This are the rules for Time Travel that shall be obeyed by all time travelers under penalty of being caught in a causality loop until the end of the time…
The rules for Time Travel seem to have been written down somewhere and SF Television has been using and abusing for all that time. Now, the $64,000 questions are a) is there such a thing as time travel? and b) do these time travel rules mean anything?
1. You Cannot Assassinate Your Own Grandfather, Or Else…
One of the most famous arguments against time travel was the problem of temporal paradoxes. What happens if you kill one of your ancestors? If someone else did it, then the line that bore you would cease to exist and so would you. But if you did it to yourself, you would cease to exist thus undoing your murder which would bring you back into existence where you would travel back in time to kill your ancestor, etc. A paradox.
1a) … You Will Fade Into Oblivion Unless You Fix It.
The Back To The Future answer to this question was you faded out of existence unless you fixed the paradox.
1b) … Or you will instantly pop out of existence.
This was one of the more popular ones, especially when you did this to someone else.
2. If You Meet Your Future Self And Touch, *BOOM!*
Writers got this idea from the Pauli exclusion principle which, really simply put, said no two particles can occupy the same time and space. Fortunately, this does not mean if you met yourself that the Universe would spontaneously implode, explode, or you’d explode, or God would come down from Heaven and slap you silly. If you shook hands with your future self, probably the only thing that would happen is you’d notice how clammy your own palms are.
3. The Time Travelers and Those They Left Behind Will Remember The Old History When Everything Changes
When Time Travelers change history, they and their support crew back in the “present” time remember the old history and know history changed. I wonder how this works? Magic time protection aura? Isaac Asimov’s classic novel Eternity, Inc. actually does use a time protection aura.
4. If Changing History or Creating a Paradox is Forbidden, Then Everything You Do To Change History Will Fail
This one may be true. Kip Thorne is a CalTech physicist who set the scientific community ablaze when he came up with a credible method for making a time machine. After he published his seminal paper on time travel, a number of respectable physicists came out of the closet (so to speak) with their ideas. One avenue of research found that the laws of physics, as we know them, won’t allow you to create a paradox, any attempt to do so will be foiled. The other option is a branch in the quantum universes. The moment you change history, a new branch of history is created where you’ve killed your grandfather, but you can still exist because you come from a parallel universe where no one ever killed your grandfather.
This site for the PBS program Nova has the best quick-start guide to time travel I’ve come across.
Advice for Writers
If you want to be an SF writer, or if you already are one, please do a little research before you write your next Time Travel opus. Take the time to come up with clear, consistent rules for time travel for your universe and stick to them. If you would like some recommended readings or viewings, you can’t go wrong with the following:
- Isaac Asimov. Eternity, Inc.
- Robert Heinlein. Door Into Summer.