Time Travel

[raj]

Yeah, but. . . if time is repeating itself, then shouldn't their thoughts be repeating too?  In which case they never will notice that something is wrong.  Yeah, I'm nitpicking and it isn't the worst episode ever in TNG.

[Flangepart]

Jamtoy : Hummm....kinda. What i should have said, is if the integration of the bill into matter is not accomplished, then the energy potential of the bill becomes released. Kaboom, as it were.
A "Big bang for the buck", shall we say.
And that....makes me think a time machins would need some of the components of a transporter, since time travel could either be enclosing someone in a "Temporal bubble", or converting to energy, and reestablishing in another temporal "Reality"....
Oh, now my brain hurts....
Funny that, what with all the rest it gets.......

[FearlessFreep]

Oh, now my brain hurts....
Funny that, what with all the rest it gets.......

You should warm up before exercising, especially if you don't do it that often

[Scott]

Looks like we have some mental gymnast on the board. Maybe this was just a warm up.

[B0SoxSuk (Austin)]

I'm not sure about traveling back in time.  I do have a belief about traveling foward though.   According to Einstein's theory of Relativity, if you could move at the speed of light for a period of time and somehow get back to earth, you would return in a time that to you may have been minutes or even seconds.  However, from the viewpoint of everyone that is on earth during your journey, it may have been a period of months or even years.

I believe that there was a movie or two that might have made use of this theory of time travel.  Does anybody know of any?

It sounds as ridiculous as any other theory about time travel.  However, I'm not sure that it's really a "theory" at all as the common misconception about theories is that they are not proven but are actually ideas or hypothesis.  This is wrong; theories typically have an overwhelming amount of evidence to support them.  In essence, there are no (outside the bound of the theory of Relativity) that can even be considered as theories about time travel.  

So if you're looking for proof or an actual theory on time travel.  Look into Einstein's work on quantum mechanics and celestial physics.  If you want instant gratification or some kind of explanation that might help you believe that some sort of time travel actually exists, I'll take a stab at it.  

Einstein actually recorded and witnessed this (apparently as a boy, although I can't be sure).  Imagine a train passing by as you watch it at a perfect 90 degree angle.  At noontime, light from the sun will pass directly downwards through the top of a cattle car through cracks in the roof.  You would think that the light, which travels at 2.998 x 10^8 m/s (about 186,000 mps), would simply pass straight down and hit the point on the floor of the car DIRECTLY below the point that it touched on the roof.  But it doesn't.  The light actually BENDS; it hits a point farther back from the point that you would think it would hit (in the opposite direction that the train is traveling).  Now I don't believe that Einstein actually saw this as a boy, but I know that he proved it to be true.  If you want to really understand what the hell this has to do with Einstein's theory and the possibility of time travel,  I suggest you check out some of his work AND a little experiment that was performed with a certain jetplane and an atomic clock.  

Oh yeah, Andy.  I wanted to ask you...I didn't quite understand your connection between a time machine and the Heisenberg Uncertainty Principle.  I don't see how the relationship between momentum and position (if you know your exact position, you cannot know your exact momentum and vice versa) has anything to do with how a time machine might change the course of history.  Maybe I'm missing something.  Fill me in.

In case anyone missed my question...Does anyone know of any movies that include the use of Einstein's theory to (if you haven't figured it out yet, everything the equation E=mc^2 is based upon) explain the possible existence of time travel?

LATE

[B0SoxSuk (Austin)]

I'm not sure about traveling back in time.  I do have a belief about traveling foward though.   According to Einstein's theory of Relativity, if you could move at the speed of light for a period of time and somehow get back to earth, you would return in a time that to you may have been minutes or even seconds.  However, from the viewpoint of everyone that is on earth during your journey, it may have been a period of months or even years.

I believe that there was a movie or two that might have made use of this theory of time travel.  Does anybody know of any?

It sounds as ridiculous as any other theory about time travel.  However, I'm not sure that it's really a "theory" at all as the common misconception about theories is that they are not proven but are actually ideas or hypothesis.  This is wrong; theories typically have an overwhelming amount of evidence to support them.  In essence, there are no (outside the bound of the theory of Relativity) that can even be considered as theories about time travel.  

So if you're looking for proof or an actual theory on time travel.  Look into Einstein's work on quantum mechanics and celestial physics.  If you want instant gratification or some kind of explanation that might help you believe that some sort of time travel actually exists, I'll take a stab at it.  

Einstein actually recorded and witnessed this (apparently as a boy, although I can't be sure).  Imagine a train passing by as you watch it at a perfect 90 degree angle.  At noontime, light from the sun will pass directly downwards through the top of a cattle car through cracks in the roof.  You would think that the light, which travels at 2.998 x 10^8 m/s (about 186,000 mps), would simply pass straight down and hit the point on the floor of the car DIRECTLY below the point that it touched on the roof.  But it doesn't.  The light actually BENDS; it hits a point farther back from the point that you would think it would hit (in the opposite direction that the train is traveling).  Now I don't believe that Einstein actually saw this as a boy, but I know that he proved it to be true.  If you want to really understand what the hell this has to do with Einstein's theory and the possibility of time travel,  I suggest you check out some of his work AND a little experiment that was performed with a certain jetplane and an atomic clock.  

Oh yeah, Andy.  I wanted to ask you...I didn't quite understand your connection between a time machine and the Heisenberg Uncertainty Principle.  I don't see how the relationship between momentum and position (if you know your exact position, you cannot know your exact momentum and vice versa) has anything to do with how a time machine might change the course of history.  Maybe I'm missing something.  Fill me in.

In case anyone missed my question...Does anyone know of any movies that include the use of Einstein's theory to (if you haven't figured it out yet, everything the equation E=mc^2 is based upon) explain the possible existence of time travel?

LATE

[Scott]

PHILADELPHIA EXPERIMENT was a good movie.

[B0SoxSuk (Austin)]

I'm not sure about traveling back in time.  I do have a belief about traveling foward though.   According to Einstein's theory of Relativity, if you could move at the speed of light for a period of time and somehow get back to earth, you would return in a time that to you may have been minutes or even seconds.  However, from the viewpoint of everyone that is on earth during your journey, it may have been a period of months or even years.

I believe that there was a movie or two that might have made use of this theory of time travel.  Does anybody know of any?

It sounds as ridiculous as any other theory about time travel.  However, I'm not sure that it's really a "theory" at all as the common misconception about theories is that they are not proven but are actually ideas or hypothesis.  This is wrong; theories typically have an overwhelming amount of evidence to support them.  In essence, there are no theories (outside the bound of the theory of Relativity) that can even be considered as theories about time travel.  

So if you're looking for proof or an actual theory on time travel.  Look into Einstein's work on quantum mechanics and celestial physics.  If you want instant gratification or some kind of explanation that might help you believe that some sort of time travel actually exists, I'll take a stab at it.  

Einstein actually recorded and witnessed this (apparently as a boy, although I can't be sure).  Imagine a train passing by as you watch it at a perfect 90 degree angle.  At noontime, light from the sun will pass directly downwards through the top of a cattle car through cracks in the roof.  You would think that the light, which travels at 2.998 x 10^8 m/s (about 186,000 mps), would simply pass straight down and hit the point on the floor of the car DIRECTLY below the point that it touched on the roof.  But it doesn't.  The light actually BENDS; it hits a point farther back from the point that you would think it would hit (in the opposite direction that the train is traveling).  Now I don't believe that Einstein actually saw this as a boy, but I know that he proved it to be true.  If you want to really understand what the hell this has to do with Einstein's theory and the possibility of time travel,  I suggest you check out some of his work AND a little experiment that was performed with a certain jetplane and an atomic clock.  

Oh yeah, Andy.  I wanted to ask you...I didn't quite understand your connection between a time machine and the Heisenberg Uncertainty Principle.  I don't see how the relationship between momentum and position (if you know your exact position, you cannot know your exact momentum and vice versa) has anything to do with how a time machine might change the course of history.  Maybe I'm missing something.  Fill me in.

In case anyone missed my question...Does anyone know of any movies that include the use of Einstein's theory to (if you haven't figured it out yet, everything the equation E=mc^2 is based upon) explain the possible existence of time travel?

LATE

[JohnL]

>My favorite short was a new Twlight Zone episode where they had hunters of the
>future pay extra money to travel back in time on a set path and shoot dinosaurs

There was another episode where a man discovered that his radio was picking up broadcasts from during World War I. He used it to warn his son not that his ship would be ambushed. His son lived and Germany won the war.

>I have always wanted to travel through time.

I found a site on the net once, that was selling what it claimed were working time machines or plans to build them. You had to be careful using them though, because the aliens that the technology was taken from don't want humans using them and they monitor the Earth's energy centers for any disruptions.

>I recall the grandfather paradox was actually brought up in The final Countdown.
>They solved it by demonstrating that they couldn't change the past, because
>there was only one 1941, and they were already a part of it.

Except that they COULD have changed it. If the captain hadn't ordered the fighters to return at the last minute, they would have easily defeated the Japanese fleet.

The thing that always bugged me about time travel movies is that the bad guy goes back in time and the heroes stand around discussing it, say they have to catch him before he changes anything etc.  Once someone goes back in time, any changes they might make would be instantaneous (assuming that the past can be changed).

[ulthar]

JohnL wrote:

>
> Except that they COULD have changed it. If the captain hadn't
> ordered the fighters to return at the last minute, they would
> have easily defeated the Japanese fleet.
>


Ah, but they didn't.  That is what begs the question about whether the timeline was predetermined.  I COULD have had two sandwiches for lunch today, but I didn't....

[ulthar]

B0SoxSuk (Austin) wrote:

>
> Einstein actually recorded and witnessed this (apparently as a
> boy, although I can't be sure).  Imagine a train passing by as
> you watch it at a perfect 90 degree angle.  At noontime, light
> from the sun will pass directly downwards through the top of a
> cattle car through cracks in the roof.  You would think that
> the light, which travels at 2.998 x 10^8 m/s (about 186,000
> mps), would simply pass straight down and hit the point on the
> floor of the car DIRECTLY below the point that it touched on
> the roof.  But it doesn't.  The light actually BENDS; it hits a
> point farther back ...

Einstein could not have observed this, as a train is moving too slow and therefore the effect is too small to see.  The consequences of Special Relativity are only observable when the speeds are 'relativistic:' a significant fraction of the speed of light.  

Albert Einstein was  master at contriving 'everyday' examples to illustrate his points.  This train example is one of those; an example he chose to explain the theoretical idea AFTER he developed the theory.

>
> Oh yeah, Andy.  I wanted to ask you...I didn't quite understand
> your connection between a time machine and the Heisenberg
> Uncertainty Principle.  I don't see how the relationship
> between momentum and position (if you know your exact position,
> you cannot know your exact momentum and vice versa) has
> anything to do with how a time machine might change the course
> of history.  Maybe I'm missing something.  Fill me in.
>

Well, two key points here on the HUP.  First, and this is just a detail, even if neither position or momentum in that direction is exact, they are still related.  It's a minor point, but it is actually important.

Second, the HUP principle applies to ANY pair of complimentary observables.  Momemtum and position is one such pair (the one we use most often in Chemistry, for example), but ENERGY and TIME are another.  This means that you can write an analogous Uncertainty Relation for E and T, just like for x and p:

(delta-E) * (delta-T) >= h/(4 pi)

delta-E is uncertainty in energy
delta-T is uncertainty in time
h is Planck's constant

Don't believe this?  Do a Unit Analysis on position time momemtum (say m * kg m/s) and you will find that x * p has units of energy * time, which of course, are the units of Plank's constant as well.  So, in simple terms, ANY pair of observables whose product has units of (energy * time) has an associated uncertainy relation.

So, to apply to the time travel theory, I guess, one could argue that if you define energy precisely enough, time becomes quite uncertain.  If you start in a state that is of poorly known energy, but at a precise time, alter the system so that you define the energy precisely, the time becomes uncertain.  If you return the energy to it's poorly defined condition, it is likely that the time is different.

The time-energy relationship is used in Statistical Mechanics to construct ensembles.  The Stochastic Theorem states that you can sample all states of a system by either watching one system for infinite time, or an infinite number of system for an instant.  This is very important, and is used to compute bulk thermodynamic quantities from quantum mechanical properties.

There's two little flaws in using this energy-time Uncertainty Relation to describe time travel per se.  First, The HUP applies to quantum particles, not macroscopic humans (or other bulk objects composed of about 10e25 particles).  So, the uncertainties in time apply to the individual particles, but the statistical average for the bulk person is likely not really changed.

The second big flaw is how the UP is applied.  The time uncertainty relates to the natural "lifetime" of the state, not where on some externally defined timeline (or point in space-time, if you prefer) the system lies.  In other words, the time uncertainty relates to the uncertainty of time, from its creation, that the state MAY last.  A state with a very precise energy has a very uncertain lifetime.  But this does not mean that if you create a such a state (it's all the time with lasers, for example) that the system might disappear because its 'time' is uncertain and it might move to a different time.

I can only guess, but I am assuming that AndyC was refering to the energy-time version of the HUP.

Whew.

[Ash]

I posted this link in a previous post but no one commented on it.
I'm curious to know what you think of his ideas on time travel.
It's titled "Space & Time Warps"

Here's the link again:  

http://www.hawking.org.uk/pdf/warp.pdf



Post Edited (01-08-04 00:12)

[Grumpy Guy]

JohnL wrote:

>
> The thing that always bugged me about time travel movies is
> that the bad guy goes back in time and the heroes stand around
> discussing it, say they have to catch him before he changes
> anything etc.  Once someone goes back in time, any changes they
> might make would be instantaneous (assuming that the past can
> be changed).

This is a question of reletive time.  The thinking (flawed though it may be) is that if Bob goes back in time, and then affects nothing for one hour, then the folks in the future have one hour to take action.

It's silly, really.  Observation affects everything.  I read that somewhere in a book on Quantuum Mechanics...

In any case, the problem only exists in  films where the meilu allows for only one timeline.

[ulthar]

Grumpy Guy wrote:


> It's silly, really.  Observation affects everything.  I read
> that somewhere in a book on Quantuum Mechanics...
>


Technically, yes.  Observation of something causes what is called "reduction" of the wave function.  Before observation, all possible outcomes for an observation exist - the only thing that exists before the observation is the probability of an outcome.  However, once you observe it, the probability for what you observed is 1 and all others go to zero.  Hence you have reduced the wave function from all possible outcomes to only the outcome observed.  The best 'everyday' example of this is the model of Schrodinger's Cat.

This is also the basis for what is known as entanglement.  If TWO events occur simultaneously (forgetting the problems with simultaneity in Special Relativity) and a number of possible states exist, but they are linked by the initial event, then observing one state also reduces the wave function of the other.  In a sense, then, it is argued that 'information' about which state to reduce to travels faster than the speed of light.

The example generally used here is an atom that simultaneously emits two photons, but the Law of Conservation of Angular Momentum requires them to have OPPOSITE SPINS (that is, the angular momentum of the atom does not change).  However, photon A can have spin UP or DOWN, so you don't know it until you observe it; likewise, you don't know the spin of photon B, but it must compliment that of A.  As soon as you observe the spin of photon A, you instantaneously know the spin of B.  Since in the quantum theory, the real state of A just prior to observation is a mixed state

Spin Function of A = 0.5 (UP)  +  0.5  (DOWN)

you are not saying that A was UP (or DOWN) the whole time since emission.  Therefore, B was not in the compliment state the whole time either.  By reducing the function of A at observation, you also reduce the function of B - INSTANTLY, and without observing B.  Since B "knows" which state to reduce to ONLY upon your reduction of the A function, the information about which state to reduce to traveled to B in ZERO TIME.

Anyway, sorry to digress so far.  Entangled states are being studied within the context of developing fast computers and such.  Already quantum based algorithms are being used to explore super secure cryptography.

[AndyC]

JohnL wrote:
> Except that they COULD have changed it. If the captain hadn't
> ordered the fighters to return at the last minute, they would
> have easily defeated the Japanese fleet.

But there are a number of clues that suggest that the Nimitz was always part of events. They made a point of bringing up the grandfather paradox, things turned out exactly according to history even when they interfered, and only one person in 1941 saw the ship and lived, and she kept the secret. Most importantly, the guy who gets left behind in 1941 was at the dock to see the ship off before it travelled through time. The whole point was that the timeline is predetermined. The captain obviously felt it was worth the attempt if there was any possibility of saving Pearl Harbor, but circumstances prevented any noticeable involvement.