Science fiction is closely related to fantasy, for it contains mainly of things that are not real. However science fiction is closer to reality than fantasy, as science fiction is based on technological advancement, the future. It is more believeable than fantasy as some did come true. Some of the science fiction in the past has become true now, the people in the past who wrote science fiction envisions many things that became real. These things include bio-engineering, cloning, helicopter, skyscraper, and many more.
Science fiction never fail to amaze the audience. Its creativity is something else. Nowadays, many links science fiction to alien invasion and thus human have to fight back to keep Earth as their own. This pattern is common and very popular. Many shooting games or RTS are built upon this category of science fiction, where human is at war with the aliens.
I believe that although science fiction is vast, it is limited to the limits of reality. Such obvious examples are guns. No matter how far in future gun is, it always comes wif the shaft and trigger, regardless whether it fires bullet, laser or plasma.
Therefore, science fiction nowadays usually includes a pinch of fantasy to make things that is impossible to explain through science, possible. This is called science fantasy. In fact, I believe blending world of magic with science fiction is a great way if science fiction are to reach a new height, a new vast field for it to expand. This could easily improve as science fiction has always revolve around semi fantasy, unreal reality. An easy example of science fantasy is actually laser sound in space. In Star Wars, the fight in space has many different noises and explosions, however sound cannot travel in space as there is no air. So technically, if this is a pure science fiction, space war shouldn't create any sound at all.

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