Time Traveling with Hawking

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Matt Barton
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Joined: 01/16/2006

Just saw this and thought we could talk a bit about time travel, one of my favorite topics!

Hawking: Time travel will happen.

I've been having this thought a lot lately. It's my understanding that the closer we get to the speed of light, the slower time becomes. The idea is that someone traveling at near the speed of light would come back to earth and find that it's now hundreds or even thousands of years into the future. There have been many science fiction stories done on this topic, including one involving telepathy and twins by Robert A. Heinlein.

I love thinking about such things, though of course I lack the physics and mathematical background to really get at the numbers. Still, I like pondering how space, time, and light speed are related. One thing I've wondered is how could it be that you could reach a point in space that is, say, four light years away, in only two years? That would mean that you had either (a) surpassed the speed of light, which is supposedly impossible, (b) traveled in time, perhaps forwards or backwards as you progressed, or (c) warped space to contract the actual distance. Perhaps A naturally implies B and C, or some combination thereof.

One thing that often gets left out of time travel stories is the orbit of the earth and movement of planets and galaxies in general. You couldn't just "go back in time" and end up in the same spot--you'd probably be standing in the vacuum of space. You'd clearly need to also move in space as well as time. So it seems that the first order of time travel would be to determine the location to land, then either warp (contract?) either space or time to travel faster than the speed of light.

At any rate, it's fascinating to see what the physicists are up to and try to get a handle on what it might mean for the future as well as the past. ;)

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Bill Loguidice
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Joined: 12/31/1969
Ah, yes, the time traveling

Ah, yes, the time traveling issue. I mentioned that as well in some earlier forum or blog post, since it seems several science shows have been covering the subject of late. I've of course been watching Hawking's new series, and actually just finished the Time Travel episode last night from my DVR. Anyway, what's interesting is that Hawking is insistent that traveling back in time is impossible in his opinion because of the inevitability of creating paradoxes (breaking the relationship of cause and effect) and the sticky business of "feedback", particularly radiation, where nasty particles endlessly loop back and forth in time, growing in power and eventually creating an explosion. Hawking is particularly down on worm holes. As a point of contrast, the equally excellent "Sci Trek" series, had a similar time travel episode (again, one of many such series of late to cover the topic, often with the same featured scientists), but this time, they argue that traveling BACK in time is possible, essentially through creating two wormholes (ALL series seem confident in FORWARDS time travel, regardless of mechanism). As for the paradox issue, that's where parallel universes can come in handy. If you do something to destroy one timeline/continuum, a new timeline/continuum gets seemlessly created.

Bottom line - and this is really the ONLY thing that's important here - based on physics alone (whether we'll ever be able to do it is a different issue, though even seemingly impossible engineering challenges can someday become possible if they don't violate a law of the universe), traveling both backwards and forwards in time is possible. It's the same thing like traveling as fast as or faster than light. You can travel up to 99.9% the speed of light, but no faster, due to the so-called cosmic speed limit. However, as was mentioned, there are ways to manipulate space time where you can compress the distance between two points, which is really a clever way of traveling much, much faster than even light.

It's also interesting that in the Hawking episode from his series (again, excellent production values - I particularly like how in each episode they morph from the Hawking voice to the narrator voice), he mentions how the scientific issue of time travel was verboten from serious scientific discussion for a number of years. When my wife, Christina, was an STM editor for Springer-Verlag many moons ago, she put a time travel book into production (which we still have a proof copy of). Just 15 years ago, it was still a sticky scientific topic, but one that was clear from the book a topic that was beginning to interest some serious scientists with some serious mathematical chops. It's good to see another seeming impossibility at least be proven possible, though extraordinarily unlikely (given the immense power and engineering requirements) any time in the next 100 years. It also is arguable whether travel back in time further than the creation of the worm hole (or, to put it better, time traveling device) itself is possible at all, though again, there does seem to at least be the scientific backing for the possibility. Fascinating, fascinating stuff, and something to keep watching with continued interest.

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Mark Vergeer
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Joined: 01/16/2006
Interesting stuff Matt!

Mr Hawking has an amazing intellect and ditto insight into the laws of physics and beyond. Interesting read.

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