If time is relative, then you might as well walk backwards and think you are traveling back in time.
“Que sera sera” or “What will be will be” in any point in space. Time is universal and not relative. You cannot travel back in time. Theoretically (if it is possible to eliminate light dispersion), light appearing at great interstellar distances seem to hold different snapshots in time. If you travel faster than light, it is your perception that changes and you are not travelling back in time. When you reach the source of the light, irrespective of your speed, you will be dissappointed to find yourself in the present. If light travelled at the same speed as sound, you will see lightning and hear thunder at the same time, not after the fact. Einstein was a joker and his Nobel Prize was for the photoelectric effect.
There are no aliens on Earth. Interstellar distances are so great that to conquer them, aliens will need to travel at impossible speeds. Objects in the way, even a few molecules, will pulverize their vehicle to dust.
Unbelievably fast-moving UFOs are most likely government aircraft powered by motors with superconducting parts operating at near absolute zero. Real alien-abduction stories are probably those from the victims clandestine government medical experiments or sexual attacks by differently oriented space/defence personnel with weird fetishes, covered up using hypnotism-induced false memories.