When reading stories regarding time travel, it's always assumed that there will be no displacement in space. Sometimes, there is consideration given to the fact that the geography of a given area might change over long temporal jumps, but it's always assumed that if you leave Chicago in 2007 and move thru time to 1945, you will appear in Chicago in the same spot you left.

But this neglects the fact the earth itself is moving. It is rotating about it's own axis at about 1000 miles per hour. It is orbiting the sun at a speed of 66,514 miles/hour. And that the entire milky way galaxy is rotating at about 612,000 miles per hour.

Wouldn't a vehicle designed to move in time but not space find itself hundreds of thousands of miles from the earth somewhere out in space?

H.G. Well's intrepred time traveler riding a machine that resembled a bicycle, would have been in for quite a surprise.

When reading stories regarding time travel, it's always assumed that there will be no displacement in space. Sometimes, there is consideration given to the fact that the geography of a given area might change over long temporal jumps, but it's always assumed that if you leave Chicago in 2007 and move thru time to 1945, you will appear in Chicago in the same spot you left.

But this neglects the fact the earth itself is moving. It is rotating about it's own axis at about 1000 miles per hour. It is orbiting the sun at a speed of 66,514 miles/hour. And that the entire milky way galaxy is rotating at about 612,000 miles per hour.

Wouldn't a vehicle designed to move in time but not space find itself hundreds of thousands of miles from the earth somewhere out in space?

H.G. Well's intrepred time traveler riding a machine that resembled a bicycle, would have been in for quite a surprise.

Yep, and they always assume the elevation of that "one spot" has never changed, either - despite a million years (or whatever) of erosion. Even if they managed to overcome the flaw you pointed out they could still easily arrive inside solid rock or deep within a prehistoric ocean. ;)

Which is why time travel through time without movement through space is impossible.

It would seem that the safest way to time travel would be in a space ship. Of course, I suppose you could theorize some BS about how the temporal field is fixated on the gravatational well created by a planet and fixes its position that way. But the funny thing is most SciFi stories don't even bother.

Which is why time travel through time without movement through space is impossible.

I don't agree with this. If you could make your world-line PERFECTLY time-like (i.e. solely along the `t' direction), then it would be possible.

I mean, heck, this is just a minor problem once we've figured out how to travel through time :)

But the funny thing is most SciFi stories don't even bother.
There's not a lot of conceptual difference between a time machine and a teleporter. Both take you from one place in space-time to another.
So, it's not a big stretch to combine the two - when choosing your destination, you specify both the time and the place... or, you get the machine to figure out where your current location will be at the destination time.

But yes... most time travel stories gloss over those kinds of details. But there are exceptions.
Doctor Who's TARDIS sets both time and place when travelling.
I vaguely recall a novel called Billennium (I think) that also had some spatial compensation.
Any story in which there is some device to serve as a destination doesn't need to address that problem.

Maybe this is why we aren't up to our ears in time travelers. They're all out floating in space!

Maybe this is why we aren't up to our ears in time travelers. They're all out floating in space!

Could be! :D

But that's the thing about writers of fiction, they have license to make anything happen that they want. Some make a good effort to at least partially explain their wonderful machines. Others either can't figure out how or just don't want to get bogged down in fine detail.

When reading stories regarding time travel, it's always assumed that there will be no displacement in space. Sometimes, there is consideration given to the fact that the geography of a given area might change over long temporal jumps, but it's always assumed that if you leave Chicago in 2007 and move thru time to 1945, you will appear in Chicago in the same spot you left.

But this neglects the fact the earth itself is moving. It is rotating about it's own axis at about 1000 miles per hour. It is orbiting the sun at a speed of 66,514 miles/hour. And that the entire milky way galaxy is rotating at about 612,000 miles per hour.

Wouldn't a vehicle designed to move in time but not space find itself hundreds of thousands of miles from the earth somewhere out in space?

H.G. Well's intrepred time traveler riding a machine that resembled a bicycle, would have been in for quite a surprise.


According to Einstein's theory of Special Relativity, the time machine rider would enjoy the priviledged position of viewing the entire universe in the reference frame as unfolding in terms of Newton physics, which means that the rider would see himself ( or herself ) (or itself ) having no special displacement in time or space.

In Special Relativity there is no provision for any observer to see the external frame as happening faster than expected, only slower.

So, according to Special Relativity, a time machine rider could only see the universe happening slower than normal, not faster.

The time machine rider, if Special Relativity is an accurate description of reality, would age, say 50 years, while traveling 10 years into the future.

How can such a thing be proved?

The effect should be opposite to what you have described. Time traveller who uses a fast ship to go to the future would age more slowly than the ones on Earth. Otherwise, he would not be travelling, but the people on Earth would be travelling into his future.

ps: I think the readers should assume that the tie machine has some sense about the environment it is travelling through, and can control its position with some accuracy. So for example, it could be so that by default the machine just brings you to the place with the same location relative to Earth, whatever that is defined to be.

The effect should be opposite to what you have described. Time traveller who uses a fast ship to go to the future would age more slowly than the ones on Earth. Otherwise, he would not be travelling, but the people on Earth would be travelling into his future.
I think CANGAS may be referring to SR's prediction that the time traveller would 'see' universal clocks ticking slower than his own clock, the rest of the universe moving in 'slow motion'. That perdiction cannot be correct, of course. If the time traveller watched 50 years pass on Earth, he would have to see the Earth orbit 50 times around the sun, while only 10 years accumilated on his own clock. Some state the traveller would see the Earth orbit the sun only twice during the inertial phase of his journey, and 48 times during the acceleration/decelleration non-inertial phases. That kind of plays havoc with orbital mechanics in the solar system. Or, do you think the Earth will orbit the sun fewer times in one frame of reference than it does in the other?

Not again. How many times has the twin paradox been hashed over online?

I don't agree with this. If you could make your world-line PERFECTLY time-like (i.e. solely along the `t' direction), then it would be possible.

I mean, heck, this is just a minor problem once we've figured out how to travel through time :)

time travel is impossible, it is pure science fiction nothing more. i cant believe scientists actualy think you might be able to do it someday, its absurd.


how can anybody even explain how its possible even in woo woo theory. go back in time and meet yourself as a baby. what happened in the past cannot be lived again or seen. the universe is not some kind of computer software with a hard drive that saves past events.

time is not even a real physical aspect of the universe. its something we use as a way to measyre events and motion.

peace.

time is not even a real physical aspect of the universe. its something we use as a way to measyre events and motion.

I think most physicists would disagree. Don't they speak of a "time-space continium"?

As far as time travel being impossible, you may be right. If it is possible, things could get messy quite quickly.

I think that unles someone posts a time travel thread with a really well explained theory of operation it should automatically be dumped into the hoodooscience bin, or whatever this physics forum calls it.

I think that unles someone posts a time travel thread with a really well explained theory of operation it should automatically be dumped into the hoodooscience bin, or whatever this physics forum calls it.
A well explained theory of operation? So unless we can offer a mathmatical proof showing how a time machine would work, it shouldn't be discussed at all? What kind of attitude is that?

I'm no physicist, biology was my major as an undergrad and I also have a doctor of optometry degree (lots of optics, obviously). But it is interesting to discuss areas of science outside of my area of expertise. If I'm way off base, set me right. Or, if hearing a bunch of non-experts talk about your area of expertise offends you, just skip the thread in question.

A well explained theory of operation? So unless we can offer a mathmatical proof showing how a time machine would work, it shouldn't be discussed at all? What kind of attitude is that?

I'm no physicist, biology was my major as an undergrad and I also have a doctor of optometry degree (lots of optics, obviously). But it is interesting to discuss areas of science outside of my area of expertise. If I'm way off base, set me right. Or, if hearing a bunch of non-experts talk about your area of expertise offends you, just skip the thread in question.

According to the published rules of this physics forum (as if they have ever been executed fairly ) when a subject cannot be proved it is automatically subject to being put into the hoodooscience bin, where it can be discussed freely until the cows come home.

According to the published rules of this physics forum (as if they have ever been executed fairly ) when a subject cannot be proved it is automatically subject to being put into the hoodooscience bin, where it can be discussed freely until the cows come home.
Well, I did take some physics and seem to recall that time travel is not ruled out by the known laws of physics. So are you saying that discussions of theoretical physics are barred?

Please carefully read my previous post. I do not care what you discuss or try to discuss. My point is that if the published rules of this physics forum are executed honestly and fairly and if a poster has not written a post which proves that time travel is possible, the post/thread is supposed to be tossed out of the real science area.

I am sure holding my breath patiently waiting for the monitors to fairly execute their own rules. :rolleyes:

My point is that if the published rules of this physics forum are executed honestly and fairly and if a poster has not written a post which proves that time travel is possible, the post/thread is supposed to be tossed out of the real science area.
How's this?
Time travel has recently been discussed quite extensively in the context of general relativity. Time travel can occur in general relativistic models in which one has closed time-like curves (CTC's). A time like curve is simply a space-time trajectory such that the speed of light is never equalled or exceeded along this trajectory. Time-like curves thus represent the possible trajectories of ordinary objects. If there were time-like curves which were closed (formed a loop), then travelling along such a curve one would never exceed the speed of light, and yet after a certain amount of (proper) time one would return to a point in space-time that one previously visited. Or, by staying close to such a CTC, one could come arbitrarily close to a point in space-time that one previously visited. General relativity, in a straightforward sense, allows time travel: there appear to be many space-times compatible with the fundamental equations of General Relativity in which there are CTC's. Space-time, for instance, could have a Minkowski metric everywhere, and yet have CTC's everywhere by having the temporal dimension (topologically) rolled up as a circle. Or, one can have wormhole connections between different parts of space-time which allow one to enter ‘mouth A’ of such a wormhole connection, travel through the wormhole, exit the wormhole at ‘mouth B’ and re-enter ‘mouth A’ again. Or, one can have space-times which topologically are R4, and yet have CTC's due to the ‘tilting’ of light cones (Gödel space-times, Taub-NUT space-times, etc.)

General relativity thus appears to provide ample opportunity for time travel. Note that just because there are CTC's in a space-time, this does not mean that one can get from any point in the space-time to any other point by following some future directed timelike curve. In many space-times in which there are CTC's such CTC's do not occur all over space-time. Some parts of space-time can have CTC's while other parts do not. Let us call the part of a space-time that has CTC's the “time travel region" of that space-time, while calling the rest of that space-time the "normal region". More precisely, the “time travel region" consists of all the space-time points p such that there exists a (non-zero length) timelike curve that starts at p and returns to p.
http://plato.stanford.edu/entries/time-travel-phys/

Hi madanthonywayne,
CANGAS is pulling your leg. There is no problem with this thread.
I'm not sure what rules he's thinking of, but there is certainly no rule here that says a thread goes to Pseudoscience when it refers to a subject that cannot be proved.

CANGAS,
if you have a complaint with moderation, make a thread in Site Feedback where I can't edit it. :rolleyes: Please don't hijack this thread.

Time travel can occur in general relativistic models in which one has closed time-like curves (CTC's). A time like curve is simply a space-time trajectory such that the speed of light is never equalled or exceeded along this trajectory. Time-like curves thus represent the possible trajectories of ordinary objects. If there were time-like curves which were closed (formed a loop), then travelling along such a curve one would never exceed the speed of light, and yet after a certain amount of (proper) time one would return to a point in space-time that one previously visited.
Hehe, I just love some of these time travel gedankins. What would happen if the time traveller bumped into himself when he came back to his earlier location? They've got the answer! Same site:
7. Slightly More Realistic Models of Time Travel
Echeverria, Klinkhammer and Thorne (1991) considered the case of 3-dimensional single hard spherical ball that can go through a single time travel wormhole so as to collide with its younger self.Figure 12
The threat of paradox in this case arises in the following form. There are initial trajectories (starting in the non-time travel region of space-time) for the ball such that if such a trajectory is continued (into the time travel region), assuming that the ball does not undergo a collision prior to entering mouth 1 of the wormhole, it will exit mouth 2 so as to collide with its earlier self prior to its entry into mouth 1 in such a way as to prevent its earlier self from entering mouth 1. Thus it seems that the ball will enter mouth 1 if and only if it does not enter mouth 1. Of course, the Wheeler-Feynman strategy is to look for a ‘glancing blow’ solution: a collision which will produce exactly the (small) deviation in trajectory of the earlier ball that produces exactly that collision. Are there always such solutions?[3]

Echeverria, Klinkhammer & Thorne found a large class of initial trajectories that have consistent ‘glancing blow’ continuations, and found none that do not (but their search was not completely general). They did not produce a rigorous proof that every initial trajectory has a consistent continuation, but suggested that it is very plausible that every initial trajectory has a consistent continuation. That is to say, they have made it very plausible that, in the billiard ball wormhole case, the time travel structure of such a wormhole space-time does not result in constraints on states on spacelike surfaces in the non-time travel region.


:roflmao:

Although Time Travel has not been proven possible, it's still theorised and discussed in regards to Quantum Theory and Relativity Theory, this is because there are subcomponents of atomic states that do very strange things and the only way to try and express them is through theorising metaphysically since you can't think like a subcomponent you sometimes have to create elaborate stories to pose in essence what they get up to. It's also considered in regards to the future of computing especially within Parallel Processing Networking or Neural Networking since some nodes solution methods can involve gaining answers prior to other nodes of the same network and it generates the 'Paradox' usually associated with Time Travel theory.

This is the reason that not all Time Travel posts should be moved to Pseudoscience Unless you claim your from the future (John Titter) and have travelled into the past to right some wrongs then you'll likely find your way there.

When reading stories regarding time travel, it's always assumed that there will be no displacement in space. Sometimes, there is consideration given to the fact that the geography of a given area might change over long temporal jumps, but it's always assumed that if you leave Chicago in 2007 and move thru time to 1945, you will appear in Chicago in the same spot you left.

But this neglects the fact the earth itself is moving. It is rotating about it's own axis at about 1000 miles per hour. It is orbiting the sun at a speed of 66,514 miles/hour. And that the entire milky way galaxy is rotating at about 612,000 miles per hour.

Wouldn't a vehicle designed to move in time but not space find itself hundreds of thousands of miles from the earth somewhere out in space?

H.G. Well's intrepred time traveler riding a machine that resembled a bicycle, would have been in for quite a surprise.

I love that you bring this up! I tried explaining it to my dad, while watching Tim Cop (who has zero interest in the menutia of time travel) that NOT ONLY would it be infinitely impossible to travel back in time and determine the right moment, but there are also those exponentially complex equations that have to be involved in finding the right three dimentional location in space-time.

~String

I think most physicists would disagree. Don't they speak of a "time-space continium"?

As far as time travel being impossible, you may be right. If it is possible, things could get messy quite quickly.

the time space continium, ah yes i forget we live in the star trek universe :), i know its a fun idea to toy with, but honestly time travel is pure fiction.

this is no different that the god idea, we have no proof of it. there is no shred of evidence for us to observe, so why would i believe it to be true?. if i were to believe in something such as time travel, i might aswell just turn to the good book and be a catholic.

no observation, no evidence, no fact, no proof, nothing atall apart from an idea spawned from imagination without any type of scientific basis to call on to back it up.

but ofcourse in this universe it might be possible. but as for believing in it? i wouldent do that without evidence. so time travel goes in the pile with god, psycic powers, astrology and the rest of it.


peace.

I love that you bring this up! I tried explaining it to my dad, while watching Tim Cop (who has zero interest in the menutia of time travel) that NOT ONLY would it be infinitely impossible to travel back in time and determine the right moment, but there are also those exponentially complex equations that have to be involved in finding the right three dimentional location in space-time.

~String

I suppose you could only travel back in increments of one year to ensure the Earth was in the same place.

I suppose you could only travel back in increments of one year to ensure the Earth was in the same place.

yeah the problem is the placement of the earth :rolleyes:, not the fact that you could go back in time and actualy meet yourself. basicaly turning the world of physics upside down.

how on earth can you exist in more than 1 place at a time?, you guys might aswell just believe in a soul, astro projection, ESP, god, scientology, and everything else under the sun.

Ps, why is this in the physics and math forum?, if i made a thread about ESP or some other weird and unproven subject wich is classed as woo woo central topic, then i would be debunked to the cesspool or worse the psudoscience forum. or rock bottom in the religion forum.


peace.

You mean like quantum superposition?

You mean like quantum superposition?

if that is sci-fi then yes. what is the difference with believing in time travel and believing in god?


peace.

I love that you bring this up! I tried explaining it to my dad, while watching Time Cop

That's a pretty good movie. I like the scene where he appears right in front of a semi and must drop down immediately to avoid it.

why is this in the physics and math forum?, if i made a thread about ESP or some other weird and unproven subject wich is classed as woo woo central topic, then i would be debunked to the cesspool or worse the psudoscience forum. or rock bottom in the religion forum.
Our current understanding of physics makes time travel theoretically possible. Yes, it presents many paradoxes and may turn out to be impossible as a practical matter (while remaining theoretically possible).

But is quantum mechanics any different? It doesn't make any damn sense at all! Electrons are not in any particular place, light is a wave and a partical, spooky action at a distance.
I suppose you could only travel back in increments of one year to ensure the Earth was in the same place.
I thought that at first too, but the whole galaxy is moving. So even if the earth was in the same place in it's orbit, it wouldn't be in the same place in space.

I love that you bring this up! I tried explaining it to my dad, while watching Tim Cop (who has zero interest in the menutia of time travel) that NOT ONLY would it be infinitely impossible to travel back in time and determine the right moment, but there are also those exponentially complex equations that have to be involved in finding the right three dimentional location in space-time.

~String

I think this is pretty much the reason for the theory that if everything is kept the way it's suppose to be the equations are far simplified since they lack the Entropy caused by paradoxes.

I'm one hundred percent certain that time travel is impossible, and is in truth crackpot pseudoscience. What's interesting is that when I explain why, my explanation is dismissed and ignored as crackpot pseudoscience. Once you understand time and some of the other basic concepts, you really start to notice just how much ridiculous material is being discussed earnestly and quite seriously, even by professional physicists - I'm thinking of the Boltzman Brains in my New Scientist a couple of weeks back.

Hi madanthonywayne,
CANGAS is pulling your leg. There is no problem with this thread.
I'm not sure what rules he's thinking of, but there is certainly no rule here that says a thread goes to Pseudoscience when it refers to a subject that cannot be proved.

CANGAS,
if you have a complaint with moderation, make a thread in Site Feedback where I can't edit it. :rolleyes: Please don't hijack this thread.

Pete is getting our goat ( get it, Pete? ) when he says that a thread that he claims is unprovable is not tossed. He has tossed more than a few on that unproven premise.

As for the time travel thread, it has no time travel theory , no description of a time travel device, and its only redeeming feature seems to be reference to several science fiction episodes.

Where is the SCIENCE in the thread? Or is the demand for science
TOO MUCH TO ASK?

CANGAS,
Again, I ask you not to hijack this thread. If you have a complaint to make, make it in the appropriate place.

He has tossed more than a few on that unproven premise.
Not one.
You are a proven liar (http://www.sciforums.com/showthread.php?t=18984&page=3).

CANGAS,
Again, I ask you not to hijack this thread. If you have a complaint to make, make it in the appropriate place.


Not one.
You are a proven liar (http://www.sciforums.com/showthread.php?t=18984&page=3).

And where is the proof?

There are several different standard attempts to resolve or avoid the paradox. The most standard is to ignore it. By sending someone far enough into the past, we do not know what influence that person will have and thus for all we know the person caused the world as we know it today. Another way to avoid the paradox is to state up front that we cannot change the past. There are different versions of this thesis. One is that we can go back and participate in a past causal chain but only in the way that already happened and the other way is to go back merely as an observer.

Another question we may ask within this view of one timeline being replaced by another is at what point does it happen. The standard view, which seems totally incoherent, is that it happens when the traveler makes the important change.