“Memory” by Linda Nagata

The first time I read Memory by Linda Nagata I was ambivalent, it had some interesting ideas, but the plot was a bit… odd.  This time around it was a more entertaining read, and it speaks to a theme I’ve been thinking about for a few years now: multi-decade space ship journeys vs software bugs.

Spoiler Alert

Kobolds are insect like things, ranging in size of a grain of rice to as big as your thumb, that can make stuff, either by tapping the “silver” or scavenging from the atmostphere or their immediate environment (e.g. metallophores).  They have configuration codes (the description is suspiciously like damn small DIP switches) to have each kind do more than one thing.  You can also combine multiple kobolds in a “circle” (sphere) to make other, more complex kobolds.

At some point we are told that the number of kobolds in a kobold circle is always a number in the Pythagorean series.  She actually means the Fibonacci series.  Not a show stopper, but it did grate a few times.

The “players” (people) all know they live on a ringworld.  But not at the Dyson ring size (1AU).  Instead we are told the ring is 100K miles in diameter.  The ring is spinning in the plane of the ecliptic, and circling the sun.  The ring rotation is what causes day and night (unlike Larry Niven‘s Ringworld, that needed shadow panels to make day and night).

We aren’t told the width of the ring, so I can’t tell if the “daytime” is perpetually in the penumbra of the “night time” side, or if only some of it would be.  This would be noticeable to the people in the story.

The thing that really grates is that the stated size of the ring world is too small.  A little google-foo reveals that “centripetal acceleration” is

a = v^2 / r

and assuming 1g on the surface, this gives one complete rotation every 5 hours.  Oops.  So instead I solved for the radius, which gives r=2.4e6 km (1.5e6 miles) for 1g and 24 hour rotation.  That means, instead of Nagata’s 100,000 mile diameter ring, we actually have a 3,000,000 mile diameter ring.

One of the odd bits is that, while the people know they are on a ring, they don’t know what the “Bow of Heaven” is. They know it is always at the zenith. It is, of course, the day time side of the ring, as seen from the night time side.  That they had both facts, but hadn’t made the connection, seemed a bit weird.

A central “character” of the book is the “silver” that rises each night, and can dissolve structures and people, but leaves plants and most geography alone.  It can also make structures, usually out of context, and called “follies” in the book.  Occasionally it also makes some of the geography, including replenishing seams of minerals for mining, but occasionally “lettered stone” which has the (incomplete) text of previously dissolved books, rather than fossils.  The “silver” is actually a nanite soup.

The fundamental plot of the book (and this is the biggest spoiler) is that the software that runs the world, and in particular runs the nanites, is buggy.  It isn’t supposed to dissolve people, and it isn’t supposed to rise so high every night that a significant proportion of the population is at risk.  In the end, the faulty program is bound to the avatar of the woman (“goddess”) who built the world, but deliberately messed with by [another dead character] when they had a falling out over 10,000 years ago.  Killing the avatar isn’t enough, it will just be made again promptly by the nanites, inconveniently far away.  The fix is to delete the program, which requires a trip to the control room (“goddess’ temple”) and deleting the goddess.

Armed with this knowledge, the second reading of the book is much more enjoyable, and the plot stops being quite so hidden and mysterious, and instead becomes an adventure story set in a fairly limited area.

Another weirdness is that the kobold circle “mirror of the other self” allows a person to see their ideal mate (due to some weird genetic hoo-har when the world was made).  Except they are actually full-duplex teleport portals.  Rather than walking around the ring until (if) you meet your true love, why not just use one of these portals and skip all the wandering?  Odd.

A small geometry problem in the book is when one of the characters is “looking down at stars”, that is, over the wall of the ringworld, from a high mountain.  But wouldn’t that imply that the mountain the character is standing on is above the atmosphere?

What does any of this have to do with multi-decade space ship journeys?  Well, say you are on a 20 year trip to Proxima Centauri, and after 10 years, your life support system manifests a bug and isn’t working too well.  So you send an email asking for a bug fix, but that will take 2 years to arrive, and another 2.5 years to get back to you.  Except that the reply has no bug fix, instead it says that your support contract has lapsed, and do you want to pay full price for the latest version?  So now you have been surviving with a jerry-rigged life support system for 4.5 years, do you want to do that loop again?  Me neither.

It seems to me that any space ship going on a multi-decade slowboat journey must, as a matter of course, take its source code with it, and software engineers capable of finding and fixing such bugs.  It also implies having a way to verify system software, before deploying to the rest of the crew/ship.  Ditto every other system with any software in it (life support, hydroponics, propulsion, navigation, communications, automatic doors, the “auto-doc”, the microwave, even the kitchen range hood).   For the only discussion of this I have ever seen in SF, see A Fire Upon the Deep by Vernor Vinge.

The problem underlying the plot of Nagata’s “Memory” is that the people of the ring have no access to the software that keeps them alive.  They run the risk that one day the nanites (“silver”) would rise so high that it deleted all the people, leaving the ring a “Mary Celeste” artifact.