James Drury posted a comment to my previous post titled the Trouble with Time Travel:

The Alternate Reality version of time travel has been the accepted theory in Marvel Comics for some time and seems to be the easiest route to avoid most paradoxes. Even if you went back and killed your grandfather, YOU would still be alive because you can’t disrupt your own personal timeline.

 Of course, if you have multiple timelines running in parallel (like railroad tracks), who can say if you’re actually travelling in time or just switching tracks? One timeline may look like yours hundreds or thousands of years ago but is completely separate, similiar to C.S. Lewis’ view in the Narnia books.

There are all sorts of variations from which to choose!

Thanks for your comments and all of the other mind-boggling comments. There appears to be an answer to the trouble with time travel. Multiple universes? That’s a discussion for another day.

Dean Koontz has his own thoughts about the subject. In my previous post I included his dislike of time travel from a Q&A. From his Writing Popular Fiction (1972), he gives examples of the limitless paradoxes. Here’s one.

If you traveled back to last Thursday morning in a time machine and met yourself back then and told yourself to invest in a certain company because their stock would soar during the next week, what would happen if the Early You, did as the Later You wished? When the Later You returned to the present, would he find himself rich? Or perhaps, while the Early You was running to the stock broker, he was stricken by an automobile and suffered two broken legs. When the Later You returned to the present, would he find himself with two broken legs? Perhaps you would end up hospitalized, never having been able to make the trip in the first place because your legs were broken a week ago. Yet, if you had never taken the time trip, you wouldn’t have sent your early Self into the path of the car and would not have broken legs. Yet, if you did make the trip, and had the broken legs, you couldn’t have made the trip because of the broken legs and. . .

He does go on to suggest reading Up the Line by Robert Silverberg.  In it Silverberg explores “every conceivable time paradox and carries them all to their wildly absurd and fascinating conclusion.”

Anyone read this?

But Orson Scott Card presents a different view. Make up your own rules. In How to Write Science Fiction & Fantasy, he presents a few examples. (I think that’s what’s been done with the alternative reality scenario that Jim mentioned)

If you go back in time:

1. you can make any changes you want in the past and you’ll continue to exist, because
the very act of traveling in time takes you outside of the time stream and removes you from the effects of changes in history.

2. you can make changes that destroy your own society—so time travel is a closely guarded secret and those who travel in time are only the most skilled and trusted people.

3. if you go back far enough, any changes you make won’t have major effects in your own time, because history has a kind of inertia and tends to get itself back on track.

4. you are only able to make changes that have no long-term effects, since any universe in which you change your own future could not exist.

5. you’re invisible and unable to affect anything. But you can watch.

6. Time travel consists of going back into the mind of somebody living in the past, seeing events through his eyes. He doesn’t know you’re there.

And the list continues. . .

Personally I like the idea of making up specific rules to counter any paradoxes.