Warp Drive

Warp drive, which allowed the warping of space in order to travel faster than the speed of light, allowed Terrans in the original timeline, before time travel, to have contact with alien species. Aliens were generally polite, if not precisely friendly, because nuclear weaponry was a technology nearly every space-faring society was well armed with.
Entangling paired groups of particles, and the expanding or contracting them with positive or negative excitation allows space to be contracted in front of a craft, and expanded behind it, to propel the craft through space at faster than the speed of light.
Warp drive works by effectively creating a downhill slope in front of a craft, using entanglement contraction, and an uphill slope behind the craft, using entanglement expansion. The negative energy for expansion can be generated in a similar fashion to how atoms are cooled using lasers or microwaves.