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May 11, 2010

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

Posted: 01:31 PM ET

Editor's note: Geek Out! posts feature the latest and most interesting in nerd-culture news. From scifi and fantasy to gadgets and science, if you can geek out over it you can find it on Geek Out! Look for Geek Out! posts on CNN's SciTech blog.

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 Wilds, 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, Wilds' site hints that time travel may be all in your head.

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Filed under: Astronomy • Space • television • universe

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Josh J.   May 17th, 2010 1:51 pm ET

On a serious note. I contend that the abaility to travel back in time will never occur. The reasosn is that if that abaility was to ever exist, 'Wouldn't we already have seen evidence of it?'

Are you telling me that nobody from the future with the power to go back in time wouldn't have come back and stopped Hitler, the holocaust, the assassination of Martin Luther King or John F. Kennedy, or even prevented 911?

if traveling back in time would ever be possible in the future, then we would already know it!

O.K. Scholars, your retortes!

Roger   May 17th, 2010 1:53 pm ET

If I went back in time and killed my dad before I was born, then how can I ever be born? And if I can't be born, then how can I go back in time to kill my dad.

People, time travel is nothing more than fantasy. It's NOT possible. It's like the Special Olympics...if if you win (this argument), you're still a retard.

ubetya   May 17th, 2010 3:28 pm ET

The example of going back in time and killing your dad (mom, self...) is not proof you cannot go back in time. Its just proof that you cannot go back in time and kill your dad. You can go back in time, but be unsuccessful in the killing. Maybe you get hit by a bus or the gun misfires. Even for non-time travelers, killing someone is not a sure thing.

Two thoughts on the conservation law of matter/energy.

First, this is just a theory, not a “law”. The way you are looking at it may be too limited. If time and space are really connected, then maybe the conservation law of matter/energy involves all of time and space and not just this moment of time and space.

Second, it took energy to send the bar of lead into the past. Therefore, new matter was not created, just converted from energy to matter. The matter was just created in another time.

MakeUthink   May 17th, 2010 3:55 pm ET

Doctor Who got me thinking about his theory on time travel. The lead block idea of a piece of mass traveling back in time tho that piece would already be there. So what if Time travel would just be time viewing. What if you even did travel back in time it would just be the images not neccessarily the matter? What if?? What if??

Pilot to Navigator   May 17th, 2010 4:23 pm ET

I think the most challenging aspect of travelling to the future is a point of reference for locality. With the universe expanding, how do you plot your physical point of arrival? If you simply travel in time and not simultaneously in physical space, the location of your launch is not at the same physical spot at the time of your arrival. Wouldn't you have to first travel out into space, then travel in time, then determine your physical location of arrival, then travel to your desired location of arrival?

Pilot to Navigator   May 17th, 2010 4:35 pm ET

Maybe that was actually me who crashed in Roswell? My time machine worked, but my spacecraft didn't!

Z   May 18th, 2010 8:18 am ET

Who came up with the idea that time is a dimension? I remember HG Wells writing that in the Time Machine novel. If time and space are the same than time should be targeted by the space occupied at a certain time. The thought of moving to a certain point in space for a certain date of the past is an interesting thought but also rememder that the universe is also expanding at light speed or so they say. If I consider empty space as inert and the only mass within it is the universe then the only action taking place are the actions of other bodies within that inert nothing nott the actual space. All of those actions would cause various eddys and currents on the matter within that space making it extremely hard to plot a course to a specific set of corordinates

Doctor Who   May 18th, 2010 12:59 pm ET

I think the problem here is that we want to view Time like we do Space.. we can travel thru Space by movement.. we perceive objects moving in space and think we can do the same with Time... but Time is not Space.
Time is the name we give for something we cannot quite truly understand.. we see the effects of motion within it, but we dont really SEE it.
The only thing that exists in regards to Time is NOW.. there is nothing to go "back" to because it doesnt exist.. what was then exists only now..
The same goes for the Future.. it cant exist yet because it hasnt happened yet.. because what's to become is existing now.
And as far as time dilation effects of going fast in a spaceship.. that's more akin to a form of suspended animation.. ship time will slow down while the rest of the universe goes on as usual. It's more complicated than that, but the point is that the space traveller never leaps through time.. he still coexists with Time itself.

geekout   May 21st, 2010 8:47 pm ET

wormhole. like stargate. ahaa

Z   May 22nd, 2010 10:27 am ET

Let me break all the laws of physics to make a point!!!!

I construct a spacecraft capable of unlimited, multiple times speed of light speed. So now I travel to a spot 100 light years away at so at 10,000 times speed of light. I arrive in say after 3 days of travel. I then look back to where I started and the faint glow of our sun being viewed is from a hundred years ago, that is as long as it has be traveling. I return back to earth at 15,000 time light speed. I arrive back at real earth time no closer to the past or the future. Only the elapsed time I was physically gone. No matter how fast I travel I cannot go to any time earlier than the time I left plus any elapsed time . I am only changing the distance the light traveled. I can only move away to a point that allows me to view the past from a far distance. I can not take part in that past.. I can only move in present real time

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