Putting the science in fiction - Dan Koboldt, Chuck Wendig 2018
Aging properties
Earth and other planets. Yes, Pluto counts!
By Gwen C. Katz
So there’s an episode of Star Trek where Data travels three hundred years back in time and his head gets cut off and later they find his head and reattach it to his modern body and get him working again. (Star Trek plots sound weird when you summarize them.) But wait. His head is three hundred years old. Are we supposed to believe that three-hundred-year-old electronics will still function perfectly? Okay, maybe Data’s positronic brain is made of advanced future materials that don’t degrade.
How about the Doctor Who episode where Rory is replaced by a plastic Roman centurion and spends two thousand years guarding the Pandorica? (Doctor Who plots sound really weird when you summarize them.) We’re explicitly told that Rory is made of regular plastic, and if you have any hand-me-down toys from your parents, you know that most plastic gets yellow and brittle within a few decades. But two-thousand-year-old Rory is still fully functional.
One of the most common scientific errors in epic science fiction and fantasy is failure to consider the effects of aging. These genres have time scales covering hundreds or thousands of years, and often important artifacts are passed down through that time. Inevitably, these artifacts are intact, shiny, and ready to use. In real life, however, very few objects survive for thousands of years, and those that do are usually rusty, crumbling, or otherwise in poor condition.
How aging works
The main chemical reaction that causes materials to age is oxidation, and the main culprits are oxygen, water, and light. Let’s have a look at some common materials and how these factors affect them.
Metal is well known for its tendency to oxidize (rust) when wet. But individual metals oxidize in different ways. When iron and its alloys oxidize, the rust flakes off, revealing a new surface that can continue to oxidize, allowing the object to eventually rust away completely unless the surface is protected by paint or another finish. There’s not much hope for the fragments of Isildur’s sword after three thousand years.
When copper and bronze oxidize, however, the oxidation sticks to the surface, forming an attractive patina that protects the object from further damage. Objects like the Statue of Liberty can therefore last for centuries in good condition. Bronze statues age so well that most of them were lost not through aging, but through deliberate destruction when they were melted down to make cannonballs or new statues. Surviving artifacts can, however, be distinguished from new objects by the patina.
Gold does not oxidize under normal circumstances. An ancient gold artifact can indeed remain in shiny, like-new condition, although if it’s been handled, the soft metal will show a lot of wear.
Paper is subject to many kinds of environmental damage, including fire, mold, and insects, and everyone is familiar with the yellowed, brittle texture of old paper. But truly old paper might not age as poorly as you expect. The yellowing is caused by lignin, a chemical present in wood pulp that can turn acidic in the presence of light, and wood pulp only became a ubiquitous papermaking material in the late nineteenth century. Before that, most paper was made of recycled cloth fibers, which did not contain lignin. Depending on the papermaking process, ancient books could last a very long time if given the right care.
Plastics are the least stable common material. This may surprise you if you’ve heard the old factoid about a plastic bag taking five hundred years to break down in a landfill. While it’s true that plastic takes an incredibly long time to completely decompose, it doesn’t take very long at all for it to stop being good plastic. Different types of plastic have different chemical compositions, but they’re all made of polymers, which are vulnerable to various kinds of degradation. Sunlight can create free radicals that age polymers much like they age your skin. Long polymer chains can break into shorter molecules or become linked to each other, making the plastic brittle. Poor Rory would probably break at his age.
One of the most dramatic examples of aging plastic is cellulose acetate, the material film is made of. Cellulose acetate quickly degrades, releasing acetic acid, which gives the film a strong vinegar smell and causes the degradation to accelerate. As it degrades, the film shrinks, buckles, and becomes fragile enough to shatter when handled. This process can begin within a decade, and it’s irreversible.
Delaying aging
To protect an object from aging, the first step is selecting the right materials and preparing them correctly. Acid-free paper circumvents the problem of yellowing. Painted or varnished metal is sealed away from oxygen and will not corrode. Glass and ceramics, while fragile, are made of stable minerals that generally don’t degrade over time.
Favorable conditions can also do a great deal to prevent aging damage. Egyptian tombs preserve artifacts incredibly well because they are shielded from light, water, and (if the tomb is fully sealed) oxygen. Bogs provide a dark, oxygen-free environment that preserves organic materials well. A spaceship traveling through a vacuum with no exposure to air or water would be protected from most aging effects, at least on the outside.
But beyond damage caused by external factors, there’s another principle called inherent vice, which refers to materials that, by their very nature, are unstable and don’t last. For instance, magnetic storage like cassettes and VHS tapes will gradually lose their charge and be erased over time, even if they’re stored perfectly—and playing a tape causes it to be erased faster. Sorry, Star-Lord, there’s not much chance that you’re still listening to that cassette from 1988.
Once aging damage occurs, it’s usually difficult to do much about it, but an entire field, art conservation, is dedicated to preserving objects and restoring them if they’ve been damaged. Sometimes striking results are possible.
The ubiquitous lead white paint used before the twentieth century was not only toxic but unstable. Its white pigment, lead carbonate, decomposes into black lead sulfide in the presence of hydrogen sulfide—a gas released by Victorian gas lamps. Illuminated manuscripts from Victorian libraries ended up with a garish “photo negative” look because the brightest white areas had turned black. However, treatment with ordinary hydrogen peroxide oxidizes the lead sulfide to lead sulfate, which is white and stable. Badly degraded paintings have been beautifully restored to their original appearance by this method.
If your space opera or fantasy epic spans hundreds of years, think about the condition everything is in. Are things worn out or broken? Do important artifacts need to be carefully stored and handled? Have things been destroyed intentionally or through neglect?
Just don’t expect me to believe that a steel sword without a speck of rust on it is three thousand years old.