The Magic of Reality: How We Know What's Really True

by Richard Dawkins

But are we only going to call something ‘real’ if we can detect it directly with one of our five senses? What about a distant galaxy, too far away to be seen with the naked eye? What about a bacterium, too small to be seen without a powerful microscope? Must we say that these do not exist because we can’t see them? No. Obviously we can enhance our senses through the use of special instruments: telescopes for the galaxy, microscopes for bacteria. Because we understand telescopes and microscopes, and how they work, we can use them to extend the reach of our senses – in this case, the sense of sight – and what they enable us to see convinces us that galaxies and bacteria exist.

How about radio waves? Do they exist? Our eyes can’t detect them, nor can our ears, but again special instruments – television sets, for example – convert them into signals that we can see and hear. So, although we can’t see or hear radio waves, we know they are a part of reality.

So, although we can’t see dinosaurs directly with our senses, we can work out that they must have existed, using indirect evidence that still ultimately reaches us through our senses: we see and touch the stony traces of ancient life.

We should always be open-minded, but the only good reason to believe that something exists is if there is real evidence that it does.

Back in the nineteenth century, an Austrian monk called Gregor Mendel did experiments in his monastery garden, breeding peas in large quantities. He counted the numbers of plants that had flowers of various colours, or that had peas that were wrinkly or smooth, as the generations went by. Mendel never saw or touched a gene. All he saw were peas and flowers, and he could use his eyes to count different types. He invented a model, which involved what we would now call genes (though Mendel didn’t call them that), and he calculated that, if his model were correct, in a particular breeding experiment there ought to be three times as many smooth peas as wrinkly ones. And that is what he found when he counted them. Leaving aside the details, the point is that Mendel’s ‘genes’ were an invention of his imagination: he couldn’t see them with his eyes, not even with a microscope. But he could see smooth and wrinkled peas, and by counting them he found indirect evidence that his model of heredity was a good representation of something in the real world.

We come to know what is real, then, in one of three ways. We can detect it directly, using our five senses; or indirectly, using our senses aided by special instruments such as telescopes and microscopes; or even more indirectly, by creating models of what might be real and then testing those models to see whether they successfully predict things that we can see (or hear, etc.), with or without the aid of instruments. Ultimately, it always comes back to our senses, one way or another.

Indeed, to claim a supernatural explanation of something is not to explain it at all and, even worse, to rule out any possibility of its ever being explained. Why

To say that something happened supernaturally is not just to say ‘We don’t understand it’ but to say ‘We will never understand it, so don’t even try.’

What would you think of a detective who, baffled by a murder, was too lazy even to try to work at the problem and instead wrote the mystery off as ‘supernatural’?

The near end of the bookshelf has the picture of you. The far end has a picture of your 185-million-greats-grandfather. What did he look like? An old man with wispy hair and white sidewhiskers? A caveman in a leopard skin? Forget any such thought. We don’t know exactly what he looked like, but fossils give us a pretty good idea. Believe it or not, your 185-million-greats-grandfather was – a fish. So was your 185-million-greats-grandmother, which is just as well or they couldn’t have mated with each other and you wouldn’t be here.

Fossils can even be dated. We can tell how old they are, mostly by measuring radioactive isotopes in the rocks. We’ll learn what isotopes are, and atoms, in Chapter 4. Briefly, a radioactive isotope is a kind of atom which decays into a different kind of atom: for example, one called uranium-238 turns into one called lead-206. Because we know how long this takes to happen, we can think of the isotope as a radioactive clock.

Animals belong to different species if they don’t breed together.

An important difference between species and languages is that languages can pick up ‘loan words’ from other languages. Long after it developed as a separate language from Romance, Germanic and Celtic sources, for example, English picked up ‘shampoo’ from Hindi, ‘iceberg’ from Norwegian, ‘bungalow’ from Bengali and ‘anorak’ from Inuit.

The Galapagos islands are historically important because they probably inspired Charles Darwin’s first thoughts on evolution when, as a member of the expedition on HMS Beagle, he visited them in 1835.

Evolution means change in a gene pool. Change in a gene pool means that some genes become more numerous, others less. Genes that used to be common become rare, or disappear altogether. Genes that used to be rare become common. And the result is that the shape, or size, or colour, or behaviour of typical members of the species changes: it evolves, because of changes in the numbers of genes in the gene pool. That is what evolution is.

Natural selection nudges evolution in a purposeful direction: namely, the direction of survival. The genes that survive in a gene pool are the genes that are good at surviving. And what makes a gene good at surviving? It helps other genes to build bodies that are good at surviving and reproducing: bodies that survive long enough to pass on the genes that helped them to survive.

scientists in the lab, but only in tiny quantities. Pure substances that consist of one kind of atom only are called elements (same word as was once used for earth, air, fire and water, but with a very different meaning). Examples of elements are hydrogen, oxygen, iron, chlorine, copper, sodium, gold, carbon, mercury and nitrogen. Some elements, such as molybdenum, are rare on Earth (which is why you may not have heard of molybdenum) but commoner elsewhere in the universe

Metals such as iron, lead, copper, zinc, tin and mercury are elements. So are gases such as oxygen, hydrogen, nitrogen and neon. But most of the substances that we see around us are not elements but compounds. A compound is what you get when two or more different atoms join together in a particular way.

A group of atoms joined together to make a compound is called a molecule. Some molecules are very simple: a molecule of water, for example, has just those three atoms. Other molecules, especially those in living bodies, have hundreds of atoms, all joined together in a very particular way. Indeed, it is the way they are joined together, as well as the type and number of atoms, that makes any particular molecule one compound and not another. You can also use the word ‘molecule’ to describe what you get when two or more of the same kind of atom join together. A molecule of oxygen, the gas we need in order to breathe, consists of two oxygen atoms joined together. Sometimes three oxygen atoms join together to form a different kind of molecule called ozone. The number of atoms in a molecule really makes a difference, even if the atoms are all the same.

‘iron – cold iron’ (Google it. It’s from the poet Rudyard Kipling),

As I explained in Chapter 1, when scientists can’t see something directly, they propose a ‘model’ of what it might be like, and then they test that model. A scientific model is a way of thinking about how things might be. So a model of the atom is a kind of mental picture of what the inside of an atom might be like. A scientific model can seem like a flight of fancy, but it is not just a flight of fancy. Scientists don’t stop at proposing a model: they then go on to test it. They say, ‘If this model that I am imagining were true, we would expect to see such-and-such in the real world.’ They predict what you’ll find if you do a particular experiment and make certain measurements. A successful model is one whose predictions come out right, especially if they survive the test of experiment. And if the predictions come out right, we hope it means that the model probably represents the truth, or at least a part of the truth.

We define solid matter as ‘what you can’t walk through’. You can’t walk through a wall because of these mysterious forces that link the nuclei to their neighbours in a fixed position. That’s what solid means.