The Reality of Time Travel

"Time travel is theoretically impossible, but I wouldn't want to give it up as a plot gimmick."

— Isaac Asimov


So. Back to the Future. You know, the scene in the third movie where Marty complains they can't get the time machine to 88 mph because they'll run into a movie theater, and Doc says, "You're not thinking 4th dimensionally, Marty! When you go back to 1885, none of this will be here."

It's clever, cuz see, even though you're traveling to a different time, you're still in the same place. So while there's a movie theater in 1955, it's all prairieland in 1885. Where a bridge is under construction, 100 years later it'll be finished and you can just sail across.

But if you think about it, that's ridiculously Earth-centric.

See, during the time you skip, the Earth will have moved. For one thing, it rotates constantly. California (where the movies take place) moves through space at about 700 mph. So unless you are arriving at the exact same time of day as you left, the Earth will have shifted underneath you.

In the DeLorean's inaugural voyage, Ein would've crashed into a house 12 miles west of the mall.

Also the Earth is traveling around the sun at about 67,000 mph. So not only would you have to arrive at the exact same time of day, but also the exact same time of year (we won't talk about that quarter of a day that makes Leap Day). So Einstein would have appeared somewhere past the International Space Station.

"Was that . . . a DeLorean?"

But that's assuming the sun is our central reference point, which is just as arbitrary. Why not use the galactic center? Or the (impossible to define) center of the universe? By some measurements, Earth is shooting through the universe at over 1 million miles per hour.

Poor Ein would end up a tenth of the way to the moon. And that's just for traveling one minute in to the future. Marty's first jump would land him somewhere past Neptune. His final 100-year trip would shoot him out of the solar system entirely.

Don't get me wrong, I love time travel stories. But writing them gives me a headache.

Who's not thinking 4th dimensionally now, Doc?