Genres

Joseph Shoer looks at some of the [uncomfortable science](http://gizmodo.com/5426453/the-physics-of-space-battles) behind these science-fiction mainstays:

> Explosions are basically a waste of energy in space. On the ground, these are devastating because of the shock wave that goes along with them. But in the vacuum of space, an explosion just creates some tenuous, expanding gases that would be easily dissipated by a hull.

Better choices for weapons include radiation, lasers and old-fashioned bullets. But don’t expect fast-and-nimble dogfights, because steering a ship in space is laborious. With no atmosphere to cut against, changing directions takes time and lots of fuel.

The z-axis fighting we’ve recently come to embrace — the new Star Trek did it a lot — only makes sense in certain circumstances. Orbiting a planet, things get flat again:

> 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 […] 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.

In writing your space epic, do you even need to worry about any of this?

Only to the degree your viewers will.

Each movie and TV series establishes its own level of plausibility, and as long as it plays within that range, audiences are largely satisfied. Space in Apollo 13 is nothing like space in Star Wars. A viewer who complains too much about the Millennium Falcon’s propulsion system will be justifiably shunned.

A general rule for screenwriters is to stick with genre conventions unless there is a story benefit to changing them. For example, in modern space adventure movies you get artificial gravity, warp drive, and shields for free. You can roll your own if it suits your story, but that screen time is likely better used in service of your characters and plot.

(Thanks to [Nima](http://twitter.com/nyousefi/status/6763548593) for the link.)

Zombies are more than the walking dead. They’re a useful paradigm for a range of common scenarios in many genres.

Whenever your hero is facing off against a system or mob rather than an individual, that’s potentially a zombie-class situation. Any given opponent isn’t necessarily that formidable; it’s the sheer numbers that make it so difficult for the hero.

War movies are frequently zombie-class, as are comedies about plucky outsiders. Science-fiction and horror revel in zombie-class situations, from the Borg to the Visitors to those troublesome tribbles.

If you find yourself writing a zombie-class situation, here are some helpful class features to keep in mind:

* **You can’t fight the ocean.** In a zombie-class situation, heroes ultimately won’t get far trying to defeat their opponents, who have the advantage of both numbers and replaceability. Rather, your hero must set an achievable goal such as escape, survival, or retrieval of a key asset.

* **Ants vs. Elephants.** It’s great to be big, but it’s better to be numerous. Just as heroes will often rally a crowd, opponents can do the same — popular opinion is a hard thing to fight. And look for ways to use your hero’s size (or reputation) against him.

* **Zombie processes.** In programming, zombies are bits of code that unintentionally keep running in the background, sucking cycles and threatening a crash. That’s a useful framework for many stories: noble intentions run amok. Just as [every villain is a hero](http://johnaugust.com/archives/2009/every-villain-is-a-hero), every zombie was somebody’s baby.

* **One of us.** In the Romero tradition, zombies eat brains. But this can be generalized to assimilation: your hero has something the opponents need. Can your hero figure out what they’re after — what makes the hero special — before it’s too late?

A zombie-class situation is a key difference between Alien and Aliens.

In the former, Ripley and company mostly battle a single creature. Survival means killing it, so that’s pretty much the only goal.

In the sequel, the aliens are so numerous that there is no hope of defeating them. Rather, Ripley’s goal is simply escape. Once Newt is captured, Ripley must face off against the Queen, but defeating her in no way impacts the hordes of aliens left behind.

That’s how zombie-class situations often end: the hero’s victory leaves the world just as dangerous as before.