I had an idea last night before going to bed, that was still in my head on the way to work (usually a good sign!), for a possible science fiction novel. What if there was a pseudo-humanoid race that “saw” using gravitons (i.e. gravity) instead of light (i.e. electromagnetism)?
Small physics lesson, for background: there are four fundamental forces – in order from weakest to strongest, they are Gravitational, Weak, Electromagnetic, Strong. All of them except gravity have to do with interactions at the atomic scale; gravity is the only one that, due to some of its special properties, has major effects at the macroscopic level. If electricity and magnetism didn’t have opposites (like positive and negative charge) it would have a far greater effect macroscopically — gravity only attracts, and has infinite range, and can’t be shielded against, so it has the largest impact at the macro level.
We interact with the world using our eyes primarily, and then less so through our other senses. But our eyes, as amazing and complex as they are, are really only capable of observing a small portion of the electromagnetic spectrum. I’m no expert on how eyes work, but essentially photons (the carrier of EM) are reflected off of objects and then absorbed by our retinas. In this way, we form a picture of our surroundings – quite a detailed picture!
So what about a story in which this hypothetical g-human race had “eyes” that sensed gravitational force? I imagine the beings form sort of a 3-d “sonar” map of their surroundings, based on the raw attractive power of objects near them. They’d have to be hypersensitve (gravity is a literal hojillion times weaker than EM), and they’d probably develop “microgravity” to differentiate themselves from each other — like plumage, but due to very dense spots in their physical makeup.
One of the major challenges with writing this story will be how hard it is to SHOW things – it would take a great deal of effort to immerse a human reader in the g-human world. Also, what would the story be about? I don’t think it’s a good idea to have a human meet a g-human; I think the story is more interesting if it is entirely within the context of this gravity-sense world. Maybe there’s a fundamental problem that this species had “solved for them” by happenstance – think of their “sun” as a black hole, and that their planet is somehow in a stable orbit around it due to (some reason), that they took for granted for a loooong time. And now, it’s becoming undone and they have to figure out why their planet is sliding into the “sun” and how to stop it!