time travel

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dragonboy
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14 May 2007, 3:54 pm

anyone think that time traval is not space/time but is actually extra-planar and any reasons why.

Scramjet
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14 May 2007, 4:30 pm

Wow, that's a mighty interesting can of worms you're opening there. For starters, let me just add to the mix that the extra-planar thing has actually been proven for subatomic particle -- the "only" question is: Can it be proven for "larger" items, such as whole atoms, or the ~5 x 10^27 atoms that forms an entire human being.

For non-physics-nerds: The "extra-planar" thing we're on about, is a theory that says each time in anyone's and anything's "life" there are two or more possible outcomes, a corresponding number of "parallel universes" are "spawned". When you cross the street, there's one universe in which you actually made it across the street, and another in which the "copy" of you got hit by a car. It goes all the way down to every little even in your lift (and in that of everybody else) where things could have come out a tad either better or worse, there's a "parallel universe" in which each of those possibillities is a reality...

Oh, I'll shut up before this turns in to a four-hour lecture... :oops:

the-over-analyzed
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14 May 2007, 4:31 pm

Umm..I have no idea what you mean because I don't have the background vocabulary to understand this. Could you give a link to a website that will explain the background information for things like: "space/time" and "extraplanar", or offer a brief explanation.

Thanks!

ahayes
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14 May 2007, 4:56 pm

Scramjet wrote:

quantum immortality *shudders*

matt271
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14 May 2007, 6:10 pm

extra-planar?? that does mean an extra plane then the 3 dimensions of space?? like a 4d 5d 6d etc
i have trouble accepcted there could be more then 3d in space. i asked my phy teacher before and he said time is a dimention. he knows i program for a hobby and explained each dimension as like an array of arrays. i understood but didnt believe it. i think time exists, and could be considered a dimension, but its not a dimension of space. space has 3 dimensions, space = volume. u add time to the mix, its just another dimension of something else. you could then say anything is a dimension like that. heat is a dimension, make a 5 d graph x by y by z by time by heat. graph the heat in every part of a volume of space over a period of time.
as for time travail, i think its not possible.
probability is just guessing the possibe outcome of something based on little information about it. u roll a dice and all u know is ur rolling it and it has 6 sides, to the odds of rolling a 2 is 1/6.
now if u knew everything about the dice, how it was going to be rolled, how the wind was, how the table it was being rolled onto was, and measured everything exactly, knowing ALL the variables, you could say exactly what it will land on, say 2.
so if you knew every detail of every atom in the entire universe, knew every law of nature, even those we dont know yet, and calculated them PERFECTLY, you could say exactly what will happen.
now i know there is the uncertainty principle, but to my understanding, thats simple the result of not being able to measure such small particles. say u want to find exactly where an electron is. u bounce light off it and see its reflection in some kind of meter. u can see its reflection, but that light has also now moved the electron, so its no longer where u think it is. correct me if im wrong there. so if u could somehow messure every peace of the universe w/out changing it, or account for the changes ur measurements make, and u could simulate every law of physics, even what we have not discovered yet, you could play out the entire universe in a simulation.
but then the concept of free will becomes a problem. you could read that u will do w/e in 1 minute, so simply decide not to do it. my thoughts on that are the simulation would see that you saw this, then decided to not do it. but then you will see that the simulation saw it, and the simulation see that you did, and you see that, and the sumlation see that..... <head explodes>

that reminds me of something i though of when i was a kid. future teller scam w/e ppl say the reason your future does not happen like they said, is because them telling you it changes it. but why does them telling you your future not be account for in your future?? why cant u predict that w/e will happen, while you already know it will happen when it happens?

TrishC7
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15 May 2007, 3:45 am

Scramjet, thanks for the explanation. I know just a bit about this but don't tend to remember the vocabulary. I have not idea what's possible, but generally speaking tend to think anything's possible, though some things are highly unlikely. I just listened to something by scientist Richard Dawkins that's related; a friend sent me the link. It runs about 22 min.; I could only concentrate by not watching the screen, but pretty much 'got it.' Some of you here might find it interesting, and/or other items on this site. Here's the link:

http://www.ted.com/index.php/talks/view/id/98

The site has pretty cool talks by a number of people in various areas of interest.

the-over-analyzed
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15 May 2007, 5:59 am

When I was a kid I spent like a month building a time machine out of popsicle sticks and twine wrapped around a lazy susan. I was really into it, was really confident that it would work. I thought I could make a time machine out of popsicle sticks.

MagmarFire
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15 May 2007, 9:04 pm

There is an easier way to travel through time, though: just sit on your butt. There you go! You're travelling forward through time. :wink:

In a more non-Euclidean sense (I think), the faster a body moves through space, the slower you move forward through time in relativity to someone who's sitting much like the former. I have heard that the speed of light is absolute, so if you move as fast as the speed of light, time is pretty much stopped for you. Of course, your mass would be greater than if you were sitting still, but that's irrelevant if we leave out one of the factors that makes speed-of-light travel impossible.

If you were to go faster than the speed of light, I think that maybe time would be reversed for you. Of course, the whole "time slowing" thing could be related to logarithmic calculations, as they can get closer and closer to 0, which would be time at a complete halt, but never reach it because of the domain of logarithmic functions. Also, travelling at the speed of light is pretty much impossible, so I think time can slow down only to a certain extent. I have a feeling that logarithmic functions and "time speed decay" are related in some way because of this.

ahayes
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16 May 2007, 2:15 am

If you could instantaneously go from STL to FTL, then applying less propulsion would actually make you go faster, how cool is that?!

Soopervilin
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16 May 2007, 3:45 am

Here's the way I understand the speed of light/variable time discussion:

Imagine an everyday ordinary clock. Now start moving away from it, accelerating as you go. As you get faster and faster, your relative speed to the light refracting off the clock face takes longer and longer to catch up to you, so the clock appears to slow down infinitely as you approach the speed of light. So, the faster you go, the slower time appears to go...

If you keep looking backwards, that is. Imagine that you're heading toward an identical clock. As you accelerate toward the clock, the time displayed by that clock appears to be accelerating as well, until you approach the speed of light (and the clock appears to be moving infinitely fast?). In both of these situations, the passage of time hasn't changed, merely the visual perception of it.

Anywho, as for the idea of time travel, logically it does not make much sense.

I see two ways of time travel working, at least into the past: 1.) The time traveler would not be able to interact with anything in any way, merely an observer as it were (think Quantum Leap holograms), or 2.) The time traveler would be able to interact with anything and everything, thus changing the present and future.

Now for version 1, that can theoretically be done, but not by literally placing someone back in time. Find a reflective object X number of light years away, and with proper magnification, you would be able to see back in time 2X years.

Version 2 is much trickier and involves causality loops. Someone goes back in time, and attempts to change the past, if they succeed, then their trip to the past would become unnecessary when time catches up again, so they would not do it and as a result nothing would have been changed, so they go back to change things, succeed, and no longer need to again...it's a causality loop, cause and effect leading into cause and effect, negating each other. Someone goes back in time and fails, then nothing got changed, and yet another causality loop is formed, this one much simpler.

Here's a simpler explanation.

A man goes back in time, for whatever reason, to prevent his own birth.

Somehow he succeeds, and erases his own existence. Now, he does not exist to go back and prevent anything, so he is born. He goes back and succeeds...and so on and so on. It's endless.

Or, he fails, and when the time comes again, he goes back only to fail again...and again...

So, if I'm right - and I'm not claiming to be - then time travel would either be absolutely pointless, if not absolutely impossible.

Anywho, these are just my thoughts on the matter.

ExeterChris
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16 May 2007, 5:15 am

I could be misinterpreting the question, but I think time-travel is totally impossible; if it were possible, we would have been visited by people from the future already.

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dragonboy
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16 May 2007, 10:48 am

ExeterChris wrote:

I could be misinterpreting the question, but I think time-travel is totally impossible; if it were possible, we would have been visited by people from the future already.

not necesarily if the future already found the answer maybe they found it was stupid and/or dangerous to dabble in the past.

Aysmptotes
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16 May 2007, 12:35 pm

So do you mean that instead of actually doing time travel, you just go to another parallel universe that started late. Which I wouldn't really consider time travel just trans-universe travel. BUt how would one find and pick a particular universe similar enough to our own since there technically there should be an infinite about of parallel universe. I just think of the book Timeline, because that is how it did time travel, but how does that explain that the evidence of people traveling back in time appears in our universe since we just went to a different one to go back in time. So if "time travel" is possible we will never see it in our universe inless someone travels to our universe of which it would just be apart of our history and there is nothing that we can change about that.

Also, if we were able to travel back in time in our own universe then it would have already happen regardless if we knew about it, thus it is already in our history and the consequences have established the world in which time travel was made possible. So its like the cat eating its own tail. The time traveler would be a product of what his is going to do in the past. So it would be cyclic and a circle has to start from some where but where? And I don't buy that if he doesn't really do anything but observe becaues we have no knowing how small things effect history or how the effect of small things grow. He could step on a leaf which if he didn't step on it a girl would have found it and then wrote a poem about it inspiring her to connect with nature more and then she could have become a famous poet and married rich and had a kid who started a hugh company or yada yada. But if she didn't find that leaf she just married a farmer next door. I think about things like that alot.

matt271
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16 May 2007, 1:36 pm

Soopervilin wrote:

Imagine an everyday ordinary clock. Now start moving away from it, accelerating as you go. As you get faster and faster, your relative speed to the light refracting off the clock face takes longer and longer to catch up to you, so the clock appears to slow down infinitely as you approach the speed of light. So, the faster you go, the slower time appears to go...

hmmm. from what i understand, the time between the clocking saying the time, and you seeing the light reflected off it, should be such a small time, no matter how fast you accelerate, it should never make a difference.
now i also read that the speed of light is constant. so if u turn on a light and run towards it, or run away from it, the light should still appear to be at the same speed if you where to measure it. like if u take a lamp and go on a space ship at almost the speed of light, then turn on the lamp, the light comming off the lamp in the direction the space ship is going, relative to someone not on the space ship, should STILL be the same speed. in order for this to still go by the lays of physics, time has to change to compensate.

Mandelbrot
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23 May 2007, 8:14 am

I have asked quite a few of the physicists which attended the Cambridge-MIT conference on quantum computing that same question; including prof. Bell and Prof. Stephen Knight. They all agree that there is most likely to be a number of 'extraplanular' possibilities. I, as a physicist, agree. [All dependent upon P = NP eh?]
But yes, it is a form of 'time-travel' so-to-speak.

The scary thing is, if one did time travel, one would not know from which reality one came, and nor might he be able to recognise it.

P.S. light might be constant, but that is only in a pure vacuum medium (which only exists in the minority of cases). This means that the medium through which light travels can change its properties from wave-particle behaviour, slowing down or (in theory of advanced potentials) speeding up. This can depend upon whether there is intense radiation, a dense region of space such as a black hole or even a rotating universe as proposed by Gödel.
Also, time only compensates for equilibrium in a closed system, and the universe is not always closed (this is a topic of debate for topological cosmologists for this reason i.e. ZPE).

And with regards to time travellers having visited already: 1.) maybe you haven't met them and they're keeping it quiet. 2.) Perhaps they travelled to a different point in history. 3.) Perhaps, if the multi-verse model is correct, they do not exist in our version of reality. 4.) perhaps, if they are from the future but living in the present, then they have not actually made that (from the future to the present) trip yet, but have memories of having time travelled and so can remember parts of the future.

I had a very peculiar dream about coming back from the future once, a dream which, had I not had it, I would not have studied physics. Of that I am certain.

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