Mohs Scale Of Science Fiction Hardness - Television Tropes & Idioms

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alt title(s): Mohs Scale Of Sci Fi Hardness; ptitlekov7423el8ye

The fun, and the material for this article, lies in treating the whole thing as a game. I've been playing the game since I was a child, so the rules must be quite simple. They are: for the reader of a science-fiction story, they consist of finding as many as possible of the author's statements or implications which conflict with the fact as science currently understands them. For the author, the rule is to make as few such slips as he possibly can.

— Hal Clement, "Whirligig World" (1953)

Isaac: Interesting. What's the explanation for how it actually works?

Warren: The hyperdrive utilizes IJD technology.

Isaac: Inter...dimensional jump? IDJ?

Warren: IJD. "It Just Does".

Absurd Notions, pg. 111

Speculative Fiction fanatics are always raving about how "hard" the science is in various stories — but it's not like you can rub a story with a piece of quartz and see if it leaves a scratch on the plot. So what is "hardness" in SF? Why do people want it? And how do we put a number to it?

Beginning with the first question: "Hard" Science Fiction is firmly grounded in reality, with few fantastic flights of fancy not justified by Science™. "Soft" Sci Fi is more flexible on the rules. Even the fantastical aspects of the story will show a divide — in hard SF, they operate through strict, preferably mathematical, laws, where in soft SF they just work however the author feels like. What this leads to for hard SF — and this is part of the attraction for many people — is a raised bar for the amount of work the writer must put into the story.

Example: A character is shown a time machine and asks, "How does it work?"

In hard SF: "A good question with an interesting answer. Please have a seat while I bring you up to speed on the latest ideas in quantum theory, after which I will spend a chapter detailing an elaborate, yet plausible-sounding connection between quantum states, the unified field theory, and the means by which the brain stores memory, all tied into theories from both Einstein and Hawking."
In soft SF: "You sit in this seat, set the date you want, and pull that lever."

Unfortunately for analytical purposes, this pattern is not universal - hard SF stories can skip over the details as long as the basic explanation doesn't seem to conflict with anything that's been established so far. Therefore, regardless of the typical stylistic flourishes

of hard SF, the only way to define it is self-consistency and scientific accuracy.

Which leads us to the Scale.

0. Softest: The MST 3 K Mantra is your Survival Mantra. Your Mileage May Vary as to how soft these marshmallows are.

1. Imported Alien Phlebotinum: There are technologies that break the laws of physics, but we don't have any real idea how they work, or they are dependent on a resource that apparently appeases some higher power.

2. Minovsky Particle: The laws of physics are broken in a specifically declared way. Expect hundred-page dissertations on fictional physics and consistent internal rules.

3. FTL Travel: The only intentional departure from the laws of reality is that we've finally outsmarted Einstein, or just made him look the other way while we slip by — at the very least to send messages. Everything else will be justifiable under known scientific principles.

4. No FTL: Mostly justifiable under known scientific principles, including any (necessarily sub-lightspeed) space travel, limited mostly to Interplanetary Voyages, with anything greater being a massive undertaking— Casual Interstellar Travel is an impossibility. Even if some aspects are slightly softer than in a story with FTL, the physicists will forgive it in exchange for appeasing their Einstein-worship. (Ken Burnside has a particularly scathing rant

to that effect.) Home of the Generation Ship.

5. Unobtainium: Contains only theoretical yet plausible elements. NO FTL in any way, shape or form.

6. I Want My Jetpack: Real Life plus Space Travel. The only objective way to grade these is by their age: newer generally means harder. Zeerust hits hard here - one can always tell when Science and/or Tech Marches On. Arguments as to why we do not have space travel do not belong on this wiki, but EVERYONE agrees that its lack is part of the reason We Suck.

7. Next Sunday AD: Exactly What It Says On The Tin. Just like now, but some interesting techologies are more effective and/or more accessible. This may or may not be a good thing.

8. Hardest: Real Life.

Bear in mind, of course, that no simple single-dimensional scale can encompass the full nuances of the idea of "hardness" in Science Fiction. (Just look at the arguments on the discussion page!) Other scales might be made - for example the Kheper scale

. Consider also the Mundane Manifesto — an attempt to define a set of rules for writing a hard SF story or series by deliberately forbidding many of the traditional tropes of media Sci-Fi.

Many find "hard" sci-fi superior for two reasons: First, maintaining internal consistency makes for tighter plots, and the Mundane Manifesto is a literal jungle-gym of hoops to jump through. You really don't have to care if you're making all it up. Whereas if you show your work on a complex project, everyone can tell that you are Doing It For The Art.

Second, both keeping track of your Acceptable Breaks From Reality and refraining from them altogether assist greatly in maintaining a Willing Suspension Of Disbelief. Compare: Imagine Helium-3

fusion

, and we'll have a reason to go back to the Moon. Imagine Minovsky Particles and we will build Humongous Mecha. Imagine Element Zero and we have Faster Than Light Travel. Imagine a Green Lantern Ring, and ... well, yeah.

Please recall, though, that harder is not always a good thing. Some authors try so hard to make a story realistic they forget plot and characterization, or end up justifying their occasional break from reality with layers of technobabble (never mind that the most famous example of that is on the soft end). Textbooks cannot replace storytelling - at least while you're telling stories. No degree of hardness is intrinsically better than any other, and any given person's preferences will depend on their personal tastes and the strength of their Willing Suspension Of Disbelief. Sturgeons Law trumps the laws of physics 90% of the time.

The name comes from the Mohs scale of mineral hardness

. Compare Sliding Scale Of Realistic Versus Fantastic and Sliding Scale Of Like Reality Unless Noted.

Please note: This list of examples is ranked. That means Soft stuff goes on top, and Hard stuff goes on the bottom. Softer items are closer to the top, while Harder items are further away towards the bottom. So, if you know about a really, really hard work of sci-fi, don't place it under "Hardest"; instead, place it at the very bottom of the list, right above "Hardest".

Please also note: Science Fiction only, please — no Fantasy.

Softest : The MST 3 K Mantra is your Survival Mantra. Your Mileage May Vary as to how soft these marshmallows are.

MST3K: Stuff happens. Don't think too much how. Characters breathe in space on at least two occasions. Artificially intelligent robots built entirely out of random spare parts. A VW Microbus converted into a spaceship. As the theme song says: "It's just a show. You really should relax."
Futurama: Chock full of every single popular science fiction trope, often with intentionally silly Reverse The Polarity style answers to justify them. Only "harder" than MST 3 K because there's no MST 3 K Mantra in the opening.
The Hitchhiker's Guide To The Galaxy: Packed full of all kinds of bizarre nonsense (one example — the fastest mode of travel through the universe is by bistro. Yes. Bistro. As in "place you eat in" or "second most overworked word in food marketing after new "), but the stories are fully aware of how absurd it is, and the reader is encouraged to think about it.
- The word 'bistro' is very likely derived from Russian "bystro" which means -quickly- or -fast-.
Tengen Toppa Gurren Lagann: The universe is not run not by the laws of physics, but by the Rule Of Cool. While the show remains *relatively* non-screwing with physics in the first arcs, the latter one more than makes up for it.
Getter Robo: being pretty much Gurren Lagann's Spiritual Grandaddy, it's pretty much just as unscientifically ludicrous and run by Rule Of Cool (hell, Spiral Energy's a giant Expy of Getter Rays). The only reason why it's "harder" is we have yet to see Ryoma kill a giant robot using a pair of sunglasses.
Digimon: Kids traveling with data-based lifeforms from a parallel universe founded Earth's Communications network. If it the explanation didn't involve technology, most seasons would be considered pure fantasy. Digimon Tamers is slightly harder, but not by much.
Star Trek Voyager: Ship went so fast that it was everywhere in the universe at once and then the crew "evolved" into lizards? Yow! (Specifically the episode "Threshold", recapped here.)
- It never happened.
EarthBound: Psychic powers, zombies, a living tent, mind-controlled sentient animals, a dog possessed by a member of the dev team, a cult that worships the color blue, an idol that makes people greedy and an Azathoth clone as a Big Bad. And the sequel is even weirder.
Air Gear: Where to start? Start by forgetting everything you've heard about inertia, gravity, and especially aerodynamics. Wielding motorized Rollerblades the right way will allow you to fire hurricanes at people. Hundred-foot drop? No problem, your A-Ts will absorb the impact. The awesome part is that all of it is explained in the manga. While air gear starts off semi-realistically, it's as if the author just keeps making up laws of physics on the go, purely to to justify increasingly unrealistic attacks.
Pokémon: Takes place in an Alternate Universe where the only major difference is that evolution took a completely different route. Some of the creatures have rather fantastic powers, though most of the more outrageous ones are given at least some justification (Slowking is superintelligent because toxins reacted with its brain chemistry, burns from Houndoom's fire never heal because enzymes in the flames prevent skin from regrowing, etc.). There are also several technologies which are somewhat unrealistic, such as teleportation and the ability to convert a creature into Pure Energy for storage and reconstruct it later.
Kingdom Hearts: Extremely condensed universe, yet each planet is somehow represented as a distant star. Faster than light travel, deflector shields, tiny Single Biome Planets, Asteroid Thickets, a Space Whale, do-anything computers (including an Inside A Computer System sequence), and the softest of mad science.
Command And Conquer Red Alert series: It starts off with Einstein traveling back in time to assassinate Hitler. By the time we're finished, we have dolphin commandos, psychically-controlled giant squid, electricity-draining UFOs, psychic soldiers that set people on fire with their minds, cloning machines, teleporting commandos who erase their targets from space-time, and bear paratroopers.
- Bearatroopers.
- Lampshaded when in in the Red Alert 2 mission "Fallout", where after being given control of dolphins to fight mind-controlled squids, Lieutenant Eva, asks "What's next, killer whales?"
Transformers: Okay, so there are these impossibly ancient space robots, right? And they come to Earth in search of energy, right? And to disguise themselves, they turn into cars and trucks and guns and stuff, right? And the cars have realistic engines and passenger compartments and tires and everything, even though it's actually a giant outer space robot. Oh, and some of them can shrink down from giant space robot size to tape deck sized. And some of them are entire living cities and planets and stuff. Throw in a bunch of coked-out 80s kiddie TV writers who are just in it for the cash, and you've got a recipe for insanity.
Warhammer 40000: Chainsaw swords, psychic spacemen, elves in space, orcs in space, undead robots, planet-eating bugs, three-hundred-metre-tall millennia-old walking battle cathedrals, soul-eating space stations and vehicles that travel faster because they're painted red (justified). The primary means of FTL is flying through Hell. In 40k, Rule Of Cool is physics.
Power Rangers: It varies from season to season, but within a fairly narrow range. It sets its own rules and follows them surprisingly well; its just that none of those rules make any sense whatsoever from a physics standpoint, biological standpoint, or otherwise, even if you count morphing itself as the One Big Lie break from reality. This one-exception-granted break explains a great deal, but not enough to place it higher on the list.
Neon Genesis Evangelion: A lot of the Applied Phlebotinum in this series involves branches of biology and engineering that neither exist in real life nor are ever likely to exist. "Metaphysical biology," for example — Doctor Kozo Fuyutsuki's specialty — is kind of like genetics, only it involves human souls instead of genes.
The Lensman novels: A classic pulp SF series, which originated the trope of Space Police armed with incredibly powerful and flexible weapons, and arguably, the whole Space Opera genre. Lensmen had intertialess drives, habitable gas giants (with surfaces you could land on)... it was pretty soft even when the first stories were published (in the 1930s), and since then, the march of science has made hash out of most of its assumptions.
Star Trek (the 2009 film): One of the squishiest incarnations of the franchise yet. Just a small sample of how soft it is: it contains (1) Time Travel (2) by flying through a black hole. Black. Holes. Don't. Go. Anywhere. They're extremely dense objects in space with an immensely strong gravitational field, not some sort of actual hole you can go through. Had they used wormholes — as other Trek series occasionally have, clearly distinguishing them from black holes — they might have had a stronger justification, but they very explicitly made it a black hole. They could have also gotten away with having a ship fly back in time by "warping" around a black hole (or star), which is an established in-universe rule. But instead, they literally went into the black hole. Which was just a hole. In space. And then they came out the other end, in the past. So Yeah...
- Even the best theoretical justifications (involving, for example, Kerr black holes) do not provide a way to exit a black hole before entering it.
- There is, admittedly, a very limited amount of No Sound In Space — from the audience's point of view, there is sound, but when shown from the point of view of the individual characters, there is no sound.
Suzumiya Haruhi. The series has already enough problems with Science Fiction Versus Fantasy. Vaguely defined Applied Phlebotinum doesn't help! At least the Time Travel is clearly elaborated.
- Haruhi is entirely consistent; it's just that its "one big lie" is bigger than most.
Freelancer: Space Is An Ocean in its top splendor. The space battles look like World War II air battles, only without the limitation of gravity. And on top of that, the in-game scale is warped enough to have entire planets with a 200 meters atmosphere, and no more than 2 km of diameter. These "softnesses" can be considered Acceptable Breaks From Reality, though, because they actually make the game more playable.
Farscape: Generally let the needs of the plot come first while known science could take a flying leap for all it cared. Sort of lampshaded in "I Shrink Therefore I Am" when Sikozu starts pointing out all of the reasons being shrunk to one one-hundredth your normal size shouldn't work and Rygel tells her that he's learned to accept the universe as it comes and not worry about what he thinks he knows.
Star Wars: Magic is present, though it is not called magic. The Death Star runs on Applied Phlebotinum and the Rule Of Cool. Lightsabers. Dramatic Sound In Space. Old School Dogfighting. Etc.
- The Star Wars Expanded Universe ranges up and down the Scale Depending On The Writer. Relatively easy interstellar travel, the existence of the Force, and many and varied alien species are all constants, but otherwise it's largely up to the writer. Some books actually try to explain away some of the soft elements from the movies.
Ratchet And Clank: Almost every entry in the series has an item which can turn enemies (including entirely non-organic robots) into a chicken/sheep/duck/pig/cow/penguin in seconds. So Yeah.
Red Dwarf: Hard to place because, as a comedy, it naturally has many absurd elements, but the Absent Aliens, the fact that it takes time to go places, the way robots are treated and (in earlier series) soft light holograms make it seem a lot harder than most. The novels are harder.
Doctor Who: Varies, being harder and softer at certain points in its extremely long run. The whole Timey Wimey Ball that's part of its premise tends to soften it.
Star Trek Deep Space Nine: Although taking place in the same era as Voyager and The Next Generation, there was much less technobabble and fantastic plots, with instead a greater focus on diplomacy and personal interaction. The honking great war that dominated the last few seasons probably helped harden things up too.
Star Trek The Original Series: Debatable though, many aspects of the show were pretty hard sci-fi when it was created, and only seem strange now after decades of science. Though the setting is stranger than other Star Trek shows, the ships and the technology are much more grounded.

Imported Alien Phlebotinum: There are technologies that break the laws of physics, but we don't have any real idea how they work, or they are dependent on a resource that apparently appeases some higher power.

The Stargate Verse: Considering the entire premise of the show is that ancient Earth religions were based off of alien snakes that take over your body or little grey men, that Atlantis is really a flying city in another galaxy, and that if you die, you can pop back again good as new after ascending/sleeping in a sarcophagus/being rebuilt by nanobots... it's surprising how hard they can get if they put their minds to it. StargateSG-1 got softer as it progressed, letting mystical concepts like Life Energy, Ascention, Evolutionary Levels and the power of belief take center stage. It also loses points for having each show's Omnidisciplinary Scientist actually figure out how to mass produce much of the Phlebotinum. Just In Time for the SGC to Save The Day. Over and over again.
Andromeda: Tries to be harder than Star Trek. Set farther in the future, and teleporters, interstellar radio (they use couriers to deliver mail), and holodecks (they use virtual reality instead) are all still impossible. Rather than hand phasers, they use small tracking bullets, or if they're desparate, plasma bursts, though they can only fire a few shots of those. Also, their main weapons are small missiles traveling near the speed of light that hit with their kinetic energy. Trouble is, a lot less stuff is actually explained, meaning you usually have to take their word for it or make something up yourself whenever they use technology.
Command And Conquer Tiberium series: Uses only one form of real Applied Phlebotinum, in the form of the titular Tiberium, but Tiberium itself has all manner of weird properties. By the third installment, though, the Sufficiently Advanced Aliens arrive with all manner of odd and physics-bending technology.
HP Lovecraft, by his own admission, preferred to "supplement reality rather than contradict it." His fiction takes a serious look at humanity's true place in the universe, and is full of Extradimensional beings, Starfish Aliens, and scarily plausible explanations; there's no use of Aliens Speaking English or Rubber Forehead Aliens unless they're played for horror (since neither trope should naturally occur). Lovecraft stories also provide scientific-ish sounding rationales for merfolk, time travel, and the effects of witchcraft (it's really math).
The Uplift series, by David Brin: Hard science mixed with a lot of Imported Alien Phlebotinum to make one of the 'hardest' of the Space Operas, a sub-genre that is usually very 'soft'.
The Halo; some of the technology used by the UNSC is upgraded real-world tech or technology based off predicted future developments, like railguns and AIs. The primary form of FTL are extremely dangerous and unpredictable "Slipspace" drives. Things get a lot weirder with time-and-space-bending Forerunner technology, which is made worse by the comparative weirdness of their tech and flatly refusing to explain how anything works.
Macross: Plenty of Humongous Mecha, No Sense Of Scale and ships that pack more than their own weight in missiles. On the other hand, space combat scenes are not particularly fanciful and there are realistic depictions of zero gravity environments, decompression and the like.
Babylon 5: No Space Friction, the Starfuries are a particularly sensible fighter designed for space, Artificial gravity is a prized technology beyond the means of humans and has a significant impact on the maneuverability of ships, whereas many others need to simulate gravity via rotating sections in the ships or space stations. Objects destroyed in space most decidedly do leave debris behind, at least as much as the CGI effects of the mid-90s could portray. FTL travel exists, but is but no means easy — Hyperspace is decidedly different from normal space and hard to maneuver in, and only large ships can access it on their own power without Jumpgates. JMS loves all kinds of aliens, and they run the gamut from Human Aliens and Rubber Forehead Aliens (implied to be the result of genetic tampering rather than natural evolution) to full-blown Starfish Aliens, all with their distinct customs and religions, and biology is treated fairly logically (there are two cases of Half Human Hybrid occuring, and both are the result of one parent using Applied Phlebotinum to make themselves compatible with the other species), diseases cannot cross species without distinct biological similarities and obtaining medical information and blood supplies of all the different species is an important point for the station's doctor. There are no Translator Microbes either; learning other species' language is important at many points in the series and many aliens retain a distinct accent when speaking English. While Translator devices exist, they are also fairly realistic — of visible size, tailor-made for a specific language rather than universal, and they translate in a flat, dull monotone. However, Sound In Space, Sufficiently Advanced Aliens and Psychic Powers do exist. The biggest problem are probably that JMS wouldn't know about scales if you hit him on the head with a lightyear long yardstick, and the Explosive Instrumentation make any savvy viewer cringe. Some of this may be Executive Meddling, though.

Minovsky Particle: The laws of physics are broken in a specifically declared way. Expect hundred-page dissertations on fictional physics and consistent internal rules.

While not a sci-fi anime in the traditional sense, Fullmetal Alchemist can actually be considered surprisingly hard. Alchemy, once a widely accepted science, is shown to not only follow consistent rules, but actually maintain conservation of energy. (In the movie while Ed was in the "real world" it was even mentioned how Newton’s laws disproved alchemy.) Finally, for the time period (if the time period is parallel with the other world) the technology is close to the same level albeit using alchemy instead of science (e.g. Model T — looking cars, a "new" refrigeration truck, and so on...) And as for automail? Goetz von Berlichingen had an amazingly versatile prosthetic even without Functional Magic.
Last Exile: Like Fullmetal Alchemist, this odd duck is not a sci-fi anime in the traditional sense. However, this Steam Punk anime transposes Age Of Steam warfare with aircraft made possible by a single fictional element; a reactionless fuel known as Claudia.
Anne McCaffrey's Talent series was, for the most part, a rather hard Sci-Fi. She supplied understandable ways in which psi powers might manifest and how they worked. Since psi powers were primarily limited by how much energy a human being could create, being able to gestalt with an electrical generator to supplement one's psi makes sense. Also, screw using any sort of advanced technology for FTL travel or communications, let's use our psi's!! Although, the series did begin to head a bit more towards the "softer" side with the more aliens contacted (a grand total of two species), but she also did a fairly good job with them as well. One was insectoid, one was...vaguely humanoid. The energy requirements also tended to go out the window as each generation got more powerful and had less and less reliance on generators.
Sid Meiers Alpha Centauri: The Tech Tree expands based on our current understanding of science, the quotes from the in-game characters always make sense, nonsensical Technobabble is almost nonexistent, and a lot of in-game scientific and technological advancements have already been predicted by several writers and scientists. Would be smack in the middle of "Unobtainium" if the Psychic Powers didn't look a bit too much like magic.
Mobile Suit Gundam: UC only; the later ones tended to add more fantastic flights of fancy, but the original only had Psychic Powers, Minovsky Particles, and the basic unlikeliness of Humongous Mecha (which it goes to great length to justify).
- Which series/universe is more "real" than others has lead to a massive number of flame wars. For instance, Gundam Wing doesn't go as far to justify the use of Humongous Mecha (largely using Unobtanium instead of Minovsky Particles,), but has no Psychic Powers and is the only series which has AI-operated mecha.
Infinite Ryvius: While its Space Is An Ocean (quite literally, in fact), complete with Space Whales, and contains Phlebotinum-based gravity-manipulating Humongous Mecha fights, the series also features relatively realistic Artificial Gravity and remembers to avert such things as Infinite Supplies and Sci Fi Writers Have No Sense Of Scale.
Alastair Reynolds' Revelation Space series: Has no FTL travel but does contain several superscience technologies, e.g. the Conjoiner near-lightspeed drive, space/time manipulating weaponry, messages from the future to the past (also the basis for FTL messaging). There is a form of FTL travel present, but it tends to get one's civilization eaten by the Inhibitors; realistic Cosmic Horrors.
The works of H. Beam Piper: Uller Uprising opens with an essay explaining the silicon-based Ullerans. There are no death rays, just bullets. Nuclear power is used. There's no full-on explanation of FTL, but when he gives a detail (such as gadolinium being key, or it including time dilation), he doesn't contradict it. (The Paratime series, on the other hand, is quite soft, right down to giving reincarnation a free pass in one story; granted, that was a case of Writer On Board).
A Miracle Of Science: Everything that's used is explained via modern theory, with the exception of a few staples such as FTL and Deflector Shields — which is only used by a sect of Sufficiently Advanced humans. Fairly impressive for a series based around mad scientists running amok.
Jerry Pournelle's Co Dominium Shared Universe: Military Science Fiction hard enough to chip teeth. It has a Portal Network and a Force Field designed by Dan Alderson, a Real Life celebrated scientist at JPL. Two books co-authored with Larry Niven introduce a species of distinctly non-Human Aliens, but they are sublimely well-constructed and everything else — everything, is real, proven or entirely plausible near-term technology. Pournelle even counted on Science Marching On, justifying it with Medieval Stasis enforced by the namesake Obstructive Bureaucracy.
Both the Night's Dawn and Commonwealth books by Peter F. Hamilton. FTL is done by the use of ZTT (Zero Temporal Transit) drives, which work by a well-explained principle based on wormholes, and stasis technology based on the same effect takes the place of Human Popsicles. In every other respect, very, very hard indeed, subverting the vast majority of the Space Does Not Work That Way tropes and just plain avoiding the rest; no dogfights in space, explosive decompression is only occasionally dealt with, and is done so with great accuracy, and space is far more like...well, space, than it is like an ocean.
The Honor Harrington book series: Space Is An Ocean, but the series demonstrates admirable internal consistency, relies on essentially only one piece of "new" technology (gravity control methods), mostly merely extending other pieces of current technology (medical science, nuclear fusion containment, lasers). Additionally, space combat is very three-dimensional and ship-to-ship engagements are often fought at fractional light-second distances (contrast the traditional Star Trek Starship Standoff).
Mass Effect: Its only fictional element is perhaps the Trope Codifier for the Minovsky Particle: Element Zero, a form of Unobtainium which defines every use of sci-fi technology. Quite realistically, something as important as eezo and the mass effect fields it generates fundamentally influences every aspect of society, meaning Kinetic Weapons Are Just Better even with man-portable Deflector Shields, and people born with the stuff in their systems can manipulate gravity. The programmers definitely have a great Sense Of Scale, as you traverse the galaxy via the Portal Network even with your mass effect drive. All the aliens speak English because of ubiquitous computers and translation software. The Rubber Forehead Aliens are in fact the most alien, with truly Bizarre Alien Biology. Everything else in the setting reflects realistic science, including accurate geography, geology, astrology, physics, alien biology, computing, and military tactics and strategy. Think of it as Planetes with a squishy eezo center, like a Everlasting Gobstopper.
Vernor Vinge's The Peace War, The Ungoverned and Marooned in Realtime: Mostly explore the consequences of a single fictional technology: time-stopping stasis bubbles.
Larry Niven's Known Space stories: No Human Aliens here! Er... with one exception, and the humans tend to simply do very unlikely things. A variety of "interesting" planets are explained by way of a subtle bug in the first generation of colony seedships: Instead of seeking a habitable planet, they settled for a habitable point (and didn't examine that too thoroughly). Thus, one colony is on a plateau of habitable land in the upper atmosphere, above a Venusian miasma, while another is swept by hurricane-force winds for most of its year (the probe arrived in the calm season). The FTL, Artificial Gravity, Psychic Powers, stasis fields and other Wondertech keep this from being rock-hard scifi, but the astronomy is very solid, and much of the supertech is purchased from Sufficiently Advanced Aliens. Niven gets uber bonus points for having obsessively Shown His Work, and occasionally retconning fan-discovered errors. ("The Ringworld is unstable!")
Schlock Mercenary is almost entirely plausible scientifically, although little of the theory appears in the work. Its placement is primarily due to limiting its Applied Phlebotinum to gravity manipulation(but not generation — ships are built around spheres of neutronium as sources of gravity to manipulate), taking it for granted that the process is as well developed as electronics, and playing the result to its natural conclusions; ubiquitous flight, Deflector Shields, traversable wormholes(one example which justifies a Time Travel storyline), and quantum teleportation. Some find the easy nanotechnology a bit of a stretch.
Eve Online: FTL speeds are possible, but only applicable within a single solar system. As far as players are concerned, bridging the massive space that separates solar systems requires advanced stargate technology or highly costly specialized equipment that costs even more to use because of fuel limitations. The latter method requires a ship or particular structure already be in the system, while the stargate network was built by absolutely massive ships traveling between systems at roughly .3c. Weapons are fairly realistic, employing relatively justifiable laser technology, magnetic railcannons, particle weapons, missiles, drones and even good old fashioned bang-you're-dead projectile weaponry. The universe is ridiculously huge, much like actual space, with over 7000 unique solar systems, though it falls short of the following category because, as New Eden's space is based on fluid physics and has the viscosity of firm gelatin, ships have a "Top speed" and decelerate once the engines turn off. The fluff states that this is an effect of the warp drive and that a ship without one would travel through space realistically, but be limited to sublight speeds within a system.
Battlestar Galactica: The 2003 series, despite taking place in another solar system, had mostly real-world technology as far as the humans were concerned with the exception of FTL technology. However, Cylon Resurrection technology involved downloading a Cylon's memories upon their death and frequently beaming them across vast distances of space. The process was usually handled pretty consistently but was never explained in detail as to how it is possible.

FTL Travel: The only intentional departure from the laws of reality is that we've finally outsmarted Einstein, or just made him look the other way while we slip by — at the very least to send messages. Everything else will be justifiable under known scientific principles.

Starship Operators has FTL travel (called warp drive, no less) and inertial dampeners but is otherwise very hard.
C.J.Cherryh's Hell Burner books. FTL travel does exist, but usually happens to someone else. The peculiar nature of near-light-speed combat is very seriously considered, as are the dangers of space, the nature of large-scale construction projects, and the proper procedures for pressure suit maintenance.
Freefall: Tends to limit itself to 'theoretically possible but difficult' technologies, such as genetically enhanced sapient animals, terraforming, AI and cryogenics. Even artificial gravity is absent (as the name suggests), and though the Dangerous and Very Expensive(D.A.V.E.) Drive enables interstellar voyages measured in days, it is explicitly not Casual — Planet Jean was colonized by slower-than-light ships carrying Human Popsicles.
Contact by Carl Sagan: Scientists spend the first third of the book struggling to raise money for the SETI program amid sponsoral skepticism. Once they finally find an alien transmission, they spend the second third deciphering the transmission, considering all the possibilities involved, and thoroughly applying the scientific method, all the while showing the social impact of knowing that we're not alone. It would rank even lower in the list if the last third was not about building borderline Imported Alien Phlebotinum, but it could be softer, because the setting and the clearly established rules actually make the alien device look rather hard.
Alien and its sequels. Spaceships have slow FTL travel, during which the crew lie in cryogenic sleep for months or even years. The many discovered planets go by numbers, but almost none of them are naturally inhabitable.
Three Worlds Collide has the physics associated with the "Alderson starlines" edging it up the scale, but is otherwise fairly realistic in the physics department.
Blue Planet: A semi-hard SF RPG. FTL travel only through wormholes. The biotechnology is very soft in places, and gilled mammals have certain thermodynamic issues.
Robert L. Forward's Timemaster: probably one of the few hard science fiction stories you'll ever encounter that has Time Travel at the core of the plot. The only iffy element is a substance with a negative rest mass: although such a material has never been observed, several mainstream theories of physics predict its existence.
Ursula K Le Guin's Hainish Cycle novels: There is no FTL travel, although there is FTL communication using the Ansible. Travel between stars involves nearly-as-fast-as-light ships, and comes with "realistic" time dilation effects. Very little super-technology is discussed beyond this, except for some hints about genetically engineered species. Nearly — human aliens appear, but a major plot point is that they all share a common ancestor with us; so essentially, they are literally human aliens. On the other hand, the novels tend to focus on people and societies, so relatively little space is dedicated to describing how technology actually works. Telepathy also makes an occasional appearance, though it is discarded in later novels (Le Guin wrote that essentially, she did away with it because Science Marches On — telepathy seemed more plausible when she was writing the earlier works).

No FTL: Mostly justifiable under known scientific principles, including any (necessarily sub-lightspeed) space travel, limited mostly to Interplanetary Voyages, with anything greater being a massive undertaking— Casual Interstellar Travel is an impossibility. Even if some aspects are slightly softer than in a story with FTL, the physicists will forgive it in exchange for appeasing their Einstein-worship. (Ken Burnside has a particularly scathing rant

to that effect.) Home of the Generation Ship.

Firefly: No sound in space (except for inside the ion cloud in The Movie, where the sound has a medium to travel through) and no aliens, and a few other things that seem like the writers actually did do the research (such as how nasty stomach wounds are), but there are some things, such as terraforming, temporary cryonics, Artificial Gravity and space ships that may or may not be viable 500 years from now — though all of them seem to have problems. Terraformed worlds all have "quirks" such as unique diseases that crop up or "black rock" failures, cryonics can cause a bit of a shock if you come out of it too quickly, spaceships break down easily, etc. The most improbable feature of the world is probably River's apparent telepathy, and even the characters aren't sure they believe it. The ships also move at the speed of plot, with Whedon waffling back and forth as to whether or not they can travel faster than the speed of light — it's eventually revealed that it's all in one (fairly large) solar system, so given that ships travel between planets in a timeframe of days or weeks, travel is definitely subluminal, if still fairly fast. The ships that left Earth took a "generation" at least to get to the system, but that was presumably generations before the story takes place.
- It was. Extra materials note that even just the completion of terraforming on most of the non-Core worlds was completed in 2435 (the series/movie is set in 2517 and 2518), and before that was the arrival of humans at the system and colonisation of major Core worlds such as Sihnon, Londinium and Osiris, with those worlds being overpopulated by 2435.
Dollhouse. The core speculation is that people are purged of their identities and imprinted with others - the rules are pretty consistent, and space travel doesn't enter into it at any point, but the internal science is still covered with loads of Techno Babble.
Cowboy Bebop: Has no Space Friction (except during dog fights), Artificial Gravity, travel outside this solar systems, and no FTL Travel. The least realistic thing is the Portal Network, which was only included to keep travel time between planets down — but is explicitly not faster than light. It takes place in an Alternate History where we had a Space Age instead of a Cold War, and developed efficient spaceplanes and Terraforming by the 2070s (and those things on Mars that look like Deflector Shields? Air curtains.). Much like Firefly above, a more improbable element is that they could terraform most planets and moons of a solar system to habitability.
Max Headroom: Strongly related to its Twenty Minutes Into The Future premise, though still spiced with the occasional TV commercial that makes people's brains explode. Which may be a comedic exaggeration of a Reverse Funny Aneurysm; certain TV shows have been known to trigger grand mal seizures.
The works of Greg Egan: Tend to include in-depth discussions of physics, maths, computer science and biochemistry in a non-Techno Babble way, and many start from the assumption that, given time, modern science will go the way of Newtonian Physics. He gets bonus points by never using this as a cheap excuse for FTL travel.
Charles Stross's Accelerando series: An Einsteinian universe without FTL but with traversable slower-than-light wormholes, with some handwaving of uploading and computronium. The characters speculate about distant aliens performing a timing channel attack on the computational ultrastructure of space-time itself, and the eventually-weakly-godlike-robot-cat claims to have a Halting Oracle, but that might be intimidation.

Unobtainium: Contains only theoretical yet plausible elements. NO FTL in any way, shape or form.

Stellvia Of The Universe never clearly contradicts anything we know to be science fact, and goes out of its way to show such elements as journeys between Foundations within and around the solar system taking several months. The Starfish Aliens being able to plant a spy among the humans does kind of hiccup the Starfishness of the Aliens, the amount of energy the lasers can fire is astronomical, and the Fracture is based on a somewhat questionable physical model, but the writers nonetheless have a pattern of Showing Their Work.
Robert L. Forward's Rocheworld setting was quite hard (it should be, he's a physicist). The only major implausibilities in the first book are alien life and a life-prolonging drug. Points are lost to Sequelitis; In the third and later books, the science softens to mush, including finding native coffee beans on the moon of a gas giant circling a red dwarf.
Ben Bova's Grand Tour novels: Perfectly credible spaceflight-within-the-Solar-System stories. The only Phlebotinum is nanotechnology, which is at least theoretically possible. Some extraterrestrial life features, but it is plausibly primitive.
Allen Steele's Near Space series. Spaceflight-within-the-Solar-System stories with no Phlebotinum at all, except in the farthest-future setting, A King of Infinite Space, which features reversible cryosuspension and a class of humans genetically engineered to function in space.
Century City: The science tried to be hard. The plots, on the other hand...
Gattaca: The gamete selection technology portrayed in the movie is a reasonable extrapolation from technology that already exists; indeed, the furthest-out thing in the film is a manned expedition to Titan (and given an entire world population of geniuses, it's not much of a stretch except for the fact they don't wear spacesuits or seatbelts).
Vernor Vinge's Rainbows End: Set Twenty Minutes Into The Future. The most speculative parts concern the existence of certain vulnerabilities in the human brain against information-based attacks.
Strange Days: A film with one innovation ("playback" of memories via portable superconducting quantum interference devices) and the consequences thereof.
Patlabor: What giant, humanoid robots would be like in the real world. All units are awkward to pilot and their abilities are extremely limited. Police-issue labors can brawl with rogue worker mecha but will get utterly trashed by a simple gatling gun. Military labors are few and far between, and common anti-tank weapons are quite effective against them. Pilots need months of training and software assistance to perform well, and so on.
The works of the dearly departed Michael Crichton. He frequently showed his work about plausible technology as it becomes workable and just before It Got Worse; usually because arrogant humans insist on Tempting Fate. Once he acquired a degree of Protection From Editors, he took advantage of that to move into more controversial territory.
- The novel State Of Fear was arguably the low point of his career in terms of hardness, as it attempted to pass off a great deal of debunked, misleading, and generally bad science as fact in order to claim that global warming was a hoax. The softer elements range from honest cases of Did Not Do The Research, like getting the mechanics of hurricane formation completely backwards, to arguments about natural forcings that have been refuted by research conducted both before and after the book was published. See the book's page for more.
- The films even less so, primarily due to Executive Meddling.
The works of Thomas Pynchon. Mr Pynchon studied engineering physics in the '50s, and studied WWII in the '60s, and it shows.
- There is, however, an unexplained oddity that calls Causality Itself at the core of Gravity's Rainbow.
GURPS Transhuman Space: So far possibly the hardest SF RPG released, no FTL whatsoever. Biotech is harder than Blue Planet, but still somewhat soft in places. The AI (and especially "uploading") are speculative at best.
The Ghost In The Shell franchise — particularly the first manga. Shirow Masamune goes to great lengths to make his Technology Porn look as realistic as possible - for example, Project 2501 is a learning algorithm for gaming prediction pools. Most of the problems this troper sees with it are due to Science Marches On, or (more frequently) political changes unrelated to the technology. The author is apparently a retired science teacher.
- Man-Machine Interface adds Psychic Powers to Shirow's Post Cyber Punk universe. His opinion is that Science will March On, validating theories previously discarded, so your mileage may very well vary:
  Masamune Shirow: It's easy to shrug off psychic phenomena as being "unscientific", but assuming the person experiencing them isn't totally faking it, it's probably more scientific to consider such experiences in psychological or neuro-physiological terms. They could, for example, be considered the result of "naturally-occurring magnetic or electrical phenomena that affect the brain," or they could be analyzes as a type of "mass hypnosis," etc. It's unscientific to laugh off poorly understood phenomena instead of trying to analyze them.
Neal Stephenson's Cryptonomicon and The Baroque Cycle. They'd be straight-up historical fiction if not for the Solomonic Gold.

I Want My Jetpack: Real Life plus Space Travel. The only objective way to grade these is by their age: newer generally means harder. Zeerust hits hard here - one can always tell when Science and/or Tech Marches On. Arguments as to why we do not have space travel do not belong on this wiki, but EVERYONE agrees that its lack is part of the reason We Suck.

The movie Destination Moon; written by Robert A Heinlein with assistance from that worthy's many, many friends in the United States Armed Forces.
The Tintin stories Destination Moon and Explorers on the Moon. The print medium enables Hergé to better display the colossal engineering needed to develop interplanetary spaceflight. Though science has marched on considerably since it was written, at the time it was practically a student's primer on both nuclear energy and spaceflight.
2001: A Space Odyssey: Unusually among films and TV series with space travel, the vacuum of space is actually silent. Oddly enough, this is one of the few cases where the book is softer than the movie, due to going further into the details. The iconic monolith is ill-defined, but never really breaks any physical laws. Unscientific elements tend to be part of a Mind Screw.
- One difference between the film and novel is that the novel explicitly contains an instance of Faster Than Light Travel, while the equivalent point in the movie is kept vague. The events shown could instead be interpreted as a metaphorical, psychological journey, for instance - nothing is shown or stated to make it clear one way or the other. Since the book and film were created at the same time and differ on a number of other points, the book's more explicit explanation need not take priority. Clarke's later sequels to the 2001 novel also eventually ret conned the FTL travel away.
- In the sequel novel (2010: Odyssey Two) and movie (2010: The Year We Make Contact), Jupiter gets turned into a mini-sun. When one of the characters starts to complain about the scientific problems with this, another one tells them to shut up; obviously it can happen because it is happening, and the scientists will have plenty of time to think up an explanation for it later.
Star Cops: Very hard in its late '80s way.
Space Odyssey Voyage To The Planets: Set an indeterminate number of decades in the future, this docufiction tells the story of a manned mission to Venus, Mars, Jupiter, Saturn and Pluto. Contains some (relatively mild) examples of Space Does Not Work That Way, though. Will most likely be highly vulnerable to Science Marches On in the near future.
Planetes: Commercial spaceflight less than a century in the future and almost completely limited to the Earth Sphere itself. Detailed orbital mechanics, realistic effects of space on health, dependency theory, diapers under spacesuits, and invisible laser beams. INVISIBLE LASER BEAMS. Even the gratuitous In Space Everyone Can See Your Face is justified as mere thematic close-ups on the characters' faces — with their faceplates down. Its premise — the collection of space garbage to prevent multimillion-dollar spacecraft from being scrapped by screws — technically a real problem but economically unfeasible, but this is actually a major plot point — though the job is essential to commercial space travel, the fact that nobody can find a way to make money off it but companies are required to do it by government regulation means that it's done by office drones with gear older than they are.
Moonlight Mile: Planetes with raunchy sex. Set in a present day where Helium 3 fusion has become viable; the Space Race has begun anew. What Do You Mean Its Not Political?
Rocket Girls: Moonlight Mile without raunchy sex. The first private company to conduct satellite maintenance has hit a snag - their rocket is underpowered and their astronaut has freaked out. Solution? Find new astronauts... lighter astronauts... The only improbable thing is getting high school girls to be astronauts. And fully functional skintight spacesuits, though these ones will shortly replace those big bulky spacesuits from nowadays.
Moon: Minus the Space Is Noisy and cloning it was so spot on, NASA personnel who screen tested the film just to see how close they got it were pretty impressed. The best explaination is when one of them asked the Director, "Why does the base look like a bunker?", he replied that he figured that it would just be easier (and cheaper) to transpose stuff that already existed onto the moon — and then another in the group stated that she's in fact working on just that.
Shattered Horizon: An FPS set in space, featuring true zero-G manuevering and combat, inertia, a story that is completely feasible given the timeline (man colonises and mines the moon around 2040) and no sound- while there are battle noises, these are generated by the suit to help with situational awareness. Should the suit be powered down, all you hear is your heartbeat.
The Moon Is A Harsh Mistress: Minus Mike itself, pretty much everything is already around, or could easily be put together in the next half-century (the book is set in 2075-2076). The only fly in jam here is that we had a moonbase for a minimum of thousands by the 90s.

Next Sunday AD: Exactly What It Says On The Tin. Just like now, but some interesting techologies are more effective and/or more accessible. This may or may not be a good thing.

Ace Combat: Planes are almost all realistic. Of the fictional planes featured, two late 20th century/early 21st century ones (namely the X-02 Wyvern and ADF-01F Falken) have been modeled in X-Plane and found to successfully fly under modern aerodynamics knowledge limits, while the rest generally are found a while down the road. You have some funky stuff like "burst" missiles, cluster air-to-air missiles, fighter-scale and superweapon-scale lasers and neural synapse flight-control systems, but most of these have some real-life basis and it's not too great a stretch to think that some could be created IRL with enough funding and political will. There are some key implausibilities like being able to shake off missiles without using countermeasures... or the Hyperspace Arsenal... or the downplaying of BVR combat... but these fall under Rule Of Fun - the games would be far less playable without those features.
- I understand that the background setting is very realistic, but the arcade game style really stretches to what can be "hard". I accept that a lot of the gameplay isn't played as canon for it to be realistic, but at a point you have to stop. The fact that wars are literally determined by one plane or squadron is shown as what really happens in the history of it's world, but these would be incredible odds. You can only stretch it so far without breaking past reality by having two planes go up against 8 extremely and highly trained pilots with motivations to match with 4 in stealth F-23 level planes then somehow even have the fuel to make it to the next stage which has even more obstacles that require missiles.... This is just the tip too... I consider this much higher in the ladder to softness.
Dennou Coil: Cyberspace via Goggles That Do Something Unusual. As with 2001, the more unscientific elements are part of a Mind Screw.
Twenty Four: A cell phone like Jack Bauer's would cost several grand, but it's not at all impossible. The plots on the other hand are another story. Points are lost to Syphon Filter-like viruses and nuclear meltdown-inducing laptops.
Re Genesis: Set in the present, Re Genesis uses bleeding edge biology for its science fiction aspects. Sometimes it's less science-fictiony than CSI.
Real Life: A Shared Universe which spawned its own genre, known as "The Documentary". Real Life has spawned much imitation, and comes close to the hardest end of the scale, but Reality Is Unrealistic.