The Science of Discworld (Science of Discworld, #1)

by Terry Pratchett

The better the monkeys got at answering those questions, the more baffling the universe became; knowledge increases ignorance. The message they got was: Up There is very different from Down Here.

They didn’t know that Up There – the rest of the universe – isn’t like that. Most of it is empty space, a vacuum. You can’t breathe vacuum. Most of what isn’t vacuum is huge balls of overheated plasma. You can’t stand on a ball of flame. And most of what isn’t vacuum and isn’t burning is lifeless rock. You can’t eat rock.*1 They were going to learn this later on.

All this gave rise to a general feeling that Up There was different from Down Here for a reason. Down Here was clearly designed for us. Equally clearly, Up There wasn’t.

Life is like a space elevator. What life self-sustains is not energy, but organization. Once you have a system that is so highly organized that it can reliably make copies of itself, that degree of organization is no longer ‘expensive’. The initial investment may have been huge, as for a space elevator, but once the investment has been made, everything else is free.

This is one reason why science often seems inhuman, because it looks at how the universe drives us, rather than the other way round.

POTENTIALITY IS THE KEY. Our immediate task is to start from a lot of vacuum and a few rules, and convince you that they have enormous potentiality. Given enough time, they can lead to people, turtles, weather, the Internet – hold it. Where did all that vacuum come from? Either the universe has been around forever, or once there wasn’t a universe and then there was. The second statement fits neatly with the human predilection for creation myths. It also appeals to today’s scientists – possibly for the same reason. Lies-to-children run deep.

Let us leave becomings for a moment, and think about beginnings. Thanks to our evolutionary prejudices, we tend to think of the beginning of the universe as being some special time, before which the universe did not exist and after which it did. Moreover, when the universe changed from not being there to being there, something must have caused that change – something that was around before the universe began, otherwise it wouldn’t have been able to cause the universe to come into being. When you bear in mind that the beginning of the universe is also the beginning of space and the beginning of time, however, this point of view is distinctly problematic. How can there be a ‘before’ if time has not yet started? How can there be a cause for the universe starting up, without space for that cause to happen in – and time for it to happen?

Maybe there was something else in existence already … but now we have to decide how that got started, and the same difficulties arise. All right, let’s go the whole hog: something – perhaps the universe itself, perhaps some precursor – was around forever. It didn’t have a beginning, it just was, always.

Everything that there is, today, right out into the furthest depths of space, stems from that astonishing ‘beginning’. Colloquially, the event is known as the Big Bang. The name reflects several features of the event – for example, that tiny speck of space/time was enormously hot, and grew in size exceedingly rapidly. It was like a huge explosion – but there was no stick of cosmic dynamite, sitting there in no-space with its non-material fuse burning away as some kind of pre-time pseudo-clock counted down the seconds to detonation. What exploded was – nothing. Space, time, and matter are the products of that explosion: they played no part in its cause. Indeed, in a very real sense, it had no cause.

The ‘draw a line’ philosophy offers a substantial political advantage to people with hidden agendas. The method for getting what you want is first to draw the line somewhere that nobody would object to, and then gradually move it to where you really want it, arguing continuity all the way. For

Two recent books by top-ranking scientists explore how rules could be ‘invented’. The most recent is Stuart Kauffman’s 2000 Investigations.

The other noteworthy book on this topic is Lee Smolin’s 1997 The Life of the Cosmos, which asks: can universes evolve?

Science is not about building a body of known ‘facts’. It is a method for asking awkward questions and subjecting them to a reality-check, thus avoiding the human tendency to believe whatever makes us feel good.

The conclusion was that the universe is a lot weirder than common sense tells us, although they probably didn’t use that actual word. Objects shrink as they approach the speed of light, time slows down to a crawl, mass becomes infinite … and nothing can go faster than light. Another key idea was that space and time are to some extent interchangeable. The traditional three dimensions of space plus a separate one for time are merged into a single unified spacetime with four dimensions. A point in space becomes an event in spacetime.

In ordinary space, there is a concept of distance. In Special Relativity, there is an analogous quantity, called the interval between events, which is related to the apparent rate of flow of time. The faster an object moves, the slower time flows for an observer sitting on that object. This effect is called time dilation. If you could travel at the speed of light, time would be frozen.

Science certainly does not claim to get things right, but it has a good record of ruling out ways to get things wrong.

As for the solar system being an act of special creation by a supernatural being – why would any self-respecting supernatural being make the thing so complicated?

Because it makes itself complicated – that’s why. We now think that the solar system was formed as a complete package, starting from quite complicated ingredients. But it us took a while to realize this.

Before the disc formed, the solar system and the Sun started out as a random portion of a cloud of interstellar gas and dust. Random jigglings triggered a collapse of the dustcloud, with everything heading for roughly – but not exactly – the same central point. All it takes to start such a collapse is a concentration of matter somewhere, whose gravity then pulls more matter towards it: random jigglings will produce such a concentration if you wait long enough. Once the process has started, it is surprisingly rapid, taking about ten million years from start to finish.

The Earth is the densest planet in the solar system, with an average density 5.5 times that of water.

According to Alfred Wegener, the German who first publicized the idea, all of today’s separate continents were originally part of a single supercontinent, which he named Pangea (‘All-Earth’). Pangea existed about 300 million years ago.

A forest is full of plants, and plants produce oxygen. No, they don’t. The net oxygen production of a rainforest is, on average, zero. Trees produce carbon dioxide at night, when they are not photosynthesizing. They lock up oxygen and carbon into sugars, yes – but when they die, they rot, and release carbon dioxide. Forests can indirectly remove carbon dioxide by removing carbon and locking it up as coal or peat, and by releasing oxygen into the atmosphere. Ironically, that’s where a lot of the human production of carbon dioxide comes from – we dig it up and burn it again, using up the same amount of oxygen.

if you burn a rainforest you add a one-off surplus of carbon dioxide to the atmosphere, but you do not also reduce the Earth’s capacity to generate new oxygen.

Triploblasts played a crucial role in evolution, precisely because they did have internal organs, and in particular they could ingest food and excrete it. Their excreta became a major resource for other creatures;

But where did all those triploblasts come from? Were they an offshoot of the Ediacarans? Or did they come from something else that didn’t leave fossils? It’s hard to see how they could have come from Ediacarans. Yes, an extra layer of tissue might have appeared, but as well as that extra layer you need a lot of organization to exploit it. That organization has to come from somewhere.

It used to be thought that life was a delicate, highly unusual phenomenon: difficult to create, easy to destroy. But everywhere we look on Earth we find living creatures, often in environments that we would have expected to be impossibly hostile. It’s beginning to look as if life is an extremely robust phenomenon, liable to turn up almost anywhere that’s remotely suitable. What is it about life that makes it so persistent?

Life seems to contradict the usual rules of chemistry and physics, especially the rule known as the second law of thermodynamics, which says that things can’t spontaneously get more complicated. Life does this because, like the space elevator, it has lifted itself to a new level of operation, where it can gain access to things and processes that were previously out of the question.

When you bred dogs, what you got was a different kind of dog – not a banana or a fish. And breeding animals was the purest kind of magic: if a human being wanted a long thin dog, and if they started from short fat ones, and if they knew how the trick worked (if, so to speak, they cast the right ‘spells’) then they would get a long thin dog. Bananas, long and thin though they might be, were not a good starting point.

This was the mechanism of natural selection. Herbert Spencer, who did the important journalistic job of interpreting Darwin’s theory to the masses, coined the phrase, ‘survival of the fittest’ to describe it. The phrase had the advantage of convincing everybody that they understood what Darwin was saying, and it had the disadvantage of convincing everybody that they understood what Darwin was saying. It was a classic lie-to-children, and it deceives many critics of evolution to this day, causing them to aim at a long-disowned target, besides giving a spurious ‘scientific’ background to some extremely stupid and unpleasant political theories.

HSP90 ‘insists’ that proteins fold into the orthodox shape, even if there are a few mutations in the DNA that codes for those proteins. When the organism is ‘stressed’, diverting HSP90 to other functions, these cryptic mutations suddenly get expressed – the proteins acquire the unorthodox shape that goes along with their mutated DNA codes. In effect, this says that you can trigger a genetic change by non-genetic means.

Dang

More importantly, genes may well be like this. Biologists habitually talk of ‘the function of a gene’ – what it does. The unspoken assumption is that it does only one thing, or a small list of things. This is pure magic: the gene as a spell. It is conceived as being a spell in the same sense that ‘Cold Start’ in a car is. But a lot of genes may not do anything that can be summed up in a simple story.

But most scientists think that climate change results from variations in five different factors: the sun’s output of radiant heat, the Earth’s orbit, the composition of the atmosphere, the amount of dust produced by volcanoes, and levels of land and oceans resulting from movement of the Earth’s crust. We can’t yet put together a really coherent picture in which the measurements match the theory as closely as we’d like, but one thing that is becoming clear is that the Earth’s climate has more than one ‘equilibrium’ state. It stays in or near one such state for a while, then switches comparatively rapidly to another, and so on.

According to the ‘Snowball Earth’ theory, proposed by Paul Hoffman and Daniel Schräg in 1998, ice covered the entire Earth at this time. However, if ice really covered the whole Earth, it should have done more damage than the fossil record indicates. And that’s not the only problem. One key piece of evidence for the Big Freeze is a layer of sedimentary rock that formed just after the glaciers melted and left huge quantities of debris. This layer contains less carbon-13, in proportion to ordinary carbon-12, than normal. Marine photosynthesis converts carbon-12 into carbon dioxide more readily than it does carbon-13, so an excess of carbon-13 is left behind in seawater and in the layers of sediment in it that later turn to rock. So a low ratio of carbon-13 to carbon-12 indicates low biological activity.

Life is a rarity; Earth may be the only place in the entire universe where that fragile miracle happened.

Aren't miracles considered contradictory to science?

An important implication of evolution is that life automatically adapts itself to whichever environment happens to be available.

So then why don't we find life on more planets?

Simple forms of life can put up with a lot, and did. And they changed the planet, or at least its outer skin, by putting in feedback loops that made it less liable to change. They started Gaia. This is the name that James Lovelock gave in 1982 to the concept of the Earth as a complex living system – metaphorically, an organism in its own right. The idea has been romanticised into the Earth being a kind of Earth-mother, but what do you expect when you attach the name of a goddess to your new scientific concept?

If things were changing into other things, and no one had seen that happen yet, why were the original things still the original things? If the land was so great, why were any fish left in the sea?

It’s quite difficult to get the span of geological time to make sense. In his book In Search of Deep Time, Henry Gee does an excellent job of reminding us just how flimsy the ‘fossil record’ is. A few bones here; a few others five thousand miles away and ten million years later; from these we attempt to tell a story of evolutionary ancestry. It’s like claiming to have reconstructed human history from one flint flake and a half-eaten hamburger. Well, not as coherent as that, actually.

There are few surviving human artefacts more than ten thousand years old,

Dinosaurs are the ultimate icon for an evolutionary fact which we generally ignore, and definitely find uncomfortable to think about: nearly all species that have ever existed are extinct. As soon as we realize that, we are forced to look at conservation of animal species in new ways.

To live in harmony with nature, we must know how to sing the same song as nature. To do that, we must understand nature. Good intentions aren’t enough. Science might be – if we use it wisely. *1

The evolutionary history of the placental mammals is controversial and has not been mapped out in detail.

The most striking feature of humans is the size of our brains: bigger, in comparison to body weight, than any other animal. Strikingly bigger. A detailed story of what makes us human must be extraordinarily complicated, but it’s clear that big, powerful brains were the main invention that made it all possible. So we now have two obvious questions to think about: ‘Why did we evolve big brains?’ and ‘How did we evolve big brains?’

On the Internet, the full diversity of views is, or at least can be represented. It is quite democratic; the views of the stupid and credulous carry as much weight as the views of those who can read without moving their lips. If you think that the Holocaust didn’t actually happen, and you can shout loud enough, and you can design a good web page, then you can be in there slugging it out with other people who believe that recorded history should have some kind of connection with reality.

Alexei Leonov published a painting of a space elevator in action in 1967.