Difference between Space Opera and Science Fiction?

A while back a guy came into the place where I was working. He had a book (I don't remember the name). The book was, according to him, SciFi. I told him, "Great! My favorite SciFi is the Skylark Series by EE Doc Smith!" He sort of tsked this, saying, "Oh, that's only space opera." I really didn't know what to think of what he said. The funny thing was, I remembering looking at his book thinking, what makes his book SciFi any more than mine.

I started thinking about this incident the other day and am once again curious:

What is the difference between Space Opera and Science Fiction? What identifies each genre specifically?

NOTE: I had originally asked this on meta due to the closed question: What is the relationship between fantasy and science fiction? which is very similar to my question. It was subsequently moved to the main site.

Answer

Science Fiction is the genre heading for a kind of literature which uses extrapolations of scientific, engineering or social theories to posit a point in time where those ideas change society for better or worse (usually worse).

Science fiction is a genre of fiction dealing with imaginative content such as futuristic settings, futuristic science and technology, space travel, time travel, faster than light travel, parallel universes and extraterrestrial life. It often explores the potential consequences of scientific and other innovations, and has been called a "literature of ideas." (Wikipedia: Science Fiction)

• Space Opera is a subset genre positing a relatively optimistic future of grand technologies, space faring civilizations both Human and Alien and often a tumultuous relationship between them. Once considered a pejorative, it has slowly become an accepted term.

Space opera is a subgenre of science fiction that often emphasizes romantic, often melodramatic adventure, set mainly or entirely in outer space, usually involving conflict between opponents possessing advanced abilities, weapons, and other technology. The term has no relation to music but is instead a play on the term "soap opera". (Wikipedia: Space Opera)

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  Science fiction is the parent genre, space opera is a sub-genre specifically targeting:

  
  
  
  
  • scientifically advanced future societies built around amazing technologies
  
  
  • Humanity spread out through the galaxy (or even multiple galaxies)
  
  
  
  • Some space opera include Alien life forms (but many early ones did not)
  
  
  • There are often fantastic abilities associated with space operas in addition to technology, including psychic prowess, advanced mental powers, or unexplained abilities such as Star Wars' Force Powers.
  
  
  
  

There are questions of what defines a space opera over just a science fiction novel set in space. Is Star Trek considered a space opera? How about Star Wars?

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  Space operas were basically Old West tales in space. Deriving from radio's horse-opera formats, these were adapted tales where the Old West was replaced with Deep Space and the six-shooter became the ray-gun.

  
  



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  A space opera tended to have a serial format, far-reaching stories, spanning long periods of time where individuals often alter the fabric of entire cultures or even the entire galactic community.

  
  


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  The early space operas such as E.E. "Doc" Smith's Lensmen or Skylark series were considered the seminal works of Space Opera from which most modern space-based science fiction is now derived. Smith's work in space opera started as far back as 1930s and he is often considered the father of modern space opera, with his ideas often duplicated, adapted and paid homage to over the decades. Even comic books were not exempt from his influence as the Green Lantern Corps bears similarities to ideas in his early Lensmen works.

  
  


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  Modern Space Opera writers include: Isaac Asimov's "Foundation" saga, Dan Simmons "Hyperion Cantos" series, Vernor Vinge's "Fire Upon the Deep", Lois McMaster Bujold's "Vorkosigan Saga" and the legendary Frank Herbert's "Dune Saga" to name a few off the top of my head.

  
  


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  For the record: Both Star Trek and Star Wars qualify as space opera since they both have vast galactic empires, impossibly advanced sciences, diverse alien civilizations and have had individuals alter the fabric of their entire cultures, i.e. Captain James T. Kirk, Captain Jean-Luc Picard, Captain Catherine Janeway, and Captain Benjamin Sisko for the Star Trek Universe, and Anakin Skywalker, Emperor Palpatine, Padmé Amidala, Obi-Wan Kenobi, and Darth Vader for the Star Wars Universe.