Spiderman was bitten by a spider and developed spider-like abilities. Superman is from a different planet and afraid of a glowing rock, even if this human-like creature can shoot lasers from his eyes. The Incredible Hulk is... Hulk...

If you are looking for a non-comic example take a look at the Metro series. Post-apocalpyse after the nuclear war. Everywhere there are creepy mutants wandering around and people are living from pigs and mushrooms in the Moscow Metro. When reading it I wasn't thinking about realism - I was thinking about the interesting story and what the auther did with this unrealistic premise.

I could list dozens of books I have read that don't have a realistic premise. Especially once you introduce superpowers nobody will care. Your readers are not the ones to complain about non-realistic stuff if that is your premise. Nobody can force you to stick to reality.

Heck, I am currently reading something about a great war between dwarves and dragon-riding elves. My dragon army will grill your "physics" :D

There are lots of genres out there that don't care a bit about realism. Post-apocalypse radiation superheroes are definitely in one of those.

No, people won't say that, not even full time working scientists (like me). I know a great deal about genetics; I've published academic articles about it. That did not prevent me from enjoying the TV series "Heroes" for several seasons. Supposedly, their super-powers were due to "genetic mutations" (including immortality, time-travel, psychokinesis, irresistible "command" voice, fire-starting, invisibility, etc.)

That's B.S. to the power of infinity, but I get it: you need an explanation for your fantasy universe, and "radiation" and "genes" are a stock answer, like "quantum" anything.

Personally, I'd embrace the magic. You are writing a fantasy, and in fantasy magic generally exists without explanation (rules of magic are common, magic systems are common, but where the actual "magic" comes from is just an assertion that something exists, like "life force", or "the force" in Star Wars, or whatever). You can do the same; just use your imagination and make something up. Meaning, the radiation isn't causing genetic mutations; it just released some kind of magic into the world and now some people are learning to use it. Maybe all the magic was used up, and now (due to the nuclear explosions) there is a fresh supply of it.

There is no need to justify your explanation scientifically. But. You must not, under any circumstances try to scientifically justify anything else. In effect, by making a scientifically implausible claim to establish your world, you've shifted from SF to fantasy.

However, fantasy does not have to include unicorns or vampires, or anything else. Just establish your world and get on with the story.

As an example of something very much along the lines of what you're talking about, but even more so, try finding David Drake's "Men Like Us", about a post-nuclear war world, with 3 characters roaming the country making sure that nobody resurrects nuclear power. The trio are ultimately revealed to be immortal, and they got that way by being caught close to a nuclear blast.

So, that's not remotely science, but the story's pretty good nonetheless.

What you're writing appears to me to be "science fiction".

There are at least two kinds.

Hard science fiction:

Hard science fiction is a category of science fiction characterized by an emphasis on scientific accuracy.

Soft science fiction:

Soft science fiction, or soft SF, is a category of science fiction with two different definitions.

1. It explores the "soft" sciences, and especially the social sciences (for example, anthropology, sociology, or psychology), rather than engineering or the "hard" sciences (for example, physics, astronomy, or chemistry).


2. It is not scientifically accurate or plausible; the opposite of hard science fiction.

Soft science fiction of either type is often more concerned with character and speculative societies, rather than speculative science or engineering. The term first appeared in the late 1970s and is attributed to Australian literary scholar Peter Nicholls.

There are good examples of both kinds in the world.

As a reader of SF I've read and enjoyed both kinds (and Fantasy too).

I tend to have favourite authors (as an avid reader if I find a book I like I might read everything by that author).

But does my story need to be scientifically accurate or plausible?

I don't think accuracy is as as important as with "historical fiction" -- I mean of course the world is imagined, even when it makes an effort to be hard-science (perhaps as a way to make it more interesting to people who are interested in science).

Even supposedly-hard science fiction requires some "handwavium" a story which introduces space elevators to earth orbit, or linear accelerators on the moon, introduces a concept but ignores real-world practical difficulties. It's fiction.

If there's not much science in the book then I'd hope there's something else.

Will I lose readers because all they can think of is "that would never happen"? Can a story like mine with inaccurate/nonexistent science still be appealing?

For example one book I read once was like the one you suggested: i.e. a world with mutations. Society was rural/agricultural, no longer mostly-urban, and any mutants were killed. So anyway, there, some children were travelling alone somewhere with a "great horse" -- a huge horse, a cart horse, I forget whether it was mutated or just bred, a big breed, but its being so unusually big meant that the people in the lands they were passing through would kill it if they found it, so they were trying to stay hidden. And I wanted to know more: about the children, the horse, the land they were travelling through, what would happen, and so on.

Edit to add: it turns out that I was remembering The Chrysalids. The post-industrial characters don't really know what causes the mutations:

The inhabitants of post-apocalypse Labrador have vague knowledge of the "Old People", a technologically advanced civilisation they believe was destroyed when God sent "Tribulation" to the world to punish their forebears' sins. The inhabitants practise a form of fundamentalist Christianity; they believe that to follow God's word and prevent another Tribulation, they must preserve absolute normality among the surviving humans, plants and animals, and therefore practice eugenics.

The scientific cause of the tribulation is hinted at for the reader's benefit ...

Though the nature of "Tribulation" is not explicitly stated, it is implied ...

... but knowing (being told, or seeing from the characters' perspective) that it was "God-sent" makes me dial-back the scepticism and get on with reading the story on its own terms. I guess I was sophisticated reader at the age when I read that, but when the author effectively says, "this is a Deus ex machina") then as a reader I know to treat that as background scenery -- like people watching a play know that they're meant to not see the Kuroko.

It wasn't even a plot-point, it was a fait accompli, past history, no need nor opportunity to explore that premise any further.

As a general rule, if there is any portion of your premise that you do not want your audience to concern itself with, you need only avoid bringing it up.

This is especially true for fantasy and soft-sci-fi. We never got explanations for light sabers, the TARDIS, dilithium (handwavium) crystals, or infinity stones either; and that very restraint has benefited the respective series that they belong to. So no, you do not have to explain it; just take care not to also question it.

No.

You can have unrealistic elements as parts of your premise but you need to introduce them to the reader as parts of your premise. Otherwise the reader will not understand your premise and things will go downhill from there.

People do not generally care about lack of realism. What bothers them is not being able to understand what is going on. Realism or verisimilitude just happens to be what readers use to understand what is happening unless the author has already told them that it works different.

So just tell the reader how it works in time for them to understand it when you use it. This is not a scientific explanation of how it works. It is an explanation of how it works in the context of the story. It may include pseudo science or even real scientific speculation but its function is to help explain how you use it in your fictional universe. The rules you, the author, follow using this element when telling the story.

The rule against unrealistic elements is actually that you should not have them unless they are part of your premise and the reader knows it.

Note that if your premise starts with "a fantasy world with magic and elves and dragons and.." you can get away with lots of unrealistic elements.

Science is all about establishing rules that helps us understand how the world works. If your work is set in a different world and things in-universe work in a different way, that's fine. But here's the important point: if the science is different, the readers need to understand how the in-universe science works. When authors violate this principle, and have the hero pull out some new trick that has no basis in the existing narrative in order to fix things, it feels like the author is just making up random crap.

Especially if we're talking about the hero's powers, what you need most of all is a consistent explanation. The reason why is Sanderson's First Law of Magics: "An author’s ability to solve conflict with magic is DIRECTLY PROPORTIONAL to how well the reader understands said magic."

In laying out the principle, Brandon Sanderson actually uses radioactive superheroes as an example. While the in-universe explanation may not be "magic," from a writing standpoint it does the same things that a magic system does, so the same principles apply:

Narratively, superhero magic tends to be rather specific and explicit. (Depending on the story.) We generally know exactly which powers Spider-man has and what they do. He 1) Can Sense danger 2) has superhuman strength and endurance 3) Can shoot webs from his hands and 4) Can cling to walls. While in the comics, he does sometimes gain other strange powers (making the system softer), he does generally stick to these abilities in the movies.

Therefore, we’re not surprised when Spider-man shoots a web in a bad guy’s face. We’ve established that he can do that, and it makes sense to us when he does it.

If your story is not scientifically accurate or plausible, I would recommend to not enter too deeply in explanations. That would be a way to explain why it's not believable, which you may want to avoid.

After this caveat, stories that are not scientifically accurate are fine. Some really great stories enter in that category. Frankenstein, the Fantastic Four, Fallout... Those stories are not accurate scientifically.

No, you don't need a scientific explanation (unless you want to).

I think your discomfort comes from your desire to mix two subgenres: Post-apocalypse (which is usually soft sci-fi) and Superhero genre (which is usually non-scientific fantasy). Superhero genre tends to use Technobabble to explain things, and you are, of course, welcome to use it.

If you want superheroes in your book, you would lose the readers who don't like them and gain readers who do like superheroes. Scientific basis here is unimportant, but logical coherence is.

Obviously, super powers aren't scientific, so your readers will not expect a fully scientific explanation.

But what they do expect is this thing called suspension of disbelief. It needs to be close enough to be believable/realistic that in their minds they can make the jump without too much effort.

So as long as radiation mostly is bad, as it is in reality, you can add some mutants as exceptions and get away with it.

It is not about being scientifically correct. It is about serving the readers and their imagination and not stretching it too far with absurd challenges.

As long as your work is fiction (specifically science fiction), absolutely not.

The plot is about a war which is as serious as WWIII, which has not even started. Therefore, you have assumed a deadly future war. Now, adding sci-fi elements to it won't do much harm because who knows if such weapons are developed after centuries which might cause certain DNA mutations in human beings and turn them into superhumans!

But, obviously, you can't add such theories to plots where no fiction is involved or the war has a purely realistic description.

Of course you don't need to...

Most fictional characters in movies today have zero science basis and further, grossly violate multiple laws of physics. So it's better to go ahead and make-up something interesting rather than trying to explain the science behind it.

...but you can.

Just make-up a fancy name for a wide-spread chemical used along side with your nuke war and due to the experimental chemical you have the plausible basis for science too and such thing can also become something quite deep into the storyline if you decide to at a point.

Peter Parker got his powers from a radioactive spider bite.

The Hulk got his from gamma radiation. In Kimba the White Lion, it makes grasshoppers gigantic.

Fiction doesn't have to be perfectly realistic. It just needs to be consistent with what it chooses not to be realistic about. If the spider bite or gamma radiation wouldn't have turned most people into a superhero, explain what makes Parker or Banner different in the event somebody were to try and fail to do the same. Don't just dismiss it if it comes up again. If your story is a long-enough series, don't forget to bring it up at some point also.

Reality itself is pretty unrealistic. Lots of wacky things happen. Who would have thought a man could literally fly in a lawn chair attached to balloons? Who would have thought My Little Pony would have developed such a largely adult male fanbase? Who would have thought anyone would see Megumin as a viable option? People will suspend their disbelief, but they ask that you don't make them need to pause and unpause that suspension too often. Keep things consistent and you should be fine.