Suspension of disbelief

The suspension of disbelief is what the creator of a fictional work asks of her audience/reader: To suspend their disbelief in those aspects of her fictional world that are fictional -- the existence of those characters, that place, that time, those behaviors, those events, that technology, etc. -- so that the creator can tell a story and the audience can hear it.

While suspension of disbelief is required for all fictional aspects of a work, including character, SF poses the particular challenge of consistent and realistic worldbuilding. While SF readers may be prepared to accept aliens or magic, these things must operate within a consistent structure of rules -- the rules that we know apply to our physical universe, for instance, in the case of aliens; or a consistent set of rules that makes sense, in the case of magic.

Some SF tropes, while unrealistic so far as we know, have become accepted without need for much explanation. The audience suspends their disbelief on credit, as it were. These include:

• FTL travel - Not possible according to the laws of physics as currently understood
• Time travel - Not necessarily theoretically impossible, but highly improbable
• Psychic powers - Otherwise realistic or science fictional worlds often introduce psychic powers, without any plausible scientific explanation.
• Religion - Sometimes otherwise realistic or science fictional worlds introduce some religious concept that the audience permits: e.g., destiny; prophecy; deities; souls.