Sometimes we can literally count the number of ways you can reshuffle a series of bits - as with a pack of cards, for instance, where the 'bits' are the individual cards.

Suppose the dealer shuffles the pack and deals them out to four players, so that they each have 13 cards. I pick up my hand and gasp in astonishment. I have a complete hand of 13 spades! All the spades.

I am too startled to go on with the game, and I show my hand to the other three players, mowing they will be as amazed as I am.

i of the other players lays his cards on the table, and the gasps of astonishment grow with each hand. Every one of them has a Z perfect' hand: one has 13 hearts, another has 13 diamonds, and the last one has 13 clubs.

Would this be supernatural magic? We might be tempted to think so. Mathematicians can calculate the chance of such a remarkable deal happening purely by chance. It turns out to be almost impossibly small: 1 in 536,447,737,765,488,792,839,237,440,000. I'm not sure I would even know how to say that number! If you sat down and played cards for a trillion years, you might on one occasion get a perfect deal like that. But - and here's the thing - this deal is no more unlikely than every other deal of cards that has ever happened! The chance of any particular deal of 52 cards is 1 in 536,447,737,765,488,792,839,237,440,000 because that is the total number of all possible deals. It is just that we don't notice any particular pattern in the vast majority of deals that are made, so they don't strike us as anything out of the ordinary. We only notice the deals that happen to stand out in some way.

Find a picture of yourself. Now take a picture of your father and place it on top. Then find a picture of his father, your grandfather. Then place on top of that a picture of your grandfather's father, your great-grandfather. You may not have ever met any of your great-grandfathers. I never met any of mine, but I know that one was a country schoolmaster, one a country doctor, one a forester in British India, and one a lawyer, greedy for cream, who died rock-climbing in old age. Still, even if you don't know what your father's father's father looked like, you can imagine him as a sort of shadowy figure, perhaps a fading brown photograph in a leather frame. Now do the same thing with his father, your great-great-grandfather. And just carry on piling the pictures on top of each other, going back through more and more and more great-great-greats. You can go on doing this even before photography was invented: this is a thought experiment, after all.

How many greats do we need for our thought experiment? Oh, a mere 185 million or so will do nicely!

[...]

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... 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.

Let's now walk along our three-mile bookshelf, pulling pictures off it one by one to have a look at them. Every picture shows a creature belonging to the same species as the picture on either side of it. Every one looks just like its neighbours in the line - or at least as much alike as any man looks like his father and his son. Yet if you walk steadily from one end of the bookshelf to the other, you'll see a human at one end and a fish at the other. And lots of other interesting great-... great-grandparents in between, which, as we shall soon see, include some animals that look like apes, others that look like monkeys. others that look like shrews, and S(SO on. Each one is like its neighbours in the line, yet if you pick any two pictures far apart in the line they are from humans back far enough you^u come to a a fish. Flow can this be?

Actually, it isn't all that difficult to understand. We are quite used to gradual changes that, step by tiny step, one after the other, make up a big change. You were once a baby. Now you are not. When you are a lot older you'll look quite different again. Yet every day of your life, when you wake up, you are the same person as when you went to bed the previous night. A baby changes into a toddler, then into a child, then into an adolescent; then a young adult, then a middle-aged adult, then an old person. And the change happens so gradually that there never is a day when you can say, 'This person has suddenly stopped being a baby and become a toddler.' And later on there never comes a day when you can say, 'This person has stopped being a child and become an adolescent.' There's never a day when you can say, 'Yesterday this man was middle-aged: today he is old.'

[...]

You are Homo sapiens and your 50,000-greats-grandfather was Homo erectus. But there never was a Homo erectus who suddenly gave birth to a Homo sapiens baby.

So, the question of who was the first person, and when they lived, doesn't have a precise answer. It's kind of fuzzy, like the answer to the question: When did you stop being a baby and become a toddler? At some point, probably less than a million years ago but more than a hundred thousand years ago, our ancestors were sufficiently different from us that a modern person wouldn't have been able to breed with them if they had met.

Whether we should call Homo erectus a person, a human, is a different question. That's a question about how you choose to use words - what'* called a semantic question. Some people might want to call a zebra a stripy horse, but others might like to keep the word 'horse' for the species that we ride. That's another semantic question. You might prefer to keep the words 'person, 'man and 'woman for Homo sapiens. That's up to you. Nobody, however, would want to call your fishy 185-million-greats-grandfather a man. That would just be silly, even though there is a continuous chain linking him to you, every link in the chain being a member of exactly the same species as its neighbours in the chain.

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. Radioactive clocks are rather like the water clocks and candle clocks that people used in the days before pendulum clocks were invented. A tank of water with a hole in the bottom will drain at a measurable rate. If the tank was filled at dawn, you can tell how much of the day has passed by measuring the present level of water. Same with a candle clock. The candle burns at a fixed rate, so you can tell how long it has been burning by measuring how much candle is left. In the case of a uranium-238 clock, we know that it takes 4.5 billion years for half the uranium-238 to decay to lead-206. This is called the 'half-life' of uranium-238. So, by measuring how much lead-206 there is in a rock, compared with the amount of uranium-238, you can calculate how long it is since there was no lead-206 and only uranium-238: how long, in other words, since the clock was 'zeroed'.

And when is the clock zeroed? Well, it only happens with igneous rocks, whose clocks are all zeroed at the moment when the molten rock hardens to become solid. It doesn't work with sedimentary rock, which has no such 'zero moment', and this is a pity because fossils are found only in sedimentary rocks. So we have to find igneous rocks close by sedimentary layers and use them as our clocks. For example. if a fossil is in a sediment with 120-million-year-old igneous rock above it and 130-million-year-old igneous rock below it, you know the fossil dates from somewhere between 120 million and 130 million years ago. That's how all the dates I mention in this chapter are arrived at. They are all approximate dates, not to be taken as too precise.

Uranium-238 is not the only radioactive isotope we can use as a clock. There are plenty of others, with a wonderfully wide spread of half-lives. For example, carbon-14 has a half-life of only 5,730 years, which makes it useful for archaeologists looking at human history. It is a beautiful fact that many of the different radioactive clocks have overlapping timescales, so we can use them to check up on each other. And they always agree.

The carbon-14 clock works in a different way from the others. It doesn't involve igneous rocks but uses the remains of living bodies themselves, for example old wood. It is one of the fastest of our radioactive clocks, but 5,730 years is still much longer than a human lifetime. so you might ask how we know it is the half-life of carbon-14, let alone how we know that 4.5 billon years is the half-life of uranium-238! The f answer is easy. We don't have to wait for half of the atoms to decay. We can measure the rate of decay of only a tiny fraction of the atoms, and work out the half-life (quarter-life, hundredth-life, etc.) from that.

Just as some species are more similar than others and are placed in the same family, so there are also families of languages. Spanish, Italian, Portuguese, French and many European languages and dialects such as Romansch, Galician, Occitan and Catalan are all pretty similar to each other; together they're called 'Romance' languages. The name actually comes from their common origin in Latin, the language of Rome, not from any association with romance, but let's use an expression of love as nr example. Depending on which country you are in, you might declare your feelings in one of the following ways: 'Ti amo', 'Amote', 'T'aimi' or 'Je t'aime'. In Latin it would be 'Te amo' - exactly like modern Spanish.

To swear your love to someone in Kenya, Tanzania or Uganda you could say, in Swahili, 'Nakupenda.' A bit further south, in Mozambique, Zambia, or Malawi where I was brought up, you might say, in the Chinyanja language. Ndimakukonda. In other so-called Bantu languages in southern Africa you might say 'Ndinokuda, 'Ndiyakuthanda or, to a Zulu, 'Ngiyakuthanda. This Bantu family of languages is quite distinct from the Romance family of languages, and both are distinct from the-Germanic family which includes Dutch, German and the Scandinavian languages. See how we use the wore 'family' for languages, just as we do for species (the cat family, the dog family) and also, of course, for our own families (the Jones family. the Robinson family, the Dawkins family).

It isn't hard to work out how families of related languages arise over the centuries. Listen to the way you and your friends speak to each other, and compare it to the way your grandparents speak. Their speech is only slightly different and you can easily understand them, but they are only two generations away. Now imagine talking, not to your grandparents but to your 25-greats-grandparents. If you happen to be English, that might take you back to the late fourteenth century - the lifetime of the poet Geoffrey Chaucer, who wrote descriptions like this:

He was a lord ful fat and in good poynt,
Hise eyen stepe, and rollynge in his heed,
That stemed as a forneys of a leed;
His bootes souple, his hors in greet estaat.
Now certeinly he was a fair prelaat;
He was nat pale as a forpyned goost.
A fat swan loved he best of any roost.
His palfrey was as broun as is a berye,

The number of neutrons in an atom's nucleus is less fixed than the number of protons: many elements have different versions, called isotopes, with different numbers of neutrons. For example, there are three isotopes of carbon, called Carbon-12, Carbon-13 and Carbon-14. The numbers refer to the mass of the atom, which is the sum of the protons and neutrons. Each of the three has six protons. Carbon-12 has six neutrons. Carbon-13 has seven neutrons and Carbon-14 has eight neutrons. Some isotopes, for example Carbon-14, are radioactive, which means they change into other elements at a predictable rate, although at unpredictable moments. Scientists can use this feature to help them calculate the age of fossils. Carbon-14 is used to date things younger than most fossils. for example ancient wooden ships.

The difference between night and day is dramatic - so dramatic that most species of animal can thrive either in the day or in the night but not both. They usually sleep during their 'off' period. Humans and most birds sleep by night and work at the business of living during the day. Hedgehogs and jaguars and many other mammals work by night and sleep by day.

In the same way, animals have different ways f coping with the change between winter anc summer. Lots of mammals grow a thick, shaggy coat for the winter, then shed it in spring. Many birds, and mammals too, migrate, sometimes huge distances, to spend the winter closer to the equator, then migrate back to the high latitudes (the far north or far south) for the summer, where the long days and short nights provide bumper feeding. A seabird called the Arctic tern carries this to an extreme. Arctic terns spend the northern summer in the Arctic. Then, in the northern autumn, they migrate south - but they don't stop in the tropics, they go all the way to the Antarctic. Books sometimes describe the Antarctic as the 'wintering grounds' of the Arctic tern, but of course that's nonsense: by the time they get to the Antarctic it is the southern summer. The Arctic tern migrates so far that it gets two summers: it has no 'wintering grounds' because it has no winter. I'm reminded of the joking remark of a friend of mine who lived in England during the summer, and went to tropical Africa to 'tough out the winter'!

If you want to see a rainbow you ' have to have the sun behind you when you look at a rainstorm. Each raindrop is more like a little ball than a prism, and light behaves differently when it Sits a ball from how it behaves when it hits a prism. The difference is that the far side of I raindrop acts as a tiny mirror. And that is /hy you need the sun behind you if you want 0 see a rainbow. The light from the sun turns somersault inside every raindrop and is reflected backwards and downwards, where it hits your eyes.

Here's how it works. You are standing with the sun behind and above you, looking at a distant shower of rain, The sunlight hits a single raindrop (of course it hits lots of other raindrops too, but wait, we're coming to that). Let's call our one particular raindrop A. The beam of white light hits A on its upper near surface, Adhere it is bent, just as it was on the near surface of Newton's prism. And of course the red light bends less than the blue, so he spectrum is already sorting itself out. Now all the coloured jams travel through the raindrop until they hit the far side. stead of passing through into the air, they are reflected back towards the near side of the raindrop, this time the lower part i the near side. And as they pass through the near side of the raindrop, they are again bent. Again the red light bends less than the blue.

So, as the sunbeam leaves the raindrop, it has been splayed out into a proper little spectrum. The separated coloured beams, having doubled back around the inside of the raindrop, re now hurtling back in the general direction of where you are standing. If your eye happens to be in the path of one of those beams, say the green one, you'll see pure green light. somebody shorter than you might see the red beam coming from A. And somebody taller than you might see the blue beam from A.

Nobody sees the full spectrum from any one raindrop. Each of you sees only one pure colour. Yet all of you say you see a rainbow, with all the colours. How come? Well, so far, we have only been talking about one raindrop, called A. There are millions of other raindrops, and they are all behaving in the same way. While you are looking at A's red beam, there is another raindrop called B, which is lower than A. You don't see B's red beam because it hits you in the stomach. But B's blue beam is in exactly the right place to hit you in the eye. And there are other raindrops lower than A but higher than B, whose red and blue beams miss your eye but whose yellow or green beams hit your eye. So lots of raindrops together add up to a complete spectrum, in a line, up and down.

But a line up and down is not a rainbow. Where does the rest of the rainbow come from? Don't forget that there are other raindrops, stretching from one side of the rain shower to the other and at all heights. And of course they fill in the rest of the rainbow for you. Every rainbow you see, by the way, is trying to be a complete circle, with your eye at the centre of it - like the complete circular rainbow you sometimes see when you water the garden with a hose and the sun shines through the spray The only reason we don't usually see the whole circle is that the ground gets in the way.

Newton wasn't the first person to make a rainbow with a prism. Other people had already got the same result. But many of them thought the prism somehow 'coloured' the white light, like adding a dye. Newton's idea was quite different. He thought that white light was a mixture of all the colours, and the prism was just separating them from each other. He was right, and he proved it with a pair of neat experiments. First, he took his prism, as before, and stuck a narrow slit in the way of the coloured beams coming out of it, so that only one of them, say the red beam, passed through the slit. Then he put another prism in the path of this narrow beam of red light. The second prism bent the light, as usual. But what came out of it was only red light. No extra colours were added, as they would have been if what prisms did was add colour like a dye. The result Newton got was exactly what he expected, supporting his theory that white light is a mixture of light of all colours.

The second experiment was more ingenious still, using three prisms. It was called Newton's Experimentum Crucis, which is Latin for 'critical experiment' - or, as we might say, 'experiment that really clinches the argument'.

On the left of the picture above you see white light coming through a slit in Newton's curtain and passing through the first prism which spreads it out into all the colours of the rainbow. The spread-out rainbow colours then pass through a lens, which brings them all together before they pass through the second of Newton's prisms. This second prism had the effect of merging the rainbow colours back into white light again. That already neatly proved Newton's point. But just to make quite sure, he then passed the beam of white light through a third prism, which splayed the colours out into a rainbow again! As neat a demonstration as you could wish for. proving that white light is indeed a mixture of all the colours.

The Epic of Gilgamesh is one of the oldest stories ever written. Older than the legends of the Greeks or the Jews, it is the ancient heroic myth of the Sumerian civilization, which flourished in Mesopotamia (now Iraq) between 5,000 and 6,000 years ago. Gilgamesh was the great hero king of Sumerian myth - a bit like King Arthur in British legends, in that nobody knows whether he actually existed, but lots of stories were told about him. Like the Greek hero Odysseus (Ulysses) and the Arabian hero Sinbad the Sailor, Gilgamesh went on epic travels, and he met many strange things and people on his journeys. One of them was an old man (a very, very old man, centuries old) called Utnapashtim, who told Gilgamesh a strange story about himself Well, it seemed Strange to Gilgamesh, but it may not seem so strange to you because you have probably heard a similar story... about another old man with a different name.

Utnapashtim told Gilgamesh of an occasion, many centuries earlier, when the gods were angry with humankind because we made so much noise they couldn't sleep.

The chief god, Enlil, suggested that they should send a great flood to destroy everybody, so the gods could get a good night's rest. But the water god, Ea, decided to warn Utnapashtim. Ea told Utnapashtim to tear down his house and build a boat.

It would have to be a very big boat, because Utnapashtim was to take into it 'the seed of all living creatures.'

Utnapashtim built the boat just in time, before it rained for six days and six nights without stopping. The flood that followed drowned everybody and everything that was not safely inside the boat. On the seventh day the wind dropped and the waters grew calm and flat.

Utnapashtim opened a hatch in the tightly sealed 3at and released a dove. The dove flew away, looking for land. but failed to find any and returned. Then Utnapashtim released a swallow, but the same thing happened.

Finally Utnapashtim released a raven. The raven didn't come back which suggested to Utnapashtim that then was dry land somewhere and the raven had found it.

Eventually the boat came to rest on a mountaintop poking out of the water. Another god, Ishtar, created the first rainbow, as a token of the gods' promise to send no more terrible floods. So that is how the rainbow came into being, according to the ancient legend of the Sumerians.

It is possible to measure how far away from us each galaxy is. How? How, for that matter, do we know how far away anything in the universe is? For nearby stars the best method uses something called 'parallax'. Hold your finger up in front of your face and look at it with your left eye closed. Now open your left eye and close your right. Keep switching eyes, and you'll notice that the apparent position of your finger hops from side to side. That is because of the difference between the viewpoints of your two eyes. Move your finger nearer, and the hops will become greater. Move your finger further away and the hops become smaller. All you need to know is how far apart your eyes are, and you can calculate the distance from eyes to finger by the size of the hops. That is the parallax method of estimating distances.

Now, instead of looking at your finger, look at a star out in the night sky, switching from eye to eye. The star won't hop at all. It is much too far away. In order to make a star 'hop' from side to side, your eyes would need to be millions of miles apart! How can we achieve the same effect as switching eyes millions of miles apart? We can make use of the fact that the Earth's orbit around the sun has a diameter of 186 million miles. We measure the position of a nearby star, against a background of other stars. Then, six months later, when the Earth is 186 million miles away at the opposite side of its orbit, we measure the apparent position of the star again. If the star is quite close, its apparent position win have 'hopped'. From the b length of the hop, it is easy to calculate how far away the star is.

Our search for life elsewhere is not haphazard or random: our knowledge of physics and chemistry and biology equips us to seek out meaningful information about stars and planets vast distances away and to identify planets that are at least possible candidates as hosts for life. There is much that remains deeply mysterious, and it is not likely that we will ever uncover all the secrets of a universe as vast as ours: but, armed with science, we can at least ask sensible, meaningful questions about it and recognize credible answers when we find them. We don't have to invent wildly implausible stories: we have the joy and excitement of real scientific investigation and discovery to keep our imaginations in line. And in the end that is more exciting than fantasy.

It's easy to see that predators (animals that kill and then eat other animals) are working for the downfall of their prey. But it's also true that prey are working for the downfall of their .fedators. They work hard to escape bei and it they all succeeded the predators would starve to death. The same thing holds between parasites and their hosts. It also holds between members of the same species, all of whom are actually or potentially competing with on another. If the living is easy, natural selection will favour the evolution of improvements in enemies, whether predators, prey, parasites, hosts or competitors: improvements that wilvill make life hard again. Earthquakes and tornadoes art unpleasant and might even be called enemies. but they are not out to get you' in the same 'Sod's Law' kind of way that predators and parasites are.

liis has consequences for the sort t of mental attitude that any wild animal, such as an antelope, might be expected to have. If you are an antelope and you see the long grass ri tling, it could be just the wind. Ihat's nothing to worry about, for the wind is not out to get you: it is completely indifferent to antelopes and their well-being. But that rustle in the long grass could be a stalking leopard, and a leopard is most definitely out to get you: you taste good to a leopard and natural selection favoured ancestral leopards that were good at catching antelopes. So antelopes and rabbits and minnows, and most other animals, have to be constantly on the alert. The world is full of dangerous predators and it is safest to assume that sometl a bit like Sod's Law is true. Let's put that in in the nguage of Charles Darwin, the languagige e of natural selection: those individual animals tha act as though Sod's Law were true are more likely to survive and reproduce than those individual animals that follow Pollyanna's Law.

Our ancestors spent much of their time in mortal danger from lions and crocodiles, pythons and sabretooths. So it probably made sense for each person to take a suspicious - some might even say paranoid - view of the world, > to see a likely threat in every rustle of the grass. every snap of a twig, and to assume that something was out to get him, a deliberate agent scheming to kill him. 'Scheming' is the wrong way to look at it if you think of it as deliberate plotting, but it is easy to put the idea into the language of natural selection: 'There are enemies out there, shaped by natural selection to behave as though they were scheming to kill me. The world is not neutral and indifferent to my welfare. The world is out to get me. Sod's Law may or may not be true, but behaving as if it is true is safer than behaving as Pollyanna's Law is true.'

The body has a very ingenious and usually effective system of natural defence against parasites, called the immune system. The immune system is so complicated that it would take a whole book to explain it. Briefly, when it senses a dangerous parasite the body is mobilized to produce special cells, which are carried by the blood into battle like a kind of army, tailor-made to attack the particular parasites concerned. Usually the immune system wins, and the person recovers. After that, the immune system 'remembers' the molecular equipment that it developed for that particular battle, and any subsequent infection by the same kind of parasite is beaten off so quickly that we don't notice it. That is why, once you have had a disease like measles or mumps or chickenpox, you're unlikely to get it again. People used to think it was a good idea if children caught mumps, say because the immune system's 'memory' would protect them against getting it as an adult - and mumps is even more unpleasant for adults (especially men, because it attacks the testicles) than it is for children. Vaccination is the ingenious technique of doing something similar on purpose. Instead of giving you the disease itself, the doctor gives you a weaker version of it, or possibly an injection of dead germs, to stimulate the immune system without actually giving you the disease. The weaker version is much less nasty than the real thing: indeed, you often don't notice any effect at all. But the immune system 'remembers' the dead germs, or the infection with the mild version of the disease, and so is forearmed to fight the real thing if it should ever come along.

The immune system has a difficult task 'deciding' what is 'foreign and therefore to be fought (a 'suspected' parasite), and what it should accept as part of the body itself. This can be particularly tricky, for example, when a woman is pregnant. The baby inside her is 'foreign' (babies are not genetically identical to their mothers because half their genes come from the father). But it is important for the immune system not to fight against the baby. This was one of the difficult problems that had to be solved when pregnancy evolved in the ancestors of mammals. It was solved -- after all, plenty of babies do manage to survive in the womb long enough to be born. But there are also plenty of miscarriages, which perhaps suggests that evolution had a hard time solving it and that the solution isn't quite complete. Even today, many babies survive only because doctors are on hand - for example, to change their blood completely as soon as they are born, in some extreme cases of immune-system overreaction.

Another way in which the immune system can get it wrong is to fight too hard against a supposed 'attacker'. That is what allergies are: the immune system needlessly, wastefully and even damagingly fighting harmless things. For example, pollen in the air is normally harmless, but the immune system of some people overreacts to it and that's when you get the allergic reaction called 'hay fever': you sneeze and your eyes water, and it is very unpleasant. Some people are allergic to cats, or to dogs: their immune systems are overreacting to harmless molecules in or on the hair of these animals. Allergies can sometimes be very dangerous. A few people are so allergic to peanuts that eating a single one can kill them.

[...]

It is not surprising that the immune system sometimes overreacts, because there's a fine line to be trodden between failing to attack when you should and attacking when you shouldn't. It's the same problem we met over the antelope trying to decide whether to run away from the rustle in the long grass. Is it a leopard? Or is it a harmless puff" of wind stirring the grass? Is this a dangerous bacterium, or is it a harmless pollen grain? I can't help wondering whether people with a hyperactive immune system, who pay the penalty of allergies or even auto-immune diseases, might be less likely to suffer from certain kinds of viruses and other parasites.

Such 'balance' problems are all too common. It is possible to be too 'risk averse' - too jumpy. treating every rustle in the grass as danger, or unleashing a massive immune response to a harmless peanut or to the body's own tissues. And it is possible to be too gung-ho, failing to respond to danger when it is very real, or failing to mount an immune response when there really is a dangerous parasite. Treading the line is difficult, and there are penalties for straying off it in either direction.

Sometimes we can actually pin down the explanation of a weird coincidence. A great American scientist called Richard Feynman tragically lost his wife to cancer, and the clock in her room stopped at precisely the moment she died. Goose-pimples! But Dr Feynman was not a great scientist for nothing. He worked out the true explanation. The clock was faulty. If you picked it up and tilted it, it tended to stop. When Mrs Feynman died, the nurse needed to record tl the time for the official death certificate. The sickroom was rather dark, so she picked up the clock and tilted it towards the window in order to read it. And that was the moment at which the clock stopped. Not a miracle at all, just a faulty mechanism.

Even if there had been no such explanation, even if the clock's spring really had wound down to a stop at exactly the moment when Mrs Feynman died, we shouldn't be all that impressed. No doubt at any minute of every day or night. quite a lot of clocks in America stop. And quite a lot of people die every day To repeat my earlier point, we don't bother to spread the 'news' that 'My clock stopped at exactly 4.50 p.m., and (would you believe it?) nobody died.'

There are things that not even the best scientists of today can explain. But that doesn't mean we should block off all investigation by resorting to phoney 'explanations' invoking magic or the supernatural, which don't actually explain at all. Just imagine how a medieval man - even the most educated man of his era - would have reacted if he had seen a jet plane, a laptop computer, a mobile telephone or a satnav device. He would probably have called them supernatural, miraculous. But these devices are now commonplace; and we know how they work, for people have built them:, following scientific principles. There never was a need to invoke magic or miracles or the supernatural, and we now see that the medieval man would have been wrong to do so.

[...]

The more you think about it, the more you realize that the very idea of a supernatural miracle is nonsense. If something happens that appears to be inexplicable by science, you can safely conclude one of two things. Either it didn't really happen (the observer was mistaken, or was lying, or was tricked); or we have exposed a shortcoming in present-day science. If present-day science encounters an observation, or an experimental result, that it cannot explain, then we should not rest until we have improved our science so that it can provide an explanation. If it requires a radically new kind of science, a revolutionary science so strange that old scientists scarcely recognize it as science at all, that's fine too. It's happened before. But don't ever be lazy enough defeatist enough - to say 'It must be supernatural' or 'It must be a miracle'. Say instead that it's a puzzle, it's strange, it's a challenge that we should rise to. Whether we rise to the challenge by questioning the truth of the observation, or by expanding our science in new and exciting directions, the proper and brave response to any such challenge is to tackle it head-on. And, until we have found a proper answer to the mystery it's perfectly OK simply to say. 'This is something we don't yet understand. but we're working on it.' Indeed, it is the only honest thing to do.