Time Travel and Why the CrackerJack Dimension Shifting Bracelet is Inadequate
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05-06-2014, 11:13 PM
Time Travel and Why the CrackerJack Dimension Shifting Bracelet is Inadequate
You’ve done it. You’ve built the first successful time machine in your basement and now it’s time to try it out. You decide a modest test would be prudent, so set the controls to take you a mere ten minutes back into the past. You squooch into the capsule seat more comfortably (no seat belts; you’re only going to transit time, not space, so there’ll be no spatial acceleration), recheck the dials and with an expectant smile, engage the temporal warp generator. It buzzes busily; the world outside your capsule goes blurry and indistinct. A half second later the warp generator clicks off. You’ve shifted ten minutes backward in time. What will you see when you open the capsule hatch?

A. Your basement as it appeared ten minutes earlier.

B. Your basement as it appeared ten minutes and one half second earlier.

C. Your basement as it appeared ten minutes and one half second earlier with a
surprised double of yourself trying to climb on top of you into the capsule.

D. The earth as seen from an altitude of something between 3,300 to 11,000 miles above it, receding away from you at 67,000 MPH. This will only be a brief glimpse because you didn’t bring a jacket and some other things suddenly necessary you neglected to consider.

E. The earth as seen from some incalculable altitude above it, receding away from you at an incalculable velocity. Briefly glimpsed.


E, of course, is the correct answer, as not only is the earth orbiting the sun (answer D), the solar system is orbiting the center of the galaxy, the galaxy is transiting space, and the galactic region is transiting space. As you can see, anyone building a time machine would have to build one hell of a motion machine as part of it, and one hell of a galactic positioning navigational system as another part of it, if the idea is to not just transit time but stick around on planet earth while doing so.

While that barrier to achieving practical time travel is formidable, mankind has a terrific resume full of proving the impossible not impossible after all.

But I think even that barrier is child’s play against a barrier to time travel I cannot see surmounted. That barrier is the barrier of insufficient information. Here’s the thing: there’s more than one way to reach identical states. Consider two chessboards, each in an identical state. One state was arrived at by play of the game. The other state was arrived at by just placing the pieces on the board. What is impossible is determining how that state was arrived at by examination of the board alone. More information is necessary. But if the only information you have is the state of the board, you don’t even know where to look for the additional information needed – or even if it exists.

And that’s the real rub. Not everything that happens leaves a recording. Stuff happens that leaves no trace of its prior state - out of many possible prior states.

Thus, it is impossible to correctly ascertain prior state from current state alone.
Nor would reversing the arrow of time guarantee that prior states regressed thru were the actual prior states extant when time’s arrow was as it was.

This is disappointing.

I have never regarded actual transit of time backward as ever possible, but the problem of insufficient information makes even just deducing the past impossible. Archeology and anthropology dig up new information daily; we can form fair approximations of the past. But the information is spotty; there are some aspects of the past permanently unknowable because not everything that happened left traces of its prior states.

Not only is time travel backward impossible by machine, it isn’t even possible by book.

Dr. Who has a lot to answer for.
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06-06-2014, 12:02 AM
RE: Time Travel and Why the CrackerJack Dimension Shifting Bracelet is Inadequate
So... if all that is kind of the case...

Then aren't you actually kind of building a rather limited 'Space fold' drive? :/

Much cheers to all.
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06-06-2014, 12:04 AM (This post was last modified: 06-06-2014 12:08 AM by EvolutionKills.)
RE: Time Travel and Why the CrackerJack Dimension Shifting Bracelet is Inadequate
The spacial problem could be tackled with a setup that creates a start point whenever the device is turned on. This would limit your time travel options to only the time while the device has been in continuous operation, with the earliest you can go back to being the activation of the device itself. This would require the device to always be on, maintaining a localized breach in space-time (a wormhole), but it's time travel ability would be limited to the most recent continuous operation of the device. For example a device turned on in 2100 and left on for 100 years could potentially allow you to travel back to when the device was activated, but that is it; the opening of the wormhole would always be anchored at it's activation point. Certainly not as free roaming as the Doctor's Tardis by any means.

And while travel back in time may not be possible, let alone practical, time is still relative. If one were to go and spend a few years doing laps around a black hole's event horizon (or traveling at 99% the speed of light), once they returned back to a comparable time reference, they'd see that decades (if not centuries) had passed during their few years.

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06-06-2014, 02:13 AM
RE: Time Travel and Why the CrackerJack Dimension Shifting Bracelet is Inadequate
(05-06-2014 11:13 PM)Airportkid Wrote:  ...
This is disappointing.
...

You're telling me!

But I really appreciate your analysis of where I've been going wrong...

I've being using particle rather than wave theory.

Your chessboard analogy highlights the difference.

Waves have history; particles don't.

Maybe at last I can get back home.

Thank you so much! Thumbsup

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06-06-2014, 10:18 AM
RE: Time Travel and Why the CrackerJack Dimension Shifting Bracelet is Inadequate
Hang on. Did you travel backwards in time, occupying space as you travel... or dematerialize some where when and rematerialize some where when else? In the latter case there is probably no reason to think your machine couldn't travel in space as well as time, so the key thing to overcome would be velocity rather than absolute position in space. In the former case you might be able to hold on somehow to the matter around you as you travel in time. However you would probably cause a thermonuclear event as you reach a speed of zero seconds per second and start to wind backwards.

Give me your argument in the form of a published paper, and then we can start to talk.
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06-06-2014, 10:55 AM (This post was last modified: 06-06-2014 11:03 AM by pablo.)
RE: Time Travel and Why the CrackerJack Dimension Shifting Bracelet is Inadequate
Just bolt the damn thing to the floor. Big Grin
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06-06-2014, 01:14 PM
RE: Time Travel and Why the CrackerJack Dimension Shifting Bracelet is Inadequate
If this doesn't get me a dinosaur Imma be so mad.Dodgy

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06-06-2014, 01:30 PM
RE: Time Travel and Why the CrackerJack Dimension Shifting Bracelet is Inadequate
(05-06-2014 11:13 PM)Airportkid Wrote:  E, of course, is the correct answer, as not only is the earth orbiting the sun (answer D), the solar system is orbiting the center of the galaxy, the galaxy is transiting space, and the galactic region is transiting space.

Nitpick: what happened to one's angular momentum?

Ten minutes would leaves stellar motion negligable; one's path (slightly faster or slower ahead of the Earth in its orbit) would depend on which side of the Earth one had been on.

Notwithstanding that such a question seems to presuppose an absolute system of coordinates - which is odd, to say the least, relativistically speaking.

(05-06-2014 11:13 PM)Airportkid Wrote:  Thus, it is impossible to correctly ascertain prior state from current state alone.
Nor would reversing the arrow of time guarantee that prior states regressed thru were the actual prior states extant when time’s arrow was as it was.

True; it is not possible to infer past behaviour in a deterministic sense. But we can't determine anything deterministically.

A probabilistic path-integral formulation may be the best we can do, but that nonetheless tells us a hell of a lot.

As with all things quantum, this goes back to the double slit experiment... A path integral is, crudely, a sort of double-layered inegral; a single integral can measure/describe/predict classical behaviour along a single discrete path; the embedded path integral evaluates all the possible paths according to their quantum weight. Knowing the rules of the game we can reconstruct the behavior of a given photon; the final pattern in fact results from the interference of the multiple possible paths with each other.

Er, but anyway. You were saying?

It is, of course, entirely possible (but probably inconveniently time-consuming) to simulate chess games until one reaches the desired end state. Those paths wouldn't interfere with each other, and as such, it's statistically unimportant which actually resulted - so long as that system is in isolation.

(05-06-2014 11:13 PM)Airportkid Wrote:  I have never regarded actual transit of time backward as ever possible, but the problem of insufficient information makes even just deducing the past impossible.

That's not a view I've encountered before; propagation of information beyond the speed of light (ie, time travel) would violate all sorts of things, but you're taking a more information-theory entropy view... Interesting. But I'm not sure that's warranted.

(05-06-2014 11:13 PM)Airportkid Wrote:  Archeology and anthropology dig up new information daily; we can form fair approximations of the past. But the information is spotty; there are some aspects of the past permanently unknowable because not everything that happened left traces of its prior states.

Ah, but all information is spotty. Aspects of the present are mutually exclusive!

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06-06-2014, 04:22 PM
RE: Time Travel and Why the CrackerJack Dimension Shifting Bracelet is Inadequate
Time travel is already possible. You just have to go faster than the speed of light. As your absolute speed approaches the speed of light time slows down to compensate, becoming zero at the speed of light (and thus making acceleration impossible, because motion, relative to the particle, has stopped). If you go even faster than that you should get negative time and go backwards. Its already happened before... apparently. At the creation of our universe. Don't look at me, I don't understand it Undecided . So you wouldn't have to worry about all this direction nonsense, you would only need to set a path and calculate your speed so that you end up in the place you want to.

Of course, if you only want to go forward in time you just need to go just as fast as the speed of light, or maybe just really really close to it. The universe would keep going at a normal rate, but time relative to you would essentially stop. You wouldn't be able to go backwards though, and, unless you could change direction, which would cause you to decelerate thus making time relative to your position normal again (at least until you speed up again) you would end up somewhere in deep space. Probably not ideal Consider .

Its a fun problem to think about. When you consider motion during time travel you do end up with two interesting problem; getting the right time but the wrong place, or colliding with some object in the intermediate path before ending your trip. Neither seems ideal does it Yes .
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