science Line was not fazed by this, nor by questions like ‘can you describe a method for determining electron dn configurations?’ – which sounds suspiciously like homework to me. Instead of scratching their heads, the experts forged contacts with the wider academic community and turned to them for definitive answers. As a result, all the answers carried authority, readability and sometimes no small measure of humour.

Then, just as Science Line was becoming part of people’s lives, the government pulled the funding plug and it passed peacefully away. Its website carried the sad statement, ‘Due to lack of funding Science Line will close on the 26th September 2003. We are sorry but we can no longer take any questions.’

By great good fortune, before the website closed and the dedicated team of question answerers moved on to other things, they had already explored the possibility of a book based on their vast, wide-ranging database, which by now contained over 16,000 questions and answers. This is where I came in, although at this early stage I was entirely unprepared for the breadth, depth and often sheer entertainment value of the material Science Line had collected. I have always thought that the idea of the undiscovered treasure chest which opened to reveal jewels and sparkling gems was the stuff of children’s books. But now on my desk were two slim computer disks, which opened to reveal equally dazzling contents. Together those two slim disks added up to a mountain of knowledge which we all agreed should not go to waste. The questions and answers would no longer be on the Internet, but why shouldn’t the best of them be brought together in a book?

I hadn’t read far into the megabytes of knowledge before I realized that here were the answers to questions that had dogged me all my life. I already knew why the sky was blue, honestly, but I had no idea why flies circle round light bulbs, or why jelly made with fresh pineapple will never set – but I do now. I understand reflections in mirrors now – did you know they’re not ‘flipped’ at all? And if you have ever lain awake at night wondering whether or not penguins have kneecaps, the answer is here. You will also learn why cows can walk up stairs but not down again – that’s to do with kneecaps too.

There can be no greater pleasure than sifting through these questions, not only for the satisfaction of discovering the answers, but for the sheer enjoyment of the lateral thinking and mischievous minds which asked, ‘how easy is it, scientifically, to fall off a log?’ or ‘do bacteria have sex?’.

The task of choosing the questions to include in this book was an easy one – I picked the ones that not only fascinated me most, but also those which provided surprising or unusual answers. The selection was made purely on entertainment value: the sort which leads not to a giggle or a belly laugh, but to the warm glow that flows from a nagging scientific question answered in an understandable way. No doubt someone else would make an entirely different selection.

The questions, remember, belong to the people who asked them, and for the education they provide we must thank them. And to those who patiently answered them I can only express the most enormous respect for what they clearly believed was a vital public service. I herewith salute and give full credit to Siân Aggett (Biology), Alison Begley (Astronomy and Physics), Duncan Kopp (author of Night Patrol), Khadija Ibrahim (Genetics), Kat Nilsson (Biology), Jamie McNish (Chemistry), Alice Taylor-Gee (Chemistry) and Caitlin Watson – as well as the numerous distinguished experts whose knowledge they drew upon when their own was stretched to its limits.

On occasions I have reworded their answers for clarity, and sometimes added to them if I thought further explanation was needed. But this book is really the work of those who asked the questions and the dedicated few who answered them.

I hope that after reading it we might be able to convince Mr Lévi-Strauss, were he still alive, that mastery of both the question and the answer leads to the supreme scientific mind.

Paul Heiney

2005

1

Where it All Began: Secrets of the Universe

Atoms to Big Bangs

What does an atom look like?

That is very difficult to say because they are so small and we cannot see them even when we use the best microscopes we have. But scientists are now using a new kind of microscope to make images of atoms: these machines still can’t see the atoms, but they can feel them in a similar way you feel a prickly sensation when you hold your palm very close to the TV screen but don’t actually touch it. This is complex nanotechnology but, clever though it is, it still doesn’t let you see an atom. If you could, you’d find there is a tiny core at the centre called the nucleus, consisting of particles called protons and neutrons. Protons and neutrons have about the same mass. Protons have a positive charge. Neutrons have no charge.

Hydrogen was the very first atom to be created at the moment of the Big Bang – the start of the universe – and it was created by the coming together of a quark (yet another sub-atomic particle) and an electron. The Big Bang theory of the creation of the universe occupies many volumes and some of the finest minds, but in a nutshell it says that the universe began with all its matter concentrated at very high density and temperature 15 billion years ago. An explosion caused it to expand, which it is still doing to this day.

If atoms are mainly space, why doesn’t your hand fall through a table?

Everything around us is made of atoms – even the air we breathe. The difference between the air we breathe and, say, a table is that the atoms are much more tightly packed in a table. So while you can pass your hand through the air – where you are essentially pushing atoms out of the way – you can’t put your hand through a table because the atoms can’t move out of the way. It’s like trying to walk through a tennis court filled with 100,000 tennis balls as opposed to one with 100 tennis balls: you just can’t do it. But it’s not just the space that’s a problem. There are also very strong forces holding atoms together. So although atoms are mainly space, the strong forces holding them together and the tightness with which they’re packed mean you can’t put your hand through a table. It’s not the space within the atoms that prevents you, it’s the forces that hold them together.

I’ve heard that if you remove all the space from around the atoms then all the atoms in the universe would fit into a matchbox. Is this true?

This is one of the tales you hear now and again. I could simply tell you it’s not true, but it would be better if we worked it out. It won’t be an accurate calculation, but it will give us an indication as to whether there’s any truth in this ‘universe in a matchbox’ theory.

This is how it goes:

Volume of electron:

Volume of proton:

This means that the total volume taken up by the proton and electron is approximately 1 x 10–43 m3

2. We now need to know the volume of a matchbox, which is approximately 3 x 10–5 m3.

3. The next step is to work out how many atoms can fit in this matchbox. This can be calculated by dividing the volume of the matchbox (3 x 10–5) by the volume of the atom (1 x 10–43), giving the answer 3 x 1038 atoms.

4. The final step is to see how this number compares with the number of atoms in the universe. There are a couple of ways of estimating this. There are about 100,000,000,000,000,000,000 stars in the universe – and that’s a guess. How many atoms in a star? Impossible to say, although we can have another guess. Let’s say the sun is a typical star and it’s made up totally of hydrogen. The mass of the sun is 2,000,000,000,000,000,000,000,000,000,000kg. The mass of a hydrogen atom is 0.0000000000000000000000000017kg. Divide one by the other and the number of atoms in the sun is 1,200,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000.

Now multiply that by the number of stars in the universe and you have: 1 with 77 zeros after it as the number of atoms in the universe.

Looking at it another way, the mass of the observable universe in kilograms is 1 with 52 zeros after it. That’s about 90 per cent of the total mass of the universe, we think, so the total mass of the universe in kilograms is 10 with 52 zeros after it. Divide that by the mass of a hydrogen atom (the vast majority of the universe is hydrogen) and the number of atoms is 6 with 79 zeros after it.

These two figures are similar enough to suggest that they’re about right, so we will take as an educated estimate of the number of atoms in the universe.

5. Comparing the answer to point 3 with the answer to point 4, it is clear that even if all the atoms in the universe were as small as a hydrogen atom they wouldn’t fit into the matchbox. Since there are many atoms that are much larger than hydrogen the actual number that will fit in the matchbox will be smaller than we worked out in 3.

So how much volume would all the atoms in the universe take up if they were all only made of an electron and a proton and no space? This can be worked out by multiplying the answer to 4 by the answer to 1:

A rather big matchbox!

What is time?

Do you want a psychologist’s answer, or a physicist’s? I suspect the latter, in which case you have to prepare yourself to confront the theories of Albert Einstein, one of the most important scientific thinkers of the first half of the twentieth century who established the theory of relativity.

According to Einstein, time and space are closely tied together and he went on to show that asking when an event takes place is much the same thing as asking where it takes place. He said that we could not separate the world into space and time but that space and time are actually parts of something called space-time. Space-time has four dimensions: three to give a position in space and one to give a position in time. When you walk, you move through space-time; when you stand still (because time passes) you are also moving through space-time. Our experience of time is a result of moving forward in this time dimension of space-time. So time is really another dimension, the difference being that in the other three dimensions we have a choice about which direction we want to travel in. But with time there’s only one direction and that is forward – except in the case of Dr Who.

Was there a time when time ‘began’? And what was there before the beginning of time?

What is the main cause of gravity? Why is there an attraction betweentwo masses?

Sir Isaac Newton in the seventeenth century first formulated a law of gravity: it said that two masses will attract each other with a force which depends on their distance apart and their masses. It was one of those laws which came about through observation and experimentation, and only then was it set out mathematically. As to what actually caused the forces of attraction, not much thought seems to have been given to that at the time.

It had to wait until Einstein in the twentieth century turned his attention to gravity. He equated gravity with the acceleration of a body and went on to show that light bends in a gravitational field. Since light has no mass, Newton’s theory could not explain this bending. Einstein’s great contribution was to show that space-time actually curves owing to mass. Imagine a heavy ball sitting on a large, stretched rubber sheet – space would curve near the mass but remain reasonably flat further away. Only if light passes close to the large mass will its path be appreciably deviated. Experiments have now been performed which show that light really does bend near a mass owing to the curvature of space-time.

But that’s not really the answer to what gravity actually is, and no one has yet come up with a theory which enables us to describe it.

I know that the length of the days and years is due to the spinning of the planets on their own axis and their orbit round the sun,but whatstarted themspinning in the first place? What got them going?

To answer the question you have to go back to the formation of the solar system which was created out of a massive ball of gas and dust which slowly started to pull together under the effects of gravity. As this dust came together, particles colliding as it did so, the centre of the ball got hotter and hotter until it became hot enough to form what we call the sun. As the temperature rose, the sun reached a point at which it became ‘switched on’, like a fire suddenly igniting. This ignition caused gas and dust to be flung away from the sun to form the basic building materials of the planets.

Now for the spinning. There is a law of motion called the ‘conservation of angular momentum’ which says that as something gets smaller, it spins faster and faster. This is why, for example, a skater speeds up if she brings her arms into her body making herself smaller. It’s the same with a ball of dust and gas: any slight rotation which it already had would have become bigger and bigger as it decreased in size. Now, as things spin, centrifugal forces push the middle out and pull the top in. This happened with the ball of dust so that eventually it wasn’t a ball any longer, but a disc surrounding the sun. The planets then formed from this disc, which is why they all orbit in roughly the same plane around the sun.

That original ball of gas wouldn’t have needed much spin to produce the rotation we see in the solar system, although what produced that original spin is not known. But things in the universe generally like to spin if they have any choice. Virtually everything from galaxies to planets spins.

Does light stop existing, or would it travel on for ever into eternity if nothing got in its way?

The answer lies in the words ‘if nothing gets in its way’. In theory, light will go on for ever if it doesn’t bump into anything, but that requires it to travel through a perfect vacuum, which in practice can never occur. Light is energy, and if nothing occurs to make it lose that energy, then it will exist for ever.

Imagine a photon, which is a parcel of light emitted from the sun. If it manages to miss all the planets and asteroids and comets (in other words all the large objects in the solar system), it may well hit a piece of dust from a comet, or a mere atom of hydrogen just floating around in space, and lose its energy that way. But some photons survive the journey and travel in a straight line until they meet, say, your eye. That is then the end of that parcel of light, for the energy the light was carrying is converted into an electrical signal that goes to your brain, allowing you to see the light.

Alternatively it might collide with an atom floating in space, or an atom in the atmosphere of a planet, or an atom in an object, like a rock. Some of that energy gets reflected – and that’s how we see things.

This Big Bang sounds awesome. Was it actually a bang, as in an explosion? And would you have heard it if you’d been there at the time?

This, of course, is a hypothetical question with no good answer to it. But how about this for a theory? Sound, which is transmitted as vibrations, needs something to travel through. At the time of the Big Bang, it’s true that the universe was infinitely dense, but there weren’t any individual particles, so I imagine that sound wouldn’t have travelled. But if you’ve got a better theory, that might be right too.

Could you ever travel fast enough to overtake the Big Bang? I mean, if you travelled at twice the speed of light would you overtake it, and then be able to watch the start of the universe?

Sorry, but even if you did get to twice the speed of light, you have to remember that the Big Bang created not only the matter in the universe, but also the space within it. How does that stop us looking back at the creation of the universe? Just after the Big Bang the universe was still tiny, just a few metres across. If we tried to travel out of it, we wouldn’t have anywhere to go because the space hadn’t been created.

Is it possible that there was more than oneBig Bang and that there are, in fact, other universes moving towards one another?

There’s no way to tell. First of all, the concept of an expanding universe is a tricky one and it’s often misunderstood. The universe is not expanding ‘into’ space: it’s not as though there’s something out there that is slowly being filled by the expanding universe – it is space itself which is expanding. In other words, the distance between two objects in the universe is getting greater, but the objects are not moving. That’s why you can’t have two Big Bangs next to each other.

Are you saying that there’s nothing outside the universe?Surely it’s got to be contained in something.

Some of these questions are for scientists and others for philosophers. This question is largely for the latter. Technically, ‘the universe’ means everything, and so there can’t be anything else beyond it otherwise that would be part of the universe too. I think where the confusion arises is because we use the word universe to describe everything we can see, when we should really be describing it more accurately as a ‘visible universe’. There is, of course, much beyond it which we can’t see because there hasn’t been time for the light from far-away bodies to reach us. The universe is around 15 billion years old, so we can see anything within a distance of 15 billion light years from us, because the light from these bodies would have travelled to us. The universe has not been around long enough for the light from anything beyond this distance to get to us.

As to the universe beyond what we can see, it’s guesswork to some extent. We can tell what it might be like because it will have a gravitational effect on us, even if we can’t see it. Einstein’s equations of general relativity, which describe how gravity affects space itself, are still the best way we have of describing our universe on its largest scales. These imply that the space is either infinite, or is closed back on itself. If it’s infinite, then it can’t be contained in anything because it goes on for ever; if it’s closed it doesn’t really have a beginning or end either. That’s kind of hard to think of in three dimensions, but imagine you are two-dimensional and wandering around on the surface of a sphere. You can move back and forward, and left and right, but you don’t have any concept of up or down. As far as you’re concerned, there is nothing else but the surface of your sphere. Then, you would be forever wandering around on this sphere but never come to an end of it. So, for us, our universe is all there is.

This space that the universe is expanding into, what is it? Is it pure emptiness, nothingness? If I took an open box out into space, closed the lid and brought it back to Earth what would be in it?

Space is not a perfect vacuum. Even if we could somehow get rid of all the interstellar dust, etc., at the quantum level space is not empty – it consists of shifting quantum fields, which are apparently due to the universe’s gravitational field. So your box wouldn’t be filled with nothing. Space is not really ‘pure distance’: it is the name we give to the (almost vacuum) surroundings containing all the galaxies, and describes the gravitational field of the universe. This is something we still don’t fully understand, so a ‘playground for the celestial bodies’ seems as good a term as any!

What are the so-calledblack holes in the universe?

John Michell, an English astronomer, first suggested in 1783 that a mass could create a gravitational field so strong that light could not escape from it. A few years later the French mathematician and philosopher Pierre Laplace arrived at the same conclusion. Then, when Einstein proposed his theory of general relativity in 1915, a black hole as a real object became a possibility. John Wheeler coined the term black hole in 1967.

There is no absolute proof that any black holes exist, but there is evidence for them. The first black hole to be ‘discovered’ was Cygnus X-1 in 1971. Although no one can say for certain that this is a black hole, few people now doubt that it is.

But why can’t lightescape from a gravitational field? Light doesn’t ‘weigh’ anything, so what holds it back?

Explaining black holes is very difficult if you simply stick to Newton’s ideas of gravity. They work fine when we talk about everyday activities like playing pool or throwing balls – even launching rockets works with Newtonian gravity. But when it comes to complicated things like black holes, you have to start looking at what gravity does to space. This is what Einstein was doing in the early twentieth century. His theories of gravity say that gravity affects a combination of space and time called space-time. Einstein said gravity bends space-time so that light doesn’t travel in straight lines. The quickest way from A to B is always a straight line, unless it isn’t!

This might help you understand: you’d think that planes flying from London to Vancouver on the west coast of Canada would simply fly straight across the Atlantic, but they don’t. They fly north towards Scotland and then head over Greenland because this is actually the straightest and shortest route, although it doesn’t look like it. Our normal view of the world is a flat one – all the maps we use are flat – so it looks as though the shortest route is straight across the ocean. But if you look at a globe – a true representation of the world – you’ll easily see that the shortest route is what’s known as a Great Circle over Greenland.

It’s the same with space-time. Our view of space is that it is flat, and that view is perfectly acceptable as long as all we want to do is go to the moon. But as soon as we start talking about areas of space where the gravity is very strong – black holes, for example – we have to start taking into account the effects of gravity on space-time. Imagine a trampoline with a grid of straight lines drawn on it. If you put a heavy sack of potatoes in the middle of it, the trampoline will sag into the middle and the straight lines won’t be straight anymore. If you then roll a marble from one end of the trampoline to the other, it will no longer go in a straight line but will follow the bent lines on the trampoline. And that’s what happens with space-time and light. Gravity bends space-time, and light follows the straight lines that have been bent out of shape through it. A black hole bends space-time so much that the straight lines actually bend right round on themselves and the light ends up going round and round in circles. That’s how black holes work.

What would happen if I fell into a black hole?

The first thing to understand is that you’re never going to get out again. As you approach, you won’t feel much at all. Like an astronaut orbiting the Earth, you’ll be in free fall and every part of your body will be under the same gravitational forces – you’ll feel weightless. But once you start to get closer to the immense gravitational field of a black hole, about half a million miles from the centre, you come across what is known as the black hole’s tidal force. If you happened to be heading towards the hole feet first, your feet would feel more gravitational pull than your head and you would suffer the sensation of being stretched. This would get worse to the point where your body ‘twanged’, and that would be the end of you.

Most likely, this would happen before you crossed something called the black hole’s ‘horizon’. At this point the speed at which you would have to be travelling to make your escape becomes equal to the speed of light. All gravitational fields have an escape velocity; on Earth it’s the speed at which a rocket has to travel to get into space. Once you cross the horizon of a black hole you need to travel faster than the speed of light in order to escape, which is impossible. Once you’re over the horizon, you’re trapped, if you haven’t already been stretched beyond endurance.

What would I see as I fell in?

Things may look a little distorted since the light from distant objects would be bent by the huge gravitational field, but even when you’ve crossed the inescapable horizon, light from outside can still be seen from the inside. Of course, no one can see you because light from you can’t escape from the black hole – to do that, light would have to travel faster than light, which is clearly impossible.