Timetraveller killing himself in the past

[alek1995]

my thinking is because the time machine is built in 2030 and when came 2035 so we can just back in 2030 when the machine exist :)

 

[Dale]

No, by your logic, you would deduce that, since you've never actually seen me in china, there is something preventing me from going there. You would suggest my absence is evidence of the impossibility of intercontinental flight (or at the very least, that I am on a no-fly list).

I am not deducing anything, I am using inductive reasoning. Do you understand the difference? I have mentioned it already and you continue to talk about deduction.

In inductive reasoning, for something to be evidence of a hypothesis it merely needs to be more likely under the hypothesis than not. So, if time travel to now is impossible then the probability of us not seeing time travelers now is 1. If time travel to now is not impossible then the probability of us not seeing time travelers now is less than 1. Therefore, us not seeing time travelers now is, in fact, evidence in favor of time travel to now being impossible.

In contrast, by your own admission, your absence from China is due to personal choice, not the availability of air transport. So the probability of your being in China is no different under the impossibility of intercontinental flight than under its possibility. So it is, in fact, neither evidence for nor against the impossibility of intercontinental flight.

However, under the impossibility of intercontinental flight my presence in China is almost 0 probability, while under the possibility of intercontinental flight my presence in China is much more likely. Therefore my presence in China is strong evidence against the impossibility.

So inductively, factoring in all of the evidence available, we would have to conclude that intercontinental flight to China is possible and time travel to now is impossible.

The fact that we do not see time travelers is only evidence that not every one of the above conditions have been met. You cannot deduce the behaviour of our descendants, and then constrain their actions to a given course based on your deductions.

Fair enough (except again that I am not deducing anything). You have exposed some underlying assumptions that I have. Specifically that if technology progresses to the point that we can build a working time machine that economics would not be a factor, and that human nature would prompt the rest. Therefore I am assuming that if time travel to now is possible the probability of us not seeing any time travelers now is relatively low.

But you are correct, those are all separate assumptions and rely heavily on my view of "human nature". Your assumptions all increase the probability of us not seeing time travelers even given that time travel to now is possible, weakening the strength of the evidence. So we should disagree about the strength of the evidence, but not on the fact that it is evidence.

 

[ianpr]

((There are, however, certain quantities that do remain constant. These constants are related to four-dimensional quantities known as metric tensors.))

Actually, I don’t think that’s correct. Minkowski spacetime (4-D) will not allow you to use Pythagoas’ theorem to decribe tensors because time needs to be expressed with the opposite sign. (please excuse my change of varibale case).

ds^2 = -c^2dt^2 + dx^2 + dy^2 + dz^2
(where ds describes timelike and spacelike trips).

The tensor we should be discussing is:
ds^2 = -a^2dt^2 + w^2(df - wdt)^2 + (r^2/ D)dr^2 + r^2dq^2

 

[dfaullin]

I find it strange that everyone assumes that something is there in the past to go back to. Is there some reason to assume that the past contains a copy of all events and objects? Like a copy of of the universe is taken and stored on a continual basis.

I find it much more likely that there is only one of you and you exist now and you no longer exist in the past. Just like when I move from my chair and stand by the door. I no longer am at the chair. I can only occupy one location in space. Would time work the same way? I can only occupy one location in time.

So while time travel to the past might be possible, you won't find anything there because Earth and all of its inhabitants have moved to a different location in the space-time continuum (here and now).

 

[DaveC426913]

I find it strange that everyone assumes that something is there in the past to go back to. Is there some reason to assume that the past contains a copy of all events and objects? Like a copy of of the universe is taken and stored on a continual basis.

I find it much more likely that there is only one of you and you exist now and you no longer exist in the past. Just like when I move from my chair and stand by the door. I no longer am at the chair. I can only occupy one location in space. Would time work the same way? I can only occupy one location in time.

So while time travel to the past might be possible, you won't find anything there because Earth and all of its inhabitants have moved to a different location in the space-time continuum (here and now).

Our current understanding is that time as a dimension, like space. Every point in the universe has a location on the y-axis and on the x-axis and on the z-axis - and on the t-axis. The difference between space-like dimensions and time-like dimensions is that we have no control over our movement through time-like dimensions.

 

[my_wan]

Breaking news: Man gets in race with self and loses.

 

[Flustered]

I don't like the argument, "where are the time travelers from the future."

1) Maybe they didn't think the time we are living in now, is worth coming back and visiting?

2) Maybe they are here, but cannot blow their cover or it will mess up all of history.

I fell if someone went back in time, than it was ment for that person to go back in time. It is part of history, and if he tried to kill a parent or grandparent, he would fail no matter how hard he tried.

 

[DaveC426913]

I don't like the argument, "where are the time travelers from the future."

1) Maybe they didn't think the time we are living in now, is worth coming back and visiting?

2) Maybe they are here, but cannot blow their cover or it will mess up all of history.

Agreed. It is a weak argument.

I fell if someone went back in time, than it was ment for that person to go back in time. It is part of history, and if he tried to kill a parent or grandparent, he would fail no matter how hard he tried.

The problem with that is it results in at least one of the following conclusions:
a] we have no free will
and/or
b] there is a supreme force that can see, know and control events anywhere, anytime by anyone.

 

[Flustered]

Agreed. It is a weak argument.


The problem with that is it results in at least one of the following conclusions:
a] we have no free will
and/or
b] there is a supreme force that can see, know and control events anywhere, anytime by anyone.

Why must the bolded sentence be an absolute?
I can understand A] about the free will, but why must a higher power be behind it?

Also about free will, is it free will if one doesn't know what their next decision will be, even though life has already been written. To the person they would feel as if they had free will because they could take a right or left whenever they pleased, but no matter what they did that was already written in the book of life. So is that free will?

 

[DaveC426913]

http://kck.st/xfzQ92New Equation for Time Travel Posted online 5 Days ago

Sorry, this is not an equation; it is a link to a YouTube video about a movie idea. And in the description it references "The Law of Attraction", which is such a banned topic that it is even banned from the banned list.

Reported.

 

[DaveC426913]

Either one or the other must be true. It's possible that both are true, but at least one of them must be.

Why must the bolded sentence be an absolute?
I can understand A] about the free will, but why must a higher power be behind it?

If you grant us free will, there there must be an outside entity that is always capable of actively and deliberately intervening to thwart our plans.

Also about free will, is it free will if one doesn't know what their next decision will be, even though life has already been written. To the person they would feel as if they had free will because they could take a right or left whenever they pleased,

The universe doesn't really care how people feel. Regardless of whether the reason is under the delusion that they think they have free will, they're not. (that is, if you don't grant the omniscient, omnipotent option).

no matter what they did that was already written in the book of life.So is that free will?

No. "...already written..." is a metaphor for not having free will.

 

[Antiphon]

If the many worlds theory is false then time travel was likely never invented in the future. If this isn't the case then we'd be seeing time machines from the future.

If the many worlds theory is correct there might be time travelers all over but our odds of seeing them (in any given world) are so slim we never do.

 

[DaveC426913]

If the many worlds theory is false then time travel was likely never invented in the future. If this isn't the case then we'd be seeing time machines from the future.

This is a very weak argument. There is no reason to assume that, just because we invented time travel, we should be seeing them everywhere. Or that we'd even recognize a time traveller if we did see one.

Wait. I repeat myself. Review the thread. This argument was proposed in post 24 and I refuted it.

 

[Flustered]

If someone travels from the future to the past, the people in the past are not actually living in the moment. This hints at the idea that a year is a place in time that is always "in time". What I'm trying to say is we live life frame to frame, but somewhere in another dimension each part of life is getting replayed. How else can you explain someone coming from the future, unless life has already happened. If someone popped into the room you are in now, while you are on this forum. He says he is from the future, that would mean that this frame we are in right now has already happened. Thus time travel.

 

[DaveC426913]

If someone popped into the room you are in now, while you are on this forum. He says he is from the future, that would mean that this frame we are in right now has already happened. Thus time travel.

What? This is circular logic.

"If someone time traveled from the future then that would prove time travel."

I don't think that's what you meant. Care to clarify?

 

[Flustered]

What? This is circular logic.

"If someone time traveled from the future then that would prove time travel."

I don't think that's what you meant. Care to clarify?

No if someone came from the future, that would mean that the moment we are living in now has already been lived before. How else can some travel from the future unless the moment we are in now has already been lived and the future has already happened. Do you understand what I'm trying to say?

A------>B

B comes back to A

A is the moment we both our in RIGHT NOW. B is 500 years in the future, in order for B to go back to A... A has to have already happened.

 

[DaveC426913]

No if someone came from the future, that would mean that the moment we are living in now has already been lived before. How else can some travel from the future unless the moment we are in now has already been lived and the future has already happened. Do you understand what I'm trying to say?

A------>B

B comes back to A

A is the moment we both our in RIGHT NOW. B is 500 years in the future, in order for B to go back to A... A has to have already happened.

Well, that's kind of the definition of time travel. Going back to a time that has occurred before.

 

[Antiphon]

This is a very weak argument. There is no reason to assume that, just because we invented time travel, we should be seeing them everywhere. Or that we'd even recognize a time traveller if we did see one.

Wait. I repeat myself. Review the thread. This argument was proposed in post 24 and I refuted it.

Crap, I know. I posted this reply after reading page 1. Only then did I see two more pages.

(why is there a quick post dialog on the not-last page anyway?)

 

[Flustered]

Well, that's kind of the definition of time travel. Going back to a time that has occurred before.

Therefor the time we are presently in, has already occurred?

 

[DaveC426913]

Therefor the time we are presently in, has already occurred?

To a person from the future, of course.

 

[Flustered]

To a person from the future, of course.

Yes so that would mean we have already lived our life. God knows are fate, my 10 year old self is still living in his 10 year old time frame.

 

[DaveC426913]

Yes so that would mean we have already lived our life. God knows are fate, my 10 year old self is still living in his 10 year old time frame.

Perhaps, but there are many ifs in the chain to that conclusion. Any if of them poor assumptions and the whole thing falls apart.

If time travel is possible.
If tt's visit their own past, and not an alternate.
If you believe in God and fate.

 

[Adel Makram]

the time travel is a logical result of a math consistent with speed > c. Remember the whole theory of relativity is created to make c invariant not to explain why it is so. The math foundation is based on the experiment of M&M which is liable to the experimental correction such as CERN experiment. Therefore, SR is not a true theory in physics, it is a math to fit for the invariance of c

 

[nitsuj]

not that I read more then the first few posts in this thread, but wow hows is this thread still open

 

[rbj]

i don't know why, but it appears to me that no one is mentioning the obvious. unless you spin this into something like separate time-lines (that somehow get crossed or generated when one time-travels to the past), when you step into the time machine, go back a half hour and kill your past self, then who steps into the time machine to go back in time to kill the person who steps into the time machine? the paradox could be expressed as the grandfather thing.

BTW, this is not a conceptual problem for time-traveling into the future. in fact, we're now time traveling into the future at the rate of one minute per minute. all you have to do is wait around and you'll find yourself in the future. pretty cheap and available to all.

if you don't like waiting around, it'll cost you a bit more; you'll need a spaceship and a nearby black hole to hurry it up a little (for you).

 

[nitsuj]

case & point

 

[DaveC426913]

case & point

Um. Did you mean case in point?

 

[DaveC426913]

i don't know why, but it appears to me that no one is mentioning the obvious. unless you spin this into something like separate time-lines (that somehow get crossed or generated when one time-travels to the past), when you step into the time machine, go back a half hour and kill your past self, then who steps into the time machine to go back in time to kill the person who steps into the time machine? the paradox could be expressed as the grandfather thing.

Because it is obvious. And it is known as the grandfather paradox.

Thing is, relativistic time travel (if it is possible) does not forbid this kind of paradox.

 

[ZapperZ]

Well, I'm surprised that, after 4 pages of discussion, no one mentioned the recent Seth Lloyd's idea on what could possibly save the grandfather paradox.

http://www.physorg.com/news198948917.html

Zz.

 

[PAllen]

Well, I'm surprised that, after 4 pages of discussion, no one mentioned the recent Seth Lloyd's idea on what could possibly save the grandfather paradox.

http://www.physorg.com/news198948917.html

Zz.

I took a quick look at this. I could be wrong, but it only provides QM rationale for Novikov consistency. Thus it would allow the case that I find actually more perverse than the grandfather paradox: that Beethoven's 9th symphony has no author. Someone from the future goes to the past and hands the score to Beethoven, who publishes it, allowing future person to receive it. This does not violate Novikov, or the P-ctc of this paper (at least as I understand it so far).