New-Time Travel

[ynot]

I tend to believe quite strongly that time travel will never be possible. The main reasoning I offer for this belief is as follows . . .

A particular moment of time is described by the exact relative positioning of every single part of the universe as it exists at that particular moment of time. As the exact relative positioning of everything changes, it becomes the next moment of time. If Scotty beams you back to any particular moment of past time, the very instant that you arrive, you alter that moment of time and create a new moment of time that has never existed before. In other words, you would never actually arrive at the past moment of time. I hope that makes some sense (wish I was better with words).

A fantasy ramble - I don’t see that this new time would necessarily destroy the old moment of time so perhaps a new branch of time would be created. This would mean you could kill your father in this new time and you (and he) could continue to exist in the past time.

I was talking to a 6 year old about time travel recently and he came out with this amazing comment (given his age) “If you could travel back in time you would have to take a time machine with you so you could get back”

[Soapy Sam]

Well, if you went back ten seconds without a time machine, after ten more seconds you would be back when you started.
Whether you would still be ten seconds behind when you should be is left as an exercise for the reader.

[Chaos]

That´s the problem I have with time travel... just trying to think it through logically to its full extent causes my brain to twist in some four-dimensional way :boggled:

[ynot]

Well, if you went back ten seconds without a time machine, after ten more seconds you would be back when you started.
Whether you would still be ten seconds behind when you should be is left as an exercise for the reader.

When you got back to where you started would you see another version of yourself getting in to the time machine or would you have to get back in the time machine and get caught up in a continuous loop?

[kedo1981]

Time travel is imposable, because time is nothing more than a symbolic label we humans put on our movement through space.

[steve s]

When you got back to where you started would you see another version of yourself getting in to the time machine or would you have to get back in the time machine and get caught up in a continuous loop?

I thought Marty McFly already answered that question.:D

Traveling forward through time would be possible if you had a spaceship that could travel near the speed of light. But getting back would probably be impossible. IMO, traveling backward through time would violate the second law of thermodynamics.

Steve S.

[ynot]

Time travel is imposable, because time is nothing more than a symbolic label we humans put on our movement through space.

But is this movement through sapce an irreversible succession from the past through the present to the future? I agree that the word "time" is a generic term (symbolic label) we use to explain the whole thig.

[ynot]

I thought Marty McFly already answered that question.:D



Yeah, but which version of Marty McFly?

[dogjones]

This paper (http://arxiv.org/PS_cache/quant-ph/pdf/0506/0506027.pdf) apparently eliminates the possibility of paradox, assuming that travelling backwards through time is possible. Here's a BBC article (http://news.bbc.co.uk/2/hi/science/nature/4097258.stm)on it as well.

[lumos]

Time travel is imposable, because time is nothing more than a symbolic label we humans put on our movement through space.

Although the word "time" is a symbolic label and is defined by us, we use it to define a real phenomenon. Time exists and is linked to space. Time is linked in that to move from point A to point B in space, a finite amount of time has passed.

Theoretically and experimentally proven, matter can travel much faster through time than other matter the same way matter can travel faster through space than other matter.

As your speed relative to another increases, time for you compresses (slows down).

[ynot]

Although the word "time" is a symbolic label and is defined by us, we use it to define a real phenomenon. Time exists and is linked to space. Time is linked in that to move from point A to point B in space, a finite amount of time has passed.

Theoretically and experimentally proven, matter can travel much faster through time than other matter the same way matter can travel faster through space than other matter.

As your speed relative to another increases, time for you compresses (slows down).

This apparently doesn't apply to light itself though as light can travel at c and not be slowed down.

[ynot]

This paper (http://arxiv.org/PS_cache/quant-ph/pdf/0506/0506027.pdf) apparently eliminates the possibility of paradox, assuming that travelling backwards through time is possible. Here's a BBC article (http://news.bbc.co.uk/2/hi/science/nature/4097258.stm)on it as well.

It can't happen because it can't happen, or it can't happen because TTOR says it can't is not good enough for me

[Simon Bridge]

This paper (http://arxiv.org/PS_cache/quant-ph/pdf/0506/0506027.pdf) apparently eliminates the possibility of paradox, assuming that travelling backwards through time is possible. Here's a BBC article (http://news.bbc.co.uk/2/hi/science/nature/4097258.stm)on it as well.A summary for the layman:

Time Travel violates causality.

Causality violations are commonplace in quantum mechanics.

Therefore, causality violations, by themselves, are insufficient to rule out time travel.

However - (from the conclusion of the paper), should you travel back in time (using QM loopholes) you will only see situations which could lead to your travelling back in time. The mathematics of QM exclude the possibility of their being a paradox. You will be unable to shoot your grandfather, for example.

[TV's Frank]

I "time travel" quite often. Look: I used to be in the past, now I'm in the present, and soon I'll be in the future!

[ynot]

A summary for the layman:
Hey - That's me! (layman)

Time Travel violates causality.
So it's crap then?

Causality violations are commonplace in quantum mechanics.
So it's crap then?

Therefore, causality violations, by themselves, are insufficient to rule out time travel.
Oh . . . So it's not crap then?

However - (from the conclusion of the paper), should you travel back in time (using QM loopholes).
Another name for wormholes?

you will only see situations which could lead to your travelling back in time. The mathematics of QM exclude the possibility of their being a paradox. You will be unable to shoot your grandfather, for example.
I don't pretend that I understand a lot about QM, but I must say that it all sounds like using scissors to make pieces fit in to a jigsaw puzzle.

[ynot]

I "time travel" quite often. Look: I used to be in the past, now I'm in the present, and soon I'll be in the future!

Ah - but you only travel with time, not through it.

[TV's Frank]

Ah - but you only travel with time, not through it.

If I travel Northbound on I-95, am I traveling "with North"?

[ynot]

If I travel Northbound on I-95, am I traveling "with North"?

I am guessing that I-95 is a train? If so, you are travelling on and with a train, and with time, in the direction of north. North isn't travelling. Time is travelling from moment to moment.

[Simon Bridge]

I "time travel" quite often. Look: I used to be in the past, now I'm in the present, and soon I'll be in the future!
However fast you travel in time, the present always gets there first.

(Sometimes, the present gets quite a lead ... ocasionally the present laps you and then you know you're in trouble. I think there was a Pink Floyd song...)

[toddjh]

If I travel Northbound on I-95, am I traveling "with North"?

For this kind of thing, it might be helpful to think of it in different terms. Don't think of it like "we" are travelling through time. Think instead that the physical processes involved in forming memories work only in the forward direction. In other words, our perception of the passage of time is a result of the state of our brains changing over time, and not a result of anything travelling through time.

Jeremy

[Simon Bridge]

I am guessing that I-95 is a train? If so, you are travelling on and with a train, and with time, in the direction of north. North isn't travelling. Time is travelling from moment to moment.
I-95 could be "Interstate 95" as in "highway" if this is a yank.

You lost grip on your metafore though ... though he's travelling north, that's a direction like forward or backward.

I travel forward in time in that I remember the past (so I'm not travelling backwards) and one thing happens after another (so I'm travelling). However, I am not "time-travelling" forward in time (technical use here) because I cannot pass the present time.

Now, were I to travel in time only, but keep the same reference frame as you, then you would see me stationary for a while. Then I start moving and announce "I time-travelled" here. How would you know the difference?

(Check my watch against yours?)

[ynot]

I-95 could be "Interstate 95" as in "highway" if this is a yank.
Thanks - obvious when you think about it. Like you, I live in NZ - you know what it's like.

You lost grip on your metafore though ... though he's travelling north, that's a direction like forward or backward..
Travelling in the direction of north, not with it.


Now, were I to travel in time only, but keep the same reference frame as you, then you would see me stationary for a while. Then I start moving and announce "I time-travelled" here. How would you know the difference?

(Check my watch against yours?)
Nice trick. Can you give a real life demonstration.

[Simon Bridge]

For this kind of thing, it might be helpful to think of it in different terms. Don't think of it like "we" are travelling through time. Think instead that the physical processes involved in forming memories work only in the forward direction. In other words, our perception of the passage of time is a result of the state of our brains changing over time, and not a result of anything travelling through time.

JeremyAre we having fun yet?

Similarily, we don't travel in space at all, just our memories and bodies change state with our position.

We can get even more metaphysical ... our memories point in the opposite direction as increasing entropy. This is reasonable - to have a memory, one needs a process which is basically one-way. One-way processes are entropic. So all memories must accumulate in the direction of increasing entropy.

Imagine if the Universe were contracting in some "proper" time. Then entropy would decrease with this proper time, and we would "remember" the universe being smaller. That is, we will experience the universe expanding from past to present and we will experience time as flowing from the future (proper) to the past (proper).

Everything would look just the same as now.

(It's an ill wind that blows no minds...)

[Simon Bridge]

Jeremy should note that quantum physicists are used to measuring time in meters and astro-physicists are used to measuring distance in years.

[ingoa]

I tend to believe quite strongly that time travel will never be possible. The main reasoning I offer for this belief is as follows . . .

A particular moment of time is described by the exact relative positioning of every single part of the universe as it exists at that particular moment of time.


Nothing more convincing that a strong belief without knowledge... ;)

But seriously. Your second sentence makes no sense. What the heck is a 'A particular moment of time' of the universe?

Not to mention the circular logic:
A particular moment of time is described by the exact relative positioning of every single part of the universe as it exists at that particular moment of time.

A is described as B as it exists at A. Hu?

Before starting discussing a paradox, one has to get the initial conditions right.