Time Travel is a temporal displacement that occurs when a person leaves their native time period and travels into the future or the past for any length and duration of time. According to Rommie, there are multiple theories regarding time travel, with one theory stating that timeline is fixed, meaning that no matter what a person does, history can never be changed. Another theory states that time is constantly in flux meaning changing the past in even the slightest way can have infinite consequences for the future.
Technically, anyone who ever uses a form of FTL travel such as Slipstream is traveling in a time machine.
In this timeline, Dylan Hunt lost the fight and Gaheris Rhade was frozen in time for three hundred years. After his rescue, Rhade was horrified to discover that after the war ended the Nietzscheans did not build an empire, but turned on each other, thus dragging the known worlds into centuries of chaos. Rhade then set out with the crew of the Eureka Maru much like Dylan would do in order to restore the Systems Commonwealth. A number of setbacks forced Rhade to accept that his mission had failed. He then traveled into the past, killed that timeline's Rhade, and allowed Dylan to kill him in the hope that in 300 years time Dylan would have more success restoring the Commonwealth than he did. Rhades actions prevented timeline 1 and created timeline 2.