obligatory disclaimer:
The following is a suggested rating as to the scientific authenticity of science fiction literature and popular culture. Please note that this is not a rating as to the enjoyability of the story, or its quality or value as imaginative literature! It is simply a rating as to the suggested scientific realism of the setting as described within the work in question. A soft science outlook for example is often part and parcel of the author’s desired outcome of the work.

This rating was originally developed by on the basis of discussion on the Orion’s Arm mail list, but has since been removed from the external linkOrion’s Arm website, as it was felt to be inapplicable to the OA Project. However, most links still connect to reviews on the OA website. Eventually (depending on when I can find time) these will be replaced with links to general reviews, or to amazon com pages featuring specific books.

The Need for Multiple Parameters

I now consider that the simple linear scale used in that thesis is manifestly inadequate to the complex possibilities of the hard and soft sciences and the imagination, involved in envisaging future or alternative worlds. Ideally,a number of parameters should be used. Specifically, there is the distinction between what is actually known, and what is speculation and hence can go either way.

What is actually known tells us what SF and Sci Fi themes and tropes are absolutely impossible, no matter what future developments in science and technology may bring. e.g. we know that lifeless planets cannot have a breathable atmosphere, that atomic radiation won’t give rise to “postapocalyptic mutants”, that technobabble is not the way that engineering works, that insects can’t grow as big as elephants, that 20 gigaton ray guns require an energy source and have to deal with waste heat, that aliens wont look like H. sapiens sapiens and won’t innately speak English either, and so on.

This is not to criticise any of these things as fun escapist entertainment, and/or as mytholologic metaphors, only to say that they cannot occur in the “real world”.

What is speculation and hence can go either way refers to matters regarding which we currently simply do no know. e.g. aliens may or may not exist and if they do may or may not be roughly humanoid, wormholes may or may not be allowed given current or future insights regarding the laws of physics, FTL and hence acausality may or may not apply, the current understanding of chemistry at nano scales may (wet nano only) or may not (drexlerian nanotech) apply, ditto the Heisenberg Uncertainty Principle (hence femtotech etc), ditto non-biological intelligence (hence AI and infomorph intelligence). Regarding those critics who state that certain things are absolutely impossible, Arthur C. Clarke had some choice words about pronouncements by elderly but distinguished professors. This does not mean that these things are absolutely possible. It means we don’t know. And SF should be allowed to explore either or both options.

There is a third parameter to be considered, and that is Science Fiction verses Fantasy. We can call this variable “Magic”. This constitutes a gradation from “hard science” in which everything has a physical technical explanation, to some psionic or mystical elements, to full fantasy. There can also be an overlap, in which the same universe may have elements of fantasy and hard science. For this, reason, this variable is considered distinct from “what is known”

However the current page is retained as it would be too difficult to revise everything, and a lot of what is written here is still, I feel, valid, and may be of interest.

The Hard-Soft Sci Fi Gradational Scale

On the basis of rating of common sci fi tropes from ultra-realistic to pure soft sci fi unscientificness, one can posit a grading of the genre from Ultra Hard to Very Soft. This is not intended as, and should not be taken as, a list of absolutes. It is simply one interpretation of what is more and what is less likely, given the current understanding of the universe and how it works. Future discoveries in physics, AI, etc may very well change the placement of some of these stories – some things that are here listed as implausible may become very plausible, and vice versa. However even if, say, warp drive turns out to be viable and wormholes not, there is no way that the Star Trek “bumpy-headed humanoid of the week” galactography could in any way be possible. Hence some things are patently absurd, no matter what future advances in technology or exploration of space reveal.

However, this should not be taken as a value judgment, because no grade is “better” than any other. So soft science SF as a genre is just as valid as hard science SF. Moreover, you may have a completely different, but equally valid, approach to these things. Other standards might equally well be used to define various levels of “hardness”, and we in no way wish to claim that our interpretation is the only or the best one! In addition, to reiterate, we are not trying to suggest that “hard” science fiction is in any way “better” than the soft sci fi, or pop sci fi franchises. All that is simply a matter of personal taste, opinion, and preference. None of what is written here should be taken as any sort of value judgement.

Major Categories Rating used here Common Tropes A few examples
Hard Sci Fi “Present Day Tech” Cutting edge Present Day Tech, some developments and speculation, but nothing major that has not been attained today (so no AI). Basic space exploration, very near future Technothrillers, Allen Steele’s Orbital Decay
Ultra Hard (Diamond Hard) Plausible developments of contemporary technologies – AI, Constrained Nanotech, DNI, Interplanetary colonisation, Genetically engineered lifeforms. Nothing that conflicts with the laws of physics, chemistry, biology etc as currently understood William Gibson, Neil Stephenson, Kim Stanley Robinson’s “Mars” Trilogy, Robert Forward
Very Hard Plausible developments of provocative contemporary ideas, bot nothing that conflicts with the known laws of physics, information theory, etc – Assembler Nanotech, Nano-Goo, Uploads, Interstellar colonisation, Relativistic ships, vacuum-adapted life Greg Egan, Linda Nagata, Greg Benford’s Galactic Center series, Stephen Baxter’s Manifold Series, GURPS Transhuman Space
Plausibly Hard The above but with the addition of some very speculative themes, some of which may well turn out to be impossible, others may be possible. Requires some modification of current understanding, but nothing that is logically impossible, or has been conclusively proved to be impossible (so no FTL without time travel) – Wormholes, Reactionless Drive, Sub-nanotech (Femto-, Plank, etc), Domain Walls, exotic matter, FTL drive with time travel, etc Stephen Baxter’s Xeelee universe, Greg Bear’s Forge of God series, Orion’s Arm
Firm As realistic as the above categories were it not for unrealistic/impossible plot devices (e.g. FTL without time travel paradoxes), although these are kept to a minimum as much as possible Asimov’s “Foundation” Series, “Giants” series by Hogan, Vinge’s A Fire Upon the Deep and A Deepness in the Sky
Medium Similar to the above but with a larger number of unrealistic plot devices; e.g. FTL without real explanation (ore with pseudo-explanation), alien biota in some instances very similar to terragen life, psionics, a great many alien civilizations. However still preserves plot and worldbuilding consistency, and the science is good and consistent. Niven’s “Known Space” series, Robert Heinlein’s Starship Troopers, Banks’ “Culture” novels, David Brin’s “Uplift” series, Frank Herbert’s Dune, Traveller RPG
Soft Sci Fi Soft A number of unscientific themes – e.g. aliens as anthropomorphic “furries”, handwavium disintegrator guns, Alien Cultures and psychology all extremely uniform, and so on. However, still retains story consistency. Various TV series: Babylon 5, Farscape, Andromeda, Matrix, StarGate for the most part
Very Soft As above but either even more unscientific elements (humanoid of the week, lifeless planets with beathable atmosphere, etc), and story with less consistency Various TV and movie series; for the most part the Star Trek Canon and Star Wars Canon
Mushy Soft As above but even more unscientific (alien races never before encountered speak perfect English without a translator, animals too large to stand in Earth gravity (Godzilla), weapons that make energy beams without putting energy in, interstellar travel without FTL or centuries long voyage, mutants with super energy powers, etc) Godzilla, Comic Book Superheros, badly written TV sci fi, elements of some franchises

Note that the above scale does not include Science Fantasy or proper fantasy. Also one person’s fantasy might be another person’s sci fi (e.g. Star Wars is considered “Space Fantasy” by it’s creator, but sci fi by others)

Hard Sci Fi

Hard Sci Fi is Science Fiction in which the science and tech remains plausible, and the universe is explained in a consistent rationally. It may not always be realistic, and indeed it can sometimes be very speculative and even include unrealistic or impossible plot devices, but the overall approach is one of careful research, scientific, technological, and sociological consistency, and real science rather than meaningless technobabble.

Hard Sci Fi ranges from the most realistic stories limited only to current knowledge and set in the present day or very near future, to science fiction that is only “medium” in realism, but, being more speculative, can be set much further in the future or explore more themes.

Note that some would claim that only the nearest future categories included here can be considered “Hard”, the others being too speculative. However I am following the “John W Campbell” definition of what constitutes “Hard SF” or Hard Sci Fi, and that is that while some speculative ideas are allowed, the story as a whole must be based on scientific research, avoid technobabble or cliches like Bug Eyed Monsters stealing Earth women.

“Present Day Tech” type Science Fiction

PRESENT DAY TECH sci fi deals only with known technologies and science, and only the most conservative extrapolation therefrom. This may include such things as flying cars or fusion reactors. Does not incorporate radical or controversial concept like wormholes, any kind of aliens etc. The term is given in inverted commas because the story and even technical details may still turn out to be implausible or impractical in real life, much as it reads well in fictional form. Generally “Present Day Tech” SF would generally take place in either the “present day” or the very near future, as the further ahead the harder it becomes to make decent predictions and the more likely you are to be wrong. While this makes this form of sci fi much more realistic, it can also limit the imagination.

Technologies and Themes in “Present Day Tech” SF

The following are common themes that occur in “Present Day Tech” settings. All are absolutely certain through extrapolation of current technology.

  • Current engineering technology or extrapolations therefrom
  • Novel materials and fabrics, e.g. “arachnoweave”, based on what is already been developed now.
  • Sustainable nuclear fusion (why? – already possible for very short periods)
  • Virtual Reality indistinguishable from Real Life (why? – logical progression from modern tech)
  • Space Flight, Space Habitats, even Asteroid Mining, etc, if using today’s technology
  • fancy “secret weapon” – e.g. Red October, Blue Thunder, Firefox (plot device)
  • no handwavium or unobtanium

Some Examples of “Present Day Tech” SF

Examples of “Present Day Tech” writers and stories include: The Ghost from the Grand Banks (raising the Titanic) by Clarke, Islands in the Net by Sterling, Orbital Decay (1989) and Clarke County, Space (1990) by Allen Steele, and general near future stories. Also most technothrillers (“secret weapon” based on today’s tech, first AI, etc), armageddon type stories (asteroid about to hit the Earth, climate change, etc etc), low grade cyberpunk thriller (“serial killer on the net” etc), and so on. Some of these probably don’t even qualify as sci fi (although they are usually advertised as such). Many Hollywood blockbuster movies (most of which have appalling scriptwriting) fall into this category.

Ultra Hard / Diamond Hard Science Fiction

ULTRA HARD can also be called Diamond Hard; this is so-called because it represents the most extreme (realistic) side of the Hard SF spectrum. The term DIAMOND HARD is here used as something of a pun – diamond refers to nanotech building material (diamondoid) but also in the hardness scale to very realistic sci fi. Does not incorporate radical or controversial concepts like wormholes or femtotech. Generally Ultra Hard SF would generally take place in the near future, as the further ahead the harder it becomes to make decent predictions and the more likely you are to be wrong.

In Ultra Hard Sci Fi, handwavium and anything that might be dubious is completely absent.

Technologies and Themes in Ultra Hard SF

The following are common themes that occur in Ultra Hard sci fi settings. From our present understanding, there is nothing in the laws of physics, chemistry, biology, or information theory that says these things are actually impossible.

  • Direct Neural Interface with Virtual Reality (why? – already basic advances now – e.g. a subject hooked up so their brainwaves are recorded, and using their will to control a cursor)
  • Gengineering, Homo superior, space adapted tweaks, neogen life-forms, etc (why? – because basic germline engineering possible with microorganisms, human genome being explored, only moral issues obstruct further development)
  • Terraforming other worlds (although this may take thousands of years)
  • Limited nanofactured materials (e.g. diamondoid cable) (from current development in fullerene production)
  • Bio- or “Wet” nanotech (why? – because life (natural organic nanomachines) exist on Earth)
  • Constrained Nanotech but not universal assemblers (why? – still some questions as to how a universal assembler could work, but something like vat-scale or industrial nanofacturing would certainly be reasonable)
  • Sentient and even superhuman AI – (why? – no conclusive disproof yet presented. Ray Kurzweil presents a very strong argument in favour)
  • Planets in other solar systems that are Earth-like and support complex life (why? – assuming the ubiquity of life, no reason why advanced life forms and ecologies could not evolve on other worlds, if the conditions are right)
  • no handwavium or unobtanium

Some Examples of Ultra Hard SF

Examples of Ultra Hard writers and stories include: Fountains of Paradise (space elevator – some nano for diamondoid materials, but completely plausible, rate of current development makes this possible in the very near future) by Arthur C. Clarke, the Red, Green and Blue Mars Trilogy of Kim Stanley Robinson (terraforming Mars – very plausible setting), Heavy Weather by Sterling (nearfuture cyberpunk with plausible technology), Pat Cardigan’s Synners, William Gibson’s Idoru series and similar near-future cyberpunk fiction), along with Neal Stephenson’s Diamond Age (nanotech), and near future Technothrillers involving the first AI or some such plot device. Heinlein’s The Moon is a Harsh Mistress might also go here. All books by Robert L. Forward (visionary physicist and SF writer, is careful to explain everything in terms of real physics and astronomy – sometimes the exotic aliens would be plot devices) could either be considered Ultra Hard or Very Hard, and all have the same scientific rigour of true Hard SF. The more realistic RPGs like Vanguard (spaceships) and Blue Planet (set on an ocean world) could also either be considered Ultra Hard or Very Hard. Also, while a lot of the science is dated now, the works of Jules Verne, the “father” of science fiction (Journey to the Center of the Earth (1864), From the Earth to the Moon (1865) (20,000 Leagues Under the Sea (1870), etc) were, for their time and by the standards of scientific knowledge then available, Very Hard to Ultra Hard in realism rating).

Very Hard Science Fiction

VERY HARD: Deals with known technologies and expands on existing scientific theories in a speculative, but still rigorous and plausible, fashion. The story doesn’t break any of the known laws of physics, information theory, and so on. Includes some controversial concepts, but nothing that conflicts with the laws of physics as they currently stand. A bit more speculative than Diamond Hard, and hence Very Hard SF can take place future in the future, or on a larger canvas. Handwavium is kept at an absolute minimum.

Technologies and Themes in Very Hard SF

The following are common themes that occur in Very Hard sci fi settings. According to the current understanding of how the universe works, some of these things can be considered either almost or absolutely certain, others are very probable, but may well be proved wrong in the future. However, from our present understanding, there is nothing in the laws of physics, or information theory as currently understood that says these things are actually impossible. And were they to be proved possible our understanding of how the universe works would only need to be revised in a minor way.

  • Advanced Mechanical or “Dry” nanotech (why? – because all objections to drexlerian nanotech have been conclusively replied to – see the Foresight Institute and the famous rebuttal of the Scientific American Article critical of nanotech. And even if nano doesn’t work out exactly as predicted, there will certainly be some form of advanced nano. For more on nano, see nanotech pages)
  • Virtuals, uploads, copies etc (while requiring great advances in neuroscience, these are not impossible given sufficient understanding of human psyche and brain functioning, and advanced nanotech that can record and replicate this.)
  • Megascale engineering, Jupiter Brains, etc (why? – given advanced nano these are certainly possible – see e.g. Anders Sandberg’s paper on PDF document Jupiter Brains)
  • Bioships, Vacuum Adapted life, etc (why? – although a fully organic ship is unlikely, given the harsh conditions of space, as well as the need for a propulsive system, there is no reason why a composite cyborg being could not exist, with a living interior but hard and inorganic or quasi-inorganic exterior and inorganic rocket or drive component. Some bacteria for example can survive hard vacuum. Even so, this would however require very advanced biotechnology)
  • Very rapid Terraforming (why? – given advanced nano it is certainly possible)
  • Universe with a few current alien civilizations (why? – optimistic interpretations of Fermi’s paradox)
  • very limited handwavium, no unobtanium

Some Examples of Very Hard SF

Examples of Very Hard writers and stories include: most or all books by Robert L. Forward (visionary physicist and SF writer, is careful to explain everything in terms of real physics and astronomy – sometimes the exotic aliens would be plot devices), Stephen Baxter’s Manifold Series (Manifold : Time (2000), Manifold : Space (2001), Manifold : Origin (2001) (exotic biology, realistic space ships, Fermi paradox, no FTL); Permutation City by Greg Egan (uploads/virtuals), and other works by the same writer, Also GURPS Transhuman Space roleplaying game (a number of transhuman tropes and ideas, ranging from probable to very plausible), and the Ad Astra Universe of Richard Baker and David Dye (again, very realistic, using projections from current knowledge, no speculative technology). Neal Stephenson Snowcrash and William Gibson’s Neuromancer series would probably go here too, although near-future they are more concerned with telling a story and sometimes “fudge” the realism a bit (e.g. Gibson’s neural interface (jacking in) isn’t really explained), all of which shows how misleading it is make simplistic classifications (hence the present page is a guide only, not a dogmatic statement). Michael Swanwick’s Vacuum Flowers (face paint personality change is pretty unbelievable (can one be so easily conditioned?) but for the rest the story is pretty good hard science – no FTL, dyson trees, microgravity space habitats, and so on).

Plausibly Hard Science Fiction

PLAUSIBLY HARD: Deals with known technologies and expands on existing scientific theories in a speculative, but still rigorous and plausible, fashion. The story doesn’t break any of the known laws of physics, although it may make reasonable, explained extrapolations of physical laws well beyond current leading-edge concepts, including ideas that may be controversial, but have not yet been shown to be impossible. Inevitably there is always some degree of handwavium, but it is always within the context of the story, and no unrealistic plot device sillytech or unobtanium is ever allowed. Technology has to follow a particular logical sequence, and while the advanced elements of the sequence may seem highly speculative by today’s physics, they still follow a logical chain, e.g. you can’t just jump from today’s tech to FTL or wormholes or blasters or whatever. Nothing that can be shown to be logically impossible is allowed.

Technologies and Themes in Plausibly Hard SF

The following are common themes that occur in Hard sci fi settings. As well as everything found in Ultra Hard / Very Hard SF, the somewhat less rigorous Plausibly Hard Sci Fi aspect of the genre includes things that may or may not be possible, but can still be considered plausible or reasonable, at least until proved wrong by future discoveries. Although some of these points are currently considered unlikely or even impossible by conservative physicists (but not, mind you, by all physicists), that in itself does not make them impossible (Arthur C Clarke’s comments on pronouncements by elderly and distinguished professors come to mind here too). Even so, were any of these things to be proved possible, our understanding of how certain aspects of the universe works would need some pretty radical revision, but would still be accomodatible with what we know and understand at present.

  • Picotech, Femtotech, etc – (why? – controversial (current understanding of how to derive work according to laws of thermodynamics) but not conclusively shown to be impossible, no reason why advanced tech cant get around this, see reference to Weak Measurement)
  • Navigable Wormholes – (why? – controversial but so far it seems at least as much evidence in favour of as against; however these would probably be huge engineering projects even for very advanced civilizations – refs)
  • Reactionless Drives – (why? – controversial but would seem to be possible given exotic matter or negative energy)
  • Space-time Engineering – (why? – controversial but not impossible given sufficiently advanced technology)
  • FTL with time travel – e.g. Stephen Baxter’s novel Exultant – (why? – if FTL is possible than the universe is acausal or has a completely different causality, but this is not illogical the way that FTL without time-travel is – see FTL paradoxes for why FTL has to involve time-travel)
  • Intelligent (as opposed to primitive) Life evolving in extreme environments (e.g. cold-chemistry, etc) (why? – although unlikely given the example only of life on Earth, we do not know enough about exobiology to be sure what forms life and intelligence might take)
  • handwavium allowed, but no unobtanium

Some Examples of Plausibly Hard SF

Examples include: Greg Bear’s Blood Music (1985) (sentient advanced bionano), the The Forge of God series Forge of God (1987) and Anvil of Stars (1992) (includes some OA-style tech, and a hider-like explanation of the Fermi Paradox; no FTL), Eon (1985) and Eternity (1988) (hollow asteroid that, like Dr Who’s Tardis, is bigger on the inside than the out, but the science is kept rigorous) and other works by the same author, books by A.C. Clarke (Rama (megastructure spacecraft, logically explained) 2001 (both book and film) ultrahard science except for the monolith, etc, ), Greg Benford’s Galactic Center series (In the Ocean of Night (1977), Across the Sea of Suns (1984), Great Sky River (1987), Tides of Light (1989), Furious Gulf (1994) and Sailing Bright Eternity (1995) – involving conflict between organic (mostly human) and machine intelligences, with the humans fleeing from savage artificial intelligences towards the black hole at the centre of our galaxy. Near-relativistic ships but no FTL), Singularity Sky and other transhuman stories of Charles Stross; and of course Orion’s Arm. the Xeelee series of Stephen Baxter (good attention to science and some way out hard sci fi concepts, although some ideas since found to be mistaken – e.g. cannot use a wormhole as a time-machine, but was in keeping with what was known when it was written).

Firm Science Fiction

FIRM : Deals with known technologies, sciences and theories, but often incorporates new theories or ideas with plausible explanations. Breaks some physical laws, but provides a solid rationale for it. Differs from Hard only in the inclusion of some form of FTL Plott-DeVice Drive * 🙂 or equivalent. Apart from these non-hard elements, everything is described in technical terms, using real and authentic science and engineering, and apart from the aforementioned plot devices, and the story is never allowed to make the science look silly.

Technologies and Themes in Firm SF

The following are some themes and technologies that might occur in Firm (but not in Hard) sci fi settings.

  • Alien artifacts still work after being abandoned for millions of years (highly unlikely, but not completely impossible; this is however too often an overworked cliché)
  • Universe with many current alien civilizations (why? – Fermi’s paradox, negative results so far from Seti, but not impossible assuming they may be the equivalent of hiders etc)
  • Hominids or humans from Earth transplanted to other worlds thousands of years ago by aliens unknown (not impossible, but why should they bother? This is actually a sci fi trope to make it easier to have stories of humans on other star systems)
  • Wormholes as Time machines (why implausible? – because virtual particle swamping (Matt Visser); also would result in time travel paradoxes and violation of causality. Can work given Many Worlds Interpretation of physics, but this would not involve travelling back in time to “our” universe)
  • both handwavium and unobtanium
  • Plot Devices that we know our ludicrous but are included for the sake of the story or worldbuilding

Some Examples of Firm SF

Examples include Asimov’s Foundation Series (FTL as a plot device, also antigrav cars, and the ecological absurdity of a city planet (Trantor) maintaining a breathable atmosphere, but otherwise very rationally thought out) and I Robot (again very rigorous scientifically, “positronic brain” is handwavium concession to future tech), Fred Hoyle’s The Black Cloud (1957) (deals with astronomy, chemistry, biology, panspermia scientific method and information theory; the alien intelligence in the form of a cloud of gas is very well done), Giants series by Hogan, Vinge’s A Fire Upon the Deep and A Deepness in the Sky (relativistic trade empires, toposophic-like levels, “Zones of Thought” as imaginary but still self-consistent Plot Device (does not correspond to real physics) to explain FTL and why the whole galaxy isn’t swallowed by the Singularity). Larry Niven’s Ringworld (set in his Known Space universe – science and engineering approach to Ringworld and other megastructures, Ringworld explained very realistically, although still requires unobtanium (a type of material called “Skrith”), Plott-DeVice FTL), Bruce Sterling’s Schismatrix (the aliens are rather implausible (look like giant birds) but the rest of the story gives a good medium-future look at the solar system and shows humanity clading in different directions, unlike the uniform future society of soft sci fi); Larry Niven and Jerry Pournelle’s The Mote in God’s Eye (realistic presentation of aliens, Plott-DeVice FTL not too wayout) and other good quality modern writers like Alastair Reynolds and Ken Macleod, and Anders Sandberg’s Big Ideas, Grand Vision RPG setting. ) Also intelligent RPGs like 2300AD, and perhaps Valence and Jovian Chronicles (the latter set in the Interplanetary Age and employing some genuine science).

Medium Science Fiction

MEDIUM : Breaks physical laws but attempts a rationale which sounds reasonable in context with the work, regardless whether or not it makes sense within the current scientific paradigm. Also describes things in a scientific manner. So while concepts like FTL appear, which are unproven and indeed contradictory to the laws of physics, the story is still arranged in a logical manner. This material is generally considered “hard science SF”, but is not as rigorous as the above category, and often (unlike Firm science fiction) the writer will deliberately fudge or even ignore the science for the sake of a more entertaining story.

Technologies and Themes in Medium SF

The following are some themes and technologies that might occur in Medium (but not in Firm) sci fi settings. These tropes can still be used (if not overdone) in a Campbellian hard science manner (which is a less rigorous grading than we use – e.g. an FTL drive is allowed if the rest of the story hangs together, the repercussions on society as a whole are acknowledged or explored, etc). Most traditional SF uses at least one of these tropes, as plot devices. All of these ideas have been excluded from the Orion’s Arm setting.

  • Universe crowded with alien civilizations (why? – Fermi’s paradox, negative results so far from Seti)
  • Some aliens very similar to terragen life (why? – exceedingly unlikely evolution would follow a very similar path)
  • FTL without time-travel
  • non-explained FTL drives, hyperspace jumps, etc – (why? – violates local causality and results in time-travel paradoxes, no way other than handwavium and sillytech to explain. Even so, FTL remains a staple of many otherwise harder (medium to firm) SF writers. This is however more a dramatic device than a concession to realism)
  • most or almost all the tech development (hand lasers, genetic engineering, giant ships, FTL, etc etc) occurs in the immediate near future – e.g. 21st century (this is a common problem with a lot of SF)
  • Small scale Antigrav (cars, belts, ships etc) (why? – may work given plancktech but basically handwavium)
  • Disintegrator guns and other sillytech energy beam weapons that generate a beam by no known (or patently unscientific) means, without problems of energy storage, heat dissipation, etc (why? – no basis in modern physics, doesn’t work with real engineering, pure handwavium)
  • Psionics, radio-style telepathy, etc (why? – although parapsychology has provided tantalising but ambiguous evidence, there is no evidence of reliable “psionics” or sci fi telepathy in real life. However, this theme is still common as a plot device, and is presented in a rational, rather than a supernatural or fantasy, manner)

Some Examples of Medium SF

Examples: Much of Niven’s Known Space series (FTL, psionics, a lot of handwavium, aliens seem (to me, others may disagree) one-dimensional, but from a technical viewpoint Niven’s science is always excellent (see Ringworld, under “Firm” heading)), Robert Heinlein’s Starship Troopers (has some silly elements, e.g. giant bugs shooting plasma at Earth (very soft sci fi concept), also the usual FTL plot device, but otherwise story has a lot of hard sci fi ideas. Some have criticised the politics, others sympathised with it, but this has nothing to do with the science rating. The movie version was a soft sci fi satire). Still on military SF, Forever War by Joe Haldeman has elements of both Medium and Firm (science less important than telling a story, interesting speculations on future culture, use of collapsars equates to wormholes etc and is a decent plot device; very implausible that so much tech development occurs in the late 20th and early 21st century, the rest being rather more minor; however for the rest avoids less realistic concepts). Banks’ Culture novels (technobabble FTL, handwavium or plot device antigrav, force fields, hyperspace AI, etc, the science and tech is clearly secondary to cultural speculations and the telling of a good story), the Uplift series of David Brin (many alien races, conflicts with Fermi paradox “great silence”, also many of these races are based on mammalian or avian forms, but no reason evolution would take the same pathways on other worlds. The usual plot device ultratech like FTL starships etc. In other instances, Brin keeps the science good; however he makes it clear that reliance on scientific accuracy is secondary to telling a good story), and Peter Hamilton’s Fallen Dragon (and Night’s Dawn if it did not have the supernatural elements which puts it squarely in the realm of Science Fantasy; while the concept of genetically engineered Edenists vs the “baseline” Adamists are good, and there is some decent scientific realism alongside the plot device FTL (one-shot wormholes) it is unrealistic that almost all the tech development occurs in the 21st century). For a scenario set in our Solar System, John C. Wright’s The Golden Age trilogy starts out looking like pretty decent hard SF on the realism scale (use of nanotech and direct interface with the brain to create rich experiences, plausible far future society), but the book is essentially a literary work, some of the hard science tech is left unexplained, and some of the tech later turns out to be totally ridiculous and probably better suited as “soft SF” (the 100 mile long interstellar starship made one atom at a time of a super-element); Frank Herbert’s Dune – probably most published works of science fiction – hugely researched, massive worldbuilding, the whole thing very consistent, if implausible re tech (force fields that mean only very slow projectiles can be used (plot device), native ecology of Arrakis very implausible, but consistency and detail of the worldbuilding is superb, and the physics and tech, while unbelievable, is at least explained in a consistent manner. Note that Dune was never intended as Hard SF, it is a work of Soft SF (social and literary). The fact that it is also once of the greatest works of Sci Fi ever written should show that this hard to soft science rating has absolutely nothing to do with quality of the work in question. RPGs like Heavy Gear (military mecha) go either here or in the Soft SciFi category.

Soft Sci Fi

Soft Sci Fi as defined here is Science Fiction, Science Fantasy, or (to use George Lucas’ term) Space Fantasy, in which there is little or no attempt to keep the science and tech plausible, or to have social trends follow logically from technological development. Frequent absurd elements are common (e.g. it would be impossible for Godzilla, or for giant ants or spiders, to stand or move in Earth gravity), and the universe is explained in terms of storyline entertainment rather than plausibility. In some cases technobabble is used instead of proper science.

As with Hard Sci Fi, one can suggest various grades of Soft Sci Fi.

Soft Science Fiction

SOFT: Breaks physical laws but still attempts a rationale which may sound reasonable in context with the work, although in all other respects it is very implausible. Moreover it shows pretty much complete ignorance of how real science and the real universe works. These tropes are found in almost all television and much cinema-based SF. Nevertheless, occasionally a classic SF tale will involve one or more of these tropes.
Note that the term Soft SF is often also used to refer to SF that explores sociological and psychological themes; here we are using it instead specifically in the context of works that do not attempt to be scientifically rigorous, even if they are still logically consistent.

Science, Technologies and Themes in Soft SF

The following are some themes and technologies that might occur in Soft (but not Medium Hard) sci fi settings. These things are highly improbable to impossible and cannot by today’s understanding of physics, astronomy, etc, be considered in any way realistic. Often they are the result of poor background research, or of (in the case of movies and TV shows) the limitations of working with human actors, make-up , and so on (now with improved CGI this may change). Hence they are excluded from the harder versions of Hard SF (Hard or Ultra Hard). But who knows, they may be proved correct in the future, should the laws of physics be completely and drastically turned around. This would however require a revision as great as the difference between, say, Aristotlean and Contemporary science.

  • Forcefields/ “Shields” (why? – no basis in modern physics, pure handwavium. However it is not impossible that future discoveries may allow such things)
  • Alien Cultures and psychology all extremely uniform – e.g. all Klingons are warlike, all Pupetters (Niven’s Ringworld etc) are cowardly, etc (why? – no reason why a xenosophont race or civilization should be less diverse than our own, and if it is it would not be at all competitive and easily conquered, but sure maybe only humans are diverse)
  • Aliens based on anthropomorphised terragen life – e.g. “furries”, also bumpy-headed humanoid aliens, Hominid aliens in general (why? – exceedingly unlikely evolution would follow exactly the same path, even given Star Trek’s “progenitors”), or aliens that look identical to baseline H. sapiens
  • Time travel in This Universe (no multiple timelines) without paradoxes and violation of causality.

Some Examples of Soft SF

Examples: Classic space opera like the Lensmen series (E.E. “Doc” Smith, the founder of “space opera”) and the Core Command rpg.
There are a number of other space operas that can be added here (will add titles later)

Among television sci fi franchises, Some of the earlier and better thought out episodes of Star Trek may go here, if they were taken as “stand alone” universes without the humanoid of the week syndrome or the treknobabble, the unfortunate screenplay necessity of aliens that look identical to baseline humans is permissable because one can only do so much with costumes and make-up) Babylon 5 (apart from ridiculous elements like the Prussian Centauris, which correspond to mushy soft silliness, the rest is pretty good – e.g. the Star Furies have attitude control jets (realistic / hard SF), the Babylon 5 habitat is an O’Neill type cylinder, and so on); Farscape (to their credit the writers chose not to introduce explanations to all the ultratech, thus wisely avoiding the “treknobabble” trap, however elements of the Farscape Universe are absurd, e.g. the Scarrin who are unaffected by cold and whose hide is impervious to weapons); SG-1 TV series (wormholes as an FTL device, but later also adapted classic Trekkist memes in more recent episodes (shields, etc), although the screenplay and internal consistency is far superior to almost all the post-Roddenberry Star Trek material); and the Andromeda TV series may go here, although it does include some more progressive concepts like AI and nanotech, but in any case, like all TV sci fi it is softer than most written SF. Among sci fi movies, the first Matrix movie could have been considered “medium” or “hard” (c.f. cyberpunk) in realism, were it not for the ridiculous human biobattery concept which definitely places it in the “soft sci fi” ballpark, and the two sequels also seem rather softer than the first episode. RPGs like Traveller (space opera – made unrealistic by the alien races that resemble terragen life, and resembles today’s world with space ships and ray guns – but otherwise well thought out setting), might go either here or perhaps (if well thought out and explained) in the Medium SciFi category.

Very Soft Science Fiction

VERY SOFT : Breaks physical laws and while the explanations, if any, may sound reasonable in the context of the story, the result has so many inconsistencies and implausibilities one is hard pressed to feel in any way comfortable about this material as “Science Fiction”, enjoyable as it may be as pure entertainment. Knowledge of real science, real engineering, and so on is basically non-existent. Unlike Soft Sci Fi it does not even provide any consistency within the context of the story. e.g. in Star Trek matter transports allow perfect molecular replication, but this is never used to heal illness or attain bodily immortality. Incidentally, the author of one website (don’t have the url) argued (dubiously) that much of this material is still “hard SF” because it seeks and provides a rational explanation of things. e.g. in Star Trek you know that you need some form of FTL to travel between the stars. But this is really stretching the term “hard sci fi”.

Science, Technologies and Themes in Very Soft SF

This relates to the inconsistency of these fictional universes in failing to follow through technological development into other areas of science and of society. Also some concepts that are clearly totally absurd and against the laws of physics. In addition, technobabble might be used instead of real science.

  • The majority of planets are like Earth (just look around our solar system – Earth type worlds are likely to be very rare)
  • A barren lifeless world with breathable atmosphere (oxygen is a highly reactive gas – a lifeless world would have a reducing atmosphere)
  • Alien worlds, cultures, and fashions very similar to late 20th/early 21st century America (or other periods and cultures of Earth – e.g. the Prussian Centauris of Babylon 5)
  • technobabble rather than real science (dilithium crystals, hypermatter, midichlorians, ion storms, subspace anomalies, crowded asteroid belts, etc, etc)
  • civilizations with some very advanced technology, (e.g. FTL ships, matter teleportation, etc) that still don’t have basic genetic engineering, life-extension, or other personal augmentation
  • civilizations that don’t think to apply the aforesaid extremely advanced godlike technologies to improving standard of living, quality of life, etc (e.g. ST matter transmitters can be used to replicate perfect bodies or organs and hence guarantee physical immortality)
  • civilizations with very advanced technology centuries in advance of us that suffer from conservative/luddite prejudices or fears of late 20th/early 21st century western world (e.g. “genetic engineering is bad”)
  • civilizations with very advanced technology in which however the culture, society, and psychology is identical to that of the late 20th/early 21st century western world
  • Many Sillytech SF devices

Some Examples of Very Soft SF


The Star Trek Canon goes here, as what would otherwise be a fine franchise is handicapped by numerous historical-timeline and inter-episode inconsistencies, bad science, and the “humanoid of the week syndrome”. Although Star Trek is authentic SF (and hence “hard” in the weakest definition of the term) in that it at least attempts an explanation, it is diminished by overreliance on “treknobabble” (pseudo-explanation, e.g. the “particle of the week” as well as “ion storms” etc) rather than real science, which makes it “Very Soft” (completely unscientific), and the use of the the “humanoid of the week” syndrome, rather than build on the shared universe, each episode and writer introduces a new humanoid alien). The original Star Wars might be considered Very Soft Sci Fi (combines quite reasonable Soft themes with Mushy Soft elements like ships that wheel and bank in a vacuum) with Fantasy elements (albeit not bad ones, “the Force” as a sort of New Age pop-Taoism), although George Lucas specifically defines it as “Space Fantasy”, rather than “Science Fiction”. In the second Star Wars trilogy the Force is explained in terms of “midichlorians”, this is the Star Wars version of treknobabble. Mechwarrior (they have FTL ships but the mecha have only the most primitive targeting system. However, the universe of the original RPG was very well thought out). Other examples might be LEXX and Red Dwarf (which is comedy in any case). Firefly – excellent character development but space exploration never explained (too many planets without FTL; also the wild west cultures are implausible (Mushy Soft?). Also some Cinematic sci fi – the sort of dumbed down stuff you see on TV and in the movies and which usually doesn’t even bother to be scientific; typical movies like Independence Day, Armageddon, Supernova, etc.

Mushy Soft Science Fiction

MUSHY SOFT : Differs from standard Soft Sci Fi in giving up any pretense at all of trying to be plausible. This category is often disparagingly referred to as “science fantasy” by people who are serious about Sci Fi (however this is not to be confused with Science Fantasy in the sense of sci fi that incorporates fantasy elements).

At its worst (regarding scientific plausibility or lack thereof) Mushy Soft Sci Fi does not even attempt any explanation, or else those it does are patently absurd, just complete scientific nonsense. However, it cannot be called Science Fantasy, Magical Realism, or whatever, because it is still supposedly set in the “real world”. Differs from Very Soft in that it does not even give the pretense of realism (e.g. in munchkin sci fi you can still have a zillion erg blaster beam as long as there is some technology like a big ray gun cannon to generate and “explain” it; in this category you don’t even need that). Note that, as always, this is not a value judgment, only a science and realism comparison. This material (e.g. superhero comics) can still be very entertaining and enjoyable to read.

Science, Technologies and Themes in Mushy Soft SF

The following are some themes and technologies that might occur in Mushy Soft (but not in reasonably thought out Soft ) sci fi settings. These things are impossible and often outright fantasy. We can safely say though that all these things are the result of sci fi clichés, bad science, or both. They are included in sci fi for entertainment purposes, rather than being attempts to describe an authentic reality. They show not the slightest attempt at even the most basic understanding of how the universe works.

  • Intense radiation causes a creature to evolve into a more advanced form (why? look up the effect of radiation on living cells)
  • Intense radiation cause the locals to evolve into mishapen post-apocalyptic mutants. (not a shred of evidence radiation damage works this way)
  • Never-before encountered aliens that just happen to speak English (or whatever language the TV show is in) without the aid of some sort of translator device (this happens a lot on TV sci fi and is never explained)
  • Giant animals (e.g. Godzilla, giant mutant ants or spiders) can move exactly the way they could if they were normal sized (ignores scaling law – mass is cubed while length is only doubled)
  • Travelling to different solar systems in a matter of weeks (or less) without relativistic travel or some form of FTL drive
  • WW II fighter-plane analogy – Spaceships that maneouver by wheeling and banking in a vacuum
  • Naval Analogy – Space battles that occur only in two (rather than three) dimensions
  • Ground vehicle analogy – Spaceships that only move forward when you press the thrust button, otherwise they slow down, in a vacuum, in deep space (most computer game Space ship “sims”)
  • Spaceships that go “woosh” in a vacuum (sound cannot travel in outer space)
  • Mutants or Aliens (as in comic book) with superpowers and no physical way of justifying the energy, movement, strength, speed, invulnerability, etc that these powers provide
  • Beings that can not only change shape or form but also alter their mass while doing so (Incredible Hulk, etc)
  • Disintegrator guns and other soft sci fi energy beam weapons that can disintegrate a person or object without creating a backwash of plasma, superheated steam, any other effects
  • energy beam weapons that generate multi- megaton or gigaton blasts without generating any energy or explaining where the energy comes from
  • WW II analogy – Laser or energy beams travel about as fast as tracer fire, and are visible in a vacuum (in fact lasers are not visible in a vacuum and are invisible in clear air, although you can see them in smoky air).
  • Plucky baselines
  • Munchkinism
  • Any of a number of other Overused Science Fiction Clichés

For more on the sort of absurdities one frequently finds in pop soft sci fi, I again recommend the brilliant and hilarious external link  Overused Science Fiction Clichés

Some Examples of Mushy Soft SF

Dr Who (the first regular science fiction drama for TV, and incredibly innovative for its time, preceeding Roddenberry’s Star Trek by some years, although the early episodes are extremely dated by today’s standards and one can forgive the fact that the aliens often resemble baseline humans and speak English); also giant robot anime in general (the giant robots (“evas”) in Neongenesis seem to be too large to support their weight) though some exceptions could perhaps go under Soft/Very Soft). Space:1999 (no understanding of travelling between planets and stars), Superhero comic books, universes (Marvel Universe, DC Universe, etc) derivative movies (X-Men, Superman, etc) featuring mutants or humanoid aliens with astonishing powers, Dragonball Z and other martial arts type cartoons with energy bolts and so on, and many cult SF movies (Godzilla, etc, even in terms of size alone, the original Godzilla is physiologically impossible, let alone the even bigger American movie variant).

Science Fantasy, and Fantasy

Science Fantasy is a sort of overlap with sci fi, but contains specifically fantasy elements, and hence does not describe the universe in a rational way, although it still has rational elements. Pure Fantasy, and Horror, are distinct genres to Science Fiction, although some journals publish all of them together. Often in Sci Fi Entertainment forums and media (magazines, websites, etc), “Sci Fi” is used as a generic term that also includes fantasy, horror, supernatural stories, and so on.

SCIENCE FANTASY: claims to be SF, and indeed has or is based on self-consistent SF elements that would otherwise include it under SF, but also includes one or more supernaturalist elements that remove it from the realm of pure SF. George Lucas uses the term “Space Fantasy” to describe his work, although it seems to me that – except for its fairy tale prologue (“a long time ago in a galaxy far away”) – Star Wars can more properly be included with other Soft Sci Fi popular universes. The only “fantasy” element in SW is The Force, and even this is explained in technobabble terms (midichlorians”) in the prequel trilogy.Examples include Peter Hamilton’s Night’s Dawn Trilogy and the Shadowrun rpg (both of which incorporate supernaturalist elements into an otherwise typical medium (space opera) or very hard (cyberpunk) SF setting), and the Neongenesis Evangelion anime series

NOT SF: Makes no attempt to follow physical laws as we currently understand them, or infuses a magical technology that works for unknown reasons.Examples include Lovecraft’s Cthulian mythos, Tolkein’s Lord of the Rings series, and the fantasy and horror genres in general. Jeff Noon (Vurt and Pollen) would probably also go here (“cyberpunk” magical realism) as would China Mieville (“steampunk” fantasy).