What is a science-fiction theme in Catching Fire?
One object in Catching Fire that is rooted in science-fiction is the presence of a force field, or a non-physical barrier that cannot be breached. Force fields have been part of science-fiction for many years, and are not possible with current-day technology.
"That force field at the bottom of the cliff, it was like the one on the roof of the Training Center. The one that throws you back if you try to jump off and commit suicide."
(Collins, Catching Fire, Google Books)
There are at least two types of force fields in the book; the first is benign, and serves as a net to catch people who try to break through it. The implication is that the energy of the field can stop a physical object and either hold it in place or throw it back. The second is harmful, and is present in the Game arena; this field acts as a sort of hyper-focused electrical wall, and will electrocute a person if touched. It can also cook meat. In both cases, the force field is invisible unless touched, and the only sign is a faint and intermittent flicker in the air, or a slight hum, barely audible to Katniss's enhanced hearing. Both fields serve a plot purpose to advance the story.