Time and Time Travel.

[Il Medico]

I kinda have my own ideas about these two questions I am going to ask, but I am curious as to what other think about it.
So, first question is: Is Time Travel to the past possible? Time travel into the future is relatively easy, just get an object with a massive gravitational pull, or accelerate close to the speed of light. But how would one travel into past? Is it even possible?

And my second question is what is the nature of Time? It would seem to me to depend largely on the answer to the first question. If you can't travel into the past, then time would be a linear progression of cause leading to effect until the end of time. But if you can travel into the past, then this goes out the window.

So thought?

[mikelepore]

I believe traveling into the past is not possible because it would permit contradictions. Here is a time travel paradox I made up. At 10 o'clock you go into the a store, buy a lock, and go outside. You get into at time machine and go back into the past one hour. Now it's about 9 o'clock. You put lock onto the door of the store so that no one can get in. Throw away the key. When you arrive at 10 o'clock you can't get into the store to acquire the lock because the lock is on the door. You have a contradiction. Something cannot exist if assuming its existence leads to a contradiction.

[x371322]

http://www.youtube.com/watch?v=DnLIxEso4rg

I love this kind of stuff. It makes me want to become a physicist.

[mlgb]

Is Time Travel to the past possible?


lets say for a moment that it is possible and someone builds a time machine. what would be done with it? certainly people or devices would immediately be sent back in time to observe monumental events. inevitably, however someone will change the past. either intentionally or accidentally. in fact, i suspect that this sort of thing would be much much more sensitive to mild variations then is commonly assumed and the very first probe or whatever will obliterate everything more then a hundred years or so downstream from its arrival in the past. thus, so long as time travel is possible the universe will remain in a state of flux shifting and changing until it collapses into the only stable state, a timeline in which time travel was either never invented or never used(hard to imagine this second one).

if a working past-capable time machine is invented we will all immediately cease to ever have existed. an interesting experience i imagine.

[Il Medico]

if a working past-capable time machine is invented we will all immediately cease to ever have existed. an interesting experience i imagine.
That is of course assuming that Time is a linear progression of cause and effect, mess up on thing in the past and everything changes. Paradoxes are also bound to happen, making time travel to the past impossible under this view of time anyways. I think time might be more complex than all that. Say that you are a car salesman and I buy a car from you. If I then travel to the past with the car and run you over, then you would have never existed to sell it to me, so it can not be there, but if it isn't there, then you can't die, and thus you will sell it to me and I will run you over. There are two paradoxes here, so if I can travel to the past, time must make adjustments for this.

[leftace53]

Ahh one of my favourite topics. I'm sure I'll do a wall-o-text post on this sometime, but until I format my thoughts proper, I'll dabble here with some random posts.

There is nothing (to my knowledge) in the laws of physics that actually prevent time travel to the past. I have seen things like entropy being cited for both as an argument against and an argument for time travel to the past. Since entropy is always increasing with time "increasing", and we have no real means of decreasing the total value of entropy, it can be argued that time travel to the past is impossible. However, since we specify that entropy is increasing with the increase of time (a direct relation if you will), then we can also say that entropy will decrease with the "decrease" of time (conserving the direct relation), and thus also call entropy a measure of time (whats to say its not time itself?).

I feel that the nature of time has as many philosophical implications as physical. This has obviously been a topic of thought for thousands of years. Science requires certain things of time, such as symmetry and continuity. Einstein came up with his relativity theories, and after that many scientists have adopted the thought of a (3+1) Dimension Spacetime, rather than just space and time. Since physics has not exactly disproven the Many Worlds Theory in quantum physics, I feel that we cannot rely solely on a theory of linear progression of time.

Also deeming time to be a linear progression, results in implications in the thought of free will. Of course you don't necessarily need belief in a deity to believe or not believe in free will, so that part need not be discussed. I've heard people argue that even if you go back in time, you won't be able to change anything. Of course since you are going back in the past, actions of the past have already been taken, and it can be said that you are not interfering with free will since there was a choice, and the choice was made. However since we are the ones going back in time, it also coincides with our future, and it could be argued that since we don't have the power to do anything to change our future through the past, that we have no free will.

Then there is the question of whether time even exists outside of the "mind". Augustine I find had some interesting thoughts to this in his work Confessions. Theorizing that time is only in our mind, and we measure it through impressions left behind. He also argued for a punctiform present, in that there is nothing but the present, and time has infinitely small intervals. He thought that in there being nothing but the present, there are three types of the present - the present of the past (memories), the present of the present (sight) and the present of the future (expectations). All these keeping in line with the thought that time essentially only exists in the mind.


time must make adjustments for this.

I understand what you're talking about here, but I feel that statements like these are dangerously close to giving time some sort of conciousness, which I like to think is incorrect. However I have nothing to back my argument, so for now this statement stands.


If all else fails, I like to go back to one of my favourite video game quotes:

"Most people think Time is like a river, that flows swift and sure in one direction but I have seen the face of time and can tell you they are wrong. Time is like an ocean in a storm..." - The Prince of Persia

[mlgb]

That is of course assuming that Time is a linear progression of cause and effect, mess up on thing in the past and everything changes. Paradoxes are also bound to happen, making time travel to the past impossible under this view of time anyways. I think time might be more complex than all that. Say that you are a car salesman and I buy a car from you. If I then travel to the past with the car and run you over, then you would have never existed to sell it to me, so it can not be there, but if it isn't there, then you can't die, and thus you will sell it to me and I will run you over. There are two paradoxes here, so if I can travel to the past, time must make adjustments for this.

why must the universe make adjustments? the you in the past with the car exists because you came out of the time portal. you exited linear time when you you went 'out' in the time machine and entered when you cam 'in'. you will still have come 'in' even if you never went 'out' because while(if that word can be said to mean anything outside of time) you were outside of time you could not be effected by changes in the timestream which you are not a part of.

[x371322]

Also you guys need to realize that time travel to the past doesn't necessarily mean sending people back. If we can just reach the point where we can send information (binary signals for example could be accomplished with light alone, even a form of Morse code), then the possibilities are endless. This was pointed out at the end of the video I posted, but imagine being able to receive a cure for aids, or cancer, from the future.

[Revy]

I kinda have my own ideas about these two questions I am going to ask, but I am curious as to what other think about it.
So, first question is: Is Time Travel to the past possible? Time travel into the future is relatively easy, just get an object with a massive gravitational pull, or accelerate close to the speed of light. But how would one travel into past? Is it even possible?

And my second question is what is the nature of Time? It would seem to me to depend largely on the answer to the first question. If you can't travel into the past, then time would be a linear progression of cause leading to effect until the end of time. But if you can travel into the past, then this goes out the window.

So thought?

I think the only way to travel through time to the past is to reverse the "flow" of motion.

Our concept of time is just based on the movements of everything. Without motion, nothing "happens".

But what kind of power (and knowledge) is necessary to do something like reverse the flow of motion? Is that even possible? And I suppose the purpose of the time machine would be to not only do this but to keep the person using it from being reversed as well, to keep their motion independent and normal in some kind of bubble.

Unfortunately (fortunately? Time travel would be messy and could be used by people with the wrong intentions), I think it's pretty likely that time travel is....impossible.

[Revy]

Also you guys need to realize that time travel to the past doesn't necessarily mean sending people back. If we can just reach the point where we can send information (binary signals for example could be accomplished with light alone, even a form of Morse code), then the possibilities are endless. This was pointed out at the end of the video I posted, but imagine being able to receive a cure for aids, or cancer, from the future.

If you had the cure for the bubonic plague, would you send it to the 14th century? Will people in the future want to do something like that for us? We will be long forgotten.

Imagine how that would effect history. I would guess in both good and bad ways. Sci-fi usually stresses the point of not influencing history long ago in huge ways. Because you could not have been born because of what you did. And if you stop a war, an even worse one could start later. Like preventing World War II but a nuclear war happens in the '60s.

Just something to consider....

[Il Medico]

I understand what you're talking about here, but I feel that statements like these are dangerously close to giving time some sort of conciousness, which I like to think is incorrect. However I have nothing to back my argument, so for now this statement stands.

I don't mean that it would. But Time sure must have a mechanism to cope with such if it is at all possible (Time Travel to the past that is). I also find the argument that you can't change the past interesting. Like say you arrive in Paris from, New York, go to your flat and discover you left you keys back in New York, all you'd have to do is go back in time and place the keys in your coat. But since this happened in the past, you already have the keys. So did you always have the keys? If so, then you have no need to travel to the past, thus, the effect (you having your keys) has no cause ( you never need to travel back to put them in your pocket). This is impossible in a strict Cause -> Effect view of time. Interestingly enough, this is our current view of time, the seemingly obvious. But if the endless march of science has taught us anything, it would be not to assume the obvious in observation, as our view of things, especially things as complex as time, is very limited.

[x371322]

If you had the cure for the bubonic plague, would you send it to the 14th century?

Well I couldn't. We could only go back as far as the time machine had been switched on. I would if I could though.



Will people in the future want to do something like that for us? We will be long forgotten.

Well that depends on how far into the future we're talking about here. Are people from the 60's long forgotten from our perspective? Would people in the future want to help us out? I don't know. I would hope they would of course. :D But yes, I'm aware that's mostly wishful thinking. And no one's saying there aren't consequences for changing the past. But of course that's still making the same old assumptions that time is linear. It isn't. At least, according to some theories, time and space are part of the same fabric (time being the 4th dimension, and space being the 3rd), called spacetime, and if we can manipulate space, then we can also manipulate time.

Time travel into the future is possible. As the Doctor already pointed out in the OP, all we have to do is build a space ship that can travel fast enough, and let relativity take care of the rest. Now, in order to travel into the past using this same method, we would have to be able to move so quickly beyond the speed of light, that we return to earth before we left. Of course, according to Einstein, that would be impossible, as we cannot exceed the speed of light.

BUT... this is all just shit I've seen on Television, and read online. I'm really just a big nerd at heart, so you'll have to take my views on science and technology with a grain of salt sometimes. :thumbup1:

[NGNM85]

I believe traveling into the past is not possible because it would permit contradictions. Here is a time travel paradox I made up. At 10 o'clock you go into the a store, buy a lock, and go outside. You get into at time machine and go back into the past one hour. Now it's about 9 o'clock. You put lock onto the door of the store so that no one can get in. Throw away the key. When you arrive at 10 o'clock you can't get into the store to acquire the lock because the lock is on the door. You have a contradiction. Something cannot exist if assuming its existence leads to a contradiction.

This is essentially the 'Grandfather Paradox.' My only argument is that this assumes that time is, in fact linear, that we don't just perceive it that way, and that there aren't, or can't be, multiple timelines.

[hobo8675309]

time is only a theoretical concept, the way that people perceive everything hapenning at once.

[leftace53]

time is only a theoretical concept, the way that people perceive everything hapenning at once.

I held this view for a while, but have no idea why I abandoned it.

Honestly from a personal opinion standpoint, I have no opinions on the nature of time other than I highly doubt it being linear.

[pranabjyoti]

In my opinion, time travel to the past is basically distorting the physical fabric of space-time. We have distorted the biological fabric of the Earth enough and is now facing the consequences. I am pretty sure that in future human kind will achieve the capability to travel to past but they will limit it severally because then they will also know about the adverse consequences of such distortions in the space-time fabric.

[hobo8675309]

i imagine the universe is too confusing to be real. science cannot expand our understanding outside the material universe, and i do believe that not everything is what it seems. perhaps we are actual just a timeless universe, stuck in one moment, programmed with memories from a past that never hapenned, and not understanding there will never be a future.

[NGNM85]

Honestly from a personal opinion standpoint, I have no opinions on the nature of time other than I highly doubt it being linear.

I am, similarly, skeptical.

[Aloysius]

I don't think travelling to the future is possible, 'cause I don't think it exists yet. I think the future is the sum off all the variables presented in life, be it the path you take to get to the library or which spoon you use to eat your yogurt.
Time travel to the past is possible, but not with today's technology.
If I could travel to the past, I would go back and stab Hitler in the face (and probably die in the process) and if I survive that, I would go and see what colour the dinosaurs were, 'cause it bothers me that much.

[leftace53]

I don't think travelling to the future is possible, 'cause I don't think it exists yet. I think the future is the sum off all the variables presented in life, be it the path you take to get to the library or which spoon you use to eat your yogurt.
.
This is interesting. Assuming time is linear, and there is no predestined type thing like fate. If time travel to the future was possible (which according to the current laws of physics, it very much is), where (spatially and temporally)would the traveler end up?

[Klaatu]

Assuming you could travel back in time, you might never get back again. Because in order to get back again,
you would have to be able to travel into the future. That is, we could do one, but not the other (?)

No one in the future has ever traveled backward in time (into their own past) because we would have
known about it, since they would have met with us already. That is, unless they are somehow invisible, or
otherwise undetectable by scientific instrumentation (?)

That is to say that, is the time traveler just a "ghost" or an non-material entity to the observer in the past (future) (?)

[Os Cangaceiros]

I believe traveling into the past is not possible because it would permit contradictions. Here is a time travel paradox I made up. At 10 o'clock you go into the a store, buy a lock, and go outside. You get into at time machine and go back into the past one hour. Now it's about 9 o'clock. You put lock onto the door of the store so that no one can get in. Throw away the key. When you arrive at 10 o'clock you can't get into the store to acquire the lock because the lock is on the door. You have a contradiction. Something cannot exist if assuming its existence leads to a contradiction.

Why didn't you just use the age-old "you go back and time and kill your grandparents, thus making you non-existant by virtue of your non-birth"?

[Psy]

I don't think travelling to the future is possible, 'cause I don't think it exists yet. I think the future is the sum off all the variables presented in life, be it the path you take to get to the library or which spoon you use to eat your yogurt.
Time travel to the past is possible, but not with today's technology.
If I could travel to the past, I would go back and stab Hitler in the face (and probably die in the process) and if I survive that, I would go and see what colour the dinosaurs were, 'cause it bothers me that much.

Problem is the matter of the past has changed and there is no data relating to the state of matter on Earth at the time to recreate the past. It is like looking at a computer and asking if it possible to restore the CPU to a previous state without a CPU save state.

Time travel assumes the universe has a massive archive of everything that happened.

[black magick hustla]

the short answer is no. the only thing i can think about are certain solutions to einsteins field equations but everybody who knows a little difeq knows that a differential equation can have all sorts of useless and unphysical answers.

[Klaatu]

Problem is the matter of the past has changed and there is no data relating to the state of matter on Earth at the time to recreate the past. It is like looking at a computer and asking if it possible to restore the CPU to a previous state without a CPU save state.

Time travel assumes the universe has a massive archive of everything that happened.

Thank you. That is an excellent synopsis and analogy!

[The Vegan Marxist]

Even if it was possible, it's a dangerous move to take to change the past & to try & "re-work" the future. Nothing would come out of a time-traveling machine except more wars & another commodity that'll play into the Class War as a tool for the Upper Class.

[hardlinecommunist]

Even if it was possible, it's a dangerous move to take to change the past & to try & "re-work" the future. Nothing would come out of a time-traveling machine except more wars & another commodity that'll play into the Class War as a tool for the Upper Class. What you have said is so true i have long had a fascination with time travel every since i was a little kid and i do believe that time travel is possible. but being a Communist i know that if a way to travel in tiime is found in this era in history. the era of the Class Struggle and World Imperalism. time travel would just be used as a weapon by the bourgeoisie in the Class Struggle aganist the Working Class and the oppressed Nations and Peoples of the World that is why i believe that we must frist overthow the bourgeoisie. before a time machine is invented or some other way to travel in time is found.

[mikelepore]

This is essentially the 'Grandfather Paradox.' My only argument is that this assumes that time is, in fact linear, that we don't just perceive it that way, and that there aren't, or can't be, multiple timelines.

Perhaps there are multiple timelines, but science is supposed to begin with actual observations and only then search for the reasons. We observe behaviors of mass, charge, light, sound, heat,, and we ask what's behind the processes. A hypothesis is one of the related questions.

The problem with discussions about multiple timelines, parallel universes, wormholes, faster than light transportation, etc. is that any such discussion begins with an expressible observation that has never been observed at all, and then searches for the necessary theory. We become like a lawyer who says: desired conclusion - the defendant is innocent/guilty; given that, let's try to construct a convincing argument.

If we take that approach, we might as well assume that there really exists a talking mouse named Mickey and then look for the all the implications that would have to be true of the world in order for this desired conclusion to be possible. If vocal cords are not the true source of phonation, if abstract syntax doesn't require a large brain, etc. - put all of the assumptions together and we may arrive at the talking cartoon mouse. But then why did we expend reasoning to explain an unobserved conclusion instead of an observed one?

I don't know of any successful science has ever progressed by that method of beginning with an unobserved conclusion. Relativity began with evidence that the speed of light is the same for all observers. Quantum mechanics began with the observations about the photoelectric effect and blackbody radiation.

There are times when science has to throw away a leading paradigm to explain experimental results, but science doesn't throw away a leading paradigm without any reason to do so, and then search for a justification for having done it. We have to know about the justification first. To say "it would be cool if this were true like in the movies" isn't one of the justifications, but discussions about time travel, parallel universes, wormholes, etc. are inspired by precisely that.

[ÑóẊîöʼn]

Even if it was possible, it's a dangerous move to take to change the past & to try & "re-work" the future. Nothing would come out of a time-traveling machine except more wars & another commodity that'll play into the Class War as a tool for the Upper Class.

If time travel is at all possible (which looks unlikely) then I wouldn't worry about the ruling class if we survive long enough to build a time machine.

One can ask the same question about time travellers as one can about aliens; Where Are They?

[Il Medico]

One can ask the same question about time travellers as one can about aliens; Where Are They?
If I was a time traveler, I wouldn't go around say such. The point of time travel to the past is to experience thing that happened in the past, or to observe them, no? A Time Traveler wouldn't want to particularity stand out would they?

[mikelepore]

Why didn't you just use the age-old "you go back and time and kill your grandparents, thus making you non-existant by virtue of your non-birth"?

The frequent use of that example has caused some people to think that the paradox is about preventing yourself from existing, but that's not what it's about. That's only one of many possible examples. The paradox occurs if any statement is true and false at the same time. You could travel back in time and then dismantle the time machine before you got into it. You could walk by the light of a light bulb into a time machine, go back in time, and then break the light bulb. Any one contradiction, no matter how small, is all it would take, and then time travel is proven to be impossible. *

* without resorting to the many worlds hypothesis

[mikelepore]

Suppose we could go back and change history. A lot of people speculate about saving a lot of lives by going back to assassinate baby Hitler. Actually you would wouldn't have to do something as drastic as kill anyone. Just go back to a year before fertilized egg Hitler was conceived, then stop his father on the street and cause the smallest delay, say, ask him what time it is. The delay has changed the random selection of one of millions of spermatozoa. The same child will never be born. If a child is born at nearly the same time, he or she will have a different personality.

The same thing is true of the grandfather paradox. They always phrase it in the form of killing your grandfather. That's unnecessarily violent. The same result can be achieved more simply by producing any small delay, so just ring your grandfather's doorbell and walk away. The "spin of the roulette wheel" has been altered. The same sperm cell will not fertilize the egg, so the offspring will not become you.

Most likely, your appearance in the past would be enough to change history, even if you don't choose to do anything. By appearing there, your body has pushed some air out of the way. The motion of each molecule affects the motion of every other molecule. Although major events in history will probably not be affected, the placement and timing of moving objects will be changed, and different individuals may populate the world.

[leftace53]

Most likely, your appearance in the past would be enough to change history, even if you don't choose to do anything. By appearing there, your body has pushed some air out of the way. The motion of each molecule affects the motion of every other molecule. Although major events in history will probably not be affected, the placement and timing of moving objects will be changed, and different individuals may populate the world.

Chaos Theory that shit :thumbup1::thumbup1:

[Mumbles]

Ah, oh boy, I love this topic.

I don't think traveling into the past as we think of it is possible. But I do think that if parallel universes existed there'd be an infinite number of them. And in that infinite number there'd be universes which started the amount of time you want to travel backwards. So say you wanted to go back 500 years, you'd just transition into a universe that is "500 years behind" and also having had the same historical decisions by everyone and everything (it's one of unlimited universes so the chances of finding it is where the real trick comes in, well besides getting into it).
Of course to that universe your appearance wouldn't affect the future as we think of it. It'd just continue, with your influence being part of it's normal progression of history.

I dunno if this is completely scientifically sound, but I like to think it is. Haha

[Il Medico]

I think if time travel is possible, it isn't something we can do now. Or anytime soon, unfortunately. I think in order to time travel tot the past, we would need to have a civilization that has a mastery of the universe around us, specifically blackholes/singluarities. There was a theory I was reading that Blackholes are links to other universes, as they spill out the other side or what not. So there is a bridge between the two universes, and in-between, nothing. I think the key is to get out into this void. There is no space or anything else. The cosmic speed limit for traveling through Space is c, but outside of space, you can go as fast as you want. And since traveling faster than the speed of light, necessitates backwards time travel, then you would simply need to travel at X speed over the speed of light, until you get back far enough and then re enter the universe where you want (we would need to know how to create a singularity, and thus a bridge back into our universe to do this though.Which is way beyond our current understanding, but could be done, you just need to crush matter down far enough)

Sorry if this is horribly inaccurate in therms of theory or anything, I am just kinda of an interested geek, rather than someone who actually knows this shit.

[Klaatu]

All of the theories presented here are greatly appreciated. I have been very interested in the topic of time travel all of my life.
The possibility of extraterrestrial life too.

Thanks all. Keep it up. :cool:

[chebol]

People assume that time is a strict progression of cause to effect, but actually - from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly-wobbly, timey-wimey... stuff.

Saying any more than that would be telling. ;)

[Il Medico]

People assume that time is a strict progression of cause to effect, but actually - from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly-wobbly, timey-wimey... stuff.

Saying any more than that would be telling. ;)
Doctor Who ftw.

[ÑóẊîöʼn]

If I was a time traveler, I wouldn't go around say such. The point of time travel to the past is to experience thing that happened in the past, or to observe them, no? A Time Traveler wouldn't want to particularity stand out would they?

You're right, but unless Time Travellers are infallible, one of them has to have their cover blown sooner or later.

[Il Medico]

You're right, but unless Time Travellers are infallible, one of them has to have their cover blown sooner or later.
True. But I am sure things like Mind wipes or cloaking devices, which are potential problem solvers in these cases, are probably available to any civilization capable of Time travel into the past.

[ÑóẊîöʼn]

True. But I am sure things like Mind wipes or cloaking devices, which are potential problem solvers in these cases, are probably available to any civilization capable of Time travel into the past.

Problem is, those are technological solutions, not magic wands. Technological solutions can fail.

[leftace53]

Maybe time travel to the past/future is only available to times where the Time Travel had been invented? Sort of like a teleportsra which needs to have communication from the other end to work (I'm reading Galileo's Dream, forgive me).

[Klaatu]

You're right, but unless Time Travellers are infallible, one of them has to have their cover blown sooner or later.

What I am wondering is, perhaps it may be impossible for the time traveller to actually "make contact" with others in another time frame? And that being said, would this be some sort of "fail-safe" so that established "historical" events cannot be altered?

[HammerAlias]

Of course it's not possible. Well, at least in the context of how you think it would be conceivably possible. Dimensional multi-universal travel, however, is possible if you are able to fabricate something that can access multi-universal dimensions. Of course, this means that any event you alter in that dimension doesn't affect your own dimension or universe. So, if you were to prevent the assassination of Lincoln, you would only be saving the Lincoln of that dimension and not the one of your own dimension. Quantum physics suggests such a phenomena. It prevents any contradictions or abnormalities commonly associated with time travel.

[Meridian]

Time travel is an idea fundamentally based on our misconceptions about language and in particular our use of the word "time". Time existing as a metaphysical entity, not a word. If it's an entity, it can be discussed as something which to study, something we describe, not something with a clear and defined communicative use. Notice also that even the word "travel" is entirely out of place/metaphorical. The whole idea is based on confusion.

[HammerAlias]

Time travel is an idea fundamentally based on our misconceptions about language and in particular our use of the word "time". Time existing as a metaphysical entity, not a word. If it's an entity, it can be discussed as something which to study, something we describe, not something with a clear and defined communicative use. Notice also that even the word "travel" is entirely out of place/metaphorical. The whole idea is based on confusion.

This isn't a debate over semiotics. Admittedly, these words are arbitrary and subjective but you should understand that the OP is talking about the idea of transporting a human being to a past event or period in history.

[Meridian]

This isn't a debate over semiotics. Admittedly, these words are arbitrary and subjective but you should understand that the OP is talking about the idea of transporting a human being to a past event or period in history.
That's exactly what I am talking about. Now you are misusing the word "transporting".

[Psy]

Time travel is an idea fundamentally based on our misconceptions about language and in particular our use of the word "time". Time existing as a metaphysical entity, not a word. If it's an entity, it can be discussed as something which to study, something we describe, not something with a clear and defined communicative use. Notice also that even the word "travel" is entirely out of place/metaphorical. The whole idea is based on confusion.

That and the idea that matter a place in space and time rather then time simply being the movement of matter. For example if we just want to rewind a broken drinking glass to what it was before it broke would require data that is much easier to get from simply looking a non-broken glass and rearranging the matter of the broken glass to match it as the matter of the broken glass does what its state even one second ago as matter is simply reacting to current forces on it.

IE a glass that falls of a table is acting upon the force of gravity pulling it down and breaks due to the strong force of the quarks of the floor and glass stops the glass from falling to the Earth's core, the energy of the floor stopping the glass from falling causes the glass to break and change direction to which gravity pulls shards of glass back down to the floor and the strong force of quarks once again prevents the glass from passing through the floor.

From this stand point we can see the problem of going back in time, how do we reverse the movement of matter? As that is the only was to go back in time put all mater back to what they were in the time in question, meaning we would be destroying the present as we would be moving matter back to a previous state. In this case the glass would no longer be broken but back on the table, the would no paradoxes if we stop the glass from falling (the reason we went back in time) since we did no move through "time" (as that is impossible as time in that sense doesn't exist) but restored matter to a previous state (that is a highly improbable due to the complexity)

[HammerAlias]

That's exactly what I am talking about. Now you are misusing the word "transporting".

Please. Just stop being so unreasonably dense. You understand what the OP is talking about!

[Meridian]

Please. Just stop being so unreasonably dense. You understand what the OP is talking about!
I understand perfectly well. Time is neither a tunnel nor a location, nor anything else besides a useful word. It does not make sense to travel through time. Nor does it make sense to transport to a time. Like the word "car" is not used in the following way: "The time is now car o'clock".

[leftace53]

I understand perfectly well. Time is neither a tunnel nor a location, nor anything else besides a useful word. It does not make sense to travel through time. Nor does it make sense to transport to a time. Like the word "car" is not used in the following way: "The time is now car o'clock".
Indeed, I feel that some of this misconception (that movement in time is similar to a spatial movement) comes from time often being called the "fourth dimension", yet this label would put time in the same "genre" as space, which it probably isnt.

[leftace53]

http://www.huffingtonpost.com/robert-lanza/does-the-past-exist-yet-e_b_683103.html?view=print

Kind of a sensationalist take on quantum/wave-particle duality, but it was interesting enough to sustain my attention and it goes with the topic at hand. If the past is indeed, not set in stone on a macro level, it could easily give rise to the many paradoxes that come with time travel.

[Blackscare]

From what I was reading, apparently time travel may only be possible from the point it is discovered onward. So going back in time (as in ancient Athens, for example) wouldn't be possible. All that would be possible would be to travel through the sections of time since such technology existed. Which may solve certain problems I suppose.

I have no clue why someone would willing go to any point in the past. At least to stay.

[Velkas]

Time travel to the future is relatively easy (no pun intended), due to special relativity. If an object travels at a high speed relative to another object, the first object experiences less time then the second. For instance, if you went in a high-speed rocket and travelled went on a year-long round trip through space, once you returned to the earth, a longer time would have passed (say, a century).

Time travel to the past, however... I do not know if it would be possible, but I hope it would be. The most logical explanation for how it would work, without any paradoxes and such, would be that if you travel a century back in time, the present time that you cam from no longer exists in the new time stream. Your current time is the present. You can do anything you want, killing your great grandparents and such, and it would effect nothing, since the future (your original present) has not been written yet. You would be overriding the original version of history by creating a divergent timeline from the point you went back in time to.

[Luisrah]

I don't believe time travel is possible, especially to the past.

Taking the grandfather thing again, if you went to the past and killed him, what would happen to you? Would you die? Then who created your body?
Would you disappear? How is that possible? And how was the 'you' from 5 seconds ago alive, if his grandfather was already dead, because in the future (you that are now in the past), you killed the one who made it possible for 'you' (before killing him) to exist?

This gets awfully confusing, but I'll explain in a different way.
Assuming that time is linear and there is only one time, than travel in time isn't possible righ?
If, however, there are multiple times going on, meaning, if there is a you in the past, a you 5 minutes from now, another in 5,0001 minutes from now, then that would make time travel something cyclical but still impossible.

Lets see it in the perspective of the grandfather. You are sitting in a chair, and your grandson comes and kills you. How did he show up if you just died, and never had him? How will you now have his father so that he may exist and go back in time to kill 'his' grandfather now that you are dead?

Time travel to the past is impossible because it creates the possibility to these contradictions, as someone already said.

Recently I saw a film where two people could talk to each other through letters with a difference of 2 years. Ignoring that this is impossible, what happens is this.:

B (the one 2 years later) finds out that she can't find 'the A of her time'(a) because he has died in the meantime (between the time of the A and the time of the B).


A+b---------------A dies--------------a+B

However, B sends a letter to A saying that he will die, and how to avoid it and in the film, he doesn't die, and after not diyng, he goes to meet her.

Now lets look at the incoherencies (sp?). Since B did in fact see him die in her arms (as it says in the film), how did he survive? Did he pop up somewhere?

How did A die? If B sent a letter that made him not die, how did A die in B's hands in just one instance?

What many people fail to understand in this scenario is that if someone sends himself a letter to the past, than in the past, he would have already recieved the letter from the ''future'' (present), and only then would he send the letter to his past.
Meaning that if you now developed a bomb that would blow up the Earth and traveled back to 1750 to blow it, a time paradox would exist. What would really happen is that in 1750 the people would see someone from the future coming and blowing up Earth, and then later in 2010 they would develop a bomb to go back to 1750 to blow up the Earth. Does this make sense? Of course not! How can a bomb be created to destroy it's creators, before the same bomb has been created?

I haven't studied much materialism and idealism yet, but I have the impression that assuming that travel to the past is possible is an idealistic point of view, or can take us to religion.
If traveling to the past is possible, and someone from the future visited us, then matter would be created so that he could be here with us, even if there is a 'trade' between his body and the air he will ocuppy here, from where we are, matter is created. His eyes, teeth, all just start existing.
How did that happen?

I have written a lot, lol, and this leads, atleast me, to a simple, kind of stupid, but correct conclusion.
You can't alter past simply because it has already happened. Meaning that you can't go back in time, because there is the possibility of the alteration of the past, and that is impossible, as I have explained like 20 times above lol.

[leftace53]

Recently I saw a film where two people could talk to each other through letters with a difference of 2 years.


Lake House is one of the cutest movies I've ever seen.

What about if time travel to the past could happen, but we would simply be spectators? Like all we could physically do is observe the past, but not interact with it. It would still be usefull because I mean come on, wouldn't you want to go back and see history do its thing?
Who the hell knows, maybe time machines have been invented with this sort of "fail safe" and there are observers out there right now?

[Luisrah]

Lake House is one of the cutest movies I've ever seen.

What about if time travel to the past could happen, but we would simply be spectators? Like all we could physically do is observe the past, but not interact with it. It would still be usefull because I mean come on, wouldn't you want to go back and see history do its thing?
Who the hell knows, maybe time machines have been invented with this sort of "fail safe" and there are observers out there right now?

I liked the movie too, except it's impossibility. The author makes it impossible only to have the couple be together in the end. All for commercial purpose.
It would be so much better if he actually died and the movie ended when she knew what happened.

Now that's not impossible. If they wouldn't be spectators, we would have probably seen someone already.
But the problem isn't about interfering or not, it's about it being POSSIBLE to interfere or not. It is impossible for it to be possible to interfere with past events, because it would lead to those contradictions.

However that time machine has already been invented. It's not really a machine, but you can actually see the past as a spectator because of the speed of light. Although it's impossible, atleast for now, if were 2000 light-years away from Earth and you could see Earth with a telescope, you would see the light that was emmitted by the Earth 2000 years ago.

In the same way that the Sun you are seeing is not the ''real sun'' (since the light your eyes are getting was emmitted by the sun 8 minutes or 8 hours ago (can't remember, I think it's one of those), you could watch the past on Earth IF you could travel at a speed higher than that of the light (in order to see the light that has already been emmitted)

Kind of fun to think that if we saw an alien on another planet 100 light years away from us, we'd have to take into account that right now they are probably much more advanced technology-wise.

[kitsune]

The most logical explanation for how it would work, without any paradoxes and such, would be that if you travel a century back in time, the present time that you cam from no longer exists in the new time stream. Your current time is the present. You can do anything you want, killing your great grandparents and such, and it would effect nothing, since the future (your original present) has not been written yet. You would be overriding the original version of history by creating a divergent timeline from the point you went back in time to.

Yes. This is the view according to the Many-Worlds Interpretation of QM.

Within the M-W framework, time travel is certainly possible and there is no paradox. If you went to "the past" you would diverge along another line of spacetime. You can't change anything in your own past; those spacetime moments are immutable. You would only be affecting events in separate timeline.

[leftace53]

However that time machine has already been invented. It's not really a machine, but you can actually see the past as a spectator because of the speed of light. Although it's impossible, atleast for now, if were 2000 light-years away from Earth and you could see Earth with a telescope, you would see the light that was emmitted by the Earth 2000 years ago.

In the same way that the Sun you are seeing is not the ''real sun'' (since the light your eyes are getting was emmitted by the sun 8 minutes or 8 hours ago (can't remember, I think it's one of those), you could watch the past on Earth IF you could travel at a speed higher than that of the light (in order to see the light that has already been emmitted)

Kind of fun to think that if we saw an alien on another planet 100 light years away from us, we'd have to take into account that right now they are probably much more advanced technology-wise.

8 minutes.
I know what you mean, I've always thought it was so cool that just looking at the stars is in sorts a time machine. We literally look at the history of a star because of the time light takes to travel to us. Some of the stars we look up at might be dead by now, but we wouldn't know because when you think about it, light is actually pretty damn slow :lol:

[Luisrah]

8 minutes.
I know what you mean, I've always thought it was so cool that just looking at the stars is in sorts a time machine. We literally look at the history of a star because of the time light takes to travel to us. Some of the stars we look up at might be dead by now, but we wouldn't know because when you think about it, light is actually pretty damn slow :lol:

Yeah, when you look at it ''whoa, that's so fast!'', and it is really fast. I wouldn't say light is slow, I'd say that space is REALLY big :lol:

[Klaatu]

If anyone could travel backward in time and actually observe what happened, there would be hundreds of revisions made to our history books! And crimes could be solved without any doubt as to the guilty party.

[Klaatu]

8 minutes.
I know what you mean, I've always thought it was so cool that just looking at the stars is in sorts a time machine. We literally look at the history of a star because of the time light takes to travel to us. Some of the stars we look up at might be dead by now, but we wouldn't know because when you think about it, light is actually pretty damn slow :lol:

And (if) there are extraterrestrials out there observing us, right now, they would see OUR past. For example, in the movie "Contact," an early television signal of ours was sent back to Earth. Must have been about 25 or 30 light-years away (30 to get there, 30 to get here)

But this whole idea of our radio signals getting received by others at such great distances seems almost impossible, given (A) the weak signal and (B) the fact that radiation propagates in a gaussian sphere, according to the inverse-square law. This would make signals outside our own solar system incredibly weak, as well as very tiny point-sources. If their receiving antenna was not pointed EXACTLY at Earth, they would completely miss it in their own vast sky.

[Tenka]

If traveling back in time were much more than a plot device, we would have people going back to kill Hitler in his cradle thousands of times over and it would be pretty retarded.

...And what about the Hounds of Tindalos? For God's sake plaster over the corners! The room must resemble the interior of a sphere!

[Psy]

And (if) there are extraterrestrials out there observing us, right now, they would see OUR past. For example, in the movie "Contact," an early television signal of ours was sent back to Earth. Must have been about 25 or 30 light-years away (30 to get there, 30 to get here)

But this whole idea of our radio signals getting received by others at such great distances seems almost impossible, given (A) the weak signal and (B) the fact that radiation propagates in a gaussian sphere, according to the inverse-square law. This would make signals outside our own solar system incredibly weak, as well as very tiny point-sources. If their receiving antenna was not pointed EXACTLY at Earth, they would completely miss it in their own vast sky.

Yet that is simple compared to the problem comes from a alien society deciphering our signals regardless of strength, the idea that aliens interlace anything into in a video is laughable as they have no way of knowing they are looking at a signal carrying video.

[nip]

I love this kind of stuff. It makes me want to become a physicist.
I know, isn't just awesome?

[Klaatu]

Yet that is simple compared to the problem comes from a alien society deciphering our signals regardless of strength, the idea that aliens interlace anything into in a video is laughable as they have no way of knowing they are looking at a signal carrying video.

Thanks for your comment.

I don't know. It might not be so hard to decipher, if we look at our simple video signal waveform. (http://en.wikipedia.org/wiki/Principles_of_analogue_television%22)
(A) TV is impressed upon a simple carrier wave
(B) Amplitude-modulated carrier wave (easy to extract)
(C) The luminance signal would not be too hard to figure out (it is 1920's technology):

Synchronization pulses exist at 1/60 second intervals (this means a new scan line) and
luminance signal varies in strength, which manifests a light-to-dark pixel (picture element)

While "they" may not measure time intervals in our own "seconds," that does not matter.
It is a time interval, that is all that matters. For example, suppose we received an alien
"video" signal. Their sync pulse (1.0000 "goblydjuh") which may be 1.2345 of our own "seconds."
Just "lock in" at that time interval to change frames, that is all.

This is not a too-complicated technology for an alien to figure out. (And don't forget that,
in the movie, these beings are many millions of years advanced to us; consider the incredible
space/time traveling capsule plans they sent to us to build, in order to reach their dimension)

Of course, I am assuming you have seen the movie.

HAHA "goblydjuh" how do I know what alien time intervals are? Ours are "seconds"
in our world physics "SI system."

[Klaatu]

If traveling back in time were much more than a plot device, we would have people going back to kill Hitler in his cradle thousands of times over and it would be pretty retarded.

...And what about the Hounds of Tindalos? For God's sake plaster over the corners! The room must resemble the interior of a sphere!

My belief is that, it would be dangerous to change events in the past, even if it involves killing Hitler, because there is no way to predict the outcome of this action. That is, it is possible that, killing Hitler may result in an even worse outcome of progressive events, along the timeline, than not doing so might possibly eventuate.

[Psy]

Thanks for your comment.

I don't know. It might not be so hard to decipher, if we look at our simple video signal waveform. (http://en.wikipedia.org/wiki/Principles_of_analogue_television%22)
(A) TV is impressed upon a simple carrier wave
(B) Amplitude-modulated carrier wave (easy to extract)
(C) The luminance signal would not be too hard to figure out (it is 1920's technology):

1920's broadcast would really be too weak.

Also most likely it would be our transmissions from space that aliens notice, I don't know why the movie went with the broadcast of Hitler instead of something like the images of our moon Lunar 9 broadcasted in 1966.

[leftace53]

Thought I might post this link which I found quite interesting, it has a collection of essays on the nature of time - click download essay to read them. http://www.fqxi.org/community/essay/winners/2008.1
PS. One of my prof's essays are in here, makes me feel like he's actually legit in what he knows. :lol: