Does N = 1?

I wrote the following for a past edition of the Odfellowlog

Does N = 1?

By James Hall

“The skies of our ancestors hung low overhead.”
---Timothy Ferris, Coming of Age in the Milky Way

Creation accounts from biblical Genesis to Aristotle’s Physics depict Earth and its life in the center of the universe. The accuracy of these accounts is challenged by science--modern astronomy tells us that the Earth moves around our sun, a modest G-type star in one spiral arm of the Milky Way Galaxy, itself one of 125 billion galaxies in an expanding universe. Yet these creation accounts may be right in at least one respect: Earth may well be the center of the universe, as the only planet where intelligent, technological life has yet developed.

Many space scientists now believe that the origin of life, particularly intelligent, technological life like ours, may take the confluence of so many favorable factors that it has happened only once in the history of the universe—to us.

The Golden Age of Science, SF

The scientific revolution opened up the universe for us, and the potential seemed tremendous for numerous life-bearing worlds with intelligent technological civilizations. Early SF writers like H. G. Wells and Edgar Rice Burroughs wrote stories about an inhabited Moon and Mars. Golden Age SF writers like E.E. “Doc” Smith (whose Lensman series has just been republished), A. Merritt, and John W. Campbell created vast galactic empires with every star system inhabited with intelligent alien life.

Science itself grappled with the issue of extraterrestrial life. In 1961, astronomer Frank Drake, the founder of the SETI program (the Search for Extra-Terrestrial Intelligence) developed a formula for calculating how many intelligent, communicating civilizations might inhabit the Galaxy. (See below.) Carl Sagan used Drake’s equation to calculate that the number of interstellar technological civilizations in our galaxy might be as high as ten thousand. Today the recognized scientific discipline of astrobiology studies the conditions under which life can form and prosper in a variety of difficult environments.

But recent scientific discoveries paint a cautionary picture of life in the universe. The first scientific probes to Mars and Venus took them out of the SF writer’s portfolio of human settings. Jungle Venus was really a molten hell, and desert Mars, ice. The latest scientific probes continue to suggest that if life exists in our solar system outside of Earth itself, it is small, hidden and probably unintelligent.

The latest astronomical observations also cast doubt on an intersellar neighborhood crowded with technological civilizations,. We have failed to locate the noisy signals of all the type 1, type 2, and type 3 civilizations imagined by Russian astrophysicist A. N. Kardeshev, who hypothesized advanced technological civilizations capable of using the energy of an entire planet, star, and even galaxy to communicate with each other. No sign either of huge alien arcologies like the partial Dyson sphere portrayed in Larry Niven’s Ringworld, vast artificial structures that should be plainly visible to us even at great distances.

The Fermi Paradox

Space scientists now take seriously the paradox proposed by physicist Enrico Fermi, who asked why, if intelligent space-faring civilizations exist, haven’t they visited us? People have responded to Fermi’s paradox in different ways: some assert that alien astronauts have in fact visited and left their impact on the art and architecture of ancient civilizations, others that extra-terrestrials are around but keeping their distance. One recent ingenious explanation, by SF writer Steven Baxter, is that a powerful alien civilization has surrounded our solar system with a holographic image of an empty universe to deliberately mislead us.

But some space scientists use the Fermi paradox to advance another theory: life, in particular intelligent, technological life, requires too many things to go right to ever be common. Their answer, both to the Fermi paradox and the Drake’s equation, is that N=1. No one has visited because we are the only intelligent, technological life forms out there.

Dangerous Universe

Why does this “Rare Earth” hypothesis increasingly find favor with many space scientists? In part because astronomers have found that the universe is a much more difficult and dangerous place for our kind of life than we imagined.

The peaceful, passive galaxies envisioned by Golden Age SF writers don’t exist. The galaxies we observe today are dynamic, violent, dangerous places. The discovery of super-massive black holes in the center of many if not most galaxies, including our own, makes the center of these galaxies uninhabitable. Instead of containing inhabited worlds like Asimov’s Trantor, the center of our galaxy swallows star systems whole or exposes them to high-energy radiation and disruptive gravity waves. In some galaxies, the event horizons of the central black holes are so energetic that they become blazars, releasing enough energy to sterilize any carbon-based life within those galaxies.

But the danger to life isn’t just in the galactic center. Wandering hazards pose additional dangers to life-bearing systems. Smaller black holes passing near or through planetary systems can ingest life-bearing planets or throw them out of orbit. Rapidly-spinning neutron stars called magnetars can pass close enough to inhabited planets to flood them with focused beams of ozone-destroying gamma radiation.

Supernovae occurring fairly close to life-bearing planets (within 30 light years or so) may sterilize surface life or destroy ozone layers with gamma radiation, and these occur relatively frequently—one or two per century in our Galaxy. The most dangerous hazard of all may be one we know little about: gamma ray bursters, or GRBs. We don’t know how or why they occur, but GRBs are the most powerful explosions in the universe, far exceeding supernovae. No recorded GRBs have happened close to our Galaxy, but if they did, the gamma rays they generate might well be powerful enough to sterilize the entire Galaxy.

Rare Earth and the Goldilocks Effect

Even without galactic hazards, the conditions that create and sustain our kind of complex, carbon-based life require good fortune. Complex life evolves over billions of years in a continuously inhabitable zone of a suitable star. Large Type O or B stars burn out too soon; while small, slow-burning stars may not provide enough energy for life. Like Goldilocks, life requires a range of stars that are not too hot or too cold, but “just right.”

While simple, bacterial life is hardy enough to survive in a variety of tough environments, more complex forms of life appear to require the long-term nurturing environment of a rocky, terrestrial planet with a protective atmosphere, sufficient liquid water, and available minerals to create a technological society.

Like our Earth, these planets must be in a stable orbit, and the life there probably must survive major periodic changes, including ice ages, greenhouse effects, large-scale vulcanism, and asteroid bombardments. Complex life must evolve and flourish in this kind of environment, and with it species that possess intelligence, eventually language, and finally technology and science.

To many of the scientists who study the origin of intelligence, language, technology, and science, none of these factors seem particularly inevitable. It took billions of years for life to evolve from simple bacteria to complex, single-cell eukaroyotes. Millions of years passed while animals grew in complexity and intelligence. But not until Homo Sapiens came on the scene did a species capable of using speech, developing technology, and perfecting the scientific method.

Even then, it took an additional forty-thousand years of development to create a technological, scientific culture capable of advanced communicaiton and space travel.

We also can’t forget that technological civilizations will inevitably develop ample means to destroy themselves in a variety of ways—nuclear weapons, biological plagues, bombardment from space, or environmental destruction. Along with the knowledge to concentrate technological power must come the wisdom to use that power and survive. For any civilization to spread out of its small corner into the universe, it must survive long enough to make that possible.

Considering how long it took for complex life to evolve on Earth, and since only one species, humanity, has evolved both intelligence and language, and only one human civilization, the Western European, created a systematic scientific method and advanced scientific technology, it may be difficult indeed to find other symbol-using, scientific, technologically-advanced, space-faring civilizations.

Difficulties of Space Travel

The next major hurdle for intelligent, technological life may be the difficulties of space travel. Even if intelligent, technological life exists elsewhere, it may not find space travel as simple as it is portrayed in the conventions of science fiction.

Consider our own relatively quiet solar system. Outside of Earth’s protective magnetic field and its ozone layers, interplanetary radiation and the effects of long-term weightlessness make even interplanetary travel riskier for humans than SF writers ever envisioned it would be.

By breaking apart DNA and protein molecules, radiation poses a significant threat to living things. The radiation encountered by living beings in space includes gamma rays, high-energy protons, and cosmic rays. High-energy protons are accelerated into space by solar flares; galactic cosmic rays, or GCRs, are particles accelerated nearly to the speed of light by distant supernovae, some of which are quite massive (ions of iron, for example).

NASA has estimated that travel in deep space carries an increased risk of cancer


Will we find an accurate value of N? The next generation of space-based telescopes may find, within the next decade, evidence of life-bearing planets. SETI continues to try different strategies for separating signal from noise.

Rare Earth SF

Today’s SF writers have begun to adapt themselves to the idea that the universe isn’t teeming with intelligent, space-faring life. In Vernor Vinge’s Hugo-award-winning Deep series, his galactic civilization is composed of human-descended colonies, intelligent alien life is rare, and signals of alien technological societies whisper in the background, too distant to reach or comprehend. In Greg Egan’s Schild’s Ladder, the alien species are pre-technological or non-technological. The New Space Opera of British SF writers like Alastair Reynolds, Charles Stross, and M. Harrison frequently features humans interacting with dead or dying alien empires.

At its best, the uncertainty of about extraterrestrial life offers SF writers a fruitful plot device or fields of speculation on where the aliens really are. Steven Baxter’s Manifold series is based in part on the search for the missing aliens.

Now we’re just not sure. N (the number of technological civilizations) could be a huge number, or it could equal just one--ours.


Drake’s equation
N=Rf(p)n(e)f(l)f(i)f(c)L

N=The number of civilizations with detectable emissions.
R=The rate of the formation of stars suitable for intelligent life.
F(p)=The fraction of these stars with planetary systems.
n(e)=The number of planets with an environment suitable for life.
F(I)=The fraction of suitable planets on which life actually forms.
F(l)=The fraction of life-bearing planets on which intelligent life
F(c)=The fraction of civilizations that develop a technology that releases detectable signals into space.
L=The length of time civilization release signals into space.

Finishing HaltinG StatE

I finished reading Charles Stross's HaltinG StatE the other day. I have to rate it very high on ideas, which come rapid fire in this book. It is, I think, Mr. Stross's first near-future SF book, so it was interesting to read his predictions for the near future. These included an independent Scotland (under EU auspices), and gamespace and gamers used as surreptitious spooks in spook country. I enjoyed the idea that gamers were recruited as volunteer secret agents without understanding that they were really being co opted by the security services of different countries. Nice touch there.

Stross also paints a vivid picture of a what a future cyber attack on a nation might look like. That alone is probably worth the price of the book.

That said, I wasn't as impressed with the characters and the plot as I have been with other of Stross's works. I thought that the whole plot seemed fairly contrived, that character and relationship problems were introduced at convenient times and not as part of their "natural" development, and I question whether some of the characters really needed a point of view in the novel. I saw the mysterious villain coming from a long way off and wondered why he wasn't neutralized earlier.

As I've already noted, the book begins slowly and only my previous experiences with Stross's work kept me reading. The ending is confused and lacks inevitability. (It's always troubling when the final-but-one chapter has to do the job of explaining exactly what happened during the book.) Ditto for the second-person points of view and the dense software language that a non-expert reader like me, who enjoys cypberpunk in general, found too much.

That said, the book doesn't miss the mark by too much. Stross's compelling future vision goes a long way to making this book a good read, and I would like to see more work in this setting by Stross. Perhaps what he needs is a good glossary like the one originally published in Dune. I'd rate it a solid "B" as new SF books go. If you are into the language of software, you might rate it higher.