Are you a science fiction author?
Would you like to prevent angry rants by an obscure book reviewer based in Ontario? Here are some common errors in worldbuilding that I loathe and abhor.
Please avoid from now on. TIA. (Thanks In Advance.)
The stars in our part of the Milky Way (with some notable exceptions) tend to be headed in the same general direction at the same general speed, but not exactly in the same direction and not exactly at the same speed. Over time, the distances between stars change. Today, our closest known neighbour is Alpha Centauri at 4.3 light years. 70,000 years ago, it was Scholz’s Star at as little as 0.6 light years.
This error does not come up often. It’s a timescale thing: stars move on a scale marked in increments like time elapsed since the invention of beer. That is a lot slower than plot, for the most part, unless your plot covers thousands of years. Still, if your novel is set in the Solar System a billion years from now, don’t namecheck Alpha Centauri as Sol’s closest neighbor.
Wil McCarthy’s The Fall of Sirius is set in part far enough in the future that the distribution of the local stars would have changed measurably. As I recall, his map of the near stars actually took that into account.
Massive Worlds’ Mass Is Useful
There’s an old saying in SF that “Belters learn to avoid gravity wells,” often said by Belters equipped with hilariously overpowered fusion rockets delivering delta-vees hundreds of times greater than any planet’s escape velocity. Under reasonable propulsion regimes, planetary gravity can be a useful resource. Flybys can provide free changes in velocity, while the famous Oberth maneuver allows rockets to get more oomph out of a given quantity of rocket fuel than a simple mass-ratio-based calculation would indicate. The bigger the world, the greater the potential benefit.
If you’ve wondered why so many space probes en route to somewhere other than Jupiter make a point of passing through that system—this is why. Much the same explanation is behind MESSENGER’s multiple flybys of Venus and Earth on the way to Mercury. Judicious exploitation of massive objects opens access to parts of the Solar System not otherwise easily accessible, and can provide substantial reaction-mass savings.
That sounds a bit dull but think of it this way: there are a limited number of massive bodies that provide significant potential for flybys and Oberth maneuvers. Limited resources mean the potential for conflict over control of them. Conflict means plot!
The next item is a ‘Blame Heinlein’ item so here’s credit where credit is due: Robert Heinlein’s The Rolling Stones is one of very few books I can think of that exploits the Oberth maneuver for plotty goodness when the Stones leave the Earth-Moon system. M. J. Locke’s Up Against It provides an example of an author using Jupiter (off-stage, in a minor, worldbuilding context) as a source of free delta-v .
The Utility of Orbital Kinetic Weapons Is Often Grossly Overstated
The Moon is a Harsh Mistress painted a vivid picture of an Earth battered by cargo canisters lobbed from the Moon. Alas, if one does the math, one notices that some things simply cannot work the way Heinlein has them work.
As long as the projectile collides with its target faster than about 5.5 km/s, the energies per unit mass involved will be as great or greater than chemical explosives. They will not, however, approach the 25 TJ/kg provided by our friend the thermonuclear weapon, not until one reaches velocities up around 7,000 km/s. Such speeds are an order of magnitude faster than any orbital velocities found in our solar system. Kinetic weapons working at orbital velocities should be viewed as cousins of the World War II-era Grand Slam earthquake bomb, perhaps, not nukes.
But what about the dinosaurs, you ask? Offing the dinosaurs involved dropping an object the size of a mountain on the Earth. There are objects the size of mountains available to drop on Earth…but it’s important to note that it would be hard to do this in any stealthy way. Which makes nonsense of some events in the Expanse series, and brings us to …
Stealth Is Difficult To Do in Space
A lot of energy is needed to move from one orbit to another. Rocket exhaust is bright. It is much brighter than the rest of the universe. Detection systems are getting better all the time. If asteroid droppers and droppees have comparable tech (and don’t have access to rules-breaking super-science, such as the ability to duck through a neighbouring universe ), the fact that conventional rockets can be seen by conventional telescopes as far out as Pluto means sneaking up on the other guy is going to be tricky. Throwing mountains at them without anyone noticing would be even more so.
John Lumpkin’s The Human Reach series embraces this. When ships are visible AU (and weeks) away, both sides will know full well the size and acceleration of the other fleet. This info is of little use to the weaker side if they can’t manage equivalent accelerations. All they can do is wait for their attackers to reach them….
Water Is Not Uncommon in the Solar System
It may be that writers are misled by conditions in the inner system, where extremely arid conditions prevail. The Moon, Venus, Mercury, and even Mars are essentially bone-dry when compared to Earth. On Venus, for example, water is as common as neon is on Earth. Anyone looking around the inner system might well conclude that the universe is essentially a desert. Certainly the writers of V and Battlestar Galactica did.
Water is composed of hydrogen, the most common element in the universe, and oxygen, the third most common element in the universe. It turns out a chemical composed of the most common element and the third most common element is not all that rare once one gets out past the Solar System’s frost line. If water ice is cold enough, ice in quantity can survive for geological eras. Hence Ceres has more water than all the fresh water lakes on Earth combined. Hence moons like Ganymede, Europa, Callisto, Titan, and Enceladus have internal water oceans. Water contributes a lot of the mass of the ice giants Uranus and Neptune. Anyone out in the asteroid belt or farther should be able to mine water galore.
Granted, it may be very cold ice and water has an insanely high heat capacity, so melting it may be a bother. But plots that depend on near or total absence of water in the outer solar system are just flat out nonsensical. Please do not inflict more of these on me. Thank you.
In the words of Wikipedia editor TexasAndroid, prolific book reviewer and perennial Darwin Award nominee James Davis Nicoll is of “questionable notability.” His work has appeared in Publishers Weekly and Romantic Times as well as on his own websites, James Nicoll Reviews and Young People Read Old SFF (where he is assisted by editor Karen Lofstrom and web person Adrienne L. Travis). He is surprisingly flammable.