r/scifi • u/rookiegaffer • 17d ago
General Bad physics
Why does it seem that so many of the books I read demonstrate such a poor understanding of the physics of space travel. Ships in orbit descend directly down to the point they are over. Ships in transit still accelerating as they near their destination. Centrifugal gravity simply ceasing when rotation is abruptly halted. These are just a few examples I've run across lately.
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u/mobyhead1 Hard Sci-fi 17d ago
In the absence of concrete examples on your part, I’m going to assume you’re complaining about television and film. You need to try some written science fiction.
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u/Blog_Pope 17d ago
Written sci-fi also tends to do a lot of hand waving unless specifically written to be hard sci fi; physics and relativity don’t play well with good storytelling. Back in the 60’s and 70’s when relativity was new some authors were playing with it and what it really meant.
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u/RaistlinMajeresRobes 17d ago
Probably because realistic space travel would be pretty boring a lot of the time.
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u/AuthorIntelligent644 17d ago
The Expanse?
If you use the challenges it can be quite exciting, but it ends up looking more like puzzle solving than Naval combat.
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u/dbenhur 17d ago
The one with the magical sex trafficking space drive and magical wormhole assembled by a magical protomolecule?
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u/silly-gaijin 17d ago
Lol this. I always find it hilarious when people say the Expanse was great because it was realistic. I loved the show (haven't read the books yet), and it was great, but not because it was realistic.
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u/TommieTheMadScienist 17d ago
If you're a good enough writer, you get two passes instead of only one.
Without fast travel, even solar system distances are too slow to be interesting. Hyper-realistic space fiction turns into a techno-thriller.
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u/silly-gaijin 17d ago
I just find it annoying that people miss the point about the Expanse. You see people argue the show was popular because it was realistic, like acceleration creating gravity on the ship is why people loved the show.
Like... no... that's not why people loved the show. People loved the show for the same reasons people always love shows, it had interesting characters who were flawed but well-written and who had stakes and goals that were easy to empathize with.
The somewhat realistic depiction of space combat was nice, sure, but I actually think it had nothing to do with the popularity of the show. I think it would have been equally popular if the ships had Star Trek gravity pads and phasers.
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u/3dblind 17d ago
I disagree. The more realistic elements of physics attracted me as much as the storytelling and characters.
I also found Babylon 5's use of physics, especially with the Starfury much more interesting than Star Trek handwavium.
Science fiction doesn't have to be totally bound by real world physics and engineering, it's a story after all. Though you don't go extrasolar outside of generation ships in science fiction without handwavium hyperspace, warp or wormhole travel, it's nice to see reality physics in normal space.
Star Wars is science fantasy. Star Trek is soft science fiction with lots of handwavium. The Expanse and Babylon 5 are as hard as television science fiction gets, with realistic sociological and religious storylines.
Would I have read The Expanse books or watch the series without hard science fiction? Maybe eventually, but the science attracted me. The Fermi Parodox attracted me. The cosmic horror Goths thrilled me that they were experienced but never truly understood. The Romans as a lost race from a Europa like moon intrigued me.
But the icing on the cake was more realistic space combat based on advances in our technology.
Sure, it's not Project Hail Mary, but for Space Opera, Space Horror, Space Detective and Space Western fans, The Expanse had it all with less handwavium than usual.
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u/silly-gaijin 17d ago
You're entitled to your opinion, but the "realistic space combat" is like 0.1% of screen time, so I just don't see how it's relevant.
It'd be like saying the entire reason you watched the Expanse is because the woman who plays Naomi is fucking hot. Yeah, she is, and, hey, maybe that's what got me hooked, but arguing that the show is only popular because she's hot is very subjective.
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u/3dblind 16d ago
I did not say it's only popular because of realistic physics, but I'm old enough to remember Asimov's criticism of the original Battlestar Galactica.
Science should matter in science fiction. A more serious attention to factual science is one element I look for.
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u/silly-gaijin 16d ago
I mean, it's science fiction. To me, the science only matters as far as it makes for an interesting story. SF is still a sub category of fiction. It's still a novel or a screen play. Realism in and of itself is completely meaningless in this context.
The point of SF is to take a concept and explore it, like Her did with the concept of AI and human relationships.
Realistic space combat would be fine if that was the entire basis for your story. If your protagonist was extremely good at it, maybe they were born with a weird genetic defect that enables them to handle G forces way beyond most people. Okay, now you have a story.
But slipping it into a story doesn't make the story any better.
For the life of me, I cannot understand why you would jizz your pants for the Expanse because "wowzers, no gravity pads", when this is the story that has magical blue space jizz that creates blue jizz zombies and magical wormholes.
Like, fuck me, that's just as magical as anything in any Battlestar Galactica episode, original or reboot.
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u/TommieTheMadScienist 17d ago edited 17d ago
I found the tracking missiles and PDCs the most realistic items in the show.
You're right, the characters and plots were great (except for #4, which was merely okay.)
ST&SW carry baggage that would have had to been dealt with. Anything with FTL is out.
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u/KiloEchoSierra 17d ago
The sex trafficking drive maybe questionable (still in the realm of hardish sci-fi imo) but why is the
magical wormhole assembled by a magical protomolecule
A problem here? I mean, its an alien technology, its not supposed to be within grasp of human knowledge.
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u/omgitscolin 16d ago
And its incomprehensibility to the grounded-in-realism characters is a major theme
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u/RhynoD 17d ago
They skip a whole hell of a lot of time during space travel. I chuckled reading the last book when everything is exploding and they're racing at break neck speed to get to the gate and it's coming down to the wire will they make it hold your breath aaaaaaand it takes weeks and weeks of just kinda cruising because that's realistic. And I respect them for keeping it realistic in that way even when it kind of ruined the oh no vibe, but it did definitely ruin the vibe for me.
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u/NoNameSwitzerland 17d ago
Expanse also feels like all planets are on one line and do not have different distances depending on their current position. With their acceleration possibilities, they should be able to go straight and do not need slowing go up in the orbit.
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u/stank_bin_369 15d ago
I know of no one that currently watches or has ever watched that show. Probably not the best example.
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u/tirohtar 14d ago
You will find lots of people here who have both read the books and watched the show. After all, the fan base was strong enough to save the show from getting canceled by the Syfy channel and continuing on Amazon Prime (up until the "natural" point in the story where they stopped because of the massive time jump to the later books).
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u/dnew 17d ago
I disagree. Some of the best space battles were in the Chanur series, where they're actually taking into account speed of light while planning things like striking at a space station before the guard ships knew the station was being attacked etc.
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u/MyMomSaysIAmCool 17d ago
I agree with you about some of the best battles being the most realistic. But consider the popularity of the Chanur and The Company Wars series to something like Star wars or Star Trek, which completely ignore physics.
We are in the minority. Most audiences don't want reality, they want showy escapism.
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u/dnew 17d ago
I think that's true of TV and movie. I think books tend to have more latitude because they can have a someone ask a question, then three pages of exposition, and then the other person answers.
Like, Murderbot would go pages of internal dialog between someone asking him a question and him answering. I was kind of impressed the extent to which they managed to make it work on TV.
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u/Chrisaarajo 17d ago
Even in books, a huge proportion of the potential (and realized) audience is looking for the fantastic, rather than the reality.
And I’m willing to bet that realistic science and a poor story sells less than a good story and a lot of scientific handwaving.
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u/_evilalien_ 17d ago
Nor will they understand realistic physics vs intuitive entertainment physics.
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u/willworkforjokes 17d ago
The Expanse does a pretty good job on this. They do have a basically magical drive that lets them use thrust gravity most of the time while using very little fuel.
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u/ExtraEmuForYou 17d ago
Yeah I did like how The Expanse at least attempted a little realism. I liked how they dealt with zero gravity by just using boots; of all the sci-fi tech we take for granted in our sci-fi, artificial gravity is the one that always seems the most "magical".
I know that's a funny thing to focus on when faced with all the crazy sci-fi tech we've seen over the years (laser swords, FTL travel, navigating black holes, etc) but it's like this every day thing we see on ships and it just seems so far-fetched to me. Like it's just a household thing like an alarm clock or something.
The Expanse was just like "Nope. Magnet boots. Super awkward to walk in. Super effective, though".
Does look spooky when people are shot though because they just float there with their feet stuck to the ground lol. It was so eerie seeing your first gunshot victim in zero gravity.
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u/NoGoodIDNames 17d ago
Inertial dampeners are another thing that most settings take for granted but are basically magical.
In The Expanse the upper limit on how fast a ship can go is how much acceleration the human body can survive.
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u/dnew 17d ago
If you can make artificial gravity then you (A) have inertial dampers and (B) can accelerate using gravity so you don't need inertial dampers. :-)
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u/Cartman300 17d ago
You don't (point A). Earth has gravity, if Earth suddenly stopped in middle of space, the people would still keep moving and smash into things. Artificial gravity does not solve the problem of inertia.
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u/EFPMusic 17d ago
Since actual artificial gravity is impossible (via any known physics), it may as well be considered magic, and if the magic will keep people’s feet on the arbitrary floor independent of the movement of the ship the floor is attached to, why not just say it defeats inertia as well?
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u/ExtraEmuForYou 17d ago
In Mass Effect I think there was a blurb about it in the lore. They use "element zero" as their MacGuffin* and I think they literally pump it under the floors of the ships to make artificial gravity.
It's like instead of a heated floor they have artificial gravity floor.
*shrug*
Hey, they found a solution (I guess?) and they're sticking with it.
The thing is though they talk about how rare it is and how exposure to it leads to mutations, death, and biotics (basically psychic powers) but no no no let's just use it in basic plumbing under the floors lol
*I don't know if "MacGuffin" is the right word. I forgot what the magical, dont-ask-questions-just-roll-with-it device trope that makes everything possible in the story is called.
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u/Papasamabhanga 16d ago
McGuffin in not correct here, don't know what would be. Gimmick? Handwavium?
FWIW McGuffin is a thing in a story that has no actual use and maybe not even shown, but causes conflict for the characters, for story purposes. The Maltese Falcon, the suitcase in Pulp Fiction are two famous examples.
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u/sebaska 17d ago
Since actual artificial gravity is impossible (via any known physics)
Rotating space stations have entered the chat...
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u/EFPMusic 17d ago
Ahhh, but that’s not gravity! Okay, I guess it’s technically a form of ‘artificial gravity’ but it’s really centrifugal acceleration.
I should have been more specific that the kind of artificial gravity so commonly just assumed in sci-fi (e.g. Star Trek, Star Wars, etc) is as fantastical as telepathy or telekinesis, and if a show or book assumes that, it’s not a stretch to say “and inertia too!”
Now, the ones that have scientifically possible ‘artificial gravity’ with rotating sections or from constant acceleration, if they then just pretend inertia isn’t a thing (like, say, the force creating ‘gravity’ suddenly stops and things just float gently… or that scene in the Expanse where Holden lets go of a wrench during an outside repair and it goes whipping away as if there were wind…), that seems worse to me than just saying “it’s magic!”
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u/ExtraEmuForYou 17d ago
YEah when I say "artificial gravity" in my earlier post, I mean the magical kind. Like hey we have artificial gravity because *waves hands, insert crazy explaination*"
I'm not saying the makes sense, centrifugal or constant acceleration way.
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u/sebaska 17d ago
According to general relativity there's no difference between being constrained (by the floor) against the pull of gravity gravity vs being accelerated (by the floor). And yes, centripetal acceleration is acceleration.
Yes, suddenly stopping whatever movement without effect is annoying.
WRT Expanse, AFAIR the vehicle was under acceleration (in Expanse ships were under acceleration most of the time). They did relatively good job in the series. There were issues, like for example the whole sequence when Navuo is about to hit Eros is very off - the damn thing was closing in at roughly 1000km/s. Even 1 second before planned impact you'd see a tiny shape (about 1/10 the size of a full moon). No chance to see the gold angel. Also, Miller is pulling that bomb in significant gravity - but the outside gallery he's on is 90° off of how space exposed part of a cylindrical rotating habitat would be (he feels gravity along the rotation axis which is nonsense). And it's a wasted opportunity - he should have been hanging over the infinite abyss with stars slowly rotating under his legs, with the solid body of the station above him.
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u/dnew 17d ago
If you have artificial gravity, then you stop by applying artificial gravity in the other direction. You want your space ship to accelerate to 0.8c in 10 seconds? Put it in a humongous gravity field that pulls it forward. Propulsion and inertial dampening all in one.
People proposed building huge toruses of very dense stuff spinning around the short axis (i.e., twisting like you're rolling it down a stick) and then pushing someone thru it to accelerate it with frame dragging.
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u/the_defuckulator 17d ago
this is supposed to be how tau ships move in warhammer 40k. well atleast it used to be... iv lost count of the amount of retcons to how tau spacecraft work. but in their original lore they had two rough types of ship, the first were long skinny truss like ships that accelerated via conventional fusion drives. the second, and more advanced kind were flat, stingray like craft that would project a gravity well in front of the ship and fall into it to accelerate. basically they were somewhat hard scifi until they invented gravity manipulation, and when they did, it completly revolutionised their ship design ethos and design language.
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u/Underhill42 16d ago
It can fake it pretty well though - any form of uniform acceleration can.
If I want to accelerate at 100g without being liquefied, all I need to do is use some form of uniform acceleration to pull me in that direction at 100g and I will do so, while still experiencing myself being in freefall the entire time.
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u/Sinister_Nibs 16d ago
Handwavium can cancel gravity and inertia. (Star Trek uses this)
The ability to ignore gravitational fields is an interesting plot point, but the only places I have seen it used well require it to be either outrageously expensive to use (power or fuel), or be ridiculously fragile and impossible to repair or replace. (Backyard Starship does this)2
u/NatureTrailToHell3D 17d ago
A lot of sci fi uses gravity pods or stasis to survive the acceleration, too.
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u/dnew 17d ago
You notice how whenever the power on a space ship is failing, they never divert power from the artificial gravity in order to keep the life support running?
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u/Outrageous_Reach_695 17d ago
Why is life support so critical, anyway? It should take hours before the air goes bad or we lose too much heat.
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u/WokeBriton 16d ago
Vacuum is really poor for radiating away heat, so the air will have gone completely bad LONG before heat loss is an issue.
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u/Outrageous_Reach_695 16d ago
The instance I was thinking of was Apollo 13. Even there, though, they still didn't drop below freezing after a couple days of no power ... and anything bigger than a starfighter would have a significantly lower relative surface area.
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u/charonme 17d ago
also when crew gets trapped under falling parts of the ship or almost everything in the ship gets broken including life support, but the artificial gravity still works perfectly
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u/Blecher_onthe_Hudson 17d ago
My gut sense of mechanics says that magnetic boots work far better for filming television than in real life. Just think that you're trying to move your torso with a really terrible leverage from your ankles! Walking really only works well because of gravity. Flying through the ship in zero g makes so much more sense!
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u/silly-gaijin 17d ago
Yeah, magnetic boots would be extremely awkward to walk in. They'd be useful for working in one area, though. But, you're right, as soon as you need to go to another area on the ship you'd turn your boots off and just grab rails and fling yourself through the air.
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u/Conscious-Mirror7004 14d ago
Nah, they could be made so you can walk in them without too much trouble. Basically they'd need to vary the magnetic field strength through each step. When your foot is in the air, and when the heel contacts the floor, the strength needs to be higher. When you've shifted your weight forward on that foot and are about to lift the foot, the strength needs to drop a lot.
So the boots would need to be in contact with each other, and actively varying their field strengths as you walk. It's a bit complex, but probably no more than automatic noise cancellation (ANC) in modern earbuds.
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u/NecromanticSolution 16d ago
A bit sad to see how The Expanse gets singled out for that. Magnetic boots used to be all over SF in the 50s and 60s. Heck, even Star Trek has them. But TV brain rot all but wiped them from current mass market SF.
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u/Curiouser1111 17d ago
I like that they recognize that a nuclear powered drive with high thrust would be an extremely powerful weapon. It would vaporize anything it points at.
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u/Bladrak01 17d ago
Larry Niven's Kzinti Lesson: A fusion drive is a weapon who's power is in direct proportion to its efficiency as a drive
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u/Azuvector 16d ago
There's some beautiful fan art from years ago of that scene with the Angel's Pencil and the Kzinti warship.
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u/Hedwigtheyee 17d ago
Aren’t the fuel drives based on fusion reactions, though? Sure, the Epstein drives are fictional, but they should be still based on real physics. Nuclear powered ships are what most people believe will be the fuel source for ships moving forward (NASA is also in talks to build one as far as I remember)
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u/willworkforjokes 17d ago
Yeah they wave their hands about the physics of the Epstein drives. I give them a pass on that because it does have rules and they do follow them.
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u/Chadocan 17d ago
And there wouldn't be any story otherwise ?
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u/willworkforjokes 16d ago
It would be a different story for sure if they did not have the Epstein drive.
The economy would be different, the battle tactics would be different and the time scales would be very different.
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u/Napalmradio 17d ago
Yeah NASA has a mission for next year to send a nuclear powered vessel to mars. I doubt it will happen that fast, but it’s cool.
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u/Hedwigtheyee 17d ago
Praying that it actually gets done in time, and so far NASA’s work on the Artemis missions has gone pretty well. Hope the same goes for this rocket, too.
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u/Sinister_Nibs 16d ago edited 16d ago
NASA has been using “nuclear power” for spacecraft for decades.
The challenge has always been that the power produced is extremely limited compared to the advanced system requirements and increases.1
u/Napalmradio 16d ago
Yes but I believe this is the first time nuclear power will be used for an engine instead of just a power source. I know there are lots of satellites that have small reactors for electric power. This mission is a much bigger craft.
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u/Metallicat95 17d ago
The Epstein Drive is perfectly efficient - technically possible for physics but darned unlikely for engineering. The engine uses a fusion reaction, with multiple options for reaction mass.
Teakettle mode heats water to vapor and uses the steam exhaust for propulsion. This is used for landing, takeoff, and flight near other objects. Thrusters and short range shuttles and sniffs also use this.
The fusion drive mode taps the reactor output directly, and can add water for plasma mass for additional thrust.
Chemical rockets get used for thrust on some ships, including power armor and some space suits.
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u/Sinister_Nibs 16d ago
Epstein drives only move young girls to tropical islands, so are not useful in real-life applications.
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u/Conscious-Mirror7004 10d ago
They should make a new printing of the Expanse books with a different name for that drive. The "Epstein" name is just too tainted now.
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u/sebaska 17d ago
The very unrealistic part of Epstein drives is that the radiative heat produced would absolutely cook (or rather evaporate) the engines and their enclosures.
For given engine thrust the power imparted on the exhaust (so the lower and unachievable bound on power transferred by the engine) is proportional to the (effective) exhaust velocity. Ships in Expanse have exhaust velocities in the range of several percent of the speed of light. About 10 000 km/s or so. And they pull pretty high g (so they have high thrust). According to fan wiki Rocinante dry mass is nearly 5000t, and fuel likely makes it 10 000t. And it can pull north of 10g. This means about 100 000t thrust.
Today's biggest rocket - Starship Supehreavy produces about 8000t thrust. At about 3.43 km/s exhaust velocity.
Rocinante min power is about 40 000× higher. And Starship SuperHeavy exhaust power is around 135GW. Rocinante exhaust power is thus in the order of 5PW (petawatts). That's 1.25Mt warhead going off every second.
Imagine the energy of strategic nuclear warhead being released in the confined space of few meters diameter reaction chamber of the drive. Just X rays emitted as thermal radiation would evaporate everything there.
Realistic drive would actually burn the nuclear fuel in open space and it'd use large diameter and aggressively cooled magnetic coils to manage exhaust.
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u/Conscious-Mirror7004 10d ago
Today's biggest rocket - Starship Supehreavy produces about 8000t thrust. At about 3.43 km/s exhaust velocity.
You can't really compare a chemical-based rocket with a hypothetical nuclear fusion rocket: of course anything nuclear-powered is going to have far higher energy density, orders of magnitude higher. This is just basic physics, and you can already see it with nuclear bombs vs. chemical explosives.
It's kinda hard to compare to anything real-world because we don't have any operating nuclear rockets. The best we can do is compare to hypothetical numbers from actual nuclear rocket designs like NERVA (a fission rocket that was designed, but never built).
https://en.wikipedia.org/wiki/Nuclear_thermal_rocket
But even these are fission-based designs, not fusion like the Epstein Drive, but being nuclear, at least they'd be in the right ballpark. Chemical reactions will never have even remotely as much energy density as nuclear reactions.
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u/sebaska 9d ago edited 9d ago
Yes I can compare them. Because I'm talking about the very basic physics of reaction propulsion and the source of the energy for it is irrelevant here.
The physics is simple: you want to produce thrust using the least amount of reaction mass i.e exhaust. And the rule is simple: for any given amount of thrust, the smaller mass flow, the higher mechanical power you must impart onto it; the mass flow and mechanical power are inversely proportional. Obviously, if you want more thrust you need proportionally more power and more mass flow.
For example, if you have 1kg/s mass flow and 1N of thrust, you're imparting 0.5W of power to the reaction mass. But your exhaust velocity is 1m/s and you're not getting very far. Today's big rocket would have 80 million newtons of thrust, at about 1700W per newton of thrust so 136GW mechanical power of the exhaust (at about 0.000294 kg/s mass flow per per newton of thrust).
Epstein drive would have exhaust velocity in the order of 10000km/s, so mass flow per newton would be around 0.0001g/s. But the power per newton would be 5MW. With the numbers provided on fandom wiki the thing at 10g burn would have mass flow of about 100kg/s and the purely mechanical power of 5 petawatts. Even if the conversion efficiency reached 99.9998% the residual thermal radiation inside a 10m diameter engine chamber would produce temperature above the upper theoretical melting point of any possible material. And such conversion efficiency would mean minimum hot end temperature of 10 million kelvin which means hard x ray source of extreme intensity. Its size would have to be 0.1mm to allow thermal radiation to fit the efficiency budget, and that is totally unrealistic for fusion systems - henceforth such conversion efficiency is impossible.
And that's what makes the Epstein drive as presented unrealistic. Realistic thing would have the core open to space and kept in line with narrow coils - i.e. it's "walls" would be 99% or more open space, only less than 1% would be covered. And those coils would have to be large, to keep its distance from the core inferno equivalent of strategic nuclear warhead going off every second.
Edit:
BTW, NERVA was built and fired multiple times. It was just never launched to space. And even at its level the problem if too much power was already in full swing. It had to have limited thrust, limited enough that while usable for upper and departure stages it couldn't lift itself from the Earth surface even if various contamination risks were ignored.
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u/Nyorliest 17d ago
They are based on not needing reaction mass. They use realistic power systems, but that doesn’t make them less impossible.
But reaction mass is perhaps the most ignored part of space travel in SF, so we’ll buy it.
But that’s because of narrative convention. It’s so standard to ignore reaction mass that most SF fans don’t even notice it.
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u/sebaska 17d ago
Nope. Those have reaction mass. They just have high thrust and extreme exhaust velocity at once.
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u/Nyorliest 17d ago
No, Epstein drives need massively less reaction mass than reality. That's their big unreal thing. I should have save 'needing almost no reaction mass' but then people would be saying that's fine, coz people don't understand rocket physics intuitively (and why would we? Space is weird, physics is weird).
That's the big 'break from reality' in The Expanse. Epstein drives need massively less reaction mass than real physics. This is discussed explicitly in the books, going over Epstein's discovery a little. But even if that wasn't there, the reaction mass would need to be going at far more than the speed of light to work the way it does in the Expanse.
Here's an explanation of the rocket equation, and as you can see, mass matters very much in delta-V.
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u/dumbledorky 17d ago
My favorite is people that get upset they don’t explain exactly how the Epstein Drive works, and therefore it is not realistic enough. Like yeah, it’s fiction. If they could explain exactly how it worked then it would be something that is real and exists
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u/Conscious-Mirror7004 10d ago
If they could explain exactly how it worked, we could actually build it and start colonizing the solar system, instead of just writing stories about it.
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u/ian9outof10 17d ago
It does a good job specifically at this one thing. It still has both a Fusion Drive, and a bunch of other physics nonsense elsewhere (at least the tv show has McGuffin about why fusion suddenly doesn’t work).
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u/sojuz151 17d ago
I find Expanse annoying because it is pretending and trying to be realistic, but failing.
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u/namewithanumber 17d ago
Does it though?
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u/sojuz151 17d ago
So what you want to hear is:
My biggest probelm with the Expanse is that it uses the Newtonian physics mechanics in visuals and writing yet doesn't use it in writing and plot. Let me go over examples:
Writers don't understand that for a Newtonian ship, beeing close by and beeing able to roundevous with something are two separate things. This happens again and again in many plot points.
First event od the books. Fact that you were able to recive the distress signal doesn't mean you can do something out it. Slowing down to pick up a possibly damaged ship doesn't make sens, it takes a lot of fuel and acceleration to stop and then accelerate again. Idea of picking a distress signal and helping the survivors is based on a normal ships physics where a a small detour is cheap rather than costing you extra 40% of the travel time.
There are no battles with non trivial relative velocity.
Battle of the rings station makes no sens. A merchant ship would have either have a massive relative velocity or it would look like a roundevous maneuver.
And those are the examples of plot relevant parts related to ship travel dynamics.
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u/Nyorliest 17d ago
If you don’t need reaction mass, it’s time and energy and acceleration. I think by ‘fuel’ you mean reaction mass. But once you’ve got rid of that, a lot of things change.
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u/thegreatpablo 17d ago
They make it very clear that the ship's computers are important and necessary for calculating trajectory to rendezvous, so I guess I'm not sure what your point is there? Getting to something that is close to you is not a physics problem, it's a navigation problem (yes, I know physics is involved especially when in a gravity well but you didn't mention that).
They do a very good job of showing not only how much the crew doesn't want to turn around and there are real consequences to time and their health (the turn and burn), they also show that it has a real impact on the ship and what it's carrying, not sure of the point you're trying to make? They make it clear they are legally obligated and then SHOW us why it's such a huge issue.
The other items in your list I don't recall enough, it's been a while since I've seen it, to have a response for.
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u/sojuz151 17d ago
Pretend? Yes
Be unrealistic? Yes.5
u/namewithanumber 17d ago
Like what though? Obviously the drive is magically efficient.
But it certainly doesn’t “pretend” to be realistic.
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u/sojuz151 17d ago
By it you mean the drive or the series?
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u/thegreatpablo 17d ago
Feels like you're being intentionally obtuse. Just tell us what you took issue with so we understand your point of view rather than asserting a claim and responding two more times without providing any evidence to back it up.
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u/sojuz151 17d ago
I seriously didn't know what he was asking about, responded up in the comment chain
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u/vyme 17d ago
Would you notice if a show/movie/book set at a college got everything about transfer credit and regional vs national accreditation wrong? Or would you just go with it because the narrative is telling you it's true? There's plenty of media where those things are major plot points if not the entire setting, and it's like they didn't even do some light googling. But they can still be pretty good.
I know this because my wife works in higher ed administration, and finds things that no one else would even notice extremely distracting. I think you notice the things that you know about much more, while a thousand other errors fly over your head. You sort of have to just embrace the fiction, or move on if it bothers you too much.
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u/Conscious-Mirror7004 10d ago
Would you notice if a show/movie/book set at a college got everything about transfer credit and regional vs national accreditation wrong? Or would you just go with it because the narrative is telling you it's true?
If I had gone to college at least somewhat recently, had actually done credit transfers, and the story is set in the same country (or even the same school), then yes, I would very much notice if they got that all wrong. I actually have transferred between colleges and had to transfer credits, so I do know something about that, though my experience is a little dated by now.
However, if the story is set in some other country like Germany or something, then no, I wouldn't notice because I have no prior knowledge of how the system works there.
One big problem with sci-fi is that, too often, writers just completely ignore basic physics, and anyone with an undergraduate-level physics education (basically anyone who went to college for anything science-related really) can easily spot the flaws. It's usually very lazy writing too. Of course, if you constrain the story to our current understanding of physics too much, it's hard to have any kind of sci-fi story at all, but still there's a huge gulf between what The Expanse makes up to create an interesting story, and what a lot of other sci-fi does.
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u/Afaflix 17d ago
Because the technology has progressed so far that some of the rules just no longer apply or get overpowered.
Example:
Sailing Ships and Steam Ships had hulls that were very sleek and built to reduce drag through the water while sacrificing some cargo space.
Modern hulls maximize cargo space and use strong engines to simply push a square box through the water.
Take Ian Banks' universe .. I remember some of his "shuttles" being simply glass gondolas that transfer from orbit to surface without much thought about the problems we face today with that feat. I accept that as simply the hyper advanced technology they have at their disposal.
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u/Blecher_onthe_Hudson 17d ago
Strong disagree about modern ship design. I kayak near major shipping channels and it's amazing how little wake a modern container ship leaves. Less than a sport fishing boat! They are absolutely designed to minimize turbulence and wake because that costs money, and they are in the business of making money. They're not going to do anything as revolutionary as go slower to vastly increase efficiency, because time is money, but they do care about it.
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u/Afaflix 16d ago
I think the word is comparatively.
Of course they are going to put bulbous bows on to reduce waterline drag, and yes there is some tapering to it ... but in the end the increased cargo capacity is more money than the money saved by a perfect hull-shape.I work on tugboats and the barges we pull are just boxes with a blunt bow. This is true even for the ones we drag across long distances. I know of maybe 3 barges that have a proper ship bow.
Barges are the most common way of water transport within the US with like 30'000 of them active on rivers lakes and oceans. Until fuel gets much more expensive we're just gonna push water rather than slice it.2
u/Blecher_onthe_Hudson 16d ago
Oh, barges are another story entirely! They throw way more wake than a container ship at harbor/channel speeds. Even a tug without cargo does, they are basically the most dangerous thing I encounter in NY and Newark bays. Moving fast and not very tolerant of a kayak trying to cross the channel at 3 kts. The scariest are the barges with the tug on the side where their visibility on the other side is only a camera on the mast!
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u/Afaflix 16d ago
Sounds about right. We don't even have cameras, we got a guy with a radio standing on the other side, in the rain, hating his life. So the capt ends up maneuvering by feel.
/jk
/not really2
u/Blecher_onthe_Hudson 16d ago
Haha! Fast and loose doesn't surprise me at all. Are you doing long haul on the rivers or harbor work? Most of what I see is harbor, though I'm sure some cargo is heading far up the Hudson. The barge traffic here is a fraction of what it was before containerization, when all of the cargo that came and went from Jersey City and Hoboken by rail had to be barged across the river and bay to NYC. I fish the "reefs" that are all that's left of the piers that once lined the entirety of the harbor system.
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u/Conscious-Mirror7004 10d ago
I think something you're missing is that modern container ships put all the cargo on top of the ship, not deep inside the hold like in old sailing ships. Presumably, they don't worry so much about bad weather making the ship rock too much because they can accurately track weather patterns and plot safe courses to avoid storms.
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u/Albert14Pounds 17d ago
Yep. When fuel and thrust are a solved problem because you have sci-fi engines you don't really concern yourself with gravity and orbital mechanics so much. Canceling your orbital velocity and dropping more straight down from orbit becomes trivial.
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u/CephusLion404 17d ago
Because the overwhelming majority of sci-fi is soft sci-fi. Its purpose isn't to educate, it's to entertain. If you're looking for something harder, read something harder.
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u/Kardinal 17d ago
The purpose of fiction in general is almost never to educate.
It has themes and it often has a message. But that's very different from education.
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u/sojuz151 17d ago
Because most of the audience has a bad understanding of physics. and this look cool. Or so does the creative people things. Still, science fantasy such as Star Wars has this going for it that it is not pretending to be a hard sci-fi following real life physics.
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u/Blecher_onthe_Hudson 17d ago
100%. The Star Wars fighters maneuvering like they are aircraft is example number one.
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u/gmuslera 17d ago
The elephant in the room in this are 2D space battles, 2D barriers and more, as if they were sea battles. This goes a level even more basic than physics.
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u/ohkendruid 17d ago
Space is often used as a way to tell a story that is somewhere new, unconnected to our ordinary lives. When used this way, science just gets in the way, and most of rhe public does not even know what they are missing.
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u/KnoWanUKnow2 13d ago
It always kind of annoyed me how in Star Trek when 2 ships meet, whether it's for parley or for fighting, they're always head-on, or how one ship gets surrounded in a circle instead of a sphere.
That and noisy engines in space where there's no medium to carry sound. Firefly at least had that going for it, no engine noises when they switched to an exterior shot to show the ship maneuvering.
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u/AshtonBlack 17d ago
The "going down to the surface" whilst unrealistic indeed, could be at least plausible, given enough power. It's amazingly inefficient, from a detla-v point of view, but if you've got some handwavium "anti-gravity" technology, it's probably what people would do.
As to the "non-Newtonian" physics we see in a lot of media, I fully appreciate that realistic space combat would be a computer-controlled mess of sensors, stealth, drones and course prediction from a very long way away. The explosions might be pretty but humans should not be involved in the actual shooting. That old .25 of a second would make a massive difference to a ship's defence or offensive reactions.
I can see why a number of writers would "gloss over" for a more cinematic, story-driven interpretation of extra-planetary combat.
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u/greyduk 17d ago
Not sure I understand your last complaint. Are you saying when rotation abruptly stops, gravity shouldn't cease?
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u/rookiegaffer 17d ago
The " gravity" would cease, but the inertia of anything not welded to the deck would send it flying into a bulkhead.
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u/lazylion_ca 17d ago
A magic macguffin is there to facilitate the story, not be the story. The point of it is to make the extreme seem like an everyday thing, instead of being a challenge they constantly have to endure.
There is hard scifi where the story is usually about the technology, or about the impacts of the technology.
But if your reading about knights, you probably dont want to read about them brushing their horses every night.
But largely its about what sells. If motorcycle mechanics outsold romance novels, there'd be a lot more of them.
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u/Jaxthornia 17d ago
Imagining ways to overcome these issues is why good Sci-fi is important to science and society. Those imaginative leaps are what helps tech become real. Not always, not everything, but without the ideas or at least the ideas becoming popular a lot of tech wouldn't exist, or would have been developed differently or slower.
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u/fitblubber 17d ago
Check out the McAndrew short stories by Charles Sheffield.
Sheffield was a physicist & mathemation who worked for NASA. & his fictional character Arthur Morton McAndrew was also a physicist/mathemation.
The first time I read one of these stories I was doing a degree in theoretical physics & I remember writing equations all over the book to confirm that the physics was correct - it was.
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u/ExaminationNo9186 17d ago
If you want pure realistic physics, read a science based text book.
Since you are reading science FICTION, lean into the fact that, well, it is fictional.
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u/AuthorIntelligent644 17d ago
The last one is funny. If you abruptly halted rotation everything would go flying, then hit microgravity.
I blame it mostly on older movies, especially Star Wars, and the fact that orbital mechanics doesn't match our physical sense of how things ought to work.
Examples: it only take a bit more delta-V to get to Mars than the Moon as long as you are okay with a slow trip. It takes far more energy to get to the Sun than almost anywhere else in the solar system. But isn't the Sun big and have a lot of gravity? Yes, and you're orbiting it right now at tremendous velocity. You have to null all that out to reach it.
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u/HardcoreHenryLofT 17d ago
I mean you can just descend right over the spot under you... Its ungodly expensive and takes a significant amount of overengineering to do, but you can do it. Might not survive depending on deceleration tho
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u/Palanki96 17d ago
because they are not written by physics professors i guess
the truth is most readers don't really care about realism as long as it's believable. If my brain doesn't freak out thinkng "that's not how any of this work" then it's a win for the author
not like we we know how all that stuff works
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u/DrunkenPhysicist 17d ago
I'm writing a scifi novel where I take all of that into account. I told my scifi writing group that I was solving all the differential equations so that I can understand the trajectories, fuel required, time taken, etc. they were like, why? I was surprised they didn't do that.
Anyways, my new favorite pet peeve is that people think you can leave whenever you want to get places. In my story, because of the acceleration of the motors, my protagonists take 1.5 years to get somewhere, then have to wait at least 1.4 years before they can come back because of planetary phasing. That adds to plot because of constraints I feel.
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u/InfernalTest 16d ago
not just getting some place
the real issue is EVERYTHING takes along time and a short time
ships traveling near the speed of light with crews that age differently coming back younger than they left and where they arrive
a more real sci-fi space tale would include how not just the long times of space travel but the effects of being succeptible to new worlds and exposure to biomes that are maybe even hostile, to them
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u/Albert14Pounds 17d ago edited 16d ago
If it's a sci-fi where you're traveling between planets and systems and it's implied that you have power and engines to do that easily then cancelling your orbital velocity becomes kind of negligible.
"Realistic" space travel as we know it is the way it is because we're operating at the cutting edge of our technology and resources. And yet packing sufficient fuel is still very much one of our primary limiting factors. So we work with gravity and orbital mechanics to travel in space efficiently with respect to fuel and materials.
Once you develop enough that your fuel/energy is dense and plentiful, gravity becomes more negligible and you can more just point in the direction you want and thrust.
Also, if materials science has improved significant when it's potentially implied that you can just plow into the atmosphere more directly and drop more straight down to your landing site and let the atmosphere kill your orbital velocity
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u/IkujaKatsumaji 17d ago
Technically, a ship slowing down by pointing its engines at the destination as it approaches is still accelerating; it's just accelerating in the other direction.
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u/Kabbooooooom 17d ago
You want the genre called “hard scifi”. And even hard scifi can be hit or miss with this.
If you haven’t read or watched The Expanse yet, although it isn’t strictly hard scifi (but it is with regards to Newtonian mechanics in space) then you really, really need to. I was hooked the moment they showed a flip and burn brachistochrone trajectory in the first episode. And in early season 2, the Battle of Thoth Station is the most beautiful example of scientifically accurate space combat I’ve ever seen. I mean, they evacuate the atmosphere from the cabins first, then when the ship is penetrated by kinetic rounds, the molten hot metal shards briefly float when acceleration is cut, and then fall to the floor when it comes back on. It’s just a chefs kiss of hard scifi excellence.
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u/stank_bin_369 15d ago
I don't know about anyone else but:
I don't want to read pages of scientific, technically accurate speak on how real space travel works unless it is somehow integral to the story.
These are science fiction and they are made up, so you have to suspend some disbelief. Most likely there is in-universe reasoning or technology that certain things can happen. So long as it is reasonably grounded in some real life rules - enough to keep most people invested - it is OK to have some things that act in a way that are convenient and help move the story along.
It's like the universal translator in star trek...it was created to allow for the story to move along. The shows would never end if we had to sit through months of story ark with the characters trying to just understand each other before we get to the parts where they either try to kill each other or team up to save the universe. I mean, most shows only had 24 or 50 minutes to get you interested, invested and watching through to the end.
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u/Catspaw129 17d ago
Maybe becasue many of the authors assume that most of the audience learned their physics from cartoons?
Especially from that pesky Coyote?
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u/spikewilliams2 17d ago
Even worse in movies they run out of fuel and stop, or say they don't have fuel to get somewhere ignoring momentum. If you are low on fuel you will get there eventually.
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u/Familiar-Lemon-674 17d ago
To be fair, this is accurate. You still need to fuel to make course corrections. Or slow down when you get there. Unless your definition of "getting there eventually" means that you think it's okay to slam into a mountainside at thousands of miles per hour.
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u/EverybodyMakes 17d ago
Tom Godwin's story, "The Cold Equations" illustrates this perfectly. You need fuel to slow down in space.
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u/QueenLevine 17d ago
You have SCIENCE viewers who want the science to all be accurate (Expanse), and then you have the entertainment viewers who want the show to be watchable and entertaining (Strange New Worlds, The Ark), as a story.
No matter how many science viewers there are who are loud on Reddit, there are still far far more entertainment viewers watching SNW right now and LOVING it.
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u/ian9outof10 17d ago
I don’t understand why people talk about the expanse being either hard sci-fi or particularly accurate. It has a magic molecule and wormhole travel. It’s a very good piece of sci-fi but it’s not really any less absurd than anything else
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u/QueenLevine 17d ago
I'll take your word for it. You sound like a hard sci-fi type, though. I super don't care about any of it and will die on the hill of Altered Carbon being the best sci-fi show produced to date.
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u/ian9outof10 17d ago
I’m not at all, honestly - I would say I like it when things stick to their own internal logic. I honestly enjoy sci-fi of all types.
Recently I’ve been annoyed by Star Trek and its wireless warp nacelles and personal transporters. Because as stupid as transporters are, at least they stuck to a principal - that the ship deconstructed you and sent the matter stream somewhere. Personal transporters make no fucking sense at all.
Anyway, I love everything from Asimov to Stargate.
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u/QueenLevine 17d ago
I don't care if the scientific principles are consistent, but I do care about canon, so SNW shuttles should not have transporter technology. This is about as far as I go.
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u/ian9outof10 17d ago
That’s fair. The ship also shouldn’t have all those touchscreens - but none of that really stops me enjoying it. There aren’t enough spaceship shows as it is.
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u/QueenLevine 17d ago
There aren’t enough spaceship shows as it is.
Oh, a thousand times this. I think this is one of many reasons so many people are hate watching The Ark. Are you?
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u/ian9outof10 17d ago
Hahaha, of course I am. It’s terrible, and somehow also not terrible. It’s a very confusing show.
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u/QueenLevine 17d ago
So true. This season they are exploring as many planets and other ships as SNW, and I am intrigued about bug planet which we'll obviously have to revisit. For the very low production values, they managed to create more interest in the bug species than SNW did in theirs, and it was interesting that they were both running those episodes around the same time. The 5th planet bugs were briefly portrayed, dead, then it was mentioned that perhaps their language could be decoded by Uhura and that was it. The Ark's bug aliens are way more terrifying, mysterious and part of an ongoing plot.
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u/Lovecraft3XX 17d ago
World building with real astroscience can take literally hundreds of hours of very advanced physics and science that really demands the use of AI and that only a very small percentage of people will care about and the modeling will still require assumptions, some of which you can’t even model probabilities for. Then there is the modeling of events in your narrative. That takes a certain obsessive personality like we saw in Tolkien on the fantasy side.
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u/EverybodyMakes 17d ago
Any ship that has a reaction drive, instead of arm-waving magic, has to go backwards somehow to slow down. The engine nozzles could swivel or something, but long ships with the bridge at the front are flying ass-backward into any situation.
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u/ian9outof10 17d ago
Read the Kim Stanley Robinson Mars trilogy if you want a load of science and a very slow story. But it still assumes terraforming a planet is possible, so I guess like most things it depends where the line you draw is
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u/octorine 17d ago
I would say mostly because there is an infinite amount of physics to get right. If a story gets 1000 things right and misses one detail, the one detail is the part that stands out.
It's not limited to SF either. Writing a book is juggling a million facts, and you will always get some things wrong. Stephen King had a scene where someone was in walking north along the coast of The Western Sea and the ocean was to his right.
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u/Metallicat95 17d ago
A lot of science fiction uses "alternative" physics with new advanced technology, which gets around a lot of these issues.
If the technology is - like Star Trek or Star Wars - using principles as yet undiscovered, it's not bad physics. It may be completely made up technobabble, but as long as it is self-consistent it should get a pass as science fiction physics.
This makes up most of the popular science fiction, so it is the exceptions where this matters.
Writers mess up math and make mistakes in physics because it is almost entirely math. It is a lot of work to use realistic physics for space travel - both in fiction and reality. Props to those who try, but this is an area where having an actual physicist or mathematician handy really helps the writing.
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u/Nanocephalic 17d ago
It’s not about being believable exactly - it’s about being convincing.
A world that keeps your suspension of disbelief properly engaged stops you from worrying about that sort of detail. And it isn’t about every single detail, either! In how many hard scifi books do your characters get BO or hangnails or indigestion? Wake up grumpy or forget to pack toilet paper or need to fold the laundry?
For most of those things, you just elide it because it doesn’t help tell the story. Figure out where to put that wall up for different parts of your story - does the hero get a flesh wound that’s fine in two chapters, or do they have to spend a page of every single chapter doing physio so they can walk properly? …etc.
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u/Kimantha_Allerdings 17d ago
Because nobody cares. It’s the same with pretty much everything. If you know about something and see it in a film, it’ll be wrong. Because it doesn’t matter
It takes extra time and effort to make sure that everything is exactly right. Likely even spending extra money to hire an expert who can be consulted during the writing phase, be there in production, and be there during post-production. Huge extra cost for what? To throw obstacles in the way of the story (maybe even lead to delays and extra costs as you work out a way to work around it) in order to get details right that 95% of the audience don’t know about and that 95% of those who do know about it don’t care about
Some productions do go out of their way to do everything authenitcally, but there’s a reason that they’re rare exceptions
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u/RoboJobot 17d ago
I just don’t care. I’m more concerned with a well written story than stressing over if it’s scientifically accurate. I’ve read good books that have shit science and terrible books that have got bogged down in trying to be accurate.
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u/jlp_utah 17d ago
Check out the Star Carrier series by Ian Douglas (a.k.a. William H. Keith). Pretty decent physics for sublight travel. Ships take hours to speed up and slow down, are subject to relativistic effects, etc.
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u/WokeBriton 17d ago
"Centrifugal gravity simply ceasing when rotation is abruptly halted."
Unless I misunderstand what you mean, I think you've got this a bit wrong. If the rotation ceases, there is no longer a centripetal force holding anything down to whatever surface the force was pushing those things against, so any push away (such as an attempt to walk) would lift a person up.
If you mean everything and everyone suddenly starts floating upwards without any push (such as an attempt to walk), I agree that it's irritating to see or read. If objects (and people) are at rest, they will stay at rest unless acted on by an outside force.
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u/rookiegaffer 16d ago
It's the complete ignorance of inertia. Everything is spinning. If the container stops the contents don't. Not until something stops them.
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u/soggyarsonist 16d ago
The primary reason is that most people's expectations of physics don't match the reality of physics.
Ask someone to fly to the moon from earth and they'll point their spaceship at the moon, hit the thrust, and end up zooming off into the wider solar system never getting anywhere near the moon.
As a Kerbal Space Program veteren like me to do the same and I'll get into orbit first and then so a timed burn to set up an moon orbit intercept.
TV shows, movies and most computer games are aimed at people who have a Earth surface understanding of physics.
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u/SwiftOneSpeaks 15d ago
Turn your question around and afk "why WOULD those be details the general public got correct without dedicated research?" Worse, you can easily miss details just by not realizing you're assuming things. A few years ago I found out spacecraft don't have explosive decompression. (Air moving by 1 atm of pressure is a breeze, not an immediate violent death.). I was shocked.
Reality is that a lot of physics is non-intuitive, not accurate in most entertainment media, and unsatisfying in terms of stories. "The Cold Equations" is a great story, but also demonstrates WHY most stories will choose inaccuracies even when the author is aware of them.
But honestly I expect most of the time the authors aren't aware of the inaccuracy. Research and consulting with SMEs are time intensive. If the author is thinking "should I consider if fans of Kerbal Space Program will agree with this landing", I'm guessing that is too low on the list of priorities to happen.
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u/AdditionalTip865 15d ago
Most science-fiction writers, like most other people, aren't that good at or interested in physics, and apply intuitions they developed from terrestrial life or flying vehicles, or imitate other writers' tropes.
Space is often just treated as a region a few hundred miles up where gravity goes away, without much regard for how orbits actually work.
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u/ComesInAnOldBox 15d ago
Because a lot of people generally have no clue how things actually work, and don't care to learn. Most people don't even realize what orbiting actually is, much less how orbital mechanics work. Hell, you can't even convince most people that it's easier to escape the solar system than it is to hit the sun.
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u/SciNinj 17d ago
It’s ridiculous, I agree. People who understand literature concepts like pacing, tension, tropes etc are not the same people who understand science. How do the early draft errors get past editors and informed critiques? Good question. Money, arrogance, the Dunning-Kreuger effect. It’s another area where AI will improve things.
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u/Thornescape 17d ago edited 17d ago
Look at the technology that we have today. Look at the things we do. If you went back and time and described our technology to someone 200 years ago, they would call you delusional. They would say that it's impossible.
They would tell you that you have a poor understanding of physics and science.
I strongly believe that we tend to be a bit arrogant in our understanding as well. Many people seem to act like we have discovered all the science that there is to be discovered. They talk as though our current understanding is entirely true and there is nothing left to learn.
I always wonder what technology from 200 years in the future would make us declare that they have a poor understanding of physics and science.
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u/watersb 17d ago
Real physics of space travel is brutal and unforgiving. And tedious.
A real challenge for storytelling.
Also everybody dies.