A Way to Make Time Travel Work

[K^2]

Read before it is written...seriously! Have you tried not writing it after it is read, just to see what happens? I don't think the universe has imploded from the paradox yet.

It's the same question as what would happen if you set up a camera that shows things before they are recorded, and decide that if you see yourself waving with the left hand, wave with the right and vice versa.

The answer is provided, however. IF the technique described above works, the information you receive is quantum. It may be in superposition of yes/no states. If you try to trick the system, you'll essentially be getting random results.

If, however, the outcome of the event is largely predetermined, and is simply unknown, you can receive good information about it. For example, if there is a huge asteroid heading for Earth, it's trajectory has been predetermined for hundreds of years. Yet, we would not be able to predict it until it is too late. A "time machine" described above would be able to predict the impact in advance.

[Angarsk]

Aer'ki, even if you don't want to think of time as dimension, time travel is still possible. We can set up microscopic systems where time flows backwards. (basically, everything is sent in reverse, and all dynamics is identical to reversed time) It has been done. Problem is that you cannot read/write information from these systems without upsetting the time flow. But there are ways to circumvent that, which can allow small quantities of information to be read before it is written. There is a little bit of quantum physics involved, but only stuff that has been experimentally checked. (I've seen a quantum computer run with my own eyes, so if you'll tell me you don't believe in that, I'll have to e-smack you.)

I'm sorry I don't know much of physics much less quantum physics but I'd like to clear 2 points:
1.- What would be considered as "backwards time"? doesn't the experiment start at a certain time and ends later? so, whatever happened in the system still moved forward in our time?.
2.- Quantum are pretty much different from our world, right? I mean you can transport them, accelerate them, etc... things you could never ever do in our scale of things, right?

Thank you.

[K^2]

First, you need to keep in mind that time is just order of events. If A caused B, then A came before B, not the other way around. Fact that you can remember something you thought yesterday is the only reason why you know that yesterday came before today. That's how we keep track of time "flow".

Direction of time "flow" is tied to entropy, which can in simplified way be thought of as measure of chaos. On their own, things tend from order to chaos. In some rare cases where things do self-organize, (dust into stars and planets, etc) this large-scale order comes at a cost of small-scale disorder (in this example, temperature goes up, star catches in nuclear fire, chaos all around.)

The reason this sets direction for time is because in order to record information, you must increase overall disorder of the universe. If you flip the switch, for example, the energy you put in to make it move, must turn into heat. Otherwise, the switch will just keep bouncing back and forward.

The laws of physics on their own, however, are perfectly symmetric in time. If you film yourself throwing a rock upwards and catching it, then if you run the film backwards, it still looks like you threw the rock upwards and then caught it. That's because fundamental laws of particle interaction are independent of which way the time runs. (There is something called time parity, but it is way beyond these examples.) So what happens if you took every single particle, and send it in reverse? Well, they are all going to trace back their own paths exactly. Now, the more chaotic state precedes the more ordered state. Anything that was recorded gets erased in perfectly reversed order. To us, events seem to appear in reverse. A causes B, but A comes after B. Of course, relative to that system, it is our own time that is running backwards.

This is time reversal. Experimentally, it can only be done on microscopic scale, and this reverse "flow" lasts only some fractions of a second. Still figuring out how to use this to send even a bit of information backwards even a fraction of a second would be a major breakthrough.

Now on quantum. Quantum Physics doesn't just apply to small stuff. It applies to everything. However, most of its unusual properties only manifest on small scales. If you were to try and use Quantum Mechanics to describe motion of, say, a car, you would notice that you get the same answers as if you used ordinary Mechanics.

There are a few notable exceptions, however. A superconductor is probably the best one. Superconductivity is a macroscopic quantum state. It is Quantum Mechanics making an ordinary piece of metal/ceramic do some crazy stuff. Magnetic Levitation. Even more bizarre are superfluids, but these require extremely low temperatures. Helium II.

[Solokiller]

Actually, B can cause A, yet A comes before B. The terminator movies are a good example of this: john sends kyle back in time, kyle conceives john, who then lives to send kyle back in time. A is kyle conceiving john, B is john sending kyle back in time. The only problem is that this on its own is a paradox, but probably, the original john was conceived by somebody else. That's the danger of time travel.

[Saquist]

Aer'ki, even if you don't want to think of time as dimension, time travel is still possible. We can set up microscopic systems where time flows backwards. (basically, everything is sent in reverse, and all dynamics is identical to reversed time) It has been done. Problem is that you cannot read/write information from these systems without upsetting the time flow. But there are ways to circumvent that, which can allow small quantities of information to be read before it is written. There is a little bit of quantum physics involved, but only stuff that has been experimentally checked. (I've seen a quantum computer run with my own eyes, so if you'll tell me you don't believe in that, I'll have to e-smack you.)

http://forum.gateworld.net/showthrea...vel-Work/page2

What do you make of this?

It's talking about gravitic and magnetic induction as similar. What does it mean by induction?

[K^2]

I'm not sure where you wanted to link, but you linked back to this page.

But yeah, theory of linearized gravity suggests that we can induce gravitational field the same way we can induce an electric field. The later is induced by changing magnetic field, which can be caused by the "acceleration" of current flow. Similarly, accelerating something very heavy can produce a changing gravitomagnetic field, which will induce a gravitational field.

Problem is, the field you can generate this way is still not greater than field of the massive object itself. The reason why electromagnetic induction works so well is because charges involved are simply colossal. We do not observe a strong electric field from these because the positive and negative charges compensate each other. But causing even a tiny acceleration of charge carriers results in rather strong magnetic and electric effects outside of conductor.

We cannot do this with gravity without a source of "negative" mass. And even if we had negative mass, we'd need extreme densities, at least these of neutron matter, to allow for sufficient gravity manipulation using gravitomagnetic effects.

Actually, B can cause A, yet A comes before B. The terminator movies are a good example of this

I should have qualified. I meant without time travel, which inherently requires reverse order of events.

[Saquist]

I'm not sure where you wanted to link, but you linked back to this page.

But yeah, theory of linearized gravity suggests that we can induce gravitational field the same way we can induce an electric field. The later is induced by changing magnetic field, which can be caused by the "acceleration" of current flow. Similarly, accelerating something very heavy can produce a changing gravitomagnetic field, which will induce a gravitational field.

Problem is, the field you can generate this way is still not greater than field of the massive object itself. The reason why electromagnetic induction works so well is because charges involved are simply colossal. We do not observe a strong electric field from these because the positive and negative charges compensate each other. But causing even a tiny acceleration of charge carriers results in rather strong magnetic and electric effects outside of conductor.

We cannot do this with gravity without a source of "negative" mass. And even if we had negative mass, we'd need extreme densities, at least these of neutron matter, to allow for sufficient gravity manipulation using gravitomagnetic effects.

I should have qualified. I meant without time travel, which inherently requires reverse order of events.

Sorry.

http://www.scribd.com/doc/23171571/T...ander-V-Frolov

I looked this up for Reverse Time Energy to understand what you were talking about?

[K^2]

That's a little too hypothetical. Might be something to it, but there is not really enough to go on.

What I'm talking about above comes directly from Linearized Gravity, which is an attempt to look at gravity as analog to electromagnetic forces. The theory of Linearized Gravity is well accepted because it can be derived as an approximation to General Relativity. However, fact that it is an approximation should be noted. Gravity is not actually linear.

In addition to gravitational field, LG defines also a gravitomagnetic field. The four equations, similar to Maxwell's Equations, relate divergences and curls of these fields to their time derivatives and also mass and momentum densities at each point in space. The simplest equation is for divergence of gravitational field. It states:

Div(g) = 4*Pi*G*rho

With Gauss Theorem it is easy to show that this leads for a planetary body to a solution:

g = G*M/r²

Which is the universal law of gravity stated originally by Newton. The correct equation, from General Relativity is a little different.

g = sqrt(1 - 2*G*M/(r*c²)) * G*M/r²

The first factor comes from the metric tensor, and for Earth surface it is approximately 0.999998608, which is almost exactly 1. Other predictions of Linearized Gravity are correct to similar precision until you start bending the rules to the point of breaking. For example, near event horizon of a rotating black hole, Linearized Gravity can only be used to get some qualitative ideas.

[the-alguroan]

also theres the whole if u went back in the past, everything u done has already happened so ur just fulfilling the events that are meant to happen. if u went back in time tried to set of an atomic bomb in lets say the 1800's, two things may happen, one your stopped in some way, u get killed, ur priorities change yata yata. u leaving the bomb has already happened so u haven't changed anything. the next possibility lies in a new reality being created.

[Quadhelix]

also theres the whole if u went back in the past, everything u done has already happened so ur just fulfilling the events that are meant to happen. if u went back in time tried to set of an atomic bomb in lets say the 1800's, two things may happen, one your stopped in some way, u get killed, ur priorities change yata yata. u leaving the bomb has already happened so u haven't changed anything. the next possibility lies in a new reality being created.

The problem that I have with these sorts of ideas is that you change the past just by being there displacing air and absorbing light, so if you cannot change the past then you cannot travel back in time.

[K^2]

Except, you are working with a flawed premise that there is only one time line. In reality, there is an entire network of possible universe states and infinitely many histories linking these. When you go back into past, you don't go into your own past, but rather one very similar to it, with one notable exception - time traveler is there. It then diverges to a completely different history.

[the-alguroan]

thats why i said theres two possibilities one where ur intervention in the past is already history that u help created by being there, and two sporting out from the point u entered the past u created an new time line.

course i have always wondered is it possible to control which path of time possibility u go into.

also doctor who makes a good example of my first thought, going in the past doing incredible things but if no one knows or the information is never released on what u did then ur time is still the same. thouse u would go back to try to accomplice ur mission , u succeed but the story of what u did is never published, which would set the stage for u traveling back in time, ....did i repeat myself? da*n time talks, messing with our feeble brains.

[K^2]

All possible histories already exist. So the question of whether you can choose is a complicated one. On one hand, sure, what you are is a collection of neural impulses, and these impulses are what drive your muscles allowing you to change the environment around you, and consequently the history of events. But on the other hand, all your choices are also just part of history, which as stated, already exists.

So the correct but useless answer is that it depends on what you mean by ability to control.

[Quadhelix]

Except, you are working with a flawed premise that there is only one time line. In reality, there is an entire network of possible universe states and infinitely many histories linking these.

Correct me if I'm wrong, but isn't that only one possible interpretation of Quantum mechanics? Or are you getting this from some other model/theory?

[K^2]

Correct me if I'm wrong, but isn't that only one possible interpretation of Quantum mechanics? Or are you getting this from some other model/theory?

That's the nice thing about interpretations. They are purely a philosophic point. Predictions for all possible observations are consistent across interpretations, because all the equations are the same. So whether or not there actually is a Many-World is not only unknowable, but also irrelevant. If Many-World says that time travel paradoxes are resolved, they are resolved. Copenhagen interpretation would also provide a resolution, but it might not be nearly as obvious, and would appear to result in events with impossible odds happening anyways. I don't really want to spend too much time thinking of Grandfather Paradox under Copenhagen, but for a simple example, you can take a look at something like EPR Paradox. It is also resolved under both interpretations in completely different manners, but all the equations and numerical predictions for observations are exactly the same.

Personally, I like to think of the world as Many-World, because it is a very elegant construct. You would notice that I speak as if it is the fact. But as I said, it is absolutely irrelevant, and rather a matter of taste/convenience, so if you prefer to think of the world as a result of random wavefunction collapses defying statistics and thermodynamics, that's absolutely up to you.