# Time Travel is impossible

#### fanavans

##### Junior Member
Time Travel is impossible

I know I haven?t been on the board very long?. Oh Well, here goes nothing? NB I have described it as a conjecture for now

The Fanavan?s Conjecture

A person cannot travel back in time with his/her corporeal body into the same universe if they have experienced the history of that universe.

Theory

Definitions

T is a point in time.

x,y,z are arbitary points in space. More dimensions of space can be added without change to the theory. Note that they are variables.

Working out

W, proposed time traveller, exists today at T(0),x,y,z.

If W travels back in time, his physical/corporeal body exists at T(-1),x,y,z.

No two bodies (fermions) can occupy the same point in spacetime (cf, http://en.wikipedia.org/wiki/Pauli_exclusion_principle , http://wings.avkids.com/Curriculums/Air/ti...e_in_glass.html )

If we allow W to travel to T(-1) it can be said* at T(0) that W occupies T(-1),x,y,z

Thus if W leaves T(0) W cannot arrive at T(-1),x,y,z because he is already there.

Nor can W arrive at T(-1),A,B,C because at T(0) W would already occupy that spacetime.

Nor can W arrive at T(-2),x,y,z because at T(0) W would already occupy that spacetime.

Therefore W cannot arrive at T(-t),x,y,z.

Therefore W cannot travel back in time with his corporeal body in his same universe.

Example

A Girl travels back one hundred years in her own universe in a time machine she has built. Once in the past, she does some stuff and then dies a natural death. She is born 60 years later, grows up and builds a time machine. She enters her time machine and travel?s back one hundred years. But when she gets there, she is already there. So she finds she cannot stop or materialise or whatever ? in short she can?t ?be there? because she is already there. Since she can?t be there, she can?t go there therefore time travel is impossible.

Problems(or things that need to be flushed out)

1. I marked a paragraph above with an * where I said that W could be said to occupy a particular position in spacetime. It is impossible to say any object occupies a specific point in spacetime as a result of the Uncertainty Principal. However, I do not believe that this is relevant when we are talking about bodies the size of a human. (Suggestions?)

2. You might well argue that at the point immediately proceeding W?s arrival he is not occupying that point in spacetime. You would be right. But travelling back in time is not the same as walking to the other side of the room. You are not on the other side of the room, and when you get there, time would have passed. W is in the time he travelled to, therefore he is occupying that point is spacetime, and cannot go there.
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I await fame or infamy?

Fanavans.

#### Omega

##### Junior Member
Re: Time Travel is impossible

Once you enter a time in the past in your own universe, one in which you already inhabit in the past, you have changed that timeline. And everytime you "loop" back it will change.

Try this one on for size. If a person is a lesbian in the past and still is in the present. Can that person go back in time and try to have a relationship with theirself?

#### StarLord

##### Senior Member
Re: Time Travel is impossible

Omega,

Would you be able to handle making love to yourself right this very instant, regardless if you were gay or not?

Don't you think all of that would resolve into a big confusion as neither of you could decide at that moment about who gets to bite the pillow?

#### fanavans

##### Junior Member
Re: Time Travel is impossible

<div class='quotetop'>QUOTE(\"Omega\")</div>
Once you enter a time in the past in your own universe, one in which you already inhabit in the past, you have changed that timeline. And everytime you \"loop\" back it will change. [/b]

So what you are saying is that you cannot enter the past of YOUR universe, because your presence there changes the timeline. That accords entirely with my theory.

Try this one on for size. If a person is a lesbian in the past and still is in the present. Can that person go back in time and try to have a relationship with theirself?

No. Because you can't go back to your History.

Fanavans

##### New Member
Re: Time Travel is impossible

If you believe that W at T(-1) and W at T(0) are the same then your theory has a problem, because you forgot the arrow of time. When W is at T(0) it has left T(-1). That's true for anything else in T(-1). Therefore W can travel from T(0) to T(-1) and to any spatial location. Even causality would be preserved. W wouldn't have much company, though.

#### Harte

##### Senior Member
Re: Time Travel is impossible

Fanavan,
I have a few comments on this.

<div class='quotetop'>QUOTE(\"fanavans\")</div>
The Fanavan?s Conjecture

A person cannot travel back in time with his/her corporeal body into the same universe if they have experienced the history of that universe.

Theory

Definitions

T is a point in time.

x,y,z are arbitary points in space. More dimensions of space can be added without change to the theory. Note that they are variables.

Working out

W, proposed time traveller, exists today at T(0),x,y,z. [/b]

Here you specify a point in time {T(0)} but leave unspecified the spatial coordinates. This mathematically implies that W occupies all the 3 dimensional universe at T(0). Therefore your analysis would only be correct in that the entire universe cannot be somehow brought backwards in time. I submit you should say here that W exists at T(0),Xat T(0), hence he need not occupy the same space.
Your argument could be used to "prove" the impossibility of your own existence. After all, by your statements, it's fair to say that at T(0), you also occupied T(-1),x,y,z, if you haven't moved.

<div class='quotetop'>QUOTE(\"fanavans\")</div>
Nor can W arrive at T(-1),A,B,C because at T(0) W would already occupy that spacetime.

Nor can W arrive at T(-2),x,y,z because at T(0) W would already occupy that spacetime.[/b]

You have defined repeatedly the space W occupies at T(0), why do you continue to insist that W also occupy the same space for all T?

<div class='quotetop'>QUOTE(\"fanavans\")</div>
Therefore W cannot arrive at T(-t),x,y,z.

Therefore W cannot travel back in time with his corporeal body in his same universe. [/b]

This conclusion is not supported by your statements. The only conclusion you can arrive at through these arguments is similar to the grandfather paradox. It is impossible for one to travel back in time and enter a universe where his existence was already established. Considering that a first-time time traveller must by definition never have travelled into the past, how can we explain his existence there in the past prior to his use of the time machine? This is arguing in circles, a phenomenon that time travel is replete with.

<div class='quotetop'>QUOTE(\"fanavans\")</div>
Example

A Girl travels back one hundred years in her own universe in a time machine she has built. Once in the past, she does some stuff and then dies a natural death. She is born 60 years later, grows up and builds a time machine. She enters her time machine and travel?s back one hundred years. But when she gets there, she is already there. So she finds she cannot stop or materialise or whatever ? in short she can?t ?be there? because she is already there. Since she can?t be there, she can?t go there therefore time travel is impossible. [/b]

This illustrates what I was saying above. The presence of the girl 100 years in her past cannot be explained using standard models of logic and analysis. This does not invalidate the idea of time travel into the past, however. The problem here stems from a logical progression of events in the spacetime continuum. That is, it appears that, since the time "loop" was made, the girl is fated to continue travelling into the past over and over. The way out of this process is to realize that the universe is not being made over here. The girl goes into the past, lives and then dies. The ultimate cause for what happens during her life in the past lies in the future. This is a juxtaposition of cause and effect that we are unused to. It doesn't mean that it can't happen though.

Not trying to be critical here, it's just that there is no scientific basis for the idea that time travel is impossible. At least not yet. I trust those brainiacs that sit around figuring these things out enough to take their word on this, that physics does not (currently) rule out the possibility of travelling into the past.

Harte

#### fanavans

##### Junior Member
Re: Time Travel is impossible

<div class='quotetop'>QUOTE(\"Harte\")</div>
Here you specify a point in time {T(0)} but leave unspecified the spatial coordinates. This mathematically implies that W occupies all the 3 dimensional universe at T(0). Therefore your analysis would only be correct in that the entire universe cannot be somehow brought backwards in time. I submit you should say here that W exists at T(0),Xat T(0), hence he need not occupy the same space.
Your argument could be used to \"prove\" the impossibility of your own existence. After all, by your statements, it's fair to say that at T(0), you also occupied T(-1),x,y,z, if you haven't moved.
You have defined repeatedly the space W occupies at T(0), why do you continue to insist that W also occupy the same space for all T?
[/b]

I didn't mean to maintain that W occupies the same space for all T. This was a mistake in notation.

Consider this - if you looked at a graph with two axis (T,X). This represents the universe in all space and time. If you looked at the graph, and time travel had occured, you would see a non-continous line W. The line would run up to (0,1) (Where the number for X is arbitary) It would also run from (-100,2) to (-50,3) (Again, X is arbitary.) Now, if at T=0 W tried to travel back to (100,2) he would run into the line that is already on the graph.

This conclusion is not supported by your statements. The only conclusion you can arrive at through these arguments is similar to the grandfather paradox. It is impossible for one to travel back in time and enter a universe where his existence was already established. Considering that a first-time time traveller must by definition never have travelled into the past, how can we explain his existence there in the past prior to his use of the time machine? This is arguing in circles, a phenomenon that time travel is replete with.

This illustrates what I was saying above. The presence of the girl 100 years in her past cannot be explained using standard models of logic and analysis. This does not invalidate the idea of time travel into the past, however. The problem here stems from a logical progression of events in the spacetime continuum. That is, it appears that, since the time \"loop\" was made, the girl is fated to continue travelling into the past over and over. The way out of this process is to realize that the universe is not being made over here.

I would argue that logic does apply, and that it fails is proof that it is impossible. Logical impossibilities are often used as proof. Reductio ad absurdom or somthing like that...

That the universe is not being made over is again an important point - the alternative is that the universe already exists where W is trying to get to. Because he already exists there, he cannot go there.

Not trying to be critical here, it's just that there is no scientific basis for the idea that time travel is impossible. At least not yet. I trust those brainiacs that sit around figuring these things out enough to take their word on this, that physics does not (currently) rule out the possibility of travelling into the past.

Do you think that we cannot logically exclude it? Perhaps even in another way? I know that logic is not the be all, but I wonder if effort has ever been put into this question? I also know that science says it is possible or at least hints at the possibility - but - but - I think that it is impossible to exclude it on the basis above.

Thanks for the great feedback!

Fanavans

If you believe that W at T(-1) and W at T(0) are the same then your theory has a problem, because you forgot the arrow of time. When W is at T(0) it has left T(-1). That's true for anything else in T(-1). Therefore W can travel from T(0) to T(-1) and to any spatial location. Even causality would be preserved. W wouldn't have much company, though. [/b]

Has he left T(-1)? Does T(-1) exist? If it does then W must be there. It is doesn't how can W go there? If W creates it by going there then it violates the pre requisite that W is going into his own history.

Fanavans

#### Harte

##### Senior Member
Re: Time Travel is impossible

<div class='quotetop'>QUOTE(\"fanavans\")</div>
Consider this - if you looked at a graph with two axis (T,X). This represents the universe in all space and time. If you looked at the graph, and time travel had occured, you would see a non-continous line W. The line would run up to (0,1) (Where the number for X is arbitary) It would also run from (-100,2) to (-50,3) (Again, X is arbitary.) Now, if at T=0 W tried to travel back to (100,2) he would run into the line that is already on the graph.
[/b]

Fanavans,
The traveller would have no trouble were he to leave the graph, then re-enter it at the desired point. This is the methodology for time travel (into the past). The only ways the scientific community have been able to even theorize time travel involve a departure from the universe, and then a re-entering. Usually what is involved is a trip near a source of outlandish gravity, which is known to produce holes in spacetime. That is not to say that there cannot be some other way, just that this is the only method where time travel has been shown to be possible up to this point.

<div class='quotetop'>QUOTE(\"fanavans\")</div>
I would argue that logic does apply, and that it fails is proof that it is impossible. Logical impossibilities are often used as proof. Reductio ad absurdom or somthing like that...
...Do you think that we cannot logically exclude it? Perhaps even in another way? I know that logic is not the be all, but I wonder if effort has ever been put into this question? I also know that science says it is possible or at least hints at the possibility - but - but - I think that it is impossible to exclude it on the basis above.
[/b]

I think it would be a mistake to attempt to use what we think of as logic in order to exclude the possibility of time travel. Time travel itself is full of illogicalities. It would suffice to say something like "first the vase broke on the floor, then it fell to the floor." The idea of a definite direction for causality is deeply ingrained in what we call logic. Were we to use logic, it's only necessary to say "It is illogical that an effect can precede a cause, therfore time travel is impossible." And we have end of discussion. I wish to continue the discussion. Until there is some reason to believe otherwise (i.e. scientific evidence), I will continue to believe what my previously mentioned "brainiacs" say on the subject.

Harte

#### Maggot7

##### Junior Member
Re: Time Travel is impossible

Time travel is possible there have been time slips reported all over the world and look at the philidelphia experiment it teleported from pennsylvania to Virginia and steven gibbs has teleported thousands of times and u time travel whil astral projecting