Back to the Future. Doctor Who. Futurama. LOST. Fiction loves to use time travel as a vehicle for storytelling, but one pesky topic arises that leads some to believe that time travel is impossible: paradoxes.
Time travel isn't just in the realm of science fiction. Last week, when discussing the plausibility of five fictional means of faster than light travel, we mentioned that wormholes are theoretically possible, according to physicists - their existence is invoked when solving equations in Einstein's theory of general relativity. And the fun thing about wormholes is that, in our four-dimensional universe of space and time, they can transport you to another location just as easily as another era.
Let's take a look at five time travel paradoxes that have been troubling physicists for years, then close by remedying your resulting headache with some soothing ideas that may resolve these paradoxes.
The Grandfather Paradox
You enter your time machine and travel back in time 80 years, locate your grandfather, and push him into some traffic. With your grandfather dead, your father is never conceived, and you are never born. But if you are never born, then you never lived to go back in time to kill your grandfather, so your grandfather lives. But if your grandfather lives, then you grow up to build a time machine and...
See the problem?
Whether you go back in time to kill your grandfather, your mother, your infant self, or the mad scientist who gave you the secrets to time travel, the issue remains: if you perform some action in the past that ultimately makes it impossible for you to travel in time in the present, then you never end up traveling to the past.