The science of time travel

". . . explores time travel through favorite science-fiction franchises, from the classic time travel paradoxes of Star Trek to the universe-crossing shenanigans of Doctor Who. Discover the real science behind questions such as: Can time travel really erase our past regrets like in A Christmas Carol? Is it worth killing people in the past to prevent a horrible future like in Terminator? What can we learn from living the same day over and over again like in Groundhog Day? Could time travel destroy our right to privacy like in Deja Vu?"--Adapted from description.