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“Geek Out!: Stephen Hawking and five ways to travel in time

Stephen Hawking’s new Discovery Channel series, “Into the Universe,” aired again last night and continues into next week. In it, the famed cosmologist discusses the mathematical probability of aliens, the Big Bang and time travel. Hawking’s theories on time travel in particular seem fairly optimistic - although “Back to the Future”-style DeLoreans are conspicuously absent. That will be the topic next week. Taking a cue from the show, here are five semi-practical models of time travel:

Barrel through a wormhole
If time itself is a dimension like length and height and width, then Hawking says the fabric of time contains imperfections we could take advantage of. A smooth billiards ball has microscopic crevices, and so does spacetime. We’d need to find a true “wormhole” and prop it open, and then head on through.

The caveat, of course, is that we’d be facing heavy radiation feedback concerns (a bit like the screeches you hear at rock concerts) and even without that problem, that we would create paradoxes by messing around with historical events in the past. For this reason, Hawking believes travel to the past may well be impossible.

Go near a black hole
It’s simple: All we have to do is find a supermassive black hole and get into its orbit without being sucked into it. Hawking says time would slow down for the people in orbit relative to people elsewhere. Now to find a black hole …

Go really, really fast
Hawking says if we can get close to the speed of light, a “cosmic speed limit” will kick in to prevent going any faster. Approaching roughly 186,000 miles per second, time will slow down for the traveler vs. the observer. When the traveler emerges, they will have jumped into the future. We just have to develop an engine that can go that fast. Don’t try this on the Autobahn, folks.

Live on a space station
Turns out Cosmonaut Sergei Avdeyev is said to hold the record for the most time traveled into the future: about 20 milliseconds. His cumulative experience aboard Russian space station Mir gave him an edge over the competition. Hawking discusses in his documentary how orbiting global positioning satellites must have their timekeeping adjusted every so often because of the relative time slowdown.

Become a Retronaut
This one might be a cop-out, but many scientists (including Hawking) argue that time travel to the past is paradoxical and potentially impossible. In lieu of a Wayback machine, we can turn to the work of Chris Wild, who created a website about his experiments with being a being a Retronaut. That is, a person who travels into the past by exploring perceptions of time. Whether by looking at old pictures juxtaposed with new ones (which we experimented with at CNN iReport a few weeks ago) or hunting anachronisms, Wild’s site hints that time travel may be all in your head.”

- Nicole Saidi, CNN iReport Senior Associate Producer