by Eric Flint
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The efficiency of laser light propulsion can be increased by "recycling the photons," that is, reflecting them back and forth between the laser station and the spacecraft. This requires use of one of those multilayer dielectric mirrors we disdained a moment ago. In effect, we are trading more sail weight (and thus lower acceleration) for a lower power requirement.
Conclusion
In his Conversation with the Star Messenger (1610), Johannes Kepler speculated that in the future, there would be "sails or ships fit to survive the breezes of heaven." We are on the verge of making his speculation a reality.
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The Universal Diagram
Written by Stephen Euin Cobb
Occasionally, important advances in scientific understanding are made not by gathering more or better data, or by developing a new and radical theory, but by simply experimenting with a new way of displaying the data that everyone has already examined to their satisfaction.
One example is the periodic table of the elements. It's a simple chart of all the chemical elements arranged in order of how many protons each has in its nucleus. Yet this modest little arrangement has revealed numerous secrets of the elements because so many of their relationships are interlocking.
Another example is The Hertzsprung-Russell Diagram of stars which is drawn by plotting as many stars as you wish on a sheet of graph paper such that each one's location depends on its luminosity vs. its temperature. (Usually luminosity is vertical and temperature is horizontal, with the lowest values to the lower right and the highest values to the upper left.) Armed with this simple graphical representation, many unexpected secrets of stellar evolution were made plain, and stars which at first seemed completely different were eventually discovered to be of the same kind, differing only in age.
About twenty-five years ago, based on the idea that I might be able to discover unexpected relationships, I devised a method of charting planets which in the childish vanity of my twenties I called "The Cobb Diagram." I drew it several times by hand using all the planets of our solar system, but with so few planets it was mostly empty space and so nothing of significance could be gleaned of their interrelationships. Today, however, that situation is rapidly changing.
Currently, 210 planets have been discovered outside our solar system, with new discoveries being added every few weeks. Finding more planets which orbit stars other than our sun has become a new kind of international space race. The discovery rate has accelerated during the last few years, and within a decade may well reach explosive proportions.
At least eight different organized searches are currently underway for these extra-solar planets, or exoplanets, and more are in the works. A few include:
The Darwin Space Infrared Interferometry Project.
COROTA—French photometry mission for stellar seismology and planet detection.
ASP—Arizona Search for Planets (a ground based photometric search for giant planets).
MONS—Measuring Oscillations in Nearby Stars (a Danish space mission to study stellar oscillations, but also capable of doing some transit photometry).
MOST—Microvariability and Oscillations in Stars (a Canadian microsat that uses photometry to measure stellar seismology).
STARE—Stellar Astrophysics & Research on Exoplanets at High Altitude Observatory by Tim Brown.
TEP—A search for transits of the eclipsing binary CM Draconis.
University of California Planet Search Project—The work of Geoff Marcy, Paul Butler, Steve Vogt, Debra Fischer and Chris McCarthy (who have detected most of the known extra-solar planets).
Vulcan Camera—A ground based photometric search for short period transiting giant planets by William Borucki.
And launching in October of 2008the Kepler Mission from NASA. Kepler is specifically designed to "survey our region of the Milky Way galaxy to detect and characterize hundreds of Earth-size and smaller planets in or near the habitable zone. The habitable zone encompasses the distances from a star where liquid water can exist on a planet's surface." Yes, you read that right. Kepler will spend its entire four-year mission looking for earths.
But big money projects are not likely to be the only thing to contribute in a big way to the coming explosion in exoplanet discoveries. One of the newest, and perhaps most innovative, projects is called Systemic. It's a web-based organization which lets amateur astronomers use their home computers to work with the star wobble data collected by professional astronomers. Participants select a star and tweak variables such as a planet's mass and orbital period by moving a slider on their computer screen. The goal being to design a planetary system that best matches the measured wobble for that star. Over 750 amateur planet hunters are involved so far, and you can join them by going to http://oklo.org/?page_id=33
Because of all this activity and enthusiasm and money and fascination, and because of the potential universal access and participation provided by the World Wide Web, I estimate that within three years new planets will be discovered at approximately one per day. What's more, I estimate the complete list of exoplanets to reach a thousand within four years, ten thousand within ten years, and a hundred thousand within twenty years. And I know that last estimate sounds impossible but, in truth, it's not actually going to take that long. I just wanted to make it easier for you to accept. Exponential progressions can be so hard to swallow sometimes.
But even if my own estimates are exceptionally generous—though I doubt that—it remains clear that we will soon to be faced with an abundance of exoplanets. And because of this I feel it is time we had a means of arranging them in a logical order. Ideally this logical order should be one that allows us to uncover relationships that would otherwise remain hidden. So out of the drawer comes my old method of charting planets.
While it's obvious that every planet is unique based on dozens if not hundreds of variables, I feel that three are most fundamental. These three properties working together may cause as much as 97% of a planet's unique identity. Using this notion, every planet can be reduced to three numerical values, and these values can then be plotted within a three dimensional cube.
Back in 2002, while toying with this system, I surprised myself by realizing that there is no need to limit its use to planets. By shoving the cube's metaphorical walls out a bit farther, the three numerical values could just as easily define stars. And having realized this, I next realized that all celestial objects could be plotted within the cube.
The three numerical values needed for this plotting are: 1mass (obviously), 2surface heating (usually received from an outside source, such as the earth's surface being heated by sunlight) and, 3internal heating. This internal heating can be from thermonuclear fusion, as we see in stars; or it can be from tidal friction, or radioactive decay, or even gravitational collapse. The source doesn't matter, only the amount.
But you must wonder: why these three values?
Mass is clearly the most important and hardly needs any explanation, but you might wonder why I chose energy for both of the other two values instead of, perhaps, chemical composition. Simple: in this universe, with the exception of the short-lived Population Two stars, almost all objects condense from roughly the same mixture of gasses and dust. And the reason they do is because that mixture was created by the short-lived Population Two stars and scattered all over the place when they went nova, which Population Two stars have a particular love of doing at the end of their short lives.
Consequently (especially for things smaller than stars, which most notably includes planets) the huge difference in chemical composition which we see in different objects is not a product of what they were given at their beginning, but of what they've lost in the time since. And, of course, precisely which chemicals an object will loose during its lifetime is determined by its escape velocity (and therefore mass) and by the likelihood that it's molecules will have, at some point or other, the momentum needed to achieve escape velocity—which is to say, the likelihood that
those molecules will be sufficiently heated.
For a star, internal heating is obviously a defining property, however for a planet it might seem that external heating is the only heating we need measure. But that would be wrong. Consider the four big moons of Jupiter. They are radically different from one another yet they have very similar masses and receive almost exactly the same amount of external heat from the sun. Their differences are a product of several features specific to their proximity to Jupiter, and one of those features is the different amount of interior frictional heating each one suffers by way of its tides.
Being closest to Jupiter, Io has the strongest tides. During every orbit, the material of Io's deep interior grinds against itself as this moon is deformed from and returns to its spherical shape. Its interior is heated so violently by this friction that every amateur astronomer is familiar with its yellow and orange surface which is scarred with black volcanoes and smeared with plumes of red soot. Astronomers describe its volcanism as "slowly turning Io inside out."
The volcanoes of earth, along with our plate tectonics, are also produced by internal heating; though in our case this heat is mostly the product of the decay of radioactive materials such as uranium and thorium.
I should also point out that while stars are dominated by their internal heating, which is usually thermonuclear, they are not immune to alteration by external heating. A close pair of binary stars will change one another dramatically by mutually heating each other's exterior.
These are just a few examples of the importance of these three numerical values; and of why they are sufficient to define any naturally occurring object in the universe, so long as that object has experienced a relatively natural progression of heating for its particular situation without any catastrophic interference from a passing object.
So now, let's fill in the cube.
There are trillions of trillions of celestial objects in this universe. If all these objects were plotted within a cube in which each of the three numerical values I've described controlled a dimension, nearly every point within this three dimensional plot would be overwhelmingly dominated by objects almost identical to one another.
Density of the plot points would vary. There would be clustering and crowding: regions where specific types of planets and stars, for example, would be more tightly packed.
Transition zones would also vary. Some would be gradual; places where objects would gently change from one recognizable type to another. But some transition zones would be abrupt; places where two adjacent zones would have a sharp and distinct boundary. These might be places where a small change in one of the three values would produce a big change in the properties and nature of the planet or star or other object.
Many distinct boundaries might exist, often in the form of gently curving sheets. Some of these might touch to form T-shaped intersections, others might curve themselves into the shape of a trough or a cup, and somewhere three boundaries may intersect to form a corner like that of a cardboard box. Some of these boundaries would separate things we are familiar with, such as stars, quasars, pulsars, comets, asteroids, even Earth-like planets and Venus-like planets; but some might delineate things we don't yet have names for; and some might even surround regions of the cube that are mysteriously empty. Learning why they were empty could reveal further secrets, and clue us in about strange attractors which operate on the scale of planets and stars.
And since objects which plot near one another will tend to be very similar, once enough exoplanets have been discovered and studied and plotted, it would then become possible to immediately estimate the properties of any newly discovered exoplanet just by determining its three numerical values, two of which can be measured from hundreds of light years away.
Curiously, this plotting system has a two-faced Jekyll-Hyde nature; both of which may prove valuable for our greater understanding. While the vast majority of objects will closely resemble their immediate neighbors within the cube, a tiny percentage won't. By not getting along well with their neighbors, these crazy Mister Hyde's will be waving a red flag. They will be signaling that by their uniqueness they are worthy of special attention. Some of these will be like Uranus, with its mysterious 98 degree polar tilt; some will be tidally locked to their external heat source, as we long thought Mercury to be; others may be in crazy orbits, or suffer through other periodic temperature extremes. Regardless of why they deviate from their neighbors, that they deviate is indication enough that they are worth studying. Ultimately some of the deviations may also be discovered to be attractors, and by their popularity, worthy of their own classification. So that eventually things that today have no name may be become named.
My favorite feature of this plotting system is that it allows almost everything in the universe—from the tiniest tumbling grains of dust, to quasars brighter than a million galaxies—to be placed within a single unified continuum. Beyond its appeal to my love for neatness, this could prove to be a handy little diagram, especially when we are inundated with more exoplanets than we can explore in a typical human lifetime.
And now to the naming of my simple graphic: since all naturally occurring objects can be plotted within it, I suggest it be called "The Universal Diagram," although I suppose it could be called "The Cosmic Cube."
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Stephen's podcast about the future is at http://www.thefutureandyou.com
COLUMNS
The Editor's Column February 2007
Written by Mike Resnick
So here I am, the new Executive Editor of Jim Baen's Universe. And here you are, wondering who the hell I am and what I like.
Who I am is easy. I'm Mike Resnick, I sold my first science fiction novel exactly 40 years ago (don't hunt for it; it's pretty awful). I sold my first few science fiction stories even earlier (you might very well enjoy hunting for them; they were the "redeeming social value" in a trio of men's magazines, stuck in there to make all the naked women legal). I attended my first Worldcon in 1963—I was a mature 21, my child-bride was 20—and we've been going back ever since.
I started selling stories and articles when I was a teenager. Somewhere along the way to 2007 I learned how to write acceptable prose (though I'm sure there are critics who would disagree). After producing a few million lesser words in lesser fields, I've now sold over 50 science fiction novels, close to 200 stories, more than a dozen collections, even a couple of screenplays, and I've edited close to 50 anthologies. Along the way I've won a bunch of Hugos (5), lost an even bigger bunch (23), and according to Locus I have won more awards for my short science fiction that any writer living or dead. (I have also lost more, but you have my permission to forget or ignore this fact.)
I've edited anthologies, as I said, and I spent a couple of years this decade editing science fiction for BenBella Books, but until now I have never edited a science fiction magazine. I've wanted this freedom for a long time. By freedom, I mean that just about every time you sell an anthology, you must sell it based on a theme, and while it's interesting to edit the best Alternate Kennedy stories or the best Sherlock Holmes in the Future stories, it is a bit limiting for both the writer and the editor. Here at Jim Baen's Universe I am free to select the best stories regardless of theme or subject matter, to help writers produce the best stories they can write rather than the best Space Cadet or Dinosaur or Christmas Ghost story they can write.
So what do I like?
It's going to sound like a cop-out, but I like good writing. I used to write in the "adult" field, so I guarantee you can't shock me. I've sold perhaps 60 funny science fiction stories, so you're not going to get turned away because your story isn't serious enough. I've won awards at every length, so I will not react unfavorably to any length.
But give me a story that's poorly written, carelessly conceived, clumsily worded, or filled with cardboard characters, and I don't care if you've been my friend for half a century, you're not going to sell me. Jim Baen's Universe is not just paying the best rates in the
field, but much the best, literally 3 times more than Analog, Asimov's and F&SF pay for short stories by major authors, and for that kind of money, we expect—and I demand—stories that are worth what we're paying. Simple as that.
Other than the demand for good writing, the market's wide open. I don't believe in editorial soap boxes. I learned a long time ago that trying to shoehorn a writer into a style or subject I liked, rather than helping him create what he liked, was counter-productive. I love Robert Sheckley's humor, and I loved the humor in Robert E. Howard's Breckenridge Elkins stories—and neither of them wrote the kind of humor I do. I can admire Edgar Rice Burroughs' fantastic adventures and Eric Flint's alternate historical adventures and Fred Saberhagen's futuristic adventures, and none of them read remotely like my own adventures. Indeed, when I make a list of my favorite science fiction writers—Alfred Bester, Barry Malzberg, C. L. Moore, Clifford D. Simak, Robert Sheckley, James White, a number of others—I find the one thing they have in common is that none of them writes like me. In fact, that's one of the prime reasons I admire them: because they come up with stories and styles and approaches that are fascinating to me precisely because what they write is so different from what I write. (Why in the world should I want to read Imitation Resnick or Watered-Down Resnick when I can read unique and original Heinlein and Zelazny and Willis? And on those occasions that I want to read a Resnick story, whose writing I immodestly admit to liking, well, I'm on pretty good terms with the source and will simply suggest that he write one.)
