Is Time Travel Possible? Testing the ‘Grandfather Paradox’

Seth Lloyd
July 16, 2014
Time travel is a science fiction staple, inspiring the plots of countless books, movies and Star Trek episodes. But while basic physics allows for the possibility of moving through time, practical concerns like the “Grandfather Paradox,” in which a traveler jumps back in time, kills his grandfather and therefore prevents his own existence, seem to stand in the way. Self-described “quantum mechanic” Seth Lloyd looks at an alternate mode of time travel that eliminates any events that could later prove paradoxical, making this phenomenon both theoretically possible and creatively irresistible, whether you’re an astrophysicist or just a daydreamer.

[@Sam_on_YouTube]

The philosopher David Lewis famously advocated for the view that if you travel through time, you can't change the past. The version of the Time Machine from the early 2000's was based on that idea, very different from the original story by H.G. Wells.

[@ravindra2146]

Correct me if I am wrong.....Time does not really "exist". It is only the "measure " of events happening from a certain start to a certain end. What really exists in reality is events made from "Matter ( Both seen & Unseen), Energy (Both seen & Unseen) & Space (Need to explore more about this)". So we or an alien far away cannot return to an event that already has happened which we call "Past".

[@jimmywilliamson3227]

yes time travel is possible i do it every day but in just one direction

[@quarkraven]

really fun, informative talk! Seth Lloyd is the best

[@jkallend]

i though the faster you travel the slower time goes by for you as opposed to someone watching you zip by. which is way they say that photons experience no time what so ever

[@Stinger-rq4gy]

great thank you

[@SZG65]

Seriously, time travel is ONLY a fiction created to describe the act of traveling a great distance through space in a short time. Einsteins twin paradox is suggestive of an occupant in a spacecraft that would not age *much* while crossing the great divide.

[@davemojarra4734]

No. If it were, we would have folks from the future around today, per S. Hawkings.

[@peoplez129]

Time travel can be linear, therefore it's not self correcting nor is the grandfather paradox a paradox. It's only a paradox if you assume that killing your grandfather affects your past.....it wouldn't. For the time traveler, time is always progressing forward, and even if you erase time lines, they still existed for you.....and even can exist again if you undo what you did to change them. So if you change the past and travel to the future, the future may be different, it may be one where no one knows who you are....but there is still linear progression for the time traveler.