The planetary chauvinists

In a profile in the latest issue of Wired, the journalist Steven Levy speaks at length with Jeff Bezos, the world’s richest man, about his dream of sending humans permanently into space. Levy was offered a rare glimpse into the operations of the Amazon founder’s spaceflight company, Blue Origin, but it came with one condition: “I had to promise that, before I interviewed [Bezos] about his long-term plans, I would watch a newly unearthed 1975 PBS program.” He continues:

So one afternoon, I opened my laptop and clicked on the link Bezos had sent me. Suddenly I was thrust back into the predigital world, where viewers had more fingers than channels and remote shopping hadn’t advanced past the Sears catalog. In lo-res monochrome, a host in suit and tie interviews the writer Isaac Asimov and physicist Gerard O’Neill, wearing a cool, wide-lapeled blazer and white turtleneck. To the amusement of the host, O’Neill describes a future where some ninety percent of humans live in space stations in distant orbits of the blue planet. For most of us, Earth would be our homeland but not our home. We’d use it for R&R, visiting it as we would a national park. Then we’d return to the cosmos, where humanity would be thriving like never before. Asimov, agreeing entirely, called resistance to the concept “planetary chauvinism.”

The discussion, which was conducted by Harold Hayes, was evidently lost for years before being dug up in a storage locker by the Space Studies Institute, the organization that O’Neill founded in the late seventies. You can view the entire program here, and it’s well worth watching. At one point, Asimov, whom Hayes describes as “our favorite jack of all sciences,” alludes briefly to my favorite science fiction concept, the gravity gauge: “Well once you land on the moon, you know the moon is a lot easier to get away from than the earth is. The earth has a gravity six times as strong as that of the moon at the surface.” (Asimov must have known all of this without having to think twice, but I’d like to believe that he was also reminded of it by The Moon is a Harsh Mistress.) And in response to the question of whether he had ever written about space colonies in his own fiction, Asimov gives his “legendary” response:

Nobody did, really, because we’ve all been planet chauvinists. We’ve all believed people should live on the surface of a planet, of a world. I’ve had colonies on the moon—so have a hundred other science fiction writers. The closest I came to a manufactured world in free space was to suggest that we go out to the asteroid belt and hollow out the asteroids, and make ships out of them [in the novelette “The Martian Way”]. It never occurred to me to bring the material from the asteroids in towards the earth, where conditions are pleasanter, and build the worlds there.

Of course, it isn’t entirely accurate that science fiction writers had “all” been planet chauvinists—Heinlein had explored similar concepts in such stories as “Waldo” and “Delilah and the Space Rigger,” and I’m sure there are other examples. (Asimov had even discussed the idea ten years earlier in the essay “There’s No Place Like Spome,” which he later described as “an anticipation, in a fumbling sort of way, of Gerard O’Neill’s concept of space settlements.”) And while there’s no doubt that O’Neill’s notion of a permanent settlement in space was genuinely revolutionary, there’s also a sense in which Asimov was the last writer you’d expect to come up with it. Asimov was a notorious acrophobe and claustrophile who hated flying and suffered a panic attack on the roller coaster at Coney Island. When he was younger, he loved enclosed spaces, like the kitchen at the back of his father’s candy store, and he daydreamed about running a newsstand on the subway, where he could put up the shutters and just read magazines. Years later, he refused to go out onto the balcony of his apartment, which overlooked Central Park, because of his fear of heights, and he was always happiest while typing away in his office. And his personal preferences were visible in the stories that he wrote. The theme of an enclosed or underground city appears in such stories as The Caves of Steel, while The Naked Sun is basically a novel about agoraphobia. In his interview with Hayes, Asimov speculates that space colonies will attract people looking for an escape from earth: “Once you do realize that you have a kind of life there which represents a security and a pleasantness that you no longer have on earth, the difficulty will be not in getting people to go but in making them line up in orderly fashion.” But he never would have gone there voluntarily.

Yet this is a revealing point in itself. Unlike Heinlein, who dreamed of buying a commercial ticket to the moon, Asimov never wanted to go into space. He just wanted to write about it, and he was better—or at least more successful—at this than just about anybody else. (In his memoirs, Asimov recalls taping the show with O’Neill on January 7, 1975, adding that he was “a little restless” because he was worried about being late for dinner with Lester and Judy-Lynn del Rey. After he was done, he hailed a cab. On the road, as they were making the usual small talk, the driver revealed that he had once wanted to be a writer. Asimov, who hadn’t mentioned his name, told him consolingly that no one could make a living as writer anyway. The driver responded: “Isaac Asimov does.”) And the comparison with Bezos is an enlightening one. Bezos obviously built his career on books, and he was a voracious reader of science fiction in his youth, as Levy notes: “[Bezos’s] grandfather—a former top Defense Department official—introduced him to the extensive collection of science fiction at the town library. He devoured the books, gravitating especially to Robert Heinlein and other classic writers who explored the cosmos in their tales.” With his unimaginable wealth, Bezos is in a position remarkably close to that of the protagonist in such stories, with the ability to “painlessly siphon off a billion dollars every year to fund his boyhood dream.” But the ideas that he has the money to put into practice were originated by writers and other thinkers whose minds went in unusual directions precisely because they didn’t have the resources, financial or otherwise, to do it personally. Vast wealth can generate a chauvinism of its own, and the really innovative ideas tend to come from unexpected places. This was true of Asimov, as well as O’Neill, whose work was affiliated in fascinating ways with the world of Stewart Brand and the Whole Earth Catalog. I’ll have more to say about O’Neill—and Bezos—tomorrow.

The moon is a harsh fortress

Note: I’m taking a few days off, so I’ll be republishing some of my favorite pieces from earlier in this blog’s run. This is a significantly expanded version of a post that first appeared on February 27, 2017.

In the May 1947 issue of the nonfiction magazine Air Trails and Science Frontiers, which was edited at the time by John W. Campbell, the cover story was an article titled “Fortress in the Sky.” Its author, credited as “Capt. B. A. Northrop,” argued that the existence of the atomic bomb had rendered the notion of a defensible land or naval base obsolete. The only truly impregnable military position, he wrote, was the moon, which would soon be “conquered” by mankind: “It will probably be reached in five years and completed in ten. Its possessor will be supreme over all nations and peoples of Earth.” Northrop went on to discuss the possible technologies that could be used for a moon landing, but he also made a very peculiar claim:

Here and there throughout the world many men have been thinking about rockets for some time. I recall that in 1930, L. Ron Hubbard, a writer and engineer, developed and tested—but without fanfare—a rocket motor considerably superior to the V-2 instrument of propulsion and rather less complicated.

In fact, “Northrop” was none other than Hubbard himself, who was nineteen years old in 1930, when he was allegedly conducting his rocket research. (I used to believe that his pseudonym, which is spelled “Northorp” elsewhere in the issue, was inspired by Northrop Aircraft, a frequent presence in the magazine’s pages, but it seems more likely to me now that it was a nod to Sara Northrup, Hubbard’s wife. Campbell himself may have suggested it—he had written his most famous stories as Don A. Stuart and encouraged Robert A. Heinlein to use the pen name Anson MacDonald, both of which were based on their wives’ maiden names.) “Fortress in the Sky” was Hubbard’s first major publication after the war. He had been suffering from depression and writer’s block, and before Campbell give him the assignment, he had contributed just a few poems and short articles to the Catalina Islander. As such, the piece was a turning point in his career, but as far as I know, it has never been reprinted in its entirety. Last year, however, I got my hands on a copy of the original issue of Air Trails in which it appeared, and I was able to read the whole thing. Aside from Hubbard’s gratuitous reference to himself, which Campbell either believed or was willing to let slide, it’s a surprisingly plausible piece of futuristic speculation. Campbell appears to have provided much of the science, and a lot of the material relating to a future moon colony seems to have been drawn directly from the editor’s unpublished novel The Moon is Hell.

If you’re a science fiction fan, however, the most fascinating section comes about a third of the way through. While listing the moon’s strategic advantages as an atomic missile base, Hubbard notes:

The first [factor] might be termed the “gravity gauge” comparable to the weather gauge so desirable in the days of sailing ships of the line…The gravity gauge is important in the ratio of six to one, in that a missile would have to travel with an initial velocity of six miles per second to leave Earth, but would only have to travel with a velocity of one mile per second to leave the Moon. Such a missile, leaving Earth, would have to go nine-tenths of the way to the Moon on power before the latter body would begin to pull it in by its own gravity, whereas it would only have to travel one-tenth of the distance to escape the Moon and begin to ride down on Earth gravity.

On the next page, a diagram by the artist Frank Tinsley is provided to illustrate this point, with a caption that was presumably written by Campbell:

Skippers of old-time men-o’-war early learned the advantage of the “weather gauge,” which meant being up-wind from the enemy. The Moon affords a similar “gravity gauge” over the Earth by reason of its weaker pull. A missile shot from Earth to Moon must work against the stronger Earth gravity to the point where the pulls balance, nine-tenths of the way out. Missiles fired from the Moon work against one-sixth the pull through one-tenth the total distance, and ride free the rest of the way. Also, the moon has no retarding blanket of atmosphere to slow the take-off.

If I had to guess, I’d say the concept itself probably came from Campbell, while the term “gravity gauge” sounds more like Hubbard, a nautical enthusiast who casually uses the term “weather gauge” in one of his later novels, Masters of Sleep. But this is pure speculation. (A few years later, incidentally, Hubbard would work on the script for the film Rocketship X-M, which includes the line: “Today, there is even the possibility that an unassailable base could be established on the moon to control world peace.”)

Yet if this all sounds a little familiar, it might be because you’ve read Robert A. Heinlein’s The Moon Is a Harsh Mistress, which was first published in 1966. The novel recounts the revolt of a lunar colony much like the one that Hubbard describes, and in a crucial plot point, its narrator quickly figures out the advantage that gravity provides, with the help of a computer named Mike: “Luna…has energy of position; she sits at top of gravity well eleven kilometers per second deep and kept from falling in by curb only two and a half km/s high. Mike knew that curb; daily he tossed grain freighters over it, let them slide downhill to Terra.” And they don’t need to use missiles at all. A hundred tons of anything, falling to earth from the moon, would generate six trillion joules of kinetic energy, or the equivalent of two-kiloton atomic bomb. All they have to do is throw rocks: “That terrible speed results from gravity well shaped by Terra’s mass, eighty times that of Luna, and made no real difference whether Mike pushed a missile gently over well curb or flipped it briskly. Was not muscle that counted but great depth of that well.” Heinlein had also mentioned this concept before—although, revealingly, not in Rocket Ship Galileo, which is actually about a Nazi military base on the moon, but was written before Hubbard’s piece was published. In late 1947, a few months after the article appeared, Heinlein began work on the juvenile novel Hayworth Hall, later retitled Space Cadet, in which we find the exchange:

“The spaceship is the perfect answer in a military sense to the atom bomb, and to germ warfare and weather warfare. It can deliver an attack that can’t be stopped—and it is utterly impossible to attack that spaceship from the surface of a planet.”

Matt nodded. “The gravity gauge.”

“Yes, the gravity gauge. Men on the surface of a planet are as helpless against men in spaceships as a man would be trying to conduct a rock-throwing fight from the bottom of a well. The man at the top of the well has gravity working for him.”

Heinlein first publicly made the connection to the moon at a meeting of the County Librarians’ Association in Los Angeles on May 5, 1948. (One of the other writers in attendance was Theodor Geisel, who would later become famous as Dr. Seuss.) A writeup in the Los Angeles Times quoted Heinlein as saying that the moon would make an ideal military base: “A power on the moon would have the gravity gauge. The moon has one-sixth the normal earth gravity. It would be like throwing rocks downhill.”

Over a decade and a half later, on February 24, 1965, Heinlein wrote in his typewritten notes for “a Luna-Terra novel,” which later became The Moon Is a Harsh Mistress: “Granite costs nothing and the power for a catapult [on the moon] is almost free….But the key point is that rocks are cheap and it’s downhill all the way.” Later that year, he returned to this point in a comment on his earlier essay “Pandora’s Box,” which was published in the collection Expanded Universe:

The disadvantage in being at the bottom of a deep “gravity well” is very great; gravity gauge will be as crucial in the coming years as wind gauge was in the days when sailing ships controlled empires. The nation that controls the Moon will control the Earth—but no one seems willing these days to speak that nasty fact out loud.

The italics are mine. Given the timing of its appearance in Space Cadet, Heinlein’s remarks on the subject in 1948, and his use of the term “wind gauge” in 1965, it seems clear that he read Hubbard’s “Fortress in the Sky” and was influenced by it while writing The Moon Is a Harsh Mistress. (The clincher, at least for me, is that Heinlein alludes to this concept in his screenplay for the film Destination Moon, which was based in part on Rocket Ship Galileo, but which includes an observation that isn’t in the original novel at all: “Shooting a rocket from the moon to the Earth is a great deal easier than shooting from the Earth to the moon, because it’s downhill almost all the way.”) We know for a fact that Heinlein read Air Trails. Campbell had approached him about writing an article for the magazine, and Heinlein wrote back to the editor on November 11, 1946: “Air Trails shows distinct improvement under your editing.” He was also friends with Hubbard, and there’s no question that he would have found this article interesting. The fact that the three men had all spent time together over the previous couple of years means that we can’t rule out the possibility that Heinlein came up with the notion first and passed it along to one or both of the others. But I think that the simplest explanation—that Heinlein borrowed the concept from Hubbard’s article—is the most likely one. It’s also worth noting that it doesn’t seem to have occurred to Hubbard or Campbell that the gravity well could be used to deliver anything other than missiles, and utilizing it to “throw rocks” is, frankly, a much better idea. This implies that Heinlein read the article, mentioned it in passing in Space Cadet, thought up a distinct improvement, and then set it aside until he was ready to use it. Hubbard’s official biographies refer to Heinlein as his “protégé,” which is a stretch even by their uncritical standards, but this is one case in which the arrow of influence genuinely appears to have run the other way—although it also speaks to Heinlein’s unique gifts. When it came to other writers, he usually had the weather gauge. And it’s a testament to his genius that even when he found himself downwind, he was still able to seize the advantage.

My secret book

Last week, without consciously noticing it, I passed a small but meaningful milestone—I’ve now published something on this blog every single day for the last seven years. On most weekdays, I devote at least an hour to writing a new post, and while I’ve occasionally fallen back on reruns or longer quotations to fill space, they account for a tiny minority of what appears here. Perhaps the time that I’ve spent blogging might have been more profitably used in other ways, but I doubt it. The discipline of producing a thousand words on a daily basis has been inherently constructive; it wakes me up in the morning; I’ve used it as a platform for ideas and opinions that probably wouldn’t have found a home anywhere else, now that the market for online freelancing has mostly dried up; it has provided me with a necessary emotional outlet as I continue to deal with the fallout from last year’s election; and above all else, it gives me a place where I can workshop material in plain sight that will end up being used elsewhere.

In particular, I’ve often used this blog as a kind of sandbox for elements of Astounding. (Here and there, entire phrases and sentences from these posts have ended up in the book itself, although nearly everything has been reworked substantially for publication.) I’ve also seized the opportunity that this venue affords to talk at length about subjects that won’t make it into print, and when I look back, I found that I’ve written the equivalent of a stealth book—amounting to something like sixty thousand words—in my posts on science fiction alone, most of which have appeared within the last two years. With this in mind, I’ve gone ahead and compiled many of these shorter essays on a single page, “Science fiction studies,” which you can see in the navigation bar to your right, and I’ll continue to update it going forward. It includes my reviews of classic stories; such longer pieces as “A Hawk From a Handsaw” and “The First Foundation”; and my original research on topics like L. Ron Hubbard’s lost rebuttal of dianetics and the origins of Heinlein’s The Moon is a Harsh Mistress. If you’re a science fiction fan, you might find it interesting. And best of all, it’s free.

Time for the stars

Last year, the screenwriter Terry Rossio, whose blog is the best online resource I’ve ever seen for advice on survival in Hollywood, posted a long post titled “Time Risk.” How long was it? If published, it could be sold as a short book of a hundred pages or so, and it would probably be acclaimed as one of the two or three most useful works ever written on the business of screenwriting. Rossio has spent more time than any successful writer since William Goldman on sharing his experiences in the industry, and this post is his masterpiece. (It received a flurry of attention earlier this year because of one unflattering anecdote about Johnny Depp, which is a classic instance of missing the forest for the trees.) I don’t know why Rossio invested so much effort into this essay, but I suspect that it was because he realized that he had stumbled across a single powerful idea that explained so much that was otherwise inexplicable, even cruel, about the life of a writer in the movies. It’s the fact that any investment of time presents a risk, which means that there’s an enormous incentive to transfer it to others—and the writer, for better or worse, is where the process ends. As Rossio puts it in an exchange with a producer whom he calls Jake:

At the point of sitting down to write, there was no way for my writer to know whether this particular story was going to work. She set forth on faith alone. So did thousands, tens of thousands of other writers around town, none of them knowing whether their stories would pan out, or even whether they could finish, or whether they could beat out the competition and have their work land on your desk…You [the producer] not only gain the value of the time my writer put at risk, but also the risk of every other writer who sat down to face the blank page around the same time, most of whom came up short. It’s like having everyone play the lotto, then you call the one person with the winning ticket. At the start it’s a giant risk pool, and all that collective risk is represented by this one winning screenplay.

This is a remarkable insight, and it applies to more than just screenwriting. Rossio doesn’t come out and say it, but he strongly implies there’s a fundamental cognitive divide between people who can work on more than one thing at a time and those who mostly can’t. It’s the difference between writers and agents, writers and book editors, writers and producers. The relationship doesn’t need to be adversarial, but it unquestionably creates different incentives, and it can result in situations in which the two players in the room aren’t even speaking the same language. It also lead to apparently paradoxical consequences, as when Rossio describes what he calls “Death by Sale”:

The day you sell your screenplay, you gain a small real chance it will be produced, at the same time almost guaranteeing that it will never be produced. Put another way, the same screenplay, unsold, has a much better chance of reaching the silver screen than it does when purchased by a studio…Selling a screenplay represents the exchange of all future positive outcomes of a project for a single, often unlikely, current scenario. You throw in with a particular set of players, at a particular time and place, with a particular set of restrictions and parameters.

This might sound crazy, but like everything else in Rossio’s post, it’s a logical extension of the principle in the title. If you’re a rational producer, you deal with time risk in the same way that a fund manager deals with investment risk—by diversifying your portfolio. A producer can have twenty or thirty projects in the hopper at any one time, in hopes that one winner will make up for all the losers. Writers don’t have this luxury, but they engage in a kind of simulation of it during the submission process. An unsold script has a virtual portfolio of potential buyers, one of whom might one day pay off. As soon as someone buys it, all those other possibilities disappear, and if it fails, the project might be tainted forever.

So how in the world do you deal with this? Rossio’s advice is simple, but it’s also the exact opposite of the reality that most writers face: “Spend as much time as you can making films, rather than trying to get films made.” Every strategy that he proposes comes down to knowing where to commit your time and how much of it to devote to a given situation. Take what he says about buyers and sellers:

First, understand when you’re in a room with fellow sellers, and temper your excitement accordingly. Second, commit less time risk to fellow sellers—and infinite time risk to an actual buyer. Third, understand the real value of investing time with fellow sellers. The value is not just an eventual project sale. The real value is building your team.

Rossio also advises writers to take cues from the industry players, notably producers, who have learned how to maximize the relationship between risk and return. (In financial terms, they’ve figured out an investment strategy with a good Sharpe ratio.) He quotes the producer Ram Bergman: “I told Rian [Johnson], I simply will not let you sell anything you write…The more we put it together, script, cast, producer, the more effectively we can dictate how it gets made.” If you can be a director or a novelist—or set up an animation studio in your garage, as Rossio repeatedly recommends—that’s even better. But even powerful people need to take what comes. Rossio devotes a considerable amount of space to the travails of his screenplay Déjà Vu, which set and still holds the record for the highest price ever paid for a spec script, only to run into rewrite problems and a reluctant director. When Rossio complained and suggested that they pull out, the producer Jerry Bruckheimer replied: “I have a director, a script, a star, and the studio giving me a green light. It’s not my job to not make movies.” And he was right.

I could keep quoting forever from this essay, which is loaded with throwaway insights that deserve a full post of their own. (Here’s one of my favorites: “Writers and producers often do the majority of their work with the cameras snug in their form-fitting foam cases. Actors get paid when cameras roll. And it’s only when cameras are rolling that power accumulates, and brands are established.” And another: “It’s amusing to listen to film critics assign responsibility for the content of a film exclusively to the screenwriter, the one person on the team with no final authority to insist on any particular story choice.”) But I’ll close with a story about a project in which I take an obvious interest—the adaptation of Robert A. Heinlein’s The Moon is a Harsh Mistress, on which Rossio worked while the rights to the novel were still held by DreamWorks. Here’s what happened:

The screenplay was completed about a month prior to the rights renewal date, and to be honest, we nailed it. The source material is of course fantastic, one of the top ten science fiction novels of all time, and the draft we turned in would have made an amazing film. The renewal date came and went, with no word from the studio, but a few days later we got a phone call. “We’re going to let the rights expire,” said the executive. “Did you not like the script?” we asked. “I’ll be honest with you,” said the executive, “We’ve been really busy. I’m sure the screenplay is fantastic, you guys always do good work. But we just didn’t have time to read it.”

Rossio concludes: “While this sounds insane from a business perspective—why option the book rights at all, on such a high profile project, or hire screenwriters to do an adaptation—it makes perfect sense from a time risk perspective. If you’re an executive, and you know the project doesn’t fit your production schedule, why expend the time risk to even read the screenplay?” He’s perfectly right, of course. But the real takeaway here is one that he leaves unspoken. In this situation, you don’t want to be Terry Rossio, or the producer, or even the executive on the other end of the phone. You want to be Heinlein.

The moon is a harsh fortress

In the May 1947 issue of the nonfiction magazine Air Trails and Science Frontiers, which was edited at the time by John W. Campbell, the cover story was an article titled “Fortress in the Sky.” Its author, credited as “Capt. B. A. Northrop,” argues that the existence of the atomic bomb has rendered the notion of a defensible land or naval base obsolete. The only truly impregnable military position, he writes, is the moon, which will soon be “conquered” by man: “It will probably be reached in five years and completed in ten. Its possessor will be supreme over all nations and peoples of Earth.” Northrop discusses the possible technologies that could be used for a moon landing, and he goes on to make a very peculiar claim:

Here and there throughout the world many men have been thinking about rockets for some time. I recall that in 1930, L. Ron Hubbard, a writer and engineer, developed and tested—but without fanfare—a rocket motor considerably superior to the V-2 instrument of propulsion and rather less complicated.

In fact, “Northrop” was none other than Hubbard himself, and his pseudonym, which is spelled “Northorp” elsewhere in the issue, was evidently inspired by Northrop Aircraft, a frequent presence in the magazine’s pages. (At the time that he was allegedly conducting rocket research in 1930, incidentally, Hubbard was just nineteen years old.) “Fortress in the Sky” was Hubbard’s first major publication after the war. He had been suffering from depression and, unusually, writer’s block, and before Campbell give him the assignment, he had contributed just a few poems and short articles to the Catalina Islander. As such, the piece was a turning point in his career, but as far as I know, it has never been reprinted in its entirety. Recently, however, I got my hands on a copy of the original issue of Air Trails in which it appeared, and I was able to read the whole thing. Aside from Hubbard’s gratuitous reference to himself, which Campbell either believed or was willing to let slide, it’s a surprisingly plausible piece of futuristic speculation. Campbell appears to have provided much of the science, and a lot of the material relating to a future moon colony seems to have been drawn directly from the editor’s unpublished novel The Moon is Hell.

If you’re a science fiction fan, however, the most fascinating section comes about a third of the way through. While listing the moon’s strategic advantages as an atomic missile base, Hubbard notes:

The first [factor] might be termed the “gravity gauge” comparable to the weather gauge so desirable in the days of sailing ships of the line…The gravity gauge is important in the ratio of six to one, in that a missile would have to travel with an initial velocity of six miles per second to leave Earth, but would only have to travel with a velocity of one mile per second to leave the Moon. Such a missile, leaving Earth, would have to go nine-tenths of the way to the Moon on power before the latter body would begin to pull it in by its own gravity, whereas it would only have to travel one-tenth of the distance to escape the Moon and begin to ride down on Earth gravity.

On the next page, a diagram is provided to illustrate this point, with a caption that was presumably written by Campbell:

Skippers of old-time men-o’-war early learned the advantage of the “weather gauge,” which meant being up-wind from the enemy. The Moon affords a similar “gravity gauge” over the Earth by reason of its weaker pull. A missile shot from Earth to Moon must work against the stronger Earth gravity to the point where the pulls balance, nine-tenths of the way out. Missiles fired from the Moon work against one-sixth the pull through one-tenth the total distance, and ride free the rest of the way. Also, the moon has no retarding blanket of atmosphere to slow the take-off.

If I had to guess, I’d say the concept itself probably came from Campbell, while the term “gravity gauge” sounds more like Hubbard, a nautical enthusiast who casually uses the term “weather gauge” in one of his later novels, Masters of Sleep. But this is pure speculation.

Yet if this all sounds a little familiar, it might be because you’ve read Robert A. Heinlein’s The Moon is a Harsh Mistress, which was first published in 1966. The novel recounts the revolt of a lunar colony much like the one that Hubbard describes, and in a crucial plot point, its narrator quickly figures out the advantage that gravity provides, with the help of a computer named Mike: “Luna…has energy of position; she sits at top of gravity well eleven kilometers per second deep and kept from falling in by curb only two and a half km/s high. Mike knew that curb; daily he tossed grain freighters over it, let them slide downhill to Terra.” And they don’t need to use missiles at all. A hundred tons of anything, falling to earth from the moon, would generate six trillion joules of kinetic energy, or the equivalent of two-kiloton atomic bomb. All they have to do is throw rocks: “That terrible speed results from gravity well shaped by Terra’s mass, eighty times that of Luna, and made no real difference whether Mike pushed a missile gently over well curb or flipped it briskly. Was not muscle that counted but great depth of that well.” Heinlein had also mentioned this concept before—although, revealingly, not in Rocket Ship Galileo, which is actually about a Nazi military base on the moon, but was written before Hubbard’s piece was published. In late 1947, a few months after the article appeared, Heinlein began work on the juvenile novel Hayworth Hall, later retitled Space Cadet, in which we find the exchange:

“The spaceship is the perfect answer in a military sense to the atom bomb, and to germ warfare and weather warfare. It can deliver an attack that can’t be stopped—and it is utterly impossible to attack that spaceship from the surface of a planet.”

Matt nodded. “The gravity gauge.”

“Yes, the gravity gauge. Men on the surface of a planet are as helpless against men in spaceships as a man would be trying to conduct a rock-throwing fight from the bottom of a well. The man at the top of the well has gravity working for him.”

Heinlein first publicly made the connection to the moon at a meeting of the County Librarians’ Association in Los Angeles on May 5, 1948. (One of the other writers in attendance, incidentally, was Theodor Geisel, who would later become famous as Dr. Seuss.) A writeup in the Los Angeles Times quoted Heinlein as saying that the moon would make an ideal military base: “A power on the moon would have the gravity gauge. The moon has one-sixth the normal earth gravity. It would be like throwing rocks downhill.”

Decades later, in 1965, Heinlein expanded on this point in a comment on his earlier essay “Pandora’s Box,” which was published in the collection Expanded Universe:

The disadvantage in being at the bottom of a deep “gravity well” is very great; gravity gauge will be as crucial in the coming years as wind gauge was in the days when sailing ships controlled empires. The nation that controls the Moon will control the Earth—but no one seems willing these days to speak that nasty fact out loud.

The italics are mine. Given the timing of its appearance in Space Cadet, Heinlein’s remarks on the subject in 1948, and his use of the term “wind gauge” in 1965, it seems clear that he read Hubbard’s “Fortress in the Sky” and was influenced by it while writing The Moon is a Harsh Mistress. We know for a fact that Heinlein read Air Trails. Campbell had approached him about writing an article for the magazine, and Heinlein wrote back to the editor on November 11, 1946: “Air Trails shows distinct improvement under your editing.” He was also friends with Hubbard, and there’s no question that he would have found this article intensely interesting. The fact that the three men had all spent time together over the previous couple of years means that we can’t rule out the possibility that Heinlein came up with the notion first and passed it along to one or both of the others. But I think that the simplest explanation—that Heinlein borrowed the concept from Hubbard’s article—is also the most likely one. It doesn’t seem to have occurred to Hubbard or Campbell that the gravity well could be used to deliver anything other than missiles, and utilizing it to “throw rocks” is, frankly, a much better idea. This implies that Heinlein read the article, mentioned it in passing in Space Cadet, thought up a distinct improvement, and then simply set it aside until he was ready to use it. (As far as I can tell, Hubbard was the first to use the term “gravity gauge.”) Hubbard’s official biographies refer to Heinlein as his “protégé,” which is a stretch even by their uncritical standards, but this is one case in which the direction of influence genuinely appears to have run the other way. As Heinlein wrote in Glory Road, using an image that he liked so much that he returned to it repeatedly: “That’s the way with writers; they’ll steal anything, file off the serial numbers, and claim it for their own.”