# Speed of Light - Time Travel **URL:** \ **Category:** Factual Questions\ **Created:** [August 24, 2001, 2:33pm UTC](https://boards.straightdope.com/t/speed-of-light-time-travel/77908 "2001-08-24T14:33:42Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![The\_Ryan](https://avatars.discourse-cdn.com/v4/letter/t/7feea3/32.png) [@The\_Ryan](https://boards.straightdope.com/u/The_Ryan)\ **Post date:** [August 24, 2001, 8:41pm UTC](https://boards.straightdope.com/t/speed-of-light-time-travel/77908/21 "2001-08-24T20:41:03Z")
> [@](#): > > \*Originally posted by tc \* > And we don’t like people just poping in asking silly questions before aclimatizing to the board. Well, as long as you’re correcting spelling, that should be “popping” and “acclimatizing”. Whack-a-Mole > [@](#): > > However, there a ways around this…theoretically. One method I’ve heard involves two metal plates that are charged with electricity to a high degree and form a ‘connection’ between themselves. Now, take one plate on a spaceship ride fro awhile at some significant percentage of light speed to experience noticeable time dilation. The plate on the spaceship will now be in the ‘past’ while the plate left on earth would be in the future. Step through and you can travel backwards and forwards in time at your leisure but only to the points the two plates are at. I really don’t understand what you’re saying here. What do you mean “step through”? Are you saying there’s some mechanism allowing teleportation between charged plates? Just what does the charge have to do with it? ---
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [August 24, 2001, 8:52pm UTC](https://boards.straightdope.com/t/speed-of-light-time-travel/77908/22 "2001-08-24T20:52:04Z")
> [@](#): > > Whack-a-Mole wrote: > > “As to your example of everyone agreeing that I left before I returned on a hyperspeed journey couldn’t you drawup a situation where I left point A at an apparent speed greater than C (say via wormhole) and I jumped into another wormhole that popped me back to where I started couldn’t I arrive before I left?” According to Thorne and Novikov this is theoretically possible, but now you’re into GR, and I was specifically referring to SR. All of these solutions to Einstein’s field equations involve exotic matter that has a negative energy density such as a cosmic string. The only _known_ example of negative energy density I’ve ever heard of is the Casimer effect. BTW if you decide to sing-up, let me know, maybe I’ll sing-up also. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [August 24, 2001, 10:00pm UTC](https://boards.straightdope.com/t/speed-of-light-time-travel/77908/23 "2001-08-24T22:00:54Z")
> [@](#): > > \*Originally posted by The Ryan \* > \*\*I really don’t understand what you’re saying here. What do you mean “step through”? Are you saying there’s some mechanism allowing teleportation between charged plates? Just what does the charge have to do with it? \*\* I’ll admit that is pretty vague. I’ve been searching the net for some cites but I’ve got nothing I can use here for a description. The effect I am talking about is real enough and is discussed in [Physical Review Letters: Vol. 61, P.1446](http://prola.aps.org/abstract/PRL/v61/p1446_1). The article is titled: > [@](#): > > Wormholes, time machines, and the weak energy condition > Michael S. Morris, Kip S. Thorne, and Ulvi Yurtsever > > Theoretical Astrophysics, California Institute of Technology, Pasadena, California 91125 Note the presence of Kip Thorne’s name on that paper. That guy is of a Stephen Hawking caliber and worth paying attention to. The other two guys may be excellent as well but I am unfamiliar with their names…maybe Chronos would recognize some of them. Unfortunately I do not subscribe to this journal and I’m not willing to pay the $100 subscription fee to get a cite for this board. If anyone else can get their grubby hands on this I’d be interested in hearing a synopsis of what the authors wrote. From my seriously neophyte angle the idea goes something like this: You have two metal plates some distance apart (say a few feet). You now start to pump an electrical charge through them. The ‘magic’ part that I do not know how to explain is that the plates will establish some sort of connection between them…basically a wormhole. Now, take one of the plates and put it in a space ship and drive it around for awhile at some significant percentage of the speed of light to get a good time dilation effect going. Since time slows down for the travelling plate you now have the two plates in essentially different times. Jump through the connection and voila…you just time travelled. Why doesn’t someone do this? [ul] [li] For one thing the energy required is stupendous. **Geepee** said it’d take all the energy in the universe but I don’t think so. I seem to recall that it’d ‘merely’ take the entire mass of Jupiter converted into energy to make this happen.[/li][li] Of course, energy is equivalent to mass and now you have to fly that around at some significant portion of C which can’t be easy.[/li][li] Thinking of the energy represented in those two plates would you want to get near it? Anything I can conceive of would be seriously atomized (or worse) going through the plates. A mere human wouldn’t stand a chance.[/li][li] I also seem to recall that the act of you trying to travel through the ‘wormhole’ might be enough to destabilize the connection and it would collapse. What happens to the person going through if that happened is a subject best left to sci-fi and/or horror writers.[/li][/ul] I’m sure someone could come up with a few other problems but I think you get the idea. While such a thing can be speculated and _theoretically_ would work the practical side of building such a thing seems nearly impossible. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [August 25, 2001, 2:46am UTC](https://boards.straightdope.com/t/speed-of-light-time-travel/77908/24 "2001-08-25T02:46:44Z")
Before someone starts writing their grant application for the stardrive/timeship effect, I would like to ask if anyone can link to a qualified (say masters in physics or so) discussion or publication including near luminal velocities for objects which are larger than a molecule, and closer than a megaparsec? Any discussions of effects involving pressures, temperatures, and accelerations where matter is other than plasma? What are first class accommodations on this time ship going to be like? Just wondering if there has been a lot of change in the way things are, (or were? Will be? Whatever.) while I wasn’t paying attention. ## Tris “If we are going to stick to this damned quantum-jumping, then I regret that I ever had anything to do with quantum theory.” ~ Erwin Schrodinger ~ ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 25, 2001, 3:57am UTC](https://boards.straightdope.com/t/speed-of-light-time-travel/77908/25 "2001-08-25T03:57:33Z")
OK, I just looked through the PRL article. They’re not using the charged plates themselves for FTL transportation; they’re using the charged plates to produce, via the Casimir effect, a region of negative energy density, with which to stabilize a wormhole. The thing is, they’re unsure whether they can get the energy density negative enough for this to work; it looks like the plates might need a charge to mass ratio greater than that of the electron. Without the negative energy, any wormhole would have an event horizon around at least one end, and the neck would taper to a single point, thus squeezing the bejesus out of anything that tried to go through. The method that Thorne et al. proposed for turning a wormhole into a time machine involves accelerating one end to near the speed of light and bringing it back, thereby putting the two ends out of synch with each other. In general, though, it’s possible to make a time machine out of any sort of FTL device. I (tried to) explain the details of this way back in May of 2000, in the thread [The Past Through Tomorrow](http://boards.straightdope.com/sdmb/showthread.php?threadid=23435#post446307). If you try to wade through my explanation, it might help if you keep score on index cards, and maybe doodle a few diagrams. Trisk, I unfortuneately don’t think that there’s any examples known for what you’re looking for (large, fast, close objects). Of course, there’s no inherent difficulty in moving at great speeds (it’d feel just like sitting still), but there is considerable difficulty in acheiving those speeds, if you start off at something slower. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [August 25, 2001, 3:59am UTC](https://boards.straightdope.com/t/speed-of-light-time-travel/77908/26 "2001-08-25T03:59:48Z")
mhendo: \>\> I’ve just been on the tiger thread. You’re in quite a rhyming mood today Yup, I just remembered [this one](http://boards.straightdope.com/sdmb/showthread.php?postid=1545010#post1545010) too. ---
**Author:** ![Anal\_Scurvy](https://avatars.discourse-cdn.com/v4/letter/a/c57346/32.png) [@Anal\_Scurvy](https://boards.straightdope.com/u/Anal_Scurvy)\ **Post date:** [August 25, 2001, 10:31am UTC](https://boards.straightdope.com/t/speed-of-light-time-travel/77908/27 "2001-08-25T10:31:24Z")
I have personally travelled faster than the speed of light. Not necessarily the speed of light in a vacuum, or even the speed of light in liquid, but the speed of light in a brick wall. In fact I’m doing it again. Someone should record this. ---
**Author:** ![SPOOFE](https://avatars.discourse-cdn.com/v4/letter/s/c5a1d2/32.png) [@SPOOFE](https://boards.straightdope.com/u/SPOOFE)\ **Post date:** [August 25, 2001, 11:01am UTC](https://boards.straightdope.com/t/speed-of-light-time-travel/77908/28 "2001-08-25T11:01:31Z")
> [@](#): > > Nobody knows yet for certain whether FTL is possible, though. You silly person, don’t you watch Star Trek? All you do is get some dilithium and some anti-matter, throw it all into a big glass cylinder, and _voila!_ You’re off to meet the Vulcans! Jeezum Crow, Chronos, I thought you were smart… Anyway… On a “more serious” note, how come everyone always associates “traveling FTL” with “travelling through time”? Where did that idea come from? There was one theory that required the mastery of wormholes… it assumed that if we could ever discover how to generate a large enough, stable wormhole, we’d simply need to “accelerate” one end of it, and then you could step through the wormhole and travel back to the point when the wormhole was originally created. So you couldn’t go back and kill Hitler, but you COULD do some interesting things with it. Just a theory. Personally, when you start talking about “if we could only control and manipulate a wormhole”, I suggest that you scrap that plan and work on something else, like designing better floss or something. ---
**Author:** ![KidCharlemagne](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@KidCharlemagne](https://boards.straightdope.com/u/KidCharlemagne)\ **Post date:** [August 25, 2001, 12:06pm UTC](https://boards.straightdope.com/t/speed-of-light-time-travel/77908/29 "2001-08-25T12:06:40Z")
Sometimes you guys sound like the fricking Comic Book Guy incarnate. Give the guy a break and get off your high horse. It’s sickening and reflects alot worse on you than any amount of ignorance reflects on the original poster. ---
**Author:** ![Scott\_Dickerson](https://avatars.discourse-cdn.com/v4/letter/s/f04885/32.png) [@Scott\_Dickerson](https://boards.straightdope.com/u/Scott_Dickerson)\ **Post date:** [August 25, 2001, 7:32pm UTC](https://boards.straightdope.com/t/speed-of-light-time-travel/77908/30 "2001-08-25T19:32:44Z")
1. Kurt Goedel proposed a model of the universe which was consistent with General Relativity and which allowed free travel through time by spacecraft. Although his model has not been generally accepted, neither has it been definitely refuted. 2. Add me to the list of those who object to “piling on” and “flamer”-type responses to questions. [Previous page](https://boards.straightdope.com/t/speed-of-light-time-travel/77908.md?page=1)