Similar to fantasy, anything is possible in science fiction, provided you set it up properly. The main difference between fantasy and sci-fi is whether it’s unexplained magic, related to the environment (such as crystals), or purely technological.

Whichever you choose, make it convincing. Science fiction requires some explanation, usually of a technical nature, even if you don’t go into the details. In other words, it’s likely to involve certain devices. In today’s modern world, it’s becoming more and more difficult to stay ahead of the technology as what was once science fiction becomes science fact. Thus, science fiction seems to be trending more toward futuristic stories, often dystopian, of the consequences of advanced technology.