How far did the Whorl in Gene Wolfe’s Long/Short Sun books travel? The author leaves a few hints, although they are ultimately inconclusive. Fair warning: if you haven’t read the later novels in Wolfe’s Solar Cycle, this will be of little interest to you.
First, here’s a highly relevant passage from In Green’s Jungles. Silk/Horn discusses how long the Whorl’s journey was, and other characters try to determine how much time has elapsed on Urth since the unruined if rather decadent world remembered by one of the Whorl’s hibernating passengers:
“I only know that it has been about three hundred and fifty years since the Whorl left [Urth]. A bit more than three hundred and fifty, really–three hundred and fifty five, or some such figure.”
“There are seven thousand steps in a league…From what I’ve seen here, the streets are seventy or eighty double steps apart. Say a hundred to be safe. If Eco’s correct in his estimate, four leagues, they’ve been falling down for about two-thousand, five hundred years. If your son is, three-quarters of that should be one thousand, nine hundred, unless I’ve made an error”
[…]
“Old though these houses clearly are, I can’t believe they’re as old as that. No doubt the rate at which they’re abandoned was much higher at one time; but if we accept Cuoio’s estimate and the error is fifty percent, they’re still a thousand years old, roughly.”
So the Whorl traveled for about 350 years. However, it spent an unknown and possibly significant amount of time parked around the Short Sun — possibly as long as fifty years, about the time the other gods rebelled against Pas and Quetzal entered the Whorl. Somewhere between 1000 and 2500 years passed on Urth. Before I go further, I’d like to note something: Gene Wolfe’s Urth is nowhere near as ancient as Jack Vance’s Dying Earth, where the very mountains have worn down to hills.
Anyway: here’s The Relativistic Rocket, which explains in relatively simple terms how to calculate distance, velocity, and time in separate frames given acceleration and other values — which we have.
Now, it’s actually not certain that the scenes in Short Sun set on Urth are “contemporaneous” to the narrator’s present tense. If Mark Aramini’s “Green Urth” theory is correct, then these scenes take place in the distant past. If certain other assumptions hold, they may take place in the future.
Wolfe reveals relatively little about the technical specifications of the Whorl. It’s enormous — Horn/Silk estimates its inner surface is a third the size of Blue’s surface, and cylindrical. Rotation around the cylinder axis produces the “gravity” felt by the Whorl‘s inhabitants.
The Whorl’s bridge and engine are on opposite ends of the cylinder. With the engine in operation, the ship accelerates along the axis. Simple enough. Except: at no point does anyone notice lateral acceleration (which would cause the Whorl’s inhabitants to perceive East as being “uphill”). It’s possible that the Whorl made two high-acceleration maneuvers, although constant low acceleration makes more sense for efficiency and structural integrity reasons, not to mention lowering the peak output requirement for the drive. Besides, the Relativistic Rocket page assumes a constant acceleration!
Low acceleration also provides a simple explanation for the inhabitants not noticing any effects (aside from small anomalous “earthquakes”) with the engine burning. Poking around on PubMed (e.g.), there seems to be a consensus that .01m/s^2 is the absolute minimum acceleration a human can detect (.0010526 light years / year^2, by the way — the most convenient units for the rocket equations). However, most studies are looking at vibration or other oscillating movement rather than smooth, constant linear acceleration. It’s possible that under such conditions the perceptual threshold may be lower; this one notes the effect of acceleration profile on perceptual thresholds, with most subjects failing to detect accelerations of around .2m/s^2.
All of this is to say that if the Whorl accelerated along its axis at .01m/s^2, no one would notice using his own senses. Also, the ship accelerates halfway, then decelerates the second half.
Results
If the Whorl operated under continuous .01m/s^2 for a 300 year journey — positive acceleration during the first half, negative during the second — then it traveled just under 25 light years. Unfortunately, only about 301 years passed on Urth. The distance traveled is interesting given the speculation that Fomalhaut, aka α Piscis Austrini aka “The Fish’s Mouth” as a possible destination, as a character in New Sun claims to contact a large seagoing creature around this star. Fomalhaut is 25 light years away. (It’s also much brighter than Sol, although this can be explained away.)
Fomalhaut has a planet. And it’s been imaged in the visual spectrum!
If this scenario is true, then Silk/Horn’s visions of Urth actually take place far in the future.
At a far more robust .2m/s^2 acceleration (.0212 ly/y^2), the Whorl travels 1,040 light years in 300 ship-subjective years while 1,132 years elapse on Urth. Unlike in the low-acceleration example above — where the Whorl reaches only about 15% the speed of light — in this example of the Whorl asymptotically approaches lightspeed from Urth’s frame of reference. Traveling at this acceleration for 350 years allows the Whorl to travel over 1800 light years in around 1900 years from Urth’s frame. This means that Silk/Horn’s jaunt to Urth is contemporal (so far as such things can be said), and also that the major books of the Solar Cycle occur at about the same time.
Higher accelerations would be required for the Whorl to leave and return to Urth long after the coming of the New Sun. Constant acceleration at .35ly/y^2 (about .33m/s^2) would make the journey about 5,400 years from Urth’s frame.
Other Comments
The Whorl could be slightly conical in order to compensate for the effects of constant acceleration, although this would still create a problem once the engine stopped burning as it clearly did for years once in-system. Variable geometry strikes me as unlikely given the limited technical descriptions in the novels.
Intuitively, it seems possible to lower perceived acceleration by applying the acceleration vector slightly skewed to the ship’s axis. The component of engine acceleration aligned with centrifugal “gravity” would certainly be more difficult to notice than the orthogonal component. (This suggests an intriguing possibility where a starship engine applies acceleration perpendicular to the axis of rotation; inhabitants could be made to experience clear variations in “gravity” throughout the day).
The Whorl almost certainly had to rotate perpendicular to its axis when it reached the halfway point of its journey in order to apply negative acceleration — if the “passengers” felt anything, this was probably when it happened. Off-axis acceleration might simultaneously accomplish this (slowly) while also having the benefit mentioned above.
The low-acceleration scenario is most “plausible” although plausibility isn’t such a serious concern with these books; Wolfe isn’t Clarke. Faster-than-light communication and travel does exist in the Solar Cycle universe; however, there’s probably only one FTL ship that has ever (will ever?) be built. On the other hand, the Whorl might be that ship at an earlier point than seen in Urth of the New Sun. Obviously if the Whorl is capable of FTL travel all bets are off on where it ended up or how long it took from Urth’s perspective.
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