The stopping clock

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Y00

Main Question or Discussion Point

We say you have a machine that could go back and forth in time. The machine works roughly like this: A few seconds before you press the button to travel a week forth in time it will save like an autosave. Of course time will go on as if you had pushed the button which you had. You will disappear and that´s a part of the time. You could say you jumped off a branch and will jump back on it smaller distance in front of your first jump. The branch will be affected by the jump but not your time in the air. You just jumped a week forth in time and you decide to go back in time to the "Autosave" earlier!

And here´s the question: Will you go back and forth in time forever or will this end circle end!

This is a matter of how you are viewing universe and the time and i would like to hear some different comments about this, or comments if I´ve written something wrong and such.
Just a discussion about it!
 

Answers and Replies

  • #2
Danger
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Welcome to PF, YOO.
I think that this is overly speculative, so the thread will probably be either locked or moved to GD. Backward time travel is pretty much impossible; we all travel forward in time constantly. The question, therefore, is impossible to answer.
 
  • #3
Y00
Welcome to PF, YOO.
I think that this is overly speculative, so the thread will probably be either locked or moved to GD. Backward time travel is pretty much impossible; we all travel forward in time constantly. The question, therefore, is impossible to answer.
Yes of course, it´s rather speculative but filosophy becomes physics. Hypothesis becomes theory. Philosophy has much to do with physics, maybe not the fact but rather the idea! If timetravel is impossible is hard to tell, and i certainly dont know this myself!

What i see as the big question is if their really exist true chance.
The earlier explanation was just set as an example
 
  • #4
Chi Meson
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Yes of course, it´s rather speculative but philosophy becomes physics.
No, it doesn't. Philosophy is sometimes called "metaphysics" because it is outside of physics. Physics used to be called "natural philosophy" until it was agreed that it is not at all philosophy.

Your question may be an interesting mind game, but the question itself is outside of the laws of physics. Therfore, there is no law of physics that will apply to anything that does not obey the laws. What will happen if you go back in time to the time where you jumped into the future? Heck, you decided to imagine this machine, so you can decide what happens!

Or I too can simply make something up: as you press the button, the action of creating the "autosave" function maps out the position and momentum of each of the particles of your being (every proton, neutron, and electron). I'm stealing from Star Trek here as many will recognize.
As you return to that point at which you left, you are reestablished with all your particles having the same position and momentum as they had when you jumped ahead. The Law of conservation of momentum (ooh, I contradict myself!) states that the particles must continue in the path they had been going in, therefore you will resume travelling forward in time from that point, and you will not be caught in an infinite loop.

This is the stuff of science fiction, which (despite popular outcries) is MORE fiction than science.
 
  • #5
Danger
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I'm stealing from Star Trek here as many will recognize.
Ah, yes... the good ol' Heisenberg Compensators... :biggrin:
 
  • #6
DaveC426913
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Hypothesis becomes theory.
Actually, hypothesis becomes theory once observations are made and data collected.
 
  • #7
Chi Meson
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Ah, yes... the good ol' Heisenberg Compensators... :biggrin:
Reporter: "How do these Heisenberg compensators work?"
Gene Rodenbery: "Very well."
 
  • #8
Danger
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:rofl:
 
  • #9
Backward time travel is pretty much impossible
Is backward time travel a physical impossibility or is it an impossibility coz we cant thik of a way to go back?
I mean, not being able to exceed c is a physical impossibility. There isnt anything like that for the speed of sound. But it was thought a half century earlier that it wasnt possible to break the sound barrier. There was'nt any physics prohibiting it, but everyone thought it was just not possible.
 
  • #10
DaveC426913
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I don't think there is any principle we know of that explicitly rules out time travel in either direction.
 
  • #11
in that case why are discussions of this sort just written off as 'philosophy' or 'science fiction'?
 
  • #12
Danger
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it was thought a half century earlier that it wasnt possible to break the sound barrier. There was'nt any physics prohibiting it, but everyone thought it was just not possible.
That was based upon mechanical shortcomings of the era. No one knew how to make a machine that could survive the trans-sonic shockwave. By the same token, the first automobiles were considered deathtraps; if one exceeded 15 mph, it would break the passengers' necks.
The light-speed barrier, on the other hand, is based upon relativity as pertains to the gain of relativistic mass at greater speeds. It can't be circumvented within our accessible universe.
 
  • #13
thanks danger, thats exactly what i meant. just dint put i so well.
 
  • #14
Danger
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Thanks for the vote of confidence, but that is just my opinion based upon my limited knowledge of physics. There are some theorists and experimental physicists here who might have differing opinions.
 
  • #15
Chi Meson
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That's the difference I try to make my students understand. There are somethings which are not possible due to a physical barrier, and other things that are not possible due to a technological barrier. One of these barriers is temporary.
 
  • #16
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That was based upon mechanical shortcomings of the era. No one knew how to make a machine that could survive the trans-sonic shockwave. By the same token, the first automobiles were considered deathtraps; if one exceeded 15 mph, it would break the passengers' necks.
The light-speed barrier, on the other hand, is based upon relativity as pertains to the gain of relativistic mass at greater speeds. It can't be circumvented within our accessible universe.
Of course, too, though, no one has broken the 'light-speed barrier' yet either, to find out whether that (relativity, the infinite gain of relativistic mass) is true, either. Its a 'Catch 22' in the theory.
 
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  • #17
Y00
I understand your discussion about wether it´s possible to even travel in time, but as far as I know no-one has ever proved either one way or another!
But as far as i know, the big problem of physic today is to combine all the branches of physics onetogether! In the good old days when a good old chap named Newton come up with classical mechanics everything worked just fine. But theorys are beginning to contradict eachother in all the branches of physics that exists!

But now over to something different! It´s a simple question and i want to hear a bit about different views of the problem!

Does true change really exist?
 
  • #18
Chi Meson
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I understand your discussion about wether it´s possible to even travel in time, but as far as I know no-one has ever proved either one way or another!
then you don't know very much about physics.


In the good old days when a good old chap named Newton come up with classical mechanics everything worked just fine. But theorys are beginning to contradict eachother in all the branches of physics that exists!
Newton was the first to realize that there was a huge gaping hole in his theory of gravitation that led to a paradox he couldn't solve.

And physics is still working on it, but what's the problem with that? Just because we do not yet know all the details, it does NOT mean that anything and everything is still possible. We know enough to recognize certain physical barriers that cannot be surmounted.
 
  • #19
DaveC426913
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then you don't know very much about physics.
Really? Cuz I'm in his camp. AFAIK, there's nothing that explicitly rules it out.
 
  • #20
ditto here.. i agree with dave and yoo on that..
 
  • #21
Chi Meson
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ditto here.. i agree with dave and yoo on that..
Just because we can not disprove something, it does not mean that it must still be possible. That was my point. That is exactly the difference between science and philosophy.

There is no model based on known laws of physics that allow for "time travel." Kip Thorne developed a mathematical possiblity through exploiting one of those "quantum foam" bubbles, but it required a "negative energy equivalent to the mass of Jupiter." I place that way down below walking through a brick wall on the scale of probabilities.
 
  • #22
Just because we can not disprove something, it does not mean that it must still be possible. That was my point. That is exactly the difference between science and philosophy.
i m not making a call on whether its possible or not. all i m saying is we dont know. since its not been disproven, lets keep the option open. it just might be possible howevevr improbable it may seem.

as an aside, i read a book a long time back (i think one by john gribbin), where he talks about interpreting electrons moving ahead in time as positrons going back in time. so he said by analogy, a positron moving forward in time must mean an electron going back in time.
(my memory might not serve me right, but it was definitely somethin along those lines. i ll try to dig into it a bit more and get back).
 
  • #23
Chi Meson
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i m not making a call on whether its possible or not. all i m saying is we dont know. since its not been disproven, lets keep the option open. it just might be possible howevevr improbable it may seem.

as an aside, i read a book a long time back (i think one by john gribbin), where he talks about interpreting electrons moving ahead in time as positrons going back in time. so he said by analogy, a positron moving forward in time must mean an electron going back in time.
(my memory might not serve me right, but it was definitely somethin along those lines. i ll try to dig into it a bit more and get back).
OK, I don't disagree with you as a point in philosophy, but in the realm of physics we must take the probabilities into account. Anything that we can dream up has a "non-zero probability." We have to draw the line somewhere. IT is not physics and it is not science to say that we must prove or disprove the existence or nonexistence of things. Sure, keep an open mind, but don't let your brains fall out. As soon as a new possibility is discovered we can examine new possibilities and new probabilities, but without a working model for time travel, using the laws of physics as we know them, the assumption that time travel is possible is NOT physics.
 
  • #24
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Just because we can not disprove something, it does not mean that it must still be possible. That was my point. That is exactly the difference between science and philosophy.

There is no model based on known laws of physics that allow for "time travel." Kip Thorne developed a mathematical possiblity through exploiting one of those "quantum foam" bubbles, but it required a "negative energy equivalent to the mass of Jupiter." I place that way down below walking through a brick wall on the scale of probabilities.
I agree with Chi here.

Some of relativity and quantum (and ST and MWI) has people thinking some odd things may be possible.

Is it possible that I can walk through a wall, then turn into a hippo, then a chair, then a turnip, then a star, then back to myself (or, one of many)?

You can't disprove it, can you?
 
  • #25
fuzzyfelt
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The kids and I were discussing this a while ago as we were walking through woods, and mentioning Stephen Hawking who I think said something about evidence against time travel being that it doesn’t seem as though we’ve been visited from the future. There were squirrels darting up and down the trees and in and out of bushes around us, and we joked that of course humans may not gain the capacity, but how do we know that squirrels haven’t, and haven’t let on. Ever since it has been a bit of a family joke to refer to such furry creatures as ‘intrepid-time-travelling-squirrels-from-the-future!’
 

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