Let me first off say that no, I don't believe that time travel is possible. There are no time machines or government conspiracies concerning time travel in my opinion. Maybe one day time travel will be possible, who knows? But thats not what my thread is about.

This thread is about the possibility of being able to alter the present/future by traveling to the past. Ok, lets assume time travel is possible.
No we have all heard stories and seen the movies where a person travels to the past, and their actions whilst in the past somehow change the future.
A lot of time travelers in these stories always say things like "don't do anything, don't touch anything, it could have drastic effects on the timeline and we maybe return to our own time to find it different from our own."

This isn't the best example, but most of you have probably seen the movie, Back to the Future. In the beginning Marty comes from a poor family where his father works for the man who used to bully his father at school in the 50's. Marty traveled to the 50's and his actions there gave his father courage to stand up the the bully. He then returned to the future to find his family now richer, and to find the bully works for his father, all because of his actions in the past.

I do not believe this is possible. I think that it doesn't matter what you do if you were to travel the to past, you cant change the future. Why?
Because it is the past, its already happened, you've already done it.
Let me explain with examples.


Imagine a museum a hundred years ago. The museum contains a large diamond. This diamond suddenly goes missing and it never seen again.
Lets say I have a time machine. I want this diamond. So I go back in time to when the diamond was still in that museum and I steal it for myself.
So why did the diamond go missing in the first place? Because I stole it.
I hope that makes sense.

When time travel debate is occurring, I bet you have heard somebody say "what if I went back in time to before I was born and killed my father."
I still don't think that would alter the present or pose any risk to you. Heres why:
First of all I don't think it would be possible to kill you father while you are in the past. If you manage to kill him then he obviously wasn't your father in which case Id investigate whether your mother had been fooling around with the milk man. I don't think you will be able to kill your father because if you do, you will never be born and you wont exist to go back in time and kill him. So in order for you to be alive right now, something must prevent you from killing your father.
But if you were able to kill him, I don't know what would happen. Possibly a sort of never ending paradox?
You go back in time to before you were born. Lets say you do manage to shoot your father in the head and kill him. Meaning he will not live on to get kinky with your mother and create you. Meaning you will never exist. And since you don't exist you wont be able to go back in time to shoot your father, and so he wont die. Which means he will live on to create you. And everything will be fine. But then you could just kill him again and the loop would repeat itself.

The basic idea is, you cant change anything in the past, because you have already done it.

Id like to know what you guys think of these ideas.
I know these ideas aren't foolproof, and you can probably find a lot of holes in it. In fact Id like to hear them if you have any. I might even be completely wrong and these ideas are impossible. I just tend to think about things like this late at night when I cant sleep. The mind wanders doesn't it.
I thought Id finally get my thought down in text somewhere and have a discussion rather than them swilling around my head.

If you made it to the bottom of this post, thanks for reading.
-The Sherlock

Our perspective of the past can change. That's the closet i believe that we can come to changing the past. Perspectives change through age and experience.

Excellent post, The Sherlock. You describe in a very understandable way the same thing I think about the topic. Although, being a mathematician, I'm really not good in judging what's understandable. Anyway, the diamond example is neat. Did you borrow it from somewhere, or are you to be credited for it.

The concept you explain actually has a name. It is known as the Novikov self-consistency principle.


On another note, if time travel is not possible, then changing the past could be possible.
Let me explain: If, and only if, time travel is not possible, then the past does not really exist. Memories, footprints, &c. exist, but they exist in the present and are accessible and, at least theoretically, can be altered. Okay, changing other people's memories won't really work practically. But people die, and newborns won't know. A government so repressive that it can exert complete control over what people are talking about could change past history. Still just theoretically, it's not practically possible.

I couldn't think of anything else than time travel which would prove that the past is physically existent apart from evidence. So I think only the possibility of time travel could make changing the past impossible.
Mind-boggling, eh?

Thank you. It took quite a while to explain it in terms that would make sense. And yes, the diamond idea is my own.
I had to think of an example to give to try and help people understand the concept and thats what I came up with.

I knew I probably wasn't the first to think of this idea, its nice to finally be able to put a name to it. Although I did actually come to that conclusion and think those ideas straight from my own head, years ago without any previous research into the topic. I still figured I wouldn't have been the first to think like that. Shame really, I could have been famous.

Id also like to hear if anyone does believe that you can alter the present by changing the past. Through time travel of course. Although I agree with Invader Skoodge's idea, of only being able to change the past by changing people's memory of it.

I know you said you'd like to hear from people who DO believe, but I thought I would share this anyways. I read this in a very good book by michio kaku,
At some point in the book I remember a part in which he offered a solution that described traveling in time, and why you CAN'T change the past.

Basically, the question that is often asked is whether or not if one were to travel back in time,..can they change the present?? For example, someone traveled back in time and killed their parents, would they cease to exist? how would this affect the future???

The answer is that this is impossible because there must be a "force". A force that prevents our free will. Think of life today and the force of gravity. Gravity is a force that prevents our free will. We cannot run up walls, walk on ceilings, jump 100ft, ect... Gravity is a force that in a sense, restricts our free-will. Well there may be a similar force that prevents our free will if we were to travel to the past. Unlike gravity however, this force would not restrict our movements and such on this planet, instead this force would restrict our actions towards events that would inevitably change the present...

note: even today, not a lot is known about the force of gravity, and it is still considered pretty mysterious, just think of such a force when traveling in the past. Of course it will be confusing and difficult to understand, perhaps near impossible to comprehend. For the simple fact that we haven't ever traveled back in time, such an experience would certainly unearth all sorts of new and unfamiliar things, not to mention something as complicated as this force. All we can do is theorize, in this case, we compare 'gravity' and this 'force in the past' ,... each are forces that restrict free-will, each in its own unique way.

lol I don't know if this helps anyone, but when I read this, I thought it was pretty neat.

This is a subject that intrigues me. Einstein believed that if you travelled to the past and affected the future you would affect events on a paralell earth and not the one you travelled from. Physicists believe that you could only travel back in time to the point where a time machine was invented, so they give us reason to believe that it is possible and maybe in our lifetime.

oh and also.....you all should watch the movie "PRIMER" if this subject is of any interest to you. It as an amazing movie, really makes you think about time travel and its consequences.

To truly go to the past it would need to be exactly as it was the first time around, otherwise it isn't really the past. Your presence there would make this impossible, physically anyway.

Ok I would like to ask then. The diamond was not stolen in the future. You went back to the past to steal it. What happens then.

If you went back in time to stop the twin towers from crashing down, then in the present, they would never crash down, meaning you would never have been to the past, because there would be no reason since the twin towers never crashed.

Excellent, this is exactly what I was trying to say when I gave the first example of killing your own father in the past.
"So in order for you to be alive right now, something must prevent you from killing your father." - My original post.
There must be a force that prevents you from doing so. Whether it be that you cant bring yourself to do it or something else gets in your way. Does it prevent free will? No free will is having no choice, but theres always a choice. The reason why I think you cant do it is because the past is already "set in stone." Its already happened so cannot be altered. But then there is no choice, is it destiny?


Im not sure what your trying to say. Are you saying what if the diamond didnt get stolen?
Well if the diamond was still there in the present, then it would have never been stolen in the past. Which means I wouldnt have to go there to steal it. So I dont travel back in time and the diamond remains in its place. Simple eh?

i've read many articles concerning about time travel and parallel universe
maybe if parallel universe theory is correct grandfather paradox might be solve
using 2 dimensions of space which i think the other one is the probablity which suggest that all possible outcomes are all exist in other universes
http://www.telegraph.co.uk/earth/main.jhtm.../scitime110.xml

anyway i guess i should keep myself open for there are many possible answers

When considering time travel, you need to think of the perspective of the traveler (as most do), the scientists he leaves in his origin time, and the perspective of the people that the time traveler will meet.
consider all of these points of views when thinking about time travel...

Lets say for example John and Ray are two scientists researching time travel. It takes them 3 days to set up the experiment to have John travel into the past, while Ray stays behind to observe.

Now considering that potentially anything could happen, John and Ray devise a method of communication... we will assume that a Chaotic Communicator System would be made to aid them in communicating (this is using Particles bonded together so that no matter how far apart they are able to instantaneously communicate/react) like a pair of walkie-talkies, perhaps even broadcast video if given more time, but lets just say they can talk to each other across time.



Now the day arrives that everything is ready, and John decides he will travel back 24 hours into the past. Ray gets everything ready and ZAP! John disappears from Ray's view.

John emerges in the same room as he was, only occupied with a John and Ray in the midst of setting up everything for a time travel experiment.

John and Ray are surprised at the emergence of this new John who claims he is from the experiment they are about to undertake... in fact, lets say that Ray is so surprised he drops a vital piece of equipment... thus ruining any chance of having the time travel experiment happening within the next 24 hours.

John the time traveler, looks worried... so he opens up the channel using his Communications device and contacts Ray from his origin time. (we will assume that the "Ray" and "John", who are setting up the experiment haven't turned on the CCS's yet, otherwise Ray's Communications unit will start beeping to be answered)

Ray from the Origin time picks up the Comm, John asks if anything has changed in the sequence of events since he left. Ray replies "No John, you just disappeared and nothing has changed yet, at least I don't feel any different, anything happened over there in the past?". "Yes", replies John, "I'm standing in front of our past selves, in fact I scared the pants off of both of them, and Ray here dropped a part which will delay them from making our experiment within the next 24 hours".

Now lets get into 2 possible situations, this one being that Time traveler John has no way of returning back without a time travel machine:

Eventually, 10 days later, John and Ray manage to repair the damaged part and decide to help "Time traveler John" return to his origin time, but this would mean setting the time machine to go back 9 day into the past. (remember John traveled one day into the past in his initial voyage, and due to the 10 day wait for the part to get fixed, he is now in a pickle of a situation.

Here is a second possible situation: John's time travel device is portable:

"Well thats ok" says Time traveler John to two bumbled scientists, "I'll just go forward to my origin time... just 23 hours back into the future." (we will assume Time traveler John spent only one hour visiting in the past). And he presses the button... ZAP!

John and Ray see time traveler John vanish... So they work on fixing the part that Ray dropped... eventually 23 hours of tinkering away at the broken part and ZAP! Time Traveler John re-appears before John and Ray again.

John the time traveler is perplexed, yes, he did go 23 hours forwards into the future but not to his origin time. Ray, who patiently waits at the origin time hasseen no re-appearance of Time traveling John... Time traveling John is now technically a displaced entity.


Interesting problems arise when considering all of the Points of views... The traveler himself, the buddy scientist he left at the shop, and the people he meets in the Past, and any potential future traveling thereon.

tbqh, I dont think that time travel will ever be possible. It's just so confusing to think about.
What happens with your body?

Heh, you never know.
One thing I've pondered is the effect of the person as a whole.
When someone actually does time-travel a lot of questions will be answered,
Such as body and spirit/soul questions may be a lot clearly defined, as well as understanding how our body/brain/mind works in such cases.
Like visiting yourself in the past... how does the spirit or soul cope with multiple bodies? Can the mind see through your current body and the body of your past-self? Many weird things like that.

On the Diamond and force theory, because you stole the diamond in the past, when your in the future, the 'force' makes you go into the past and steal the diamond, that way everything is balanced. No offense to 'The Sherlock' but without the 'force' telling him to do it, he would be doing it on his own free will. Lets say that it was a robber who stole the diamond, not you. When he gets to the diamond he sees that someone (you) have already stolen it, therefor changing the past. So I'm not sure if that's really clear for everyone but in dumb ass terms it means if there was no 'force' the past would be altered. so if there is no fore, the past can be altered.

I Also have a theory (after thorough research) On how to travel back in time. The international Date line. If you could somehow travel fast enough to go around the Earth so many times so you cross the international date line many times. You may only get about a few days because of a 'force' but there is no rules on how far back in time you have to go.

Yes, I see your point. But I think if my theory is correct, this is how it would go.
John and Ray decide to make a time machine in the next three days and then send John back in time to the day they decided to make it.
Now, assuming they are successful in making the machine in the future, as soon as they start to make it, future John should appear. Which confirms thier success of making it.
Your thinking of time as a straight line, I guess Im thinking of it as something that can be bent and twisted into lots of wibbly wobbly shapes.
Im not saying that WOULD happen. You could be correct for all I know. Its actually interesting to see the different perspectives on this.


Thats possible, yes. Without that force acting upon you anything is possible. You could even kill your father I suppose.
But my point was that the fact you are already alive, means that your father never died.
But I see your point about the diamond one yes, it could be possible that a regular robber stole it the first time around and the second time, you go back in time and steal it instead therefore changing history.


Im not quite sure if that would work. If you travelled around the earth in the opposite direction to its rotation. You would just end up back where you started. Lets say you took off from a certain airport and it took you an hour to travel the circumference of the earth. By the time you land at that airport again it will have moved forward by one hour. So you wont have travelled in time. But I suppose if you did a FULL lap of the earth, the point you stop at wouldnt be the point you started at. That will be an hour ahead. So your watch may say 5pm, but the time zone of the location you're at would be 4pm. Is that time travel? I have no idea. Im not even sure if what I just said actually made sense. Haha.

well if your going back an hour than yes its time travel, but i see your point in the flaw of my theory.



Lets say that their was no force for a second, (not that im saying there is) You decide to kill your father. You manage to kill him but relise your disappearing. If there was no force and you could kill your father you would cease to exist like you father. Lets say that if you do this, everyone thinks you killed yourself. Now onto your mother, she would marry someone else and have baby's, that's a new dad for someone else. Now that person's wife would get together with someone else. See what I'm saying?. If it were possible to kill your dad because the force didn't exist,Nearly
everything would change. Not only who married who but people creating things. Lets say Fred invented a time machine because his wife died and wanted to save her. He makes the time machine and goes back and his wife is saved and goes back to his time to see what has happened. Now there is more than one possibility here.

Theory 1: He goes back and see's that his wife is still dead, But not in a car crash, this time she was murdered. This theory is that whatever you do you can't change the past.

Theory 2: He goes back and see's his wife. Because he wasn't stressed because his loss of wife, he doesn't make the time machine therefor he never went in the past. This way doesn't work either.

Theory 3: If somehow he got back and everything was perfect, he built the time machine already (which is very unlikely) than all is swell Except one thing. What about the money the grave digger got? he could of really needed the money. Therefor if you can change the past it can't all go to planned. Something always goes wrong.

Who ever read this, I am proud of you to read so much.

I have always believed that time travel is more than possible that in fact I have had the pet theory that alien abduction is us in the future trying to alter the future by tinkering with the past. That having been said I think it fails, only because I truly believe that time is self encapsulating. In other words for every excursion into the past you create a new timeline, a new future that once you change you can't ever unmake.

Lets take time travel movie plots to illustrate this. The second installment of the Terminator has always seemed wrong to me in that with the destruction of the Arnold model time should have reset itself, there was no sky net, kyle was never sent back to stop it, time should have resolved itself.

The best example I've seen of this is the episode of Star Trek the Next Generation where Wharf is being shifted through multiverses where he doesn't belong, and each has subtle to dramatic differences from his own universe, all predicated on the choices made, that each choice created a new universe.

In that way I think time travel would create a different time line, the original exists, but you would have no access to it, nor the future that happened later from it, because you altered it. You would be stuck within the new timeline, unable to move forward to either the future you came from or the new future you created. Therefore the change you hope to effect in the future whatever it is, would be only known to the timeline you change. You would effect nothing in your own future, so nothing could be "fixed".

If you went back to save President Kennedy from being shot and succeeded, you would not be able to go either to the future to see the fruits of your work, nor would you be able to go back to your own future where he died. You would be stuck and have to live out your life from the moment you stopped the assassination because at that moment you created a new timeline.

(I'm a time travel geek can ya tell?) hehe...

In my explanation, Paradox is impossible.

The idea that if you went into the past and killed your father, that it would mystically make you disappear or erase you, to me seems terribly flawed.
Your history is already written, and when you enter the past, the interference you make proceeds forwards with boundless effects on what happens next... and thus scooting back to your "original" time just projects you forwards along this rewritten time. In effect you could never return to your "origin". Even if, seemingly, you did nothing to change it (but as we all know, even the observer works wonders in the double slit test... hehe.)

Interesting thing is if you instead if traveling to the past, go forth into the future, say 10 years and then return, you can return to your origin time. However the future you "see" is one without you being present during your traveling time, which would then be totally different than you being present and living/interacting along those ten years. That butterfly-effect does not cause "minor" changes, it would cause massive changes. In a sense science would then understand how critical our lives are, intertwined creating cause/effect in every thing we do as individuals.

At least... in what I believe to be true.
I cant wait to hear if someone has been able to travel time. It would be very interesting to find out what does happen when traveling into the past or the future... I only hope the traveler is prepared with proper devices to communicate with the Origin time. I'd hate to hear that the traveler simply disappeared, never to be seen again when in all likelihood he may still exist within a rewritten fold of time.

Remember the force theory, if there was a force, you wouldn't be able to kill your dad. But if you kill your dad before he helps your mum in
creating you-No you-where do you go? To where dead people go? No,you already exist in your time so i have two theory's

Theory 1: You disappear into another dimension.

Theory 2: You create another time line other from your own unable to swap lines unless you go back and undo what you did to make this happen (but because you unfortunately do not exist to do this, this has become a permanent time line) pretty much what he said.



This depends on when he tells someone. Say he tells someone in the past, this could endanger alot in the past(saying that there is no force) Although if he tells someone in the future it would not harm the time line because it would of already been made.

On the force topic, I'd just like to add this: Just think how powerful it must be, if its not like gravity, it must be within us.... Thats something to think about.

Ive thought about this too, travelling to the future.
If you were to travel 10 years into the future. It would be different to how it would be if you just waited the 10 years.
Whether its significantly different or just slight different. It would be different.
Because 10 years have passed without YOU there. To everyone else, you dissapeared for 10 years and then popped back.
So you wouldnt be able to meet your future self in that time.

Unless the alternate universe theory is correct of course. Then it would be possible.

Unless off course if after you go to the future, you decide to go back to the past if he hadn't changed anything.
The way i would do it would be to when i go back, ten years later, tell my other self that came from the past what he must do.

so are u asking whether or not history is still history if no one has any knowledge of it ?
if someone had a time machine and went into the past to try to change something, then what history records as history to those in the present would be the outcome of whatever the time traveller was able to guide or influence past events into... is that what ur saying ?

then doesn't that deny the existence of free will ?

for example, if a time traveller from 2058 went back in time to 2001 would she try to stop the September 11th attacks, or just stand by and watch them happen ? (its history to her after all, she knows they happened so why bother trying to change something that u can't change) How would she know whether or not her doing something... or anything... or nothing... when in the past contributes to the WTC disaster or helps the struggle on UA flt 93 ?

wouldn't the fact that she's there in 2001, make her part of the timeline of September 11th and so not only neccessary for events to pan out as history records, but essential that she be there for the 'present' (2058) to be what it is ?
then does it follow that if there is no free will for her in the past, then coz that past is someone elses 'present' and those 'present' events cannot be changed by the timetraveller, then events in the 'present' are also unchangeable...

i.e. there is no free will for ppl in the present either !! ?

i tend to think of time travel in this way : If the President of America, Walker Bush, today went back in time to before he first stood for Governor of Texas in 1994 and changed his name around so it read George W Bush, would we know it had ever changed ?

Min xx

Unfortunately I can garantee you that in your life time,.. you will never see "anyone" time travel. Im not saying you will never see "time travel". Infact,...there are experiments that have been conducted and one that is about to be done, which will prove information can be sent through time"

In one of your earlier posts you were talking about chaotic communicators or something. You are refering to the phenomena of "quantum Entanglement" you may like to read this very interesting article about an experiment which is to be conducted VERY soon....

these two articles talk about the experiment

(read this one first)
http://cosmiclog.msnbc.msn.com/archive/200.../17/274531.aspx

then read this one (more updated info as of jan 2008)
http://cosmiclog.msnbc.msn.com/archive/200.../09/566532.aspx

You still have that diamond ??