Eto yung hinala mo explain ko.
What if meron pala noon ancient civilization na super advance na achieve nila yung light speed travel... Pero nalaman nila na meron magaganap na global mass extinction, so they decided to build a spaceship, not to colonize other planets but to just travel away from earth in a speed of light and then go back again. Plano nila bumalik kapag nag restart na ulit yung earth.
Yung concept kasi, kapag nag travel ka faster than speed of light para sayo normal lang yung time, pero sa iba ilang taon na naka lipas depende sa layo na iyung nai-travel.
So possible na yung mga aliens na yan mga tao yan dati na nag travel nang speed of light tapos bumalik lang dito.