Last week I reviewed “Project Hail Mary” and I approved of it as high quality science fiction. But am I being consistent? Should I be calling it fantasy? In other words, can a story based on a completely impossible premise be considered science anything? So, let’s talk about this.
Andy Weir used a microorganism of extraterrestrial origin as the basis for his story. This lifeform which he called astrophage had a complement of remarkable properties that made it both the source of an existential threat to human existence on Earth and the key to human interstellar travel. Astrophage can convert light into mass and it can also convert mass into light. This is “explained” by claiming that it can harness the energy produced when neutrinos and their anti-matter opposites (which apparently are also just neutrinos) annihilate each other forming light. So somehow, the living cell can store neutrinos and then harvest them to produced light that can be used as a motive force to propel the astrophage at velocities approaching light speed.
Okay, this is gibberish. None of those things can be done in a particle accelerator, never mind inside the protoplasm of a cell. So, all of this is no different than E. E. Doc Smith pointing to his “inertialess” drive that allows the Galactic Patrol and their Boskonian enemies to hurtle through interstellar space at many time the speed of light. It’s just hand-waving to allow the action in the story to occur in a time period that allows for a fun story.
Now, granted, Weir at least restricts his velocities to the limit that General Relativity permits. And he allows time dilation and other relativistic effects to govern the fate of his astronauts. But having his starship reach 0.92 c is based on an energy production method that is completely inexplicable by any physics or biology that we can point to.
So, why isn’t that fantasy?
I think I’m going to invent a rule of science fiction.
photog’s First Law of Science Fiction – Thou shalt not change more than one basic law of physics when making a good story.
So, if Andy Weir wants astrophage to have a biological basis for matter/antimatter conversion then everything else about his story has to be “legit.” So, he can use astrophage as his workaround for amazing energy density for things like interstellar flight but everything else still requires the laws of physics, chemistry and biology to work the way they do in the real world. Now some folks might begrudge him xenonite because somehow, he turned a noble gas into unobtanium but there’s enough wiggle room in chemistry so that depending on what else besides xenon is in xenonite we could imagine all the properties of this make-believe material without calling down the lightning of the gods of the periodic table.
So, I think that’s fair. If you only make up one crazy make-believe MacGuffin to allow for the action in your story then I won’t cry foul and demote the story to the depths of the fantasy dungeon. I mean, who could ask for more than that.


