last night i was thinking the following:

asume that i was in a room with you, and we had a time machine there.
we are friends.
now, i go in to the time machine, while you will stay on guard in "present time".
i'm going to six years back and chop off your legg. Now what does that mean? that means, that you , in present time suddenly have lost a legg, and your attitude towards me has drastically changed when i come back to present time.

now on a bit larger scale:
we all have been posting crap on this forum for some time, and we decide to have a forum meeting. now everybody is there lets say 500 people. we have a good time and all. and afterwards we post on how great it was on the forum.

now asume i go back in time to that party and decide to take off everybodies right foot. You in present time will now have a missing foot, will have different memories of the meeting then before AND the messages on this forum wouldnt be the same when discussing that meeting.
so in other words,i changed the appearance of multiple people who are in different places in present time, i changed memories of different people in the present time in an instance, and i changed cyberspace!?!?!?! because one moment you are reading and thinkin back about the great meeting, and the next moment you suddenly wished you never went?

another little example. you are sitting there in you house. i decide to go back in time and smash your house where you are in right now. Then decide to built a new house on that same spot. Where would you be then in present time? your reality would suddenly change

if this could be possible, wouldnt we see reality change around us?

btw: i am in no means a violent person, but these examples where easy to follow

I agree. Besides, if a time machine was built in the future and travel to the past was possible, then someone from the future would have already traveled back in time (present day) and we would have noticed something was a little amiss.

If time travel to the past were possible, I doubt it could take place in a state of mass.

Your entire premise is based on the assumption that time is malleable--that you can change what's already happened. A more realistic scenario, I would think, would be that my leg was chopped off in the year 2000 and now when we're in that room you're going to go back and make it happen, though I already have memories of what it is you're about to do (as well as a peg leg to prove it).

Time travel to the past must be impossible because if it were to oone day be invented the wouldn't we know already?

Exactly, that was the point I was trying to make.

well if somebody did change the time you memories about the previous version would just disappear so theres no way you could see stuff changing around you, however i do agree that traveling to your past is impossible (or atleast changing something in the past, maybe its possible to travel as just an observer).

there's this paradox that you travel back in time and kill your grandfather, if effect your never born, but then who traveled to kill the guy? nobody so your still have born, but then you go to kill..... you get the point. this can be explained if we assume that other coherent realities exist, meaning you can go to the past and kill your grandfather, and in that reality your never born, but when you come back, nothing has changed in your reality.

so its basically impossible to change your own history, but it might be possible to go back in time to what happened back then. hope i made atleast some sense

You are all looking at the idea with fairly simplistic views. How do you know that there are not infinite possible timelines or "parallel realities" existing simultaneously? - Just for an example.

We simply know nothing about the workings of it all so making threads with titles like "time travel is impossible" just because you have come up with a paradox in the simplistic view of "time travel" that you have is ludicrous.

But then again you could be absolutely correct.

We just simply don't know.

whoahh, you presented me a turd , but then you put some sugar on top

i was thinking 1 day about this and say i went back in time i could do what ever i wanted to because in the present nothing would change because it already happened so dosent that give the time traveler to do what he wants?





also i was watching back to the future 2 and i relized that when he goes to his future house he hides from his future self but wouldent his future self go wait a min i rember when i was younger i came here on this date and i hid in the closet so he would know where he was the whole time? am i right?

First off, there are many different forms of time travel that have been conceptualized (such as the branching off of other universes, and what-not) but to address the direct question of going back and cutting off someone's leg: why would their leg suddenly disappear in the "present?" It was cut off in the past. If it disappeared in the present that means it wasn't cut off in the past. On a single time line, that is.

But the whole idea of time travel has been done to death from a conceptual standpoint and a technological one. Doesn't mean it isn't possible; it just means I don't think we'll ever really know. Most things that deal with time, to me, are much more related to our perception of the world around us. Time appears to alter with sleep, lower states of consciousness, altered states, and indeed physiological functions--pressing the corresponding area of the somatosensory cortex before your hand still causes your awareness to believe the hand was touched first. Even if we somehow managed to go back in time, how do we know we are still in our own time line? How do we know that the act hasn't sparked a new, seperate time line? Not to mention the implications of a something suddenly entering a sustained universe is pretty big.

As well, the whole idea of time travel implies that there is such a thing as "time." It could be argued that it is simply a human concept used to better understand our world, such as a belief in "God" (though I'm aware certain primates also express, I guess, some response to a believed deity). They serve a purpose in thought but are actually quite untangible. I'm not arguing that they don't exist; I'm simply saying that some believe they don't, and if you throw out the concept of "time," time travel is impossible. Besides, if it does exist, it's much too relative. I don't see how we could manipulate it.

All in all it makes for interesting thought, but I think that thought leads essentially nowhere.

As much as I love the Back to the Future films, they don't come close to getting time travel right. I'm going to use those films as a tool in thinking about time travel. For fun.

Let me start off by saying that if time travel is possible [for us lowly humans], I see two possibilities (assuming none of that multiple timelines gunk):

(1) Any actions taken in the past or future are "already" written in the big history book of the cosmos and nothing new happens (say you bring a certain germ to the past and cause a massive epidemic--that epidemic will have been recorded in the history books long before you hopped into your time machine) or

(2) The past is as fluid as the future is perceived to be, meaning it is in no way set in stone. The great cosmic history book could then be rewritten daily (or, depending on the amount of time travel traffic, hourly). Save Lincoln, bam, a new history is created; some other time travel doesn't like it, he assassinated Lincoln, bam, another history is created, "yours" (the one you caused) being forgotten.

Possibility number two is unsettling--it makes me uneasy. It's far too conducive to paradoxes. In that view (ignoring any parallel universe ideas), your timeline (assumed to be the only one) changes completely--the 1985 to alternate 1985 switcheroo in Back to the Future, Part II. Somehow Doc Brown is committed, yet still drives (flies?) a Delorean to 2015 to give old Biff a chance to steal it and give his younger self the sports almanac. Go figure.

Which is why I like the first one. It may abolish free will (I suppose that's debatable), but it keeps the universe clean: if it's recorded in history, it will happen (either in the future or the past; it makes no difference which). Example: before preparing a time expedition to the past, you stop at the local cemetary. Lo and behold, there's your tombstone! In view number one, you can't alter your future (even if it is in the past)--even armed with the knowledge of your death, you'll still suffer it*. It avoids paradoxes, but I have no idea how. It simply does. That is, of course, why I favor it. In view number two, you could simply give up on the expedition, not go, and not die. Yet that gets rid of the tombstone and, consequently, your very reason for not going on the trip. Ugh.

*If that sounds familiar, a variation of it occurred in BTTF, Part III. "Young" Doc Brown (c. 1955) saw his own tombstone and therefore knew (or at least, should have known) thirty years later (when jolted back to 1885) what was going to happen. Therefore, Marty's presence shouldn't have been totally unexpected.

Now let's examine the consistency of the films:

For starters, we are to believe that Marty's presence in 1955 is changing what "originally" happened (though what does that even mean?). Yet there are several indications that Marty was always a part of history: we see that he's responsible for Goldie Wilson's career choice, Johnny B. Goode, possibly the skateboard, his parents' choice of the name Marty, maybe even Doc Brown's effort to actually construct a time machine (and other things I can't think of right now). Yet the altered present he returns to at the end clearly indicates that he in fact was not always a part of history but that his presence changed what "originally" happened. The story about George being hit by the car (something that in fact never happened) supports the view that Marty really did alter (not fulfill) the past. So that's a bit unclear.

Marty's memories are also puzzling to me. He remembers things that in fact never happened! He apparently (when he returns from the past) harbors memories of a life in which Biff if still a bully, his father is still a dork, and things are just generally different (see the movie for elaboration on that part). Yet he returns to a life in which his brother has a real job, his parents are happy, etc. But he doesn't seem to remember growing up in that house with that family--his memories don't seem to have changed as we see photographs do so many times throughout the films. Can we tack that up as some special consequence of the way the mind works? Perhaps. But you can't deny that it's as if Marty is returning to someone else's life.

Jump to the second film: old Biff steals the sports almanac and delivers it to his younger self. Wasn't he doomed to fail in his bid to be rich right from the start? If Biff had become rich we see that this would lead to Doc Brown being unable to build a time machine. So Biff couldn't be rich. If Biff is rich, Biff can't be rich. And yet he apparently was successful (until Marty and Doc foiled him--which apparently didn't happen the "first time around"). Tomfoolery with time.

Or how about the issue that (more than anything else) forces us to look closely at what we mean by "past" and "future": Doc's "death" in 1885. It's discovered in 1955 that Doc will (in the future) die in the past. This is an event that has both happened and not happened (yet). Since it is (from one point of view) "in the past" it is in a sense set in stone like the rest of the past (though, of course, the movies show time and again that the past isn't set in stone); the tombstone's sitting right there, clear as day. Yet this is an event that hasn't happened yet and since Doc (1955 Doc) knows it will happen he (1985/1885 Doc) should be ready for it without Marty's help. Yet he clearly isn't because he's dead! On top of that, this is another one of those vanishing-photo events that never took place (even though Marty remembers it).

In the same vein as Doc's once and future death, we have Marty's accident with the Rolls Royce. It happened in the past from the point of view of the 2015 McFlys (so it is, in a sense, already history) yet it's in Marty's future. And it never occurs. So they went to a future that won't happen where people remember a past that never happened. How confusing.

Let's consider what Igor Novikov calls jinn: something from nothing. An example would be something I've long wondered about--where's my time machine? After all, were I to develop one in the future then I could simply drop it off with my younger self (i.e. me right now). But since younger me now has a fully functional time machine there's no need for that whole thinking/tinkering/inventing phase--you don't need to figure out how to build a time machine when you've got the plans and finished product sitting on your desk! So the concept and the design will come from nowhere, having never been developed--they're jinn. I just have to make sure to drop the time machine off with 2006 Startraveler when I get a little older so the circle is complete.

Does this show up in the movies? Well, Doc Brown dreams up the idea of a flux capacitor, the thing that makes time travel possible. What happens almost immediately? He meets a visitor from the future who came back in time using the time machine he just thought up! Who's to say that in the week Marty stayed in 1955 Doc didn't study that DeLorean very carefully--he had it right there in his workshop.

Which is what I originally suggested: imagine building a time machine, get a rough idea, whatever. Wait for future you (or perhaps a 17-year-old future friend) to pop up with your time machine, study it, understand it, and there you go. Minimal work on your part--it practically invents itself. So are the DeLorean and the working flux capacitor jinn?* Could the Doc have built a time machine if he hadn't first seen it? And if it works in the movies can it work in reality? Where the hell is my time machine?

*'Course this leads right back to the question of "original" histories--did Doc "originally" not encounter Marty and the time machine? If so, then he could indeed have built the time machine without having to study the finished product in advance.

But it seems to me that this idea of an "original" history only makes sense if there is no reference point to compare it to. Meaning memories as well as photographs should be rewritten as history is rewritten. Or else nothing should change. This [central] question essentially amounts to this: was Doc wearing a bulletproof vest in the beginning of the movie? Or was the first time we saw him get shot different from the second time due to Marty's meddling in time? To me it seems they should be the exact same event and Doc should have been wearing a vest at the beginning of the film (he should also have known that Marty was about to travel back through time to make his rendezvous with young Doc). Yet, as I've said, the film seems to indicate at various times that history really did change and that some events are fundamentally different (i.e. Doc wasn't wearing the vest the first time Marty met him in the mall parking lot). Hmmm.


Let's have a little fun tracing some paths through time:

The Delorean (we'll be following its journey "chronologically," here meaning the order in which things happened from its point of view)

1985: the Delorean is purchased and converted into a time machine; Marty takes it backwards through time to
1955: the Delorean spends several days in young Doc Brown's workshop until it's sent back...to the future!
1985: Doc drops Marty off and heads off (with the car, of course) to
2015: the car undergoes a hover conversion, Doc scopes things out, Einstein is dropped in some kind of kennel; Doc then takes the time vehicle back to
1985: he picks up Marty and Jennifer and travels back to
2015: the problem with the McFly kids is solved but a new one is created; Old Biff steals the car and takes it to
1955: Old Biff drops the sports almanac off with his younger self; The Delorean is now in two different places "at the same time" on that day--wherever Old Biff parked it and in young Doc's workshop
2015: Old Biff returns, Marty and the Doc head back to
1985 (alternate): realizing what's happened and how to fix it, Doc and Marty head off to
1955: the problem is solved but unfortunately the Delorean is struck by lightning and flung back through time; At one point the Delorean is in three places "at the same time"--in young Doc's workshop, wherever Old Biff stashed it, and behind that sign where Marty and Doc landed.
1885: unable to use it, Doc stashed the time machine in some mine where it remains for 70 years until
1955: young Doc and Marty break out the now 70 year old time machine and send it back to the past; We learn now that the damn thing was in no less than four different places "at the same time"--young Doc's workshop, Old Biff's parking spot, Marty and Doc's landing site, and buried in the old mine (in "chronological" order).
1885: the train is used to push the Delorean and Marty back to the future; Once again, the Delorean is in two places "at the same time"--hidden in the old mine and in Doc's workshop.
1985: the Delorean's journeys come to an end when it is destroyed by a train

And what journeys they were. What a long and twisted ride that was! You'll notice that when I said the time machine was in the same place at the same times I always put it in quotation marks; I did that because that's a rather fine point. Chronologically they were at different times in the Delorean's 70 year lifespan, yet they are the same slice of time, the same calendar date.

As Uversa already hinted, MWI (Many Worlds Interpretation) of quantum mechanics has these paradoxes resolved. But it is just that, an interpretation

BUT, if you do assume that time is linear and not superpositioned with all probable outcomes as in MWI, then you have more problems than initially outlined:

1) Not only is it a pradox for you to take the action of cutting of a friend's leg (whilst in your future your friend has a leg) but it is a paradox for you to exist (older) in the past! When you look at it from the conservation of energy law/principle (which really extends to include that at any one point in time the universe has to have equal energy - conserved) you are in fact removing energy of rest mass from one instance of the universe and adding it to a previous instance. The energy being moved is on the order of E=(your weight + time machine)*c^2 - quite massive! That's the kind of feat time travel would have to perform, move massive amounts of energy between specific points in time and place, IMO, highly unlikely.

2) Be prepared for your time machine to go poof when you cut off your friend's leg in the past because you are quite likely creating a different future for yourself also. The police interview, the counselling (because the real you in that timeline didn't actually do any leg cutting) - the real you during that timeline will be undergoing some repercussions. Due to this and other factors you probably never will do the time machine thingy with your friend and hence no time machine for you to travel back to the future in.

If however, time is taken as change in energy form and/or position then to imagine travelling to the past would be akin to unrolling the change for everything except for the time traveller + machine. This cannot be done though because a multitude of events to be unrolled depend on the traveller and the time machine.

IMHO, time travel other than relativistic (or perhaps some other kind in an afterlife) is as probable as an elephant learning to jump. Not impossible but highly improbable.

I just gotta say I always love reading ai_guardian's posts I was wondering when he was going to respond to this. He is one of the few people that, I believe, actually knows what he's talking about in the area of physics on this site (don't worry, there are some others). He definitely knows more than me... but that isn't hard He is able to explain things both accurately and clearly. Okay, enough fawning by me.

i knew u would post a topic like this ive been waiting 2 weeks for it to be posted

The problem with that is there isn't a global energy conservation law--one that applies to the entire universe (or at the very least its a very debatable point).

I think part of the problem is viewing time travel as being in 'one instance' of the universe vs another rather than as there being one universe extended in four dimensions. Suppose a wormhole connected two points in space (perhaps held open in some very exotic way); would you consider the mere act of travelling through it to be a violation of energy conservation? It's been shown by Kip Thorne and others (on paper, at least) that if you have a wormhole it's possible to turn it into a time machine, if only by moving one off at relativistic speeds to get them out of sync in time with each other. Traveling through such a time machine-wormhole would, at its heart, be little different from traveling through a "regular" one. You'd be crossing a bridge between two particular points in spacetime. No big deal.

isnt it kinda true that if someone was to travel back in time then a continous loop hole would follow and lead to the destruction of the universe!

If the universe is viewed in four dimensions as you stated (which it most often is... don't think I'm a loon or anything), your point definitely makes sense. On the grand scale, something moving from point A to point B in the same contained system will not disrupt any sort of conservation law (disregarding any sort of effects of the travel itself, such as what is required to open or create such a wormhole). Yet, time seems to be a slightly diffirent beast than the other three dimensions. Spatially, I can move around failry easily in three dimensions, yet time seems to limit me to only one direction. Not saying it isn't possible to go back; simply that what is needed to move in that direction requires something different than the spatial dimensions. If we simply view the four dimensions as all having the same characteristics, then, yes, it does appear possible to simply link two points in spacetime and move through it. But the fourth dimension of time, appears, to me, to require something else. I'm guessing that once we discover exactly what this is, we can truly manipulate it.

I guessing I'm not really stating anything new here, and I don't really disagree with you. I just wanted to contemplate on the idea of time and how it appears to be different in quality than the three spatial dimensions. That difference, at least to me, seems to be the biggest stumbling block and one that can't be taken likely. Hopefully some of this made sense. Most likely not

And iceman15... what you stated is actually what I believe, and that's why I believe travel backwards in time isn't allowed by certain, likely undiscovered, laws. I'll have to start reading all my physics books again!

It's true that time certainly seems different than the spatial dimensions; I imagine that's largely due to the existence of an arrow of time.

Regardless, that hasn't stopped theoretical types from cooking up methods to traverse not just space but time as well. Besides Kip Thorne's work on transversible wormholes, there are the well-known closed timelike curves of general relativity; if you've got the right set-up of mass/energy you can get spacetime to do funny things. You could also look at something like the Feynman-Stueckelberg interpretation of antimatter in which matter particles actually emit more energy than they have, do a U-turn in time, and pass themselves (as an anti-particle) going back through time. Or Wheeler-Feynman absorbed theory in which photons emitted going backwards through time (the so-called advanced wave solutions to Maxwell's equations) played a central role. I actually collected some physical time travel scenarios in this thread.

No, because its the future he has travelled to when the accident involving the rolls royce had happened...when he goes back knowing this information, he then changes his decision to race flea causing an alternate history in which marty does not travel to the future...

cause and effect

i have seen all three films over a 200times each, im a member of the fan club and good freinds with bob gale and robert zemeckis. I have written them numerous letters regarding the paradox's n the film.
back to the future series rules...
any questions on all 3films, dont hesitate to ask...

Heres a question for you...why was docs mansion destroyed?

You are right, and I am certianly aware of the pecularities of relativity. I'm not doubting that time functions in a bizarre way and curves (as you have said, there is proof of this) yet US being able to force such curves in the manner needed and contemplated at the beginning of this threed seems a little far off. Evidence involving particles is one thing; obviously a person is something much more complex, though I know we need to start somewhere I do appreciate the link to that thread; I'll check it out.

This will throw a spanner into the works and make you re-think a little...

when the delorean is sent back to 1885 after being struck by lightning, doc writes down the repair instructions for the 1955 counterpart and buries the delorean in the abandoned mine...in the future, 1985, doc brown sends einstein for a minute ride into the future, then its docs turn, only doc doesnt go to the future he ends up being shot and marty goes back to the past, at the end of the film doc, marty and jennifer go to the future...you already know that, jsut a re-cap..

this is where it gets a little tricky...

before doc wakes marty up in the early hours of the morning...he takes a visit to the future and aquires the technology of fusion to power the delorean...whilst he is in the future he has all the time he needs to construct another time machine using another delorean, he is now in the year 2015 with the knowledge of all the outcomes of the histories that have unfolded, he then visits the year 1885 and picks himself up. now he brings the doc of 1885 back to 2015 to collect the other delorean which the doc of 1885 takes back to 1885...

now, in part ii doc is off to collect einstein from the suspended animation kennels, whilst he is doing that, marty is watching the results of the game, cubs win world series, at this point, the doc of 1885 appears in disguise, with double tie, wanders up to marty and says, i wish i could go back to the beginning of the season, put some money on the cubbies, he then wanders off, he gets back in his delorean and goes back to 1885. Doc then goes back to 1985 to ring marty...

doc was responsible for putting the idea in martys head, doc is pure genius, he uses the time machine to teach marty vaulable lessons...

if you watch back to the future part ii closely, youll recognise the doc in disguise.

if you wish to add anything to this feel free...
Also notice in part ii, when they leave the year 2015 and join 1985 youll notice as they accelerate towards 88mph, in the traffic infront of them, look out for the other delorean...

also look out for the clock with doc hanging off it in the beginning of part 1...

I haven't seen the films in a while but if memory serves the double-tied guy who says that was the guy (an older version, of course) from the beginning of the first one who was handing out "save the clock tower" pamplets.

edit// Looks like I was wrong: imdb calls that guy "Old Terry," whereas "Terry" was the guy in 1955 who had to clean the manure out of Biff's car. Still, it wasn't doc.

you havent seen them in a long while, in the first back to the future, its an old lady whos handing out flyers...
lol

your spoiling the fun, an elaborate theory crushed by a technicality...
i know its old terry, i just thought when i was a kid that he looked like the doc, with the hair..i came up with the theory when i was about 13.

Well, there's also the problem of the whole thing being totally out of character for Doc, who could barely manage to hand another version of himself a wrench (and that happened after the extra trips you're suggesting). I don't think Doc would want to teach Marty lessons via an encounter that could create a time paradox, the results of which could start a chain reaction that would unravel the very fabric of the space time continuum, and destroy the entire universe! Granted, that's a worse case scenario. The destruction might in fact be very localized, limited to our own galaxy. He's just not that reckless.

Your forgetting one thing...the young doc in 1955 at the time doc handed him the wrench didnt know that he was going to encounter himself, the future version did, thats why he tried to change his voice and the nervous act was a disguise...the reason the doc seemed shocked when the younger doc asked him to hand him the wrench was because his mind was pre-occupied and he was startled...

lets say though that it was the doc who told marty, wish i could go back to the beginning of the season and not old terry, could you find a flaw in my theory...
All good fun remember, like the films
ta

The thing I don't understand is: If there are multiple realities, why would going back in time send us to another one, and not in the same time line(reality) we're currently in?

If time travel to the past were possible, I doubt it could take place in a state of mass.



This is exactly correct.....I believe time travel is impossible in the physical plane....if you want to travel back in time right now....Its very possible and it doesnt require any type of MACHINE with complex fussions and gizmos......its called the Mental Plane, or the Astral Plane, there are many different planes that exists...you can enter them and learn what you need to know. then come back into reality were satan "rules"....communication through the brain....expand your mind and you will know past times and past circumstances, and even the future, because You will be in the physical plane but your thoughts will be in the year 1950. Im telling you folks.. the mind is a powerful tool that can learn and do.


Like in the bible it says...when the last days will come and we will all know that god exists and that satan is trying to take our soul into hell.. "we will be enlightened" means we will know everything....the concept of god and the concept of what the point of the universe...we will know every physical law/ boundary ....countless information will suddenly enlighten us. That is when time travel is possible.

Cheers Ourmoonlitsun, I feel flattered We all learn from each other though, the same sentiment goes to you also.

Ah yes the spacetime manifold, in that case you have a very valid point as conservation of energy may in fact have a global (spacetime) reach. But this then still leaves us with the grandfather paradox since the MWI, IMO, would be mutually exclusive with the manifold. There are of course the rather important questions of obtaining the exotic matter (and its existence) and whether the theoretical calculations really reflect reality.

Well, if the events have already occured, as your friend stands in present time, when you travel back into past time that would create another time line of present, because you would presently be in the past.

If i remember correctly, i was told a theory of time travel as to where you would have to exceed the present "time line" (as in the travel of light and all that comes with it [matter]), that way before that present hits the present where you are in your moment, you would be able to see into the past because that line of matter and time hasn't reached your position in your present time yet.

Not neccessarily. You might just branch off into a seperate reality, a "parallel universe". Whereas your friend that you left on guard would still have his leg and all his memories, when you chopped his past selfs leg off you would branch him off into a completely seperate existence.
Its like that show "sliders" from awhile back, an infinite number of universes existed simultaneously, and in each one the same people can exist, but lets say in one reality somebody got their leg chopped off in an accident while in another reality that same person didn't, that would have no effect on each ones existence.




your basing your theory on the assumption that if time travel is possible then one day we will invent a time machine. Maybe we go extinct before we ever come close, or maybe by the time we do invent one we will have evolved into an infinitely wise being (yea right) and decide that messing with the past is not such a good idea. and then again maybe we do invent one and we have been coming back to the past, and we just dont know it.

The solution to this is simple. maybe not lol.. one theory is You would not succeed in cutting your friend's leg off. things that happened already before you even entered the time machine.. so something happened to you before you could even get to your friend to cut off his leg.. maybe you decided not to, maybe you got killed before you could. You cant change anything since all is already been done.. get it? If A time machine was or will ever be invented, we would have already and always have been affected by them ( alien sightings??) If time machine will be invented then all the bad and the good has already been done and we just don’t know it.. its just how it is.. we live here and now but history is written already//.... now another possible theory is... u go back in time.. u change something.. and creates a new timeline/dimension so it doesn’t affect the fact that you traveled back in time to cut yer friend's foot off.. since you didn’t really travel back in time.. u traveled into another time line/dimension .. to yer friend in the other time line.. you never came back... ;-)

Can we see the past without affecting it? YES!!! lol how? There are many theories that make it plausible to be able to travel to unlimited distances in literally a blink of an eye.. using those theories ( look em up cuz I don’t remember them) lets say u point a highly advanced lense 2 light years away from earth that has the ability to see the eart all the way down to the ground... transmit what it sees through a "wormhole"( or whatever a theory calls it) to earth.. the transmission would hit earth immediately, but what the camera sees is 2 years old... meh. someone is soooooo gonna rape my theories ehehe, oh well that’s why its a discussion board ;-)

Peace
-skep

Everyone has a theroy of time travel. Mine however is simple. If you had a time machine and went into the past and did anything to change the future you would be lucky to make it back to the present. And any change you made would be unnoticed by anyone who lived beyond time travel. History could be altered at any time and may have been but if so no trace would be here to prove it except for the nut who caused it. History would just be rewrote without a gap or any sign of change. That little leap would be a great leap on paper for the future.

How about some of these -

Bill Gates has no friends and is a complete loner. He spends his time constructing and studying a time machine. At completion he goes back in time taking the technology of Microsoft with him, and just awaits technology of computers to grow to a point where his work is fully useable having corrected code on his young self's computer?

What if you took a week where there were no lottery winners, and went back to choose the winning numbers.
You would only travel a week back, still have your machine, but now a nice bank balance and all appearing legitimately.

Just a few ideas.

I would suggest that the majority of us given a one off chance before losing the machine would potentially save a friend or family member. Whether forcing them to not get in the car, or going for the hospital check-up before it is too late etc...



See above

its very impossible but future travel may be possible avthink about that!then you could masaca everyone and youll be the only one left

For an idea on what could happen if you were able to travel back in time try thr film -

The Butterfly Effect.

The Butterfly Effect is a good film i like its take on time travel its similar to the method in the film Donnie Darko in many ways yet is completely different

time travel is possible , but it isnt with a machine . i.e. science , it is a dimensional side step or merging, blend shift, so to speAK as it were,see / unnerstan?plain as the nose on yer face aint it?

Um hate to break it to you but time is just a measurement. See the universe just doesnt create alternate worlds of itself with the sun a few nanometers foreward. Time is nothing but the measurement of the movements of the universe, well physical universe if your into metaphysics.
Now all these theories and books on theories from scientists sound neat but at the end of the day its just science fiction.
Remember believe in proven fact no what they think is true. And math only looks good on paper. Youd be surprised on how many equations they had to touch up on.

Indeed. That's why experiment is necessary to back up this math. Experiments like these and this.

im not aving it i still thinks its a usless waste of time as you want to go back on time already spent....it ridiculas like my spelling...its never going to happen....i just cant see it someone tell me how this could even be the slightest and i know quite abit on laws and physics...

Okay time is nothing but the measurement of change or movement etc.... Nothing stays still and nothing remains the same. Everything interacts with everything weither seen or unseen.
Motion is an unseen force or technicaly a result of a force. Physics are never constant or how can I say it there not the same for everything or for every season. What something is and what its doing determines how the universe interacts with it. So technicaly yes its time is being altered but not in the sense that they are thinking of time as some entity or force or some dimension. You can speed up somethings time, slow it down or even reverse it but not in the sense your thinking.
Think of it as a car on a hill that rolled foreward, you can pull it back to where it was 30 seconds ago but that moment will not be the same.
Sure if you reversed the time on everything in the universe and put everything in the universe at the exact spot during that moment as it was thirty seconds or years ago; technicaly u would have time traveled but good luck on that one.

Then in what sense is time altered by relative motion and gravitational fields? I'm not sure I see what you're saying.

Hi,

Well, theoretically time travel is possible (according to The Theory Of Relativity). There are, actually, several models of time travel. However, all of them deal with almost infinite amounts of energy and require some exotic things (such as worm holes). So it is nearly impossible to build a time machine and even if you manage that you probably wouldn't survive the time travel.

But even if a time machine could be built there are many other explanations why we haven't seen any timetravellers. Maybe humanity will be destroyed before such a machine is invented. Or maybe in the future people will be living in the perfect society and they will also cease to be curious so they won't have any reason to travel back in time.

wazoo.

I here some people ask "Well, if time travel was possible, wouldn't we know, because we'd have time travelers appearing all around us?", then some reply that it's possible we go back into a DIFFERENT timeline(or "universe" if you will)... My problem with this is... If that is how it happens, then the universe or alternate reality we DO go back to, the people there are seeing evidence of time travelers. Why aren't we seeing time travelers from other time lines coming into our reality? What makes you think we're the "real" ones?

Actually Im pretty sure it has been proven that objects in motion experience time slower than objects at rest.
Its just that you would have to be moving at near light speeds to see any noticeable difference.
That saying that if you traveled to another solar system at light speed, when you returned everyone would have aged a lot more than you is actually true. That seems to be a form of time travel.

I've had someone explain to me how it works, and I still have a hard time understanding how it works.. >.>

Time Travel is science fiction. It's just not practically possible.

Consider this: suppose(and that's a big suppose)you have a very powerful telescope and a space shuttle that travels much much faster than light. Now, it's common knowledge that hubble images that we get from far off galaxies are images of the universe several light years away and what we see is not what presently is. That's because light takes so much time to travel. What does this mean? It means that we can view the past from a distance.

Maybe, we could take our space shuttle, travel faster than light, go to a very very far off planet in some galaxy and then view earth from there. If we can do that, then we can see our past with our telescope. There's no way we can see our future this way and we can't go and change our past and all but we can certainly see our past, record it and return back to earth. Think about it

The easiest way to think of it is as if space and time are on opposite sides of a balance beam. The more you travel through of one, the less of the other. So when you're sitting still (i.e. not travelling through space), you're travelling through the maximum amount of time. But as you start moving faster and faster the balance starts shifting and as you approach the speed of light you're covering more and more space but less and less time.