Well, while I’m still riding the Internet-fame explosion from my last post, I’m just going to throw out there that I think this is much cooler:
Anyway, on my new To Do list are:
I had a discussion recently with friends about the various depictions of space combat in science fiction movies, TV shows, and books. We have the fighter-plane engagements of Star Wars, the subdued, two-dimensional naval combat in Star Trek, the Newtonian planes of Battlestar Galactica, the staggeringly furious energy exchanges of the combat wasps in Peter Hamilton’s books, and the use of antimatter rocket engines themselves as weapons in other sci-fi. But suppose we get out there, go terraform Mars, and the Martian colonists actually revolt. Or suppose we encounter hostile aliens. How would space combat actually go?
First, let me point out something that Ender’s Game got right and something it got wrong. What it got right is the essentially three-dimensional nature of space combat, and how that would be fundamentally different from land, sea, and air combat. In principle, yes, your enemy could come at you from any direction at all. In practice, though, the Buggers are going to do no such thing. At least, not until someone invents an FTL drive, and we can actually pop our battle fleets into existence anywhere near our enemies. The marauding space fleets are going to be governed by orbit dynamics – not just of their own ships in orbit around planets and suns, but those planets’ orbits. For the same reason that we have Space Shuttle launch delays, we’ll be able to tell exactly what trajectories our enemies could take between planets: the launch window. At any given point in time, there are only so many routes from here to Mars that will leave our imperialist forces enough fuel and energy to put down the colonists’ revolt. So, it would actually make sense to build space defense platforms in certain orbits, to point high-power radar-reflection surveillance satellites at certain empty reaches of space, or even to mine parts of the void. It also means that strategy is not as hopeless when we finally get to the Bugger homeworld: the enemy ships will be concentrated into certain orbits, leaving some avenues of attack guarded and some open. (Of course, once our ships maneuver towards those unguarded orbits, they will be easily observed – and potentially countered.)
Now, let’s talk technology.
What are a long car trip and hosting boring virtual office hours good for? Thinking about how our science and society would be different if the Earth had rings. Science fiction writers, take note.
As I was writing that earlier post, my officemates and I got into a discussion about some of the implications to (at least Western) science and philosophy of such a ring system. One of them suggested that the rings, which would be mostly aligned with the Earth’s equator but would precess with the Moon, would be quite obviously separate from both the purported “celestial spheres” and the Earth, so maybe the ancient Greeks could have dispensed with that destructive Platonic notion much earlier in the history of Western science.
I got thinking and realized that, in addition to their own dynamics, the rings would have a few other obvious effects on the science of those cultures at high enough latitudes to get a good view of the ring system, without seeing them edge-on.
First, the shadows of the Earth and Moon would be visible on the rings. These shadows would be shaped like portions of circles, and would vary in size and shape with time of day, month, and year. From observations of these shadows, easily possible with the naked eye, the Greeks, Egyptians, and Chinese ought to have been able to show without any doubt that the Earth and Moon are spherical. They may have been able to deduce the position of the Earth’s spin axis and axial tilt by comparing the shape of the rings and the shadows on them to the time to year. (These experiments could be quite simple: make a stiff, lightweight circle or hoop, hold it at arm’s length at night, move the circle in and out and tilt it back and forth until its edges line up with the shadow on the ring. Add a little simple geometry, and BAM: I would have just found the axial tilt of the Earth.) They should also have provided some kind of estimate of the distance to the Moon, as observers could compare the size of the Moon with the size of its shadow. And comparing the Earth’s shadow on the rings to the positions of the background stars would have given the ancients an incredibly accurate nighttime clock.
Second, and perhaps most importantly of all, the rings would vary radially in opacity. This would make them beautiful to behold, yes, but it would also give naked-eye astronomers an absolute scale for photometry. Annuli of the rings would block out the light from some stars, but not others. The thicker rings would block more stars than thinner rings, giving a gradation of occultation scales. By comparing which rings block out which stars, observers would have been able to make statements about the relative brightness of the stars with a degree of precision unknown until Christian Huygens arrived on the scene – even surpassing the precision of that experiment. Still more exciting, if the ring was able to occult the Sun, that same method could have been used to measure the light output of the Sun. Now, coupled with the insight that the Sun is a star and a crude estimate of the Earth-Sun distance, an observer should have been able to deduce from naked-eye observations approximate distances to the stars.
I’ll say that again: If the Earth had rings, the ancient Greeks, Chinese, and Egyptians might have had a sense of the scale of the Cosmos. The Romans and Indians might have known what a parsec is.
Furthermore, this photometry could have been used on the visible planets as well as stars. That would have told the ancient astronomers that Mercury, Venus, Mars, Jupiter, and Saturn were a lot closer to the Earth than the stars. In fact, if the ancient photometers tracked the brightness (and, therefore, distance from the Earth) of each planet over time, they would have noticed something interesting: the planets move in circles about a point that is not located within the body of the Earth, but is rather in the Sun. The heliocentric model for the Solar System would have been adopted in ancient times.
Now, knowing that the planets go around the Sun, and the stars are all rather a long way away from the Sun and from each other, ancient astronomers might have realized that other stars could have planets just like the Sun does. Think about what that idea might have done to Western philosophy and religion in their formative years: other Earths? In the sky?! Going around other Suns?
Here’s a possibility I’m not sure about: if the ring was thick enough, it’s possible that it might dim the Sun enough that an observer could safely look at our star with their naked eyes. If so, then sunspots might have been visible to the ancient civilizations. In that case, they might have known that the Sun is not a perfect glowing sphere, and that it rotates. They might have known about the 11-year solar cycle.
And then, imagine what could have happened once Galileo stormed onto the scene with his telescope. When he looked at Saturn, he would have known exactly what he was looking at. “Ears” indeed! By watching Saturn’s rings wax and wane with each Saturnian year, he would have identified the orientation of Saturn’s ringplane to the ecliptic. Knowing that Saturn has rings would have told scientists that Earth’s features are not unique to our own planet.
Early telescopes might have been powerful enough to identify some of the larger rocky chunks making up the Terrestrial rings. Observing their orbits at different radii within the ring could have lent a lot more data to scientists like Kepler and Newton, who were trying to figure out what forces kept the planets in orbit. Armed with data on the orbits of ring particles and Kepler’s Laws, early scientists might have been able to get a pretty good estimate for the mass of the Earth and fix the Earth-Sun and Earth-Moon distances pretty accurately.
I’m thinking that, given how great a dynamical laboratory the Saturnian ring system is, rings around the Earth would have allowed the progress of science to advance much more rapidly, as the rings would provide a precise tool for measurements of position, time, and distance of celestial bodies. If the laws governing those bodies had been puzzled out, say, before Christianity dominated Europe, imagine what society would have resulted….
One of the most majestic and awe-inspiring structures in the Solar System is the Saturnian ring system. My sister sent me this video, which imagines what that same ring system would look like around the Earth – and what it would look like in our sky when viewed from the surface. The result is pretty wonderful to imagine:
However, sciency guy that I am, my very first thought on seeing this video translocate the Saturnian rings around the planet Earth was, “Hey! The Cassini Division’s still there!”
The significance of that gap between Saturn’s A and B rings is that it’s one of the most clear markers of the interaction between Saturn’s moons and the rings. All of the various gaps and spaces between the rings come from orbital resonances between the rings particles and various moons. If, for example, a ring particle orbits twice around Saturn for every orbit of the moon Mimas, then Mimas will pump energy into the orbiting particle and it will move into a higher-energy orbit with a larger semimajor axis – thus clearing a space in the rings (for the 2:1 Mimas resonance, the Huygens Gap).
That made me wonder just what a Terrestrial ring system would look like. We have only one moon, but it’s incredibly massive compared to the Earth. In fact, the Earth/Moon system has the largest moon-to-planet size ratio, by any measure, in the Solar System. (Sorry, Pluto/Charon!) Our single moon compared to Saturn’s dozens means that our ring system would be much more orderly, with many fewer and much more regularly spaced gaps. However, the huge size of the Moon means that the weaker resonances would have a stronger effect. The Saturnian rings show evidence of weak resonances all the way out to the double digits – like, say, 9:14 resonances – so I’d argue that weaker-still resonances would still be visible in the Earth-Moon system.
So, I wrote a little Matlab script. Clearly, this was more important today than getting my work done.
As in that video, I placed the outer limit of my hypothetical Terrestrial ring system at the Roche Limit, ~2.86 Earth radii from the center of the orbit. This is the innermost limit at which a fluid satellite could hold itself together, by its own self-gravity, against being ripped apart by tidal forces fromt he Earth. Outside this limit, the rings could start to aggregate together into moonlets. I bounded the inside of the ring at 1.59 Earth radii on the inside, coinciding with the definition of the outer limit of the exosphere. Even in low Earth orbit, atmospheric drag would eventually cause ring particles to fall into the deeper atmosphere, so I felt this would be a good value to pick to ensure that the ring would have a long enough lifetime to persist for millions or billions of years.
I started my script with a ring opacity of 100% at all radii and put a fuzzy boundary on the ring system at either end. Then I had Matlab calculate the orbital radii of every ring-Moon resonance from 1:1 to 100:100 using Kepler’s Third Law. For each resonant semimajor axis that fell between the Roche limit and drag limit, I subtracted a narrow Gaussian from the ring opacity as a function of radius. Since my big 100×100 matrix of resonances had some repeats (like 3:4 and 6:8), several of these Gaussian functions would add together and decrease the ring opacity further, crudely estimating the effect of stronger resonances. Finally, I lowered the albedo and tweaked the color of the rings from what they are at Saturn, to make them look more like they’re made of rock rather than ice, which sublimes away in space at our distance from the Sun. This is what I got:
The rings in this image go around the Earth’s equator, inclined 22 degrees with respect to the field of view because of the Earth’s obliquity. Sadly, my Matlab graphics cannot handle casting the shadow of the rings onto the Earth, and I had to Photoshop in the shadow of Earth on the rings for effect. Still, pretty cool looking. Here’s the punchline: the ring system viewed from directly above the ring plane, with a white background so you can easily see the pattern:
You can see that the lunar resonances don’t start to have a major effect until about halfway through the ring system. This pattern, and the coloration, are mainly what that video was missing.
Of course, I don’t have the complete story, either. Again, our Moon is huge and that will do even more to the rings’ shape. The Moon’s orbit is inclined 5 degrees to the Earth’s equator, so the tidal torques from the Moon should make the rings precess around the Earth with a one-month period. (That precession would lag the Moon, so we wouldn’t always see the rings piercing the Moon in our night sky.) In addition, I suspect that the lunar tides would twist the rings a bit, pulling them into a spoked configuration like Cassini has seen at Saturn.
It’s definitely fun to think about how these rings would look from vantage points on the Earth. Actually, since my ring system starts well above low Earth orbit, I have to wonder what they would look like to spacewalking astronauts…
Recently, ABC’s new series “Defying Gravity,” starring Ron Livingston of “Office Space” fame, has caught my attention. All the current episodes (1-6 as of this writing) are available on Hulu. I think it’s been interesting enough for me to keep following it. I have a couple points of interest about the show:
First, I am impressed with how much the show’s creators, writers, and artists have paid attention to the probable operation of a near-future space program. Of course, the show makes the usual sci-fi physics gaffes. “Defying Gravity” goes to unusual lengths to rationalize shooting a space series in terrestrial gravity (“centrifuge” is a fine explanation for me, “magnetic nanospray” and “electrostatic nanofibers,” eh…not so much – novel attempt, though), there are silly numerical issues like pressurizing a spacesuit to 5 atm (never mind the entirely ridiculous idea of a human-rated “Venus suit”), and this show, like almost every other sci-fi, doesn’t come close to getting the physics of tethers right. However, I’ve just come from a summer at NASA Johnson Space Center, and I am incredibly impressed with this show’s depiction of mission control, the MCC/spacecraft communications, space jargon, uniforms and suits, the art of the spacecraft interior, potentially realizable space technology, and the fact that they do depict zero gravity with much greater frequency than most other sci-fi. From my (albeit limited, but still quite extensive compared to the general public) exposure to the astronaut office at JSC, it seems to me that this show’s depiction of the Astronaut Office and the experience of being an astronaut is about as spot-on as it could be.
Second is the point that this series was apparently, according to Wikipedia, pitched to the networks as “Grey’s Anatomy in space.” I couldn’t care less about the soap-opera-y who’s-sleeping-with-who dynamics of a show like that, but there’s plenty more going on that make “Defying Gravity’s” characters fun to watch. In contrast to shows like “Star Trek: (pick your favorite)” – which highlights some aspect of human nature or morality by having our intrepid characters encounter a planet peopled by a species that embodies a single, streotypical trait – and “Battlestar Galactica” – which explores the interactions between its characters against the backdrop of larger questions about what it means to be free, human, just, etc. – “Defying Gravity” is a show almost purely about the interactions between the characters and how their past experiences impact those relationships. Certainly, Trek and BSG include those elements, but “Defying Gravity” removes most of the external influences on the characters. (Not all, of course, because external stressors are great for getting characters to look at themselves or their companions.) Now, using a long-duration spaceflight with astronauts cooped up in close quarters, millions of miles from assistance, communication, or rescue to set up a character study is absolutely nothing new to science fiction in general (see, e.g., Poul Anderson’s Starfarers and Tau Zero, many of Ben Bova’s novels, and the beginning of Kim Stanley Robinson’s Mars saga) – but it is new to mainstream movie and television sci-fi. Fortunately, these are pretty interesting characters, they seem like three-dimensional people, and the show so far has been about how they each come to terms with their own past at the beginning of their six-year voyage. I definitely like seeing the space program as the setup for such drama. Which brings me to…
Last, and certainly not least, this show is extremely pro-space. (Just listen to Maddox Donner’s voiceover monologue at the close of the pilot episode!) I love what it says about viewing audiences: the mainstream media is comfortable with, and thinks the public is comfortable with, a relationship drama set on a spacecraft against a background of mostly-real physics and operations. It helps to make astronauts feel not just like heros, but like real people. As if – gasp – we could grow up wanting to be an astronaut and hold on to that dream even if we don’t picture ourselves as the perfectly polished John Glenn or Neil Armstrong type. We can be good at things, bad at things, have our own flaws, and still go become astronauts, mission controllers, and engineers. That is a message that I really, really want to get out into the public. If we can get the more adult audiences likely to watch “Defying Gravity” thinking that it’s okay to keep dreaming to be an astronaut, then we’ll raise a generation of kids who are willing to hold on to that dream and become the scientists, engineers, and space explorers of the future. Augustine Commission, NASA management, and politicians, please take note!
I just saw Sam Rockwell in “Moon” today. Wow, what a movie.
The two-second, non-spoiler plot outline is that Rockwell plays Sam Bell, a blue-collar astronaut who works in a one-man mining outpost on the far side of the moon with no live communications to anyone. He’s about to end his three-year contract when, after an accident, he goes out onto the surface and finds a man who happens to look and act exactly like Sam Bell. Now they have to figure out what’s going on.
The movie is a tour de force for Rockwell’s acting, since he spends most of the time playing against himself. The obvious effects aside, he handles the dialog naturally enough that I really forgot that he had to play the two separately – he was really acting with himself. It’s also incredible that he was able to bring out the subtle differences between the Sam Bell who has been in the outpost for three years and the newcomer Sam Bell. There were some physical differences between the two characters, but sometimes it was hard to tell which was which based on visual impression alone. Yet it was always easy to tell one from the other as they interacted. Rockwell really put a lot of ordinary-guy-ness into the character, and put a lot of thought into the effects of isolation and delayed communication. They way his characters handle the mystery they’ve been thrown into is simulatneously heartbreaking and triumphant.
Now I have to talk a bit about the science fiction in this movie. This is sci-fi in its purest form: science and fiction, with a strong grounding in both solid scientific concepts and in dramatic and chracter development. The science is, in fact, not too far removed from our own – perhaps fifty years off – and it looks like everything grew out of the space program as we know it today. The movie goes to show just how well adhering to real science instead of going for cheesy effects, laser sounds in space, and ridiculous robots can move the drama along. Sam Bell eats freeze-dried, reconstituted astronaut food. He has to wear a familiar white spacesuit. His lunar outpost is all form-built white surfaces, but he still uses sticky notes. He has to exercise to keep his muscle tone. And all these things contribute to the frustrations he experiences in his lonely three-year stay.
However, there is only one bit of science that is absolutely necessary to move the plot along – the explanation for Sam’s duplicate. I got the feeling that this sort of story could have happened in many different places or times, and the science fiction is only a vehicle to move the plot along and let us watch these characters deal with their situation. I definitely appreciated that – it’s about time sci-fi broke out of the rut it’s been in, where it’s all about action-adventure and CG explosions.
(Just FYI: Yeah, they really could have done a better job making 1/6 gee gravity apparent. Yeah, there are some sounds in space – but at least they’re muted, BSG-style. And yeah, the rover design is kind of poor for the Moon. But those are about the only scientific gripes I can put down, and look how tiny and insignificant they are!)
This is also a very smart movie. The film shows you enough information to show you what’s going on, and by the end, I understood all that had happened. But it doesn’t tell you straight up what’s happening. There are no scenes where a character explains to another character what just happened or why they are in the situation they are. Instead, we see Sam figuring things out, and we figure things out along with him. It felt like a very participatory movie to me, and I enjoyed that aspect of it a great deal.
This is a wonderful sci-fi movie. It’s definitely an homage to some of the classics, most obviously the spaceship scenes in 2001 (you know, the best part of that movie), and an homage to the days of the classic Heinlein-style sci-fi that followed on the heels of real space exploration; it brings back the feel of when people followed both space movies and space news. And I’m all for that.
For what it’s worth, I hope this movie gets a much bigger exposure in national release. I will also secretly hope for an Oscar nod for Sam Rockwell, because I think the critics have long overlooked SF as a genre in which great acting and writing can happen.
A loner on a skiff, drifting through the Burial Grounds in search of ancient derelicts to salvage, reveals a secret of Galactic importance. This story serves as exposition for the Cathedral Galaxy universe.
I released a significant re-write of this story on 18 Jun 22.
The population of a planet responds to the appearance of strange alien life-forms.
A government agent pursues a terrorist through the technological jungle of the future Earth – but her mission has become personal.
The beach; late on a cool, tropical night. As the moon inches above the horizon of the sea, an elder tells legends to young children.