# possible time travel

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You guys should try making this in your back yard! hehehe.

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And that the difference between (x1,y,z,t) and (x2,y,z,t) is similar to (x,y,z,t1) and (x,y,z,t2).

You do the same thing here, treating all variables as distance. But t stands for time, not distance. You are saying that x2-x1 is "similar to" t1-t. But meters aren't seconds.

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You do the same thing here, treating all variables as distance. But t stands for time, not distance. You are saying that x2-x1 is "similar to" t1-t. But meters aren't seconds.

Yes, metres arn't seconds, but we do have a conversion factor.

What is being discussed is "What is dimension?". At it's most basic a Dimension is "A direction of Measurement perpendicular to all other directions of measurement".

So, if we pick a "direction" and any line drawn in that direction is called the X Dimension. Now draw a line that is perpendicular to that (that is at right angles) and call that Y. Now draw a third line at right angles at both the X and Y lines and you call that Z.

But, what would a line drawn at right angles to the X, Y and Z lines look like?

Well to answer this we need to look more at what me mean by a real dimension.

Imagine that we have drawn these on a block of clear rubber. We can take a portion of that rubber and give it a twist. This causes a rotation of the dimensions, but, any object embedded within that rubber gets rotated too so as far as it's point of view is concerned it is the rest of the rubber that has been distorted. It would think that its Z dimension is the same as before the distortion of the rubber started.

So, if we assume that dimensions can be distorted, then we can look for them. What we need is something we know that always travels in a straight line. Well, according to Newton any object that is travelling and is not acted upon by an outside force travels in a straight line.

We know that light travels in a straight line, so we can use this as our line. So if light travels in a straight line, then two parallel beams of light (or even slightly diverging beams) will never cross each other. Two distant stars can serve as the sources of these beams.

When observing two such stars in open space (no intervening objects) we can see that they are parallel and that the never diverge. However, if a large mass passes between us and the stars, then we can see a distortion and then the two light beams do cross. We call this gravitational lenseing and it is a result of the fact that space is being bent and twisted by the gravity of the object.

So, by this we can be sure that gravity can rotate one dimension into another. But, when we examine the path of the light rays closer, we find that not only is there a distortion in space, but also of time.

Einstein worked out the mathematics of how to account for the distortion of space and it works out that if you rotate a bit of the 3 spatial dimensions into 4th dimension and a bit of that 4th dimension into the spatial dimensions the sums work out. It accounts for the missing values and predict what it should look like.

This 4th dimension, because it is a dimension, must be perpendicular to all the other dimensions. That is it is at right angles to the X,Y and Z dimensions.

Further examination of such phenomena showed that according to different observers, as a light beam passed through into gravitational field, those where the field is strongest (nearer the gravitating object) would see the light speed up (a higher frequency) where as compared to the observer near the object, someone further away would see it slowed down (lower frequency).

Since light can not be slowed down or sped up (it has a constant speed - doe to other reasons) the only conclusion (along with other evidence too) is that it is Time that is speeding up and slowing down. Time is being distorted by the gravity of the object.

Now when you do the sums and look for the distortion for the 4th dimension it exactly matches the distortions predicted for Time. So, this means that Time must be the dimension that the spatial dimensions are being distorted into.

Time, must therefore be a Dimension perpendicular to Space.

When you use any coordinate system, you are actually representing points along dimension. So if we have a point in space, we can represent it by using just 3 dimensional points (X,Y,Z). But since Time is a dimension perpendicular to space we can also give it a co-ordinate system (T), and put together we have (X,Y,Z,T).

Using this 4 dimensional coordinate system, we can precisely map the distortions that a gravitational object has on the surrounding objects. We can then check the results of those calculations and compare them to actual observations. What we find is that if we only used 3 dimension we get an incorrect mapping, but if we use 4 dimension then we get the correct mapping. This confirms that Time must be the 4th dimension (otherwise the mappings or predicted behaviours of the objects would be different from what is observed).

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And I said this is incorrect. I still say it.

I don't know if I am able to understand you correct, first you say this is incorrect, and then you continue to say:

(x,y,z,t1) certainly is not the same as (x,y,z,t2), and the (x,y,z) bit will only also be the same if there has been no motion, no movement or change in any of x, y, or z.

Where you agree with what I said.

A no-change universe means a no-time universe.

Well, I have time in my view of the Universe so I can have changes too...

You do the same thing here, treating all variables as distance. But t stands for time, not distance. You are saying that x2-x1 is "similar to" t1-t. But meters aren't seconds.

I know meters aren't seconds, and the difference between where and when, I never said they where the same !

I saved this one for last, because it seems to be the "Key-point" of the confusion:

(x1,y1,z1) will only be equal to (x2,y2,z2) at another time if and only if they haven't changed.

Did you reread the post I asked you too ? Where I said:

Motion is when objects is changing coordinates, not when the coordinates is changing.

Please, explain for me: Why the coordinate (x,y,z) must change if there is a motion of an object.

Yes, sure - the position of the object changes, the coordinate of the object changes, but the coordinates themselves don't move. The coordinate where the object was is still real, exists and has NOT moved.

(Well, they are relative, spacetime is not rigid or absolute, but thats beside the point.)

I view spacetime in 4D, there is motion of objects between all four types of coordinates, both in space and time.

Which part in the above sentence is it that you don't understand ?

Time, must therefore be a Dimension perpendicular to Space.

I fully agree.

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I get some of the things you are saying, but I think you keep making mistakes in some of them too.

For instance, you say when talking about the coordinates of something changing that:

the coordinates themselves don't move.

so you're saying when something moves, its coordinates don't change. I think.

I know meters aren't seconds, and the difference between where and when, I never said they where the same !

But you do say:

The space coordinate (x,y,z) in the past is the same as space coordinate (x,y,z) in the future.

It's not very far from saying that a position three meters away will be four meters away if I move one meter.

And also:

I view Time like a line and we are moving along it, our past and future positions on the line exists too.

Everything seems to be moving forward in time

We have already tried to talk about the coordinates being the same (or not), and not all that successfully. But saying:

(x1,y1,z1) will only be equal to (x2,y2,z2) at another time if and only if they haven't changed.

Admittedly is a bit contorted, but I'm trying to say that if the coordinates are the same at different times this is because they haven't changed (which is the really obvious induction) or they are changing but returning to the same values, for some reason (like curvilinear motion, or oscillation, say), so every time they are measured, they are perceived to be the same. But you can't say that, in general the x,y,z coordinates at time t are or will be or were the same at time tn, because the object could be moving around like this (or in a "straight" line). Recall that space (distance) is also increasing in all directions, so there are more "points of spacetime" to consider now (than there were when this thread started, for instance).

It isn't (usually) all that useful to just refer to some xyz coordinate, some point in space, unless it is in the world-line of some object, say, or represents some object (like a neutrino in which case its values would be changing "rapidly"), or is interesting for some other reason, otherwise it's just a point in space like the infinite, and rapidly increasing, set of points all over the universe.

Please, explain for me: Why the coordinate (x,y,z) must change if there is a motion of an object.

This is because:

Yes, sure - the position of the object changes, the coordinate of the object changes

But:

but the coordinates themselves don't move. The coordinate where the object was is still real, exists and has NOT moved.

(Well, they are relative, spacetime is not rigid or absolute, but thats beside the point.)

only follows if you are talking about some original point that the object has left behind. And what does this point have to tell us? What is the point of this point?

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And what does this point have to tell us? What is the point of this point?

So I was correct about the "Key-point" then...

Coordinate Systems -> http://en.wikipedia.org/wiki/Coordinate_system

EDIT: The point of the coordinate is that it's related to the observer and not the moving object.

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The point of the coordinate is that it's related to the observer and not the moving object.

In which case it will have it's own "objective" measure of time, one of the coordinates, right?

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Sure, but what happens to the entropy (the heat energy)? Doesn't work being done mean a change in entropy? I must have completely misunderstood my Physics on this.

Yes, real work increases entropy due to friction, but heat transfer out of the system more than compensates for the entropy increase. It isn't like reducing the entropy of the system takes away from how much work was done.

I'm sorry for being short with you. I am still getting used to 12 hour shifts.

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Nothing to do with what you guys are talking about but;

what if you were driving at ... say 120km/h would you age just a tinny, winny bit slower?

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what if you were driving at ... say 120km/h would you age just a tinny, winny bit slower?

Nowhere near noticeably

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What I would like to know would be the impact on a living organism of such travels. I mean if you were to time travel backwards in time, I don’t see how that could take the universe with you, and not to get into the idea of multiple universes, would you age in reverse, or would your biology even work anymore? Same with traveling into the future, or what not. I mean from the concept of the observer it would seem to apply really timelines for every single even subatomic or other entity in the universe to some extent.

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What I would like to know would be the impact on a living organism of such travels. I mean if you were to time travel backwards in time, I don’t see how that could take the universe with you, and not to get into the idea of multiple universes, would you age in reverse, or would your biology even work anymore? Same with traveling into the future, or what not. I mean from the concept of the observer it would seem to apply really timelines for every single even subatomic or other entity in the universe to some extent.

Does your biology cease to function if you move to the left? How about five minutes from now?

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Nowhere near noticeably

but just a little bit? So every time I go on the motorway (or freeway) ill turn older!

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Does your biology cease to function if you move to the left? How about five minutes from now?

I think I understand what you mean, but that really does not answer my question. What is the point for a timeline. I mean I can observe time, but does my foot also observe it because I am? Or more to the point, is each atom of my being on the same timeline as I am? I mean relative to me and all of that QM stuff its quite boggling to say the least from by position on things. Such as say I am in a car with some other people, if I were to instantly travel backwards in time would I smash into the car with infinite force? Would me and the car somehow separate into some other universe? So that means if I grab someone, they should also have to experience such right? If it were possible is all.

The list really could go on.

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but just a little bit? So every time I go on the motorway (or freeway) ill turn older!

Not Older. You would age slower than someone who didn't move.

I mean I can observe time, but does my foot also observe it because I am? Or more to the point, is each atom of my being on the same timeline as I am?

Each particle of your body has it's own "timeline". If you were to move your hand really fast then it would age slower than the rest of your body (actually any movement would do, it's just that moving it really fast would allow such a thing to be more detectable).

Your body is not 1 object, but trillion upon trillions of particles (electrons, quarks, etc) and each of those is "independent" from the others. It is just that they are bound together by forces.

Such as say I am in a car with some other people, if I were to instantly travel backwards in time would I smash into the car with infinite force?

This would depend on your method that you used to time travel. AFAIK there are 3 main ways to achieve backwards Time travel:

1) Faster Than Light: This method seems to only work by numbers. It is probably physically impossible to to. IF you plug in a speed value greater than the speed of light into some of the relativity equations, then you end up with a value of T that is negative -that is travelling backwards in Time.

2) Relativistic Wormholes: With this method, you need to set up a wormhole (which are only theoretically possible) and then move one end very fast (the closer to C the better) away form the first end, then bring them back together at the high speed. According to relativity one end will be "younger" than the other. If you enter the younger end of the Wormhole, then you will emerge from the other end at an earlier time (that is you will have travelled backwards in time). The problems with this are that wormholes are only theoretical (but as far as science knows there is no reason that they can't exist) and that you can't travel back to a point before you created the wormhole.

3) Really distort space: If you distort space/time enough with a mass (it also needs to be moving in the right way too), then you can create a loop where the future of a particle will intersect with the past of its self. Designs I have heard of for this is if you took an infinitely long cylinder and then spun it along the long axis at close to the speed of light, then it would distort space time in the correct way and orbiting around the spinning cylinder would take you forwards or backwards in time (depending on the direction you travelled). Needless to say an infinitely long cylinder is a little hard to come by, plus, and material we currently have (or is considered feasible) would break apart long before the cylinder reached anywhere near fast enough.

However, none of these would result in an infinite amount of force applied in a collision.

Actually there is maybe one more method, but there is no real agreement on whether it is physically correct.

Under some interpretations of QM, antimatter could be considered to be ordinary matter travelling backwards in time. If you were to record the movements of an electron, and then played them in reverse, this would give them the exact same movements as a particle of Antimatter would in that same situation.

So if the electron was repelled by a Negative charged plate, when you press the rewind button on the remote, it would look like the particle was attracted to the Negative plate, just as a Positron (and antimatter Electron) would. They would effectively be indistinguishable from each other.

So, if this is true, then you could achieve reverse time travel by converting all you matter into antimatter, travelling back wards as far as you need to, then reconverting your self back into normal matter.

To do this would take as much energy as you would get from slamming your self against an equal mass of antimatter. This would be a lot of energy.

E=MC^2: E= (Your mass in grams + The mass of your backwards in time counterpart in grams) * 300,000 * 300,000. Or for a 70kg person: 12,600,000,000,000,000 Joules (not infinite, but a very large amount! ).

Would me and the car somehow separate into some other universe? So that means if I grab someone, they should also have to experience such right? If it were possible is all.

Well the way I see it, except using the wormhole method, you never actually leave this space/time. So you should be able to interact with other matter and energy that exists within that space time. You are just moving relative to it in a way that you are moving backwards though Time. So you could grab someone, and they could touch you (except with the antimatter method there would be an almighty bang ).

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In which case it will have it's own "objective" measure of time, one of the coordinates, right?

A coordinate is not a thing or an observer.

But you could place an observer there to measure it's own "objective" time.

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I mean if you were to time travel backwards in time, I don’t see how that could take the universe with you, and not to get into the idea of multiple universes, would you age in reverse, or would your biology even work anymore? Same with traveling into the future, or what not. I mean from the concept of the observer it would seem to apply really timelines for every single even subatomic or other entity in the universe to some extent.

You are actually touching on something deep here, I think. Consider that every object, every particle in the universe is only where it is now because of everything that has happened (to it), every event, every particle decay and every oscillation of every particle, in the entire cosmos (since every event is, ultimately, related to every other event by the initial event, the thing that created all events). So every timeline, or world line (of every particle) stretches back billions of years to this initial event, or cause. So traveling in time does imply "taking the universe with you" in some sense.

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I interpret "traveling" as movement relative something and the Universe is everything everywhere anytime.

The Universe is defined as the summation of all particles and energy that exist and the space-time in which all events occur. -> http://en.wikipedia.org/wiki/Universe

The Universe is all, you can't "bring it with you" somewhere or sometime else, we are in it and there is no outside.

I move around the Earth one lap every 24 hours, but I don't call myself a Earth traveller because of that. The Earth revolves around the Sun, which moves through space around and with the MilkyWay, but I don't call myself a space traveller either. So even if I, IMO, moves through time, I don't call myself a time traveller.

So for me "real" time travel is movement relative "normal" movement, and as doing so you wouldn't bring along anything else than what you take with you, all other objects would continue forward in time as normal.

(IMO, "normal" movement is staying inside the light cone we have now, the ability to interact with others.)

The time traveller leaves our light cone, passes our event horizon, but from his perspective everything would be normal, his clock would continue to tick normal, his body wouldn't stop functioning.

But he wouln't have anything to interact with, since everything from the past has moved forward in time.

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The thing is, special relativity is not really viable to go on about superluminous effects or pssibilities. However, what is a bit interesting about special relativity, is that is somewhat predicts out of the 4 black hole types, only one type, and which more a subtype of it...namely extreme kerr holes...which again is most likely the ones occurring naturally. (well, if not the extreme kerr hole, certainly kerr holes..the funny thing is, most laymen will at forums like this always talk about Schwarzchild holes which maybe could be created artificially but which is rather at best, humourous to presume are existing [naturally]).

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The Universe is all, you can't "bring it with you" somewhere or sometime else, we are in it and there is no outside.

Indeed this would seem to be impossible, and so does time travel.

as doing so you wouldn't bring along anything else than what you take with you

Well, you would probably want to take all the particles that make up your body. And a bit of air to breathe in case where -sorry, when- you are going doesn't have any (like the Pre-Cambrian era, say). Something to eat might come in handy, too. Perhaps some sort of portable dwelling? Etc and etc.

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Indeed this would seem to be impossible, and so does time travel.

It seems impossible for you because you don't belive the Universe consists of a time dimension too.

But I do.

Well, you would probably want to take all the particles that make up your body. And a bit of air to breathe in case where -sorry, when- you are going doesn't have any (like the Pre-Cambrian era, say). Something to eat might come in handy, too. Perhaps some sort of portable dwelling? Etc and etc.

Just the things you also would want to take with you on a space journey, heh ?

(And I never said it didn't have air and etc. - I said it no longer has.)

The thing is, special relativity is not really viable to go on about superluminous effects or pssibilities. However, what is a bit interesting about special relativity, is that is somewhat predicts out of the 4 black hole types, only one type, and which more a subtype of it...namely extreme kerr holes...which again is most likely the ones occurring naturally. (well, if not the extreme kerr hole, certainly kerr holes..the funny thing is, most laymen will at forums like this always talk about Schwarzchild holes which maybe could be created artificially but which is rather at best, humourous to presume are existing [naturally]).

You do realize that we are discussing TIME and time travel and NOT Black Holes, in this thread ?

(And probably meant General Relativity, which deals with stuff like Gravity, not Special Relativity.)

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• 2 weeks later...

You do realize that we are discussing TIME and time travel and NOT Black Holes, in this thread ?

(And probably meant General Relativity, which deals with stuff like Gravity, not Special Relativity.)

Yes, I am referring implicitly to the 4 black hole types from GR and saying that SR , if used on relativistic escape velocities, will predict one of them (correctly or not is the notion im just pointing out is interesting). That it was not in the right forum...well it does relate to the TIME as you put it, given people here are using concepts from SR to relate to it. just felt I would add it so it make people rethink some of their 'understandings' but fair enough..noted.

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Yes, I am referring implicitly to the 4 black hole types from GR and saying that SR , if used on relativistic escape velocities, will predict one of them (correctly or not is the notion im just pointing out is interesting).

I really really doubt that and are not going to just trust your words...

The theory was called "special" because it applies the principle of relativity only to inertial frames. Einstein developed general relativity to apply the principle generally, that is, to any frame, and that theory includes the effects of gravity. Special relativity does not account for gravity, but it can deal with accelerations.

http://en.wikipedia.org/wiki/Special_relativity

In general relativity, the Kerr metric (or Kerr vacuum) describes the geometry of spacetime around a rotating massive body. According to this metric, such rotating bodies should exhibit frame dragging, an unusual prediction of general relativity that has been verified to 1% accuracy by Gravity Probe B. Roughly speaking, this effect predicts that objects coming close to a rotating mass will be entrained to participate in its rotation, not because of any applied force or torque that can be felt, but rather because the curvature of spacetime associated with rotating bodies. At close enough distances, all objects — even light itself — must rotate with the body; the region where this holds is called the ergosphere.

The Kerr metric is often used to describe rotating black holes, which exhibit even more exotic phenomena. Such black holes have two event horizons where the metric appears to have a singularity.

The Kerr metric is an exact solution of the Einstein field equations of general relativity.

http://en.wikipedia.org/wiki/Kerr_metric

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Spyman: the time dimension is "there" in that we use it to measure motion through space. But there is absolutely no scientific evidence to demonstrate that we can move through this time dimension. Yes, we say "time flows", but it simply doesn't. Yes, it's a dimension in that it's a measure, the original meaning of dimension. But it isn't something that offers freedom of movement. You can't demonstrate that it does, and you can offer no scientific evidence of this. Nor can you offer any actual evidence that "we all move forward in time at the rate of one second per second". This is an abstraction with no foundation in fact. So anybody who believes time travel is possible, believes in pseudoscience.

All of this is so incredibly simple. It's quite amazing how people, even those who pride themselves on their rationality, can cling to baseless beliefs that have absolutely no evidential support whatsoever. If you doubt me, try showing me some evidence.

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This is an abstraction with no foundation in fact.

Beautiful

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