Time Travel... the fly in the ointment

[skepticalbip]

Hiding? In space-time of course.

So they are not hiding?

Show me where they are then.

Of course they must be within spacetime. That is all we know.

The question is where in spacetime are all those prior configurations of matter and energy hiding?

And if you say they are not hiding point to where they are.

You are even asking the wrong question. Your question is assuming only a 3D space universe rather than a 4D spacetime universe. The question should be when are all those prior configurations, or more properly, when-where. We don't live in the purely Newtonian universe you are assuming.

As an analogy, assume a flatlander that only knows and accepts X and Y coordinates. When told that something exists along the Z axis (above or below them), he challenges them to tell him where it is in the X-Y plane.

 

[untermensche]

So they are not hiding?

Show me where they are then.

Of course they must be within spacetime. That is all we know.

The question is where in spacetime are all those prior configurations of matter and energy hiding?

And if you say they are not hiding point to where they are.

You are even asking the wrong question. Your question is assuming only a 3D space universe rather than a 4D spacetime universe. The question should be when are all those prior configurations, or more properly, when-where. We don't live in the purely Newtonian universe you are assuming.

As an analogy, assume a flatlander that only knows and accepts X and Y coordinates. When told that something exists along the Z axis, he challenges them to tell them where it is in the X-Y plane.

We already know when. In the past.

The question is; If the past somehow can be returned to, this implies it is out there somewhere. Where is it?

 

[skepticalbip]

You are even asking the wrong question. Your question is assuming only a 3D space universe rather than a 4D spacetime universe. The question should be when are all those prior configurations, or more properly, when-where. We don't live in the purely Newtonian universe you are assuming.

As an analogy, assume a flatlander that only knows and accepts X and Y coordinates. When told that something exists along the Z axis, he challenges them to tell them where it is in the X-Y plane.

We already know when. In the past.

The question is; If the past somehow can be returned to, this implies it is out there somewhere. Where is it?

Not "where", WHEN. You are refusing (or are incapable) of acknowledging the t- dimension, insisting on only accepting the spacial dimensions (like the flatlander that can't understand the Z-axis). We are talking about 4D spacetime. If the past still exists, as some theories maintain, then it can only be found along the t-dimension that you, like the flatlander, can't even imagine.

Again an analogy; the flatlander could not comprehend the concept of stairs or an elevator so for, this flatlander, the basement or second and higher floors can't exist.

 

[bilby]

You are even asking the wrong question. Your question is assuming only a 3D space universe rather than a 4D spacetime universe. The question should be when are all those prior configurations, or more properly, when-where. We don't live in the purely Newtonian universe you are assuming.

As an analogy, assume a flatlander that only knows and accepts X and Y coordinates. When told that something exists along the Z axis, he challenges them to tell them where it is in the X-Y plane.

We already know when. In the past.

The question is; If the past somehow can be returned to, this implies it is out there somewhere. Where is it?

It is in the past.

 

[skepticalbip]

We already know when. In the past.

The question is; If the past somehow can be returned to, this implies it is out there somewhere. Where is it?

It is in the past.

Right. It is right over then.

 

[untermensche]

We already know when. In the past.

The question is; If the past somehow can be returned to, this implies it is out there somewhere. Where is it?

It is in the past.

That does not mean it can be returned to.

If the past can be returned to that means the past has a permanent existence somewhere.

To return to something mean it exists out there somewhere to return to.

 

[bilby]

It is in the past.

That does not mean it can be returned to.

If the past can be returned to that means the past has a permanent existence somewhere.

To return to something mean it exists out there somewhere to return to.

The question of whether it can be returned to is open; your declaration that it isn't possible is not evidence either way.

Your statement that "If the past can be returned to that means the past has a permanent existence somewhere." is true only if by "somewhere" you include "somewhen"; If you do, then your statement is restating the obvious; If you don't, then you are not addressing the question at all.

A four dimensional spacetime can exist without the need for every point in that spacetime to be locatable using only the three dimensions of space. Whether or not it does cannot therefore be resolved by looking only at a three dimensional slice of four dimensional spacetime and declaring your failure to find the fourth dimension as evidence for its non-existence.

You might as well look at the floor-plan of the ground floor of a skyscraper, and declare that the building cannot have a roof, because the plan doesn't show one.

It is impossible to say anything about the number of floors a building has by looking at a plan of a single floor, no matter how detailed that plan might be. Equally, it is impossible to tell whether or not the past exists in a four dimensional spacetime (or even whether the fourth dimension itself is 'real') by reference to the three dimensional space we can observe.

Your conclusion is possible; but it is far from certain. You have presented no evidence to support taking a position on this issue. Now would be the time to do that - bearing in mind that appeals to 'it's obvious', circular arguments, or declarations about the desirability of the various possible conclusions are not valid ways to eliminate any of them.

 

[untermensche]

Your statement that "If the past can be returned to that means the past has a permanent existence somewhere." is true only if by "somewhere" you include "somewhen"; If you do, then your statement is restating the obvious; If you don't, then you are not addressing the question at all.

By asking about the past I am including the when.

But the past is not just a when. It is also a where. It is a specific arrangement of all the matter and energy and other "stuff" the universe is made up of.

In the past there was a piece of paper. In the history of that piece of paper it was burnt up.

To go back to the past is to go back to a time and place where that paper had not burnt yet.

Therefore if it is possible to go back to the past that piece of paper is out there somewhere just waiting for something to return to it.

Does anybody actually believe that piece of paper is out there somewhere, and when, just sitting there so that it is possible to return to it?

If they believe that, we know when the piece of paper was, but where is it hiding so that it is possible to return to it?

 

[bilby]

Your statement that "If the past can be returned to that means the past has a permanent existence somewhere." is true only if by "somewhere" you include "somewhen"; If you do, then your statement is restating the obvious; If you don't, then you are not addressing the question at all.

By asking about the past I am including the when.

OK.

But the past is not just a when. It is also a where. It is a specific arrangement of all the matter and energy and other "stuff" the universe is made up of.

No, when is the word for a place in the time dimension; where means a place in the other three dimensions. You might as well say "The altitude is not just a height, it is also a width". To say this is to misunderstand the meanings of the words. The past is a when; another country is a where. The past cannot be a where, any more than 'over there' is a when.

In the past there was a piece of paper. In the history of that piece of paper it was burnt up.

OK.

To go back to the past is to go back to a time and place where that paper had not burnt yet.

Yes.

Therefore if it is possible to go back to the past that piece of paper is out there somewhere just waiting for something to return to it.

Yes.

Does anybody actually believe that piece of paper is out there somewhere, and when, just sitting there so that it is possible to return to it?

Yes.

If they believe that, we know when the piece of paper was, but where is it hiding so that it is possible to return to it?

In the past.

 

[Bronzeage]

You are even asking the wrong question. Your question is assuming only a 3D space universe rather than a 4D spacetime universe. The question should be when are all those prior configurations, or more properly, when-where. We don't live in the purely Newtonian universe you are assuming.

As an analogy, assume a flatlander that only knows and accepts X and Y coordinates. When told that something exists along the Z axis, he challenges them to tell them where it is in the X-Y plane.

We already know when. In the past.

The question is; If the past somehow can be returned to, this implies it is out there somewhere. Where is it?

The problem with the concept of time travel is what to do when you get there. Imagine two alternatives.

In the first, the time traveler is only a consciousness. He is capable of observing, creating memories of events, and we hope, also capable of returning to his original place in time, that vague concept known as the present. If this were the case, time no longer exists, as we know it, because a time traveler can conscious of any place, at any point in time, past or future.

In the second, he is transported as a conscious being, not only observing and recording, but acting as well. Whatever he does, however insignificant, changes the future. This means there are an infinite number of futures, one for every possible action performed in the past. Again, time no longer exists as we know it.

Has anyone ever read Slaughter House 5? The Tralfamadorians had this all figured out a long time ago, or maybe they haven't figured it out yet. It's difficult to say which.

 

[DBT]

It implies a trail of a near infinite number of earths emanating in a time dimension like an invisible tail behind the current, present earth, which is only an instant in time. Apply that to every matter/energy object in the universe...where does all the mass come from?

The same place all the mass/energy comes from right now. The first law of thermodynamics implies that the mass/energy that exists in the past and in the future is the same as the mass energy that exists now. You might as well look at a two dimensional slice through a steel beam, measure its width as 100mm, and then ask "If the beam extends in a third dimension, where does all the width come from?".

I meant in terms of the physical state of the earth of the past. Let's say we plan to go back in time and observe the battle of Marathon....but the world at the time of the battle of Marathon was quite different to the earth of today.

How do we go back? Is the earth in the time of the battle of Marathon still in its original location in space/time, the coordinates, eternally abiding and enabling us, the time travelers, to visit the earth during the battle of Marathon in 490bc?

If so, this implies that there are countless earths representing every moment in time located in their original space/time coordinates as a form of trail embedded in the dimension of time and of the past.

The battle of Marathon still being fought its space/time coordinate, soldiers eternally maimed injured or killed, frozen in time with swords buried in their chests....?

 

[bilby]

The same place all the mass/energy comes from right now. The first law of thermodynamics implies that the mass/energy that exists in the past and in the future is the same as the mass energy that exists now. You might as well look at a two dimensional slice through a steel beam, measure its width as 100mm, and then ask "If the beam extends in a third dimension, where does all the width come from?".

I meant in terms of the physical state of the earth of the past. Let's say we plan to go back in time and observe the battle of Marathon....but the world at the time of the battle of Marathon was quite different to the earth of today.

How do we go back? Is the earth in the time of the battle of Marathon still in its original location in space/time, the coordinates, eternally abiding and enabling us, the time travelers, to visit the earth during the battle of Marathon in 490bc?

If so, this implies that there are countless earths representing every moment in time located in their original space/time coordinates as a form of trail embedded in the dimension of time and of the past.

The battle of Marathon still being fought its space/time coordinate, soldiers eternally maimed injured or killed, frozen in time with swords buried in their chests....?

Yes.

And this is a problem because...?

Of course, if there is only one past, then it would be impossible to travel back to it, because we are (or were) not there, so we can't be there. But then, time travel so far has proven to be impossible, so the hypothesis of a four dimensional space-time is not (yet) challenged by our ability to travel back in time.

And even if travel back in time were achieved, the 'many worlds' interpretation could salvage the concept - you could in principle travel back to the battle of Marathon, and your arrival would cause a split in the timeline, with the current history where you were not present going off in a different 'direction' to the new history in which you were present at the battle.

Given that travel backwards in time is not currently possible, it seems an odd basis for an objection to any hypothesis, that it would render travel backwards in time impossible. It is rather like saying that the creation of mass/energy from nothing must be possible, because if it wasn't, perpetual motion machines wouldn't work.

Sure, if the hypothesis is correct, travel back in time wouldn't work. But as travel back in time does not (currently) work, that is not (currently) a valid disproof of the hypothesis.

 

[DBT]

I don't know, it seems to me that BB theory excludes the possibility of a 'block time' universe:




'Most cosmologists believe that the universe originated in an event called the Big Bang about 13 billion years ago. We live in an expanding universe and the galaxies are receding from each other as a part of the universal expansion. Microwave back ground radiation which is a relic from the Big Bang has been extensively studied by many NASA and European satellites. There is no doubt in the minds of physicists and astronomers that Big Bang occurred.

Similarly the concept of time being a block universe is considered a holy grail by many physicists who swear to this interpretation of Lorentz transformation. There is no discussion however on how the two diametrically opposed concepts the block universe and the origin of the universe in the big bang can be reconciled.

If the universe began in the moment of the big bang and is laid out as a time-scape from the past to the present and the infinite future as required by the block universe view of time then all of the time-scape from big bang to infinite future should have begun at the moment of the birth of the universe in the Big Bang.

The whole concept when taken together is ludicrous and there is no escape form this unless we discard the block universe view of time. It can be shown that this aspect of Special Relativity which depends on an interpretation of Lorentz transformation equation can be easily be given up without affecting the experimentally verified aspects of relativity.''

 

[bilby]

I don't know, it seems to me that BB theory excludes the possibility of a 'block time' universe:


View attachment 2341

'Most cosmologists believe that the universe originated in an event called the Big Bang about 13 billion years ago. We live in an
expanding universe and the galaxies are receding from each other as a part of the universal expansion. Microwave back ground
radiation which is a relic from the Big Bang has been extensively studied by many NASA and European satellites. There is no doubt in
the minds of physicists and astronomers that Big Bang occurred. Similarly the concept of time being a block universe is considered a
holy grail by many physicists who swear to this interpretation of Lorentz transformation. There is no discussion however on how the two
diametrically opposed concepts the block universe and the origin of the universe in the big bang can be reconciled. If the universe
began in the moment of the big bang and is laid out as a time-scape from the past to the present and the infinite future as
required by the block universe view of time then all of the time-scape from big bang to infinite future should have begun at
the moment of the birth of the universe in the Big Bang. The whole concept when taken together is ludicrous and there is no
escape form this unless we discard the block universe view of time. It can be shown that this aspect of Special Relativity which
depends on an interpretation of Lorentz transformation equation can be easily be given up without affecting the experimentally verified
aspects of relativity.''

I don't see the problem. If the Big Bang is an event in block time, then the two ideas are perfectly compatible. If the Big Bang is the start of time, then that's no problem either; nothing says that block time must be infinite in both directions.

 

[untermensche]

Does anybody actually believe that piece of paper is out there somewhere, and when, just sitting there so that it is possible to return to it?

Yes.

Great. Where is it?

If you can't point to where it is then how could you possibly think it is anywhere?

 

[bilby]

Yes.

Great. Where is it?

If you can't point to where it is then how could you possibly think it is anywhere?

It's in the past, of course. I am pretty sure I have already said this to you more than once.

 

[untermensche]

Great. Where is it?

If you can't point to where it is then how could you possibly think it is anywhere?

It's in the past, of course. I am pretty sure I have already said this to you more than once.

It WAS in the past. We agree on that.

But all the atoms that made up that paper are still here.

If the paper still exists then you are claiming a duplication of matter.

It is an absurd position not supported by any evidence.

 

[bilby]

It's in the past, of course. I am pretty sure I have already said this to you more than once.

It WAS in the past. We agree on that.

But all the atoms that made up that paper are still here.

If the paper still exists then you are claiming a duplication of matter.

It is an absurd position not supported by any evidence.

I am no more claiming a duplication of matter than you are claiming its destruction.

The amount of mass/energy at any given time is the same. Why would it go away, and where would it go to?

 

[untermensche]

It WAS in the past. We agree on that.

But all the atoms that made up that paper are still here.

If the paper still exists then you are claiming a duplication of matter.

It is an absurd position not supported by any evidence.

I am no more claiming a duplication of matter than you are claiming its destruction.

The amount of mass/energy at any given time is the same. Why would it go away, and where would it go to?

The paper is more than it's atoms. It is a specific arrangement of those atoms. Again, the past is not just past time, it is past arrangements in space.

Once the structure is disrupted the paper no longer exists even though the atoms that made it up still do.

If you claim the paper still exists even after it is burnt you are proposing a duplication of matter, the atoms that made up the paper and the exact same atoms that no longer make up the paper.

 

[bilby]

I am no more claiming a duplication of matter than you are claiming its destruction.

The amount of mass/energy at any given time is the same. Why would it go away, and where would it go to?

The paper is more than it's atoms. It is a specific arrangement of those atoms. Again, the past is not just past time, it is past arrangements in space.

Once the structure is disrupted the paper no longer exists even though the atoms that made it up still do.

If you claim the paper still exists even after it is burnt you are proposing a duplication of matter, the atoms that made up the paper and the exact same atoms that no longer make up the paper.

You misunderstand; I am not claiming that the paper still exists even after it is burnt; I am claiming that the paper still exists BEFORE it is burnt.

You seem to have trouble grasping any concept involving time at all. You respond to statements about time as though they were about space. As a result it is unsurprising that you are confused.