tp4's recent thread about sci fi books made me think about what makes a sci fi story. And I think a sci fi story must contain at least one or more of the following elements. Feel free to use my list to create your own story.
1. Time Travel/ Time Machine/ Alternate Time Lines
2. Space Travel/ Space ship
3. Inter-Dimensional Travel/ Portal
4. People with paranormal abilities like telepathy, telekinesis, mind-control, etc.
5. Utopian/ Dystopian Society of the Future, including any/all of the following elements:
A. Extreme Social Caste System of Haves and Have-nots
B. Evil cabal of social elites
C. Technologically advanced civilization threatened by limited resources
D. Strictly controlled access to information for good or evil purposes.
E. Epic galactic empire threatened by war/ revolution
6. Contact with a Utopian/ Dystopian Alien Civilization
7. Invading Aliens (good or evil)
8. Mind-controlling Alien Parasitic Life Form(s)
9. Pandemic disease/ virus
10. Medical experiments on people, including harvesting people for food, replacement organs, energy, brains, etc.
11. Sentient Computer(s) (invariably evil for some reason)
12. Mutants (good or evil)
13. Clones (good or evil)
14. Cyborgs (good or evil)
15. Robots/ Androids (good or evil)
16. Zombies (invariably evil and brain-eating)
17. Dinosaurs
18. Moon Base
19. Undersea Base
20. Evil Corporation(s)
21. Evil Terrorist Organization(s)
22. Misguided genius bent on world domination and/or ensuring world peace.