Impossible, inevitable and in between

Some actions in science fiction are much more difficult than others.

We have advised several science fiction authors on how to make their stories more authentic, a service that we offer generally.  Almost all science fiction involves technology that we do not now have; that’s what makes it science fiction.  And of course the story is the main concern of the author, who may need a certain device or technique in order to make it work.  But what many authors do not realize is how much current science must be extrapolated to do a given action, and the known laws of physics bent or broken.

The easiest category, and least likely to attract objections from scientists or astute readers, is extrapolation of current technology.  There have been space probes using solar sails, humans have lived in space for extended periods, and the dynamics of going from one planet to another are well-known.  A sail-powered manned spaceship to Mars or Jupiter is therefore quite plausible.  It’s more of an extrapolation than many people realize (because of the time involved and exposure to solar radiation among other things), but there’s no obvious reason why it couldn’t be carried out.

The second category is something not directly forbidden by the laws of physics, but we cannot really see how it could be done.  Consider the idea of an artificial gravity field: at the flick of a switch, your starship has an up and down.  This is extremely convenient for movie makers, because simulating zero gravity is difficult and expensive, and with this device you can film your space epic anywhere convenient on Earth.  It also means you can accelerate your ship enormously without squashing the crew flat.  The trouble is, we know where gravity comes from: mass-energy.  Einstein produced the master equation that says how much gravity comes from how much mass (the most concentrated form of energy).  And in order to produce Earth-equivalent gravity on the surface of your ship (a few hundred meters in radius), you have to carry around something like the mass of an asteroid at the density of a neutron star.  Yes, warping space is possible and happens all the time.  However, warping on demand at small scales requires something beyond any current speculation.

The last category is the hardest.  Suppose you have just been studying the diffraction of light, how it can go around corners and through screens by acting as a wave.  Then you come upon the fact that particles can do the same thing: neutrons, for instance, tell us about the structure of matter by acting as waves.  So you have your heroine escape from her prison cell by activating her wavelength-increasing device and diffracting through the bars.

The trouble here is that the wavelength of a particle is related to its mass and momentum by a simple law involving one of the basic constants of nature.  To get her wavelength large enough to notice, your heroine must either cool down to almost absolute zero (which would be immediately fatal) or change the value of Planck’s constant.  Moreover, she’d have to do it only on the scale of her size, and somehow not change it for all the particles that make up her body.  This last category requires simply throwing away a part of well-established science.

Your story may require technology from any of these categories.  We think it would be good to know which one.