Chapter I 1 2 3 4 5 6

Borderlands of Science

Copyright 1999

by Charles Sheffield


1.1 What you are reading. This is a text for the writer or critical reader who like the science of stories to be right. We will define the limits of knowledge in many areas, then wander beyond them. We will spend little time surveying the scientific mainstream. Many other books do that, taking a detailed look at quantum theory, astronomy, spaceflight, genetics, chemistry, or any other science you care to mention. We will offer the brief summaries that we need, and list some of the better reference works. Then we'll head for the scientific outer limits.

We will not try to tell you how to write. Nothing here will address plot, character, pacing, or style; nowhere will you see anything about markets, or foreign rights, or literary agents. When backgrounds appear, it will be for their scientific content only.

Plenty of other works address the problems of being a writer, discussing everything from style to contract negotiation to royalty rates. There are also writing courses without number. These courses are valuable, especially when taught by successful writers, but not one of the courses - even when they are explicitly and specifically about science fiction - teaches anything about science. We, by contrast, will be concerned with only one thing: making the science in stories accurate, current, plausible (if the story is set in the future), and interesting. Readers of science fiction are an enthusiastic and forgiving audience. A writer of science fiction can perpetrate literary sins that are anathema in "mainstream" writing. But one thing you cannot get away with in my universe is botching the science of your story.

Or rather, you may get away with it some of the time. Your editors, who usually have a literary background but often lack a science background, may not catch you. Your readers will. Write about Shakespeare's "Paradise Lost," or say that Abraham Lincoln led America in the Revolutionary War, and the editor will jump all over you. Claim that Titan is a moon of Jupiter, and nothing may be said. I did not make up this example. It happened. Titan as a moon of Jupiter sailed right past the editor and past the copy-editor. A reader totally outside the book's production process (me) caught the blunder, and it was corrected in the published work. But you cannot rely on friendly readers being around all the time.

If you wander wildly beyond what scientists believe theoretically possible, you have to explain how and why. And you have to be reasonably current in your knowledge, because science changes constantly, and sometimes it changes fast. Three years ago, the idea of life anywhere in the universe, except on Earth, was pure speculation; today there is evidence, much disputed, for early life-forms on Mars.

As Josh Billings put it, "It's not what we don't know that causes the trouble, it's the things we know that ain't so."

Not all sciences are addressed in this book. When a field is omitted, one or more of the following will apply:

1) The topic doesn't seem to me to provide good material for science fiction stories.

2) Some other popular text covers the ground thoroughly and well.

3) I do not feel qualified to discuss the subject.

4) I do not believe that the subject, regardless of the fact that it may use the word "science" in its name, is real science.

A number of fringe areas, useful for stories whether or not you believe the theories, are described in Chapter 13.

1.2 Defining science fiction. When science fiction writers and readers get together, one of the things they are likely to talk about is the definition of science fiction. It's hard to reach agreement. I have my own definition, which, if it has no other virtue, describes the sort of science fiction that I like to read and write. It takes a few sentences and needs a brief preamble, but the definition goes as follows:

Science forms a great, sprawling continent, a body of learning and theories. Everything in science is interconnected, however loosely. If your theory doesn't connect with any part of the rest of science, you may be a genius with a new and profound understanding of the universe; but chances are you're wrong.

Science fiction consists of stories set on the shore or out in the shallow coastal water of that huge scientific land mass. Stay inland, safe above high tide, and your story will be not science fiction, but fiction about science. Stray too far, out of sight of land, and you are in danger of writing fantasy -- even if you think it's science fiction.

The purpose of this book is to define the boundaries of science. Where do the limits lie, today, that define the scientific leading edge? And can we see places where, although no land is visible, prevailing currents or the sight of breakers convince us that it must exist? That, surely, is where we will find fertile ground for science fiction. On the other hand, we don't want to find ourselves out of our depth.

1.3 The good, the bad, and the simply awful: an example.

That's probably more than enough metaphors. Let me illustrate my point with a particular case.

Suppose I decide to write a story that tells of a race of alien beings who come to Earth from a home world orbiting the star Rigel. Their ships are enormous and fast -- they are five miles long, and they can travel at 5,000 miles a second. When the aliens land on Earth and march out of their ships, it turns out that they are also huge; they are a hundred feet high and two hundred across, and they look, breed, and eat just like giant spiders.

Why are they here? To befriend humans, to educate us, to bring us into the Galactic federation of races, to enslave us, or to kill us?

One of their leaders explains to our representative. They are an ancient species, with a recorded history going back forty billion years. They were drawn to Earth by receipt of our radio signals, but humans, as primitive newcomers to the galaxy, are no more than food animals to them. They have come to overpower us, breed us, and eat us. At best, a few of us will be selected to help control the rest. As a reward, those humans who do cooperate will live a natural human life span.

Before our envoy can reply that the whole idea is intolerable, the Rigelian swallows him whole.

Humans seem doomed, until another brave earthling, a scientist, discovers that the aliens' eyes are different from ours. They see using short-wave ultra-violet light. We build a generator that can be used from miles away to beam an ultra-violet signal into the aliens' eyes. The repeating signal pattern interacts with the alien brain waves, sending them into convulsions and bringing them crashing to the ground. Humans approach and overpower them, learn the secret of the alien ship, and decide to go to Rigel and remove the alien menace from the galaxy forever.

An exceptionally dumb story? True. On the other hand, the smash-hit movie, INDEPENDENCE DAY, was packed with worse scientific impossibilities and is in many ways a lot less plausible. I have never read anything quite like the tale I've described, but I will bet that the long-suffering editors of science fiction magazines see plenty.

What we have here is not science fiction, it is fantasy. Let's see why; and let's find out if we can, with a little juggling, convert it to science fiction.

First, consider how the aliens got here. A ship that travels at 5,000 miles a second (8,000 kilometers a second) sounds fast, but Rigel is more than 500 light-years away from the Sun. Light travels at almost 300,000 kilometers a second. Our aliens must be awfully patient in waiting for their dinners, because the journey here took them at least 18,000 years. If we intend to visit their home world and seek vengeance, it will take that long to get there.

The first fix: The aliens must possess some kind of faster-than-light (FTL) drive. They only use their "slow" drive at 5,000 miles a second when they are close to Earth. It is not necessary to specify how the FTL drive works. Science fiction has certain conventions, required by and used in so many stories that no explanation is called for. The FTL drive is one of them. If you want to create your own using the ideas of Chapter 9, that's fine. But you don't need to. Just say the aliens have one.

Next problem: the aliens supposedly had their attention drawn to Earth because they picked up our radio signals. But radio waves travel at the same speed as light, and we have been generating signals for only a century. Rigel is at least five hundred lightyears away. The Rigelians ought not to know we even exist for another four hundred years or more.

The fix: In addition to the FTL drive, the aliens must possess a form of FTL communications system, able to pick up FTL emanations associated with normal electromagnetic radiation. They knew of our presence as soon as we began to broadcast.

An alternative fix, to both this and the previous problem, might suggest itself to you: although the aliens came originally from Rigel, they have been colonizing space for a long time. Their nearest colony is much closer than Rigel. Unfortunately, this doesn't help unless the aliens were already closer to us than the nearest star. The travel time from Alpha Centauri at 5,000 miles a second is more than a century and a half - too long for them to get here after receiving our first radio signals.

The Rigelians are a hundred feet high. At that size, they would not be able to march out of their ships. In fact, they would not march anywhere, or even be able to move. The largest creature on Earth, the blue whale, is as much as a hundred feet long, but it is able to grow to such a size only because its body is supported by water. A land animal a hundred feet tall would lie like a beached whale, crushed by its own weight and unable to breathe. Weight increases as the cube of linear size, the area of an animal's limbs only as the square, so something fifteen times as tall as a human has to support fifteen times as much weight per square inch of limb cross-section.

Nothing made of living tissue and walking around on land can be much bigger than an adult elephant, whose legs are short and thick. This is discussed in detail in J.B.S. Haldane's essay, ON BEING THE RIGHT SIZE (Haldane, 1927), which illustrates the size\area\weight relationship with a memorable image: "You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away. A rat is killed, a man is broken, a horse splashes."

The fix: our aliens must wear suits. Those suits include strong exoskeletons responding exactly to the movements that the alien within wishes to make. We could make a good approximation to such a suit today. It would be a trivial task for beings who build five-mile long interstellar spaceships. The suits also avoid another big question: How do aliens happen to be able to breathe our air?

They came to eat us. This may seem psychologically improbable, but let us accept that we do not understand alien motives. There is a much bigger problem. It is highly unlikely that creatures who evolved independently of Earth life will have a body chemistry close enough to ours to be able to eat the same kinds of foods. Borrowing from Chapter 6, we note that amino acids are the raw materials from which proteins are produced; that every living thing on Earth produces amino acids using coded triplets of DNA or RNA bases; and that all codings produce only a total of twenty amino acids out of the hundreds possible. We might argue that alien body chemistry will also be based on something like RNA and DNA, because it is the only system we know of today for cell reproduction. However, the chance that the very same amino acids would be generated is remote. Human flesh would be more likely to poison aliens than be relished by them.

The fix: we call on some version of the panspermia theory (Chapter 13), according to which life on Earth did not develop independently, but was carried here from space. In that case, the aliens arose from the same space-borne seeds; therefore, they can have compatible body biochemistry and can digest humans.

An alternative version, in which an early super-race colonized the whole galaxy, then vanished without trace, can accomplish the same result.

More problems: the aliens see using short-wave ultra-violet light. It's not impossible for such eyes to have developed, particularly since the aliens come from a world whose blue-white sun, Rigel, produces far more energy in the UV than Sol. But the aliens' eyes are working here on Earth. Our atmosphere absorbs UV radiation of wavelengths shorter than 0.3 micrometers, so anything that used this part of the spectrum for vision would be blind on the surface of this planet.

We will not ask how our scientist learned enough about the alien brain to realize how to disable it. Presumably she is a genius in neuroscience and signal processing. But she doesn't know much basic physics. Her UV signal generator will not be effective at long distances, as she planned to use it, since the beam is strongly absorbed by air.

The fix: give the aliens eyes that are superior to ours. Let them be sensitive to everything from short UV, at less than 0.25 micrometer wavelength, to reflective infra-red at 2 micrometers. (We see from about 0.4 to 0.7 micrometers). That way the human can see the light produced by her signal generator, and be a lot less nervous when using it in the field. ("Is this thing on?" "I don't see anything. Those aliens are getting awfully close.")

The science problems in this story were deliberately chosen as obvious. There are a couple of other, more subtle, scientific errors. They are minor, and one of them might get past a science fiction editor. Rather than discussing them here, I will let the reader discover the glitches and provide a fix.

Even when all the fantasy elements have been converted to science fiction, it remains a dumb story. But at least it is now a stupid science fiction story.

Do you really need to worry about any of this? After all, what you are going to write is fiction.

If you are writing the kind of science fiction that I want to read, you do. I have thrown books across the room and never picked them up again when they have offered some scientific howler too dumb to believe: a story in which a planet had an atmosphere of oxygen and hydrogen (watch out for that cigarette!); a man with an IQ of 5,000 (measured how?); a scientist, warning the President that an eclipse of the galaxy is on the way.

Even some of the science fiction classics are guilty. Consider H.G. Wells' THE INVISIBLE MAN (Wells, 1897). He took a drug which made his body of the same refractive index as air. But if your eyes did not absorb light, you would be blind.

There are more plausible ways of making a person invisible. Think about the problem and see what you can come up with. We will address the topic in more detail in Chapter 12.

1.4 What kind of writer? You are going to be a science fiction writer. What kind?

It's no good saying, "a rich and famous one." We need to be more specific. Let's look at the options, going back to the roots of science fiction.

When science fiction writers get together, one of the things they talk about is when science fiction began.

Was it with Lucian of Samosata, who almost two thousand years ago had his hero, Icaromenippus, wonder about the moon, and then go there? Even farther back, is Homer's Odyssey science fiction?

What about Marco Polo's travels to China, which some today say never happened, with the tale made up in a prison cell? How about the voyages of Sinbad? The idea of a bird that could carry off and dine on elephants must have seemed more probable to early Europeans than the elephant itself -- surely a fine candidate for a mythical beast.

Closer to our own time, we have Kepler's SOMNIUM (Kepler, 1634) and Francis Godwin's THE MAN IN THE MOONE (Godwin, 1638). And what about GULLIVER'S TRAVELS, travel not to the Moon but to places just as strange?

These were all 18th century works, although only Swift's stories are well-known today. If you are inclined to dismiss them as social satires, let me point out that in the Voyage to Laputa, published in 1726, Swift remarked that the astronomers of that flying island, with their superior telescopes, had "discovered two lesser stars, or 'satellites', which revolve around about Mars, whereof the innermost is distant from the center of the primary planet exactly three of its diameters, and the outermost, five; the former revolves in the space of ten hours and the latter in twenty-one and a half."

The modern values of these numbers are 1.35 Mars-diameters and 7 hrs. 39 mins. for Phobos, and 3.5 diameters and 30 hrs. 18 mins. for Deimos. However, no one knew that Mars had moons at all until Asaph Hall discovered Deimos and Phobos in 1877.

Inspired prediction? More probably, sheer coincidence — but any modern science fiction writer would be proud to do as well.

All these works have been cited as the "first science fiction." However, they all form isolated data points. They did not give rise to a "school" of writers, near-contemporaries who went on to write similar works. There was no continuity with what came after them.

That continuity came with two nineteenth century authors. The different types of story that they created persist. And the differences are relevant to writers today.

Origin number one was Mary Shelley's FRANKENSTEIN (Shelley, 1818).

This novel is significant in three ways. First, it has been continuously of interest - and read - since it was written in 1816. Second, it is fiction about science. The idea of the re-animation of a corpse was based on the science of the day. Mary Shelley wrote after the experiments of Galvani and Franklin, but before Faraday and Maxwell put an understanding of electricity and magnetism on a firmer footing. At the time when FRANKENSTEIN was written, electricity was perhaps the biggest mystery of the day. Even such authorities as Erasmus Darwin, the celebrated grandfather of Charles Darwin, did not dismiss the idea of the spontaneous generation of life. How much easier, then, it must have seemed to reanimate a corpse, rather than to create life from inanimate materials. Mary Shelley was offering legitimate scientific speculation, not fantasy.

Third, FRANKENSTEIN is a moral tale, concerned ultimately less with science than with moral issues.

You might not think about moral questions if you are familiar only with the movie versions of the story. There the monster is at center stage. The cinematic electrical effects and the harnessing of the lightning are not in the original book at all. In the movies, Baron Frankenstein loses ground to his creation. Even his name is abused. When children say, "you look like Frankenstein," we all know what they mean, while in that classic work, ABBOTT AND COSTELLO MEET FRANKENSTEIN, the Baron has gone entirely, replaced by Count Dracula (who loses out in the end to the Wolf Man).

Let me add one personal anecdote about the power of the story. My first exposure was neither to book nor to movie. The tale was told to me by my father when I was about eight, and I realize now that he talked of the movie version. It fascinated and absolutely terrified me.


Like FRANKENSTEIN, these books have been continuously read since the day that they were published. They also display a great interest in science. (Verne himself grumbled, late in life, that the upstart H.G. Wells didn't use sound scientific methods, the way that Verne had.)

Verne, however, is little concerned with moral issues. In contrast with Mary Shelley's story, Verne's plots can be summarized as "a bunch of cheerful but emotionally-challenged guys go off and have a rattling (and scientific) good time."

There is one other way in which Mary Shelley and Jules Verne differ profoundly. Verne's work directly influenced scientists -- not of his own generation, but of the one that followed. I don't think anyone reading FRANKENSTEIN around 1825 said, "Hey, let's go and collect a few bits of dead bodies and see what we can do." But we know for a fact that Tsiolkovsky, the father of the Russian space program, was inspired by Verne. Hermann Oberth, whose work in turn inspired Wernher von Braun, discovered Verne's FROM THE EARTH TO THE MOON when he was eleven years old, and was led to a life-long commitment to space flight. Finally, Robert Goddard was influenced by H.G. Wells, and THE WAR OF THE WORLDS. He later said that after reading it, "I imagined how wonderful it would be to make some device which had even the possibility of ascending to Mars, and how it would look on a small scale if sent up from the meadow at my feet... Existence at last seemed very purposive."

Today, the lines of descent from Mary Shelley and Jules Verne have converged. We all want to write stories that draw from both - morally significant tales, with first-rate science.

Given that overall desire, we have a number of options as to the type of writer we want to be. I will name and define half a dozen categories: Band-wagoners, Bards, Importers, Seers, Sensitives, and World-builders. And I will make my own recommendation as to how a new writer should proceed.

The Band-wagoner. This writer is very much of the moment. The story chooses a theme, often of current social or scientific significance, and pushes it hard. You will like the result if you are on the same intellectual wavelength, and share the same passion. Otherwise...

It is difficult to be consistently successful with this kind of writing. Causes change with the times. Not only that, the writer is likely to compete with fifty others who have responded to the same hot topic. Finally, the Band-wagoner must find an editor who shares the same point of view.

The Bard. If you can visualize an interesting character passing through a whole succession of intriguing situations, and can describe it so that other people can see the same scenes, you qualify as a Bard. If you put your character in space, you are likely to be writing space opera. If she is in Neverland, you are writing fantasy. If he is wandering the Mediterranean, a long time ago, someone else has already done the story.

Successful Bards have narrative strength, but more than that, they generate interest in the central character. Given a good tale-spinning talent, you can write these stories forever. Of course, after a while an acute reader may feel they are all the same story. Homer was smart, and wrote the Odyssey only once.

The Importer. Science fiction stories have been written about hundreds of branches of science. Fortunately for the Importer, science is a field in which new developments are reported every week. The Importer picks a subject, any subject: aardvarks to zygotes, and everything in between; quarks, game theory, prions, quasars, retroviruses, artificial life, superstrings.

There is only one restriction, but it's an important one: the subject must not have been used before in science fiction. The Importer learns enough to be convincing, then uses the subject as the background of a story.

This works better than one might suppose. Most science fiction readers have a natural interest in science, and a story is a painless way of acquiring new information. As a result, Importer stories can often be sold even when the writer violates some of the rules of good story-telling. The most common fault is in presenting science in big, lecture-like blocks - "expository lumps." The Importer gets away with it if the science is new enough, and interesting enough.

Of course, it does not have to be science. You can import historical eras, myths, systematic magic, or other branches of literature. Science has the advantage of continued development, and is therefore always a source of new material.

A good Importer imports, and then instinctively extrapolates. Many of the successful "predictions" of science fiction have come from Importers.

The Seer. If you can look at an everyday situation, and see it in a new and interesting perspective, you are a Seer. You are also a rarity. Writers of this type don't necessarily offer much in the way of plot or character, but they shed a new light on the world. If in reading a story you stop every few pages and say to yourself, "I never thought about it that way," then you have found yourself a first-class Seer.

How do you go about becoming one? I don't think you do. Unlike the Band-wagoner or Importer, which can be a learned skill, the Seer has an inborn talent, an inward eye that sees the world in a different way.

The Sensitive. It is an accident of timing or temperament that leads this writer to the science fiction field. The real interest of the Sensitive has nothing to do with science, it is in human (and non-human) emotions. The science elements of a Sensitive's stories are often non-existent. When they are also present, the stories are the strongest in the field.

The World-builder. This writer is not particularly interested in the characters in the story, or even the plot. The fascination lies in the background - a planetary system, a future society, a well-designed alien, or an artificial world.

Science is important here. Many World-builders spend much time and effort making every element of their world consistent and plausible. It is necessary, too. Science fiction readers are careful readers. They are also communicative readers. Get something wrong, and you will hear about it.

Now for the promised recommendation. If you are a beginning writer, I suggest that you try to become an Importer. All it takes is the ability to read about a science subject, and then write about it, in the context of a story, in reasonably clear language.

Am I over-simplifying? A little, perhaps - maybe because I started out as an Importer myself. On the other hand, when I read some of my early published stories I am convinced that, other than as an Importer, there is no way that I would ever have seen myself in print.

1.5 Three times ten to the fourteenth furlongs per fortnight: units and notation.

Kilometers or miles? Kilograms or pounds? Knots, or miles per hour?

In principle, the United States operates using the metric system. In practice, it does not. There are also a variety of special measures used in science, such as the fermi (10-15 meters), curie (a unit of radioactivity), dol (a measure of pain), flops (in computers, the number of floating-point operations per second), mho (conductivity, the reciprocal of resistance — ohm backwards, get it?), and barn (a unit of area, 10-24 square meters — "It's as big as a barn," another good example of physicist humor).

There are also a number of would-be humorous units from other fields. The millihelen is defined, after Marlowe, as the amount of beauty sufficient to launch one ship. The kan is a suggested unit of modesty, of which the somewhat arrogant American scientist, Millikan, was said to possess one-thousandth.

Deliberate attempts at humor aside, what units should you use in a story?

The most familiar form is the best one.

Lightyears are better than parsecs, even though astronomers almost always employ the latter. Miles per hour, rather than knots (nautical miles per hour), and feet rather than fathoms, unless you are specifically seeking a flavor of the sea — and even then, it's good to tie your numbers to something specific. "We'll never catch that sub, it must be doing over forty knots and heading down to a hundred fathoms."

Units for which the average reader has no instinct or training, such as the curie, dol, mho, and gauss (the measure of magnetic field), should be avoided completely. Kilometers are all right, and so, in general, are meters and kilograms. Even here, there are exceptions. When you watch the Olympic Games, do you, like me, have to convert the pole vault from meters to feet before you have a real idea of high the bar is set? Do you know if a long jump of nine meters is poor, good, or a world record?

There is one golden rule: numbers are there not to prove how smart you are, but to provide information to the reader. Since this book is written for anyone who wants to use a reasonable amount of science in stories, it's not unfair of me to assume the same of my potential reader. But if you yourself have to sit down and work out how big something is in a particular unit, you should probably look for another way to get your point across.

Technical vocabulary, like the occasional number, adds a feeling of solidity to a story. It should be used sparingly. And get the term right, or don't use it at all. Do not say "quasar" if you mean "quark," confuse momentum with energy, or employ "lightyear" as though it is a unit of time.

As for the notation in which very large or small numbers are written, in this book I will assume that you, the reader, are familiar with expressions such as 10+27, or 5.3 x 10-16. Even so, I advise you to avoid this form of notation whenever possible.

That point was brought home to me many years ago at, of all places, NASA Headquarters. We were in the middle of a presentation, and casually throwing around expressions like 1012 and 10-8, when a member of the audience (who happened to be NASA's Head of International Affairs) pointed at one of the numerical tables and said, "What are those little figures written above the tens?"

As we said when we left, "Thank God he's not designing the spacecraft."

Find an alternative in your story-telling to scientific notation. You never know whom you may lose when you use it.

Copyright 1999 by Charles Sheffield
Chapter I 1 2 3 4 5 6

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Baen Books 02/02/03