Though science fiction often mangles scientific truths, it is nevertheless a genre that is highly influenced by the latest trends in scientific thought and research. Here are some of the scientific (and semi-scientific) ideas that have influenced SF the most.
[Illustration by Stephan Martiniere]
I've listed these ideas roughly in chronological order, from oldest ideas to newest.
Charles Darwin's theory of natural selection, where he posited that life is shaped by inter-species competition for resources in specific environments, is fundamental to understanding science fiction. The genre is full of stories where two different species of intelligent beings - often humans and creatures from other planets - are competing for the same resources, like water, energy, or the surface of a planet. Of course it's also good to know about natural selection to debunk bad science fiction. For example, why would a bright red giant monster evolve on a planet full of ice? I'm looking at you, JJ Abrams' Star Trek.
What people often forget is that natural selection is also the theory of mutation, another idea that is near and dear to the SF genre. Mutants who survive better than their "normal" progenitors are the survivors, in Darwin's account of things. The idea of better, fitter mutants taking over the world has been a mainstay of SF since A. E. van Vogt wrote Slan in 1940.
Homework: Charles Darwin's On the Origin of the Species gives you unexpurgated evolutionary theory. A good place to start is UC Berkeley's Evolution 101 online. Stephen Jay Gould's highly readable essay collection Ever Since Darwin tackles evolutionary theory from all angles.
It may not be considered a science today, but psychoanalysis was taken very seriously as a scientific idea in the early and mid-twentieth century when SF was in its Golden Age. Writers were fascinated by Sigmund Freud's idea that you could divide the human mind up into three interlocking parts: Id (your unbridled desires), Ego (your basic sense of self), and Superego (your moral center, often derived from what your parents or your culture taught as "right" and "wrong"). Countless SF stories deal with "unleashing the Id" - most famously, Forbidden Planet features a technology that can make thoughts from the Id become real. Another psychoanalytic idea that still haunts SF today is the notion that people have an "unconscious," a part of their mind that they can't control or understand. Your unconscious mind is the realm of dreams and wishes, a cognitive wilderness that crops up in SF stories where people engage in mind control, dream-manipulation (hello, Inception), or telepathy.
Homework: Sigmund Freud, Beyond the Pleasure Principle; if you want to get into some interesting literary theory, check out Franco Moretti's essay "The Dialectic of Fear," which uses psychoanalysis and sociological theory to talk about the meaning of Dracula and Frankenstein.
Tragically, you must understand Albert Einstein's revolutionary theory about the equivalence of matter and energy simply in order to apprehend how few SF stories actually adhere to it. His theory laid the foundations for the Big Bang theory of the universe, as well as atomic weapons. It also, sadly, demonstrated that traveling faster than the speed of light - which we'd need to do, if we wanted to get anywhere cool in space - was basically not survivable by a human. That's why a lot of SF simply ignores general relativity, or invents things like teleportation or "subspace" travel to explain how spacecraft are zooming from star system to star system in a matter of days.
Homework: Albert Einstein, Relativity; NOVA has a great site where 10 contemporary physicists explain general relativity to you in layperson's terms.
In the early days of anthropology, researchers believed that the best way to understand other cultures was from an outside perspective. You would observe your subjects, talk to them, and even take statues or textiles from them, but you weren't allowed to "go native" and try to see the world from their perspective. But in the early twentieth century, a new generation of anthropologists like Margaret Mead decided that the only way to understand other cultures was to immerse yourself in them as much as possible. Famous SF author Ursula Le Guin, whose parents were anthropologists, is famous for her novels about aliens who learn about life on other planets via participant observation. In fact, this idea is extremely common in stories about aliens who come to Earth, from V to Starman, where aliens put on human guises in order to live among us and "understand humanity."
Homework: Danny L. Jorgensen, Participant Observation; Norah Vincent, Self-Made Man (a contemporary example of participant observation, where a female writer lived as a man for a year and wrote about male culture)
In the mid-twentieth century, computer scientist Alan Turing speculated that we might one day create machines that are artificially intelligent, with minds equivalent or superior to human ones. This idea has excited computer scientists and science fiction authors alike, and has become one of the mainstays of SF, leading to Isaac Asimov's famous "three laws of robotics," essentially the Superego of robotic artificial intelligence, the homicidal AI HAL from 2001, and of course contemporary AI SF creatures like the cylons in Battlestar Galatica and Wall-E from the eponymous film. Nearly all futuristic science fiction stories assume that humans will invent machines that can think exactly like us - and probably better.
Though environmental science refers simply to constellation of fields that look at how everything from ecosystems to geological processes function, for science fiction it is most important as way to understand environmental change. Your "environment" is basically a giant system of inputs and outputs, and most SF stories take for granted the idea that changing one part of an ecosystem can affect an entire planet. You cannot have the concept of terraforming, for example, without environmental science. By the same token, you can't have an environmental apocalypse like the one in The Road or Waterworld without understanding that releasing toxins into the atmosphere has consequences for the rest of the ecosystem.
Science fiction of the past thirty years has been strongly influence by the idea of the "singularity," which is essentially a way of looking at how technological change speeds up over time. I wrote an io9 backgrounder on singularity theory, which you can read here. This is how I summed up singularity theory at the beginning of that post: