there are two things that don’t get explained until later in the film but are worth covering up top. The first is that this whole movie takes place in a world where the future has declared war on the present because it’s upset about climate change. To do so, it uses a technology called “inversion,” by which objects and people can travel backward in the flow of time by reversing their entropy. This means that time-travel in this movie works according to a “closed-loop” theory — i.e., everything that has happened in the past has already happened.