In A Christmas Carol, the Christmas ghosts teach Scrooge a life lesson by bringing him back to his past, and giving him a glimpse of his future.
“From a physics point of view, he is moving back and forth in time and you should wonder, ‘How’d that happen?'” says Ibrahima “Ibou” Bah, an assistant professor of physics and astronomy at Johns Hopkins University.
“If you’re able to create such a rip in space, you could enter it and come back out, and you’ve go backward in time.”
According to Bah, the Ghost of Christmas Future had much less heavy lifting—at least on the initial leg of his trip.
“You can move forward in time—that’s actually easy,” Bah says. “All you have to do to go forward in time and meet people in the future is move at incredibly high speeds.”
If somebody is moving fast compared to someone else, his or her clock will tick slower, according to Albert Einstein’s theory of special relativity. So to travel to the future, just start moving at speeds close to the speed of light, Bah says. Since your clock is ticking slower than the person who is not moving, 10 years in your reference frame can be 30 years in theirs.
“So all that’s required is that you’re sitting still and I start to move at a fraction of the speed of light—and you can pump up somebody with sufficient rocket power to do that. The ghost could maybe take Scrooge and shoot off in space, really, really fast and then come back down. But then he has to bring Scrooge back.”
The coming back is the rub. As is the whole ‘going back in time’ thing. “Physically, we don’t think that’s possible,” Bah says.
But, if the Ghost of Christmas Past were able to gin up some negative energy (which doesn’t technically exist), he could create a loop in space-time that would allow him to take Scrooge back to see his younger self. Or, if the ghost was able to take some matter, make it spin very fast, and then collapse it into a small area to make a rip in the fabric of space, or what those in the business call a “naked ring singularity,” he could go back in time by going through the ring.
“If you’re able to create such a rip in space, you could enter it and come back out, and you’ve go backward in time,” Bah says.
Source: Johns Hopkins University