Time Machine will not be invented

[Time Machine]

What?? What parallel universe self?

Not really a serious question but more of an amusing ponder. Parallel universe as in Shrodinger's cat. Both dead and alive. If I slow time down for myself in this universe, would time speed up for me in parallel universe. Some reference was made as to Steven Hawking earlier in the thread...in that perhaps he actually did meet with time travellers as arranged in alternate universe.

As for creating gravity control in a craft, I realize the difficulties in encapsulating one field of gravity inside of the craft and keeping another out... interesting idea though.

 

[DaveC426913]

Not really a serious question but more of an amusing ponder. Parallel universe as in Shrodinger's cat. Both dead and alive. If I slow time down for myself in this universe, would time speed up for me in parallel universe.

There is no reason to suppose this.

 

[DaveC426913]

Dave, I hope I'm not going off topic here, but, from what you say, there could just be one set of elementary particles repeatedly traveling back in time until they caused the Big Bang.

What evidence do we have that particles are traveliing back in time?

Would this not violate the principle of Conservation of Energy?

LCE does not take time travel into consideration.

 

[Ash Small]

What evidence do we have that particles are traveliing back in time?


LCE does not take time travel into consideration.

We don't have any evidence (except, possibly, anti-particles)

I was just taking what you said to it's logical conclusion.

If it's possible for particles to travel backwards in time, you could start with one of each type of quark, etc., they could travel back in time, resulting in two of each type. They could then travel back a bit further, resulting in three of each type...

This process could continue until the conditions required for the Big Bang are satisfied.

(I'm not arguing in favour of this idea, it just follows from the point that you made.)

 

[Time Machine]

There is no reason to suppose this.

And also no reason to suppose not, I suppose. Not that it was a serious question...I'm not keen on parallel universes... wish I'd not mentioned it now. Time is more my area of interest.

 

[Brin]

We don't have any evidence (except, possibly, anti-particles)

I was just taking what you said to it's logical conclusion.

If it's possible for particles to travel backwards in time, you could start with one of each type of quark, etc., they could travel back in time, resulting in two of each type. They could then travel back a bit further, resulting in three of each type...

This process could continue until the conditions required for the Big Bang are satisfied.

(I'm not arguing in favour of this idea, it just follows from the point that you made.)

Three notes:
- Firstly, quarks don't exist in isolation.
- Secondly, Pauli-E says two fermions can't occupy the same quantum state/have the same quantum numbers. So even if quarks existed in isolation, they wouldn't have any problems because of the Pauli principle since basically they'd have different spatial locations.
- Thirdly, a particle spontaneously changing its four-momentum would violate something like Newton's first law (which holds in special relativity, but I don't know about GR... as I haven't gotten that far in this class!)

Then, I think you need to think a bit more about this before you arrive at its "logical conclusion." If you take ONE single particle, and make it move away from some point P in space time for like, 100 billion years, and then spontaneously jump it back to the beginning of time to have it travel out in another direction, then in essence you've altered the future of the particle, and it has never traveled 100 billion years, and so it will never see "itself" again.

Were it to travel back like fifty years and alter its own course, similar things would occur. It'd be rewriting itself.

Ergo, you'd never see a "big bang."

If there were a parallel universe theory, then one couldn't travel backwards in the same timeline. Only "sideways" to other timelines. Then you just end up with a bunch of parallel universes with particles going in different directions. You'd never see a big bang in this case either.

 

[Ash Small]

Three notes:
- Firstly, quarks don't exist in isolation.
- Secondly, Pauli-E says two fermions can't occupy the same quantum state/have the same quantum numbers. So even if quarks existed in isolation, they wouldn't have any problems because of the Pauli principle since basically they'd have different spatial locations.
- Thirdly, a particle spontaneously changing its four-momentum would violate something like Newton's first law (which holds in special relativity, but I don't know about GR... as I haven't gotten that far in this class!)

Then, I think you need to think a bit more about this before you arrive at its "logical conclusion." If you take ONE single particle, and make it move away from some point P in space time for like, 100 billion years, and then spontaneously jump it back to the beginning of time to have it travel out in another direction, then in essence you've altered the future of the particle, and it has never traveled 100 billion years, and so it will never see "itself" again.

Were it to travel back like fifty years and alter its own course, similar things would occur. It'd be rewriting itself.

Ergo, you'd never see a "big bang."

If there were a parallel universe theory, then one couldn't travel backwards in the same timeline. Only "sideways" to other timelines. Then you just end up with a bunch of parallel universes with particles going in different directions. You'd never see a big bang in this case either.

I never said quarks could exist in isolation.

I was merely taking the point that Dave made that a particle could exist in two places at the same time if it was 'older' at one location to it's logical conclusion.

The point I was making is that if there were only six quarks at the end of time, and they traveled back in time, so that there were 12, and then those twelve trevelled back in time, making 18...etc...eventually, due to the fact that they all start in the same place and have no external influence acting upon them, eventually you'd reach the conditions required for the big bang.

I personally believe that Pauli exclusion prevents time travel. I was just taking the point that Dave made to it's logical conclusion.

 

[Brin]

I misread, you wrote "Quarks etc" I didn't mean to suggest that your whole argument was destroyed because of this. You could just pick some other fermion.

Anyways, those were just notes which can be overcome, as you can see I permitted those and gave your idea a chance. I understood your idea, and it still failed.

You seem to have ignored this.

I reiterate, Pauli Exclusion doesn't prevent time travel and it doesn't have to. The time travel we seem to be talking about is pretty much impermissible for other paradoxical reasons. However, your idea makes no sense to conquer "time travel," by parallel universe theory method. So, you haven't conquered "time travel" in general, and definitely not because of Pauli-E.

 

[Ash Small]

I misread, you wrote "Quarks etc" I didn't mean to suggest that your whole argument was destroyed because of this. You could just pick some other fermion.

Anyways, those were just notes which can be overcome, as you can see I permitted those and gave your idea a chance. I understood your idea, and it still failed.

You seem to have ignored this.

I reiterate, Pauli Exclusion doesn't prevent time travel and it doesn't have to. The time travel we seem to be talking about is pretty much impermissible for other paradoxical reasons. However, your idea makes no sense to conquer "time travel," by parallel universe theory method. So, you haven't conquered "time travel" in general, and definitely not because of Pauli-E.

I never mentioned parallel universes, Brin, that was someone else's post. I merely stated that, due to Pauli Exclusion, the same particle cannot occupy two different states at the same point in time. Dave said that a particle could, if the particle was a different age, I then took his idea to it's logical conclusion,ie that the universe 'could' be comprised of only one of each elementary particle, if each particle of each type was the same particle, but a different age. I still believe that Pauli excludes this possibility.

 

[DaveC426913]

I was just taking what you said to it's logical conclusion.

If it's possible for particles to travel backwards in time, you could start with one of each type of quark, etc., they could travel back in time, resulting in two of each type. They could then travel back a bit further, resulting in three of each type...

This process could continue until the conditions required for the Big Bang are satisfied.

(I'm not arguing in favour of this idea, it just follows from the point that you made.)

I don't see how that follows. We were talking about time travel technology. How did we get to an idea of particles spontaneously travelling backwards en mass?

 

[DaveC426913]

And also no reason to suppose not, I suppose.

Yes there is. Occam's Razor and the Scientific Method.

We don't suppose faeries and unicorns for the same reason.

 

[Ash Small]

I don't see how that follows. We were talking about time travel technology. How did we get to an idea of particles spontaneously travelling backwards en mass?

Whatever the method of time travel, Dave, whether by machine or otherwise (the mechanism isn't important here), Pauli states that each fermion has it's own 'associated state' within space-time.

This has been accepted since 1927, and time travel would violate this principle.

 

[pallidin]

Ever notice how we seem unable to change the past, but most certainly capable of affecting the future?
The future, it seems, immutably relies on the "past' for part of it's "Now"

 

[DaveC426913]

Whatever the method of time travel, Dave, whether by machine or otherwise (the mechanism isn't important here), Pauli states that each fermion has it's own 'associated state' within space-time.

This has been accepted since 1927, and time travel would violate this principle.

Argh! Are you ADHD? Stay on freakin' topic!

If you want to talk about PEP, then there's nothing that excludes it. Find me a reference to PEP that talks about a particle traveling into its own past.



If you want to talk about particles traveling back in time, then well, what are we talking about? We went from a time machine to recreating the Big Bang in nothing flat.

 

[Studiot]

It's a long time since we heard from the OP.

Perhaps he really meant that a Time Machine will not be invented because he is a Time Lord and has already invented one.

 

[Ash Small]

Argh! Are you ADHD? Stay on freakin' topic!

If you want to talk about PEP, then there's nothing that excludes it. Find me a reference to PEP that talks about a particle traveling into its own past.



If you want to talk about particles traveling back in time, then well, what are we talking about? We went from a time machine to recreating the Big Bang in nothing flat.

I feel I'm repeating myself here Dave. The time machine would comprise of fermions and leptons. The fermions cannot violate PEP, PEP ties the fermions to one state in space-time. time travel would violate PEP.

Fermions can move in space-time, but they can't jump, either in space or in time, from one state to another.

Please come up with an argument that I haven't replied to already.

(BTW, I wasn't re-creating the big bang, I was extrapolating your earlier reply to 'explain' it.) :-)

 

[DaveC426913]

The fermions cannot violate PEP, PEP ties the fermions to one state in space-time. time travel would violate PEP.

Nothing in PEP addresses a particle moving backward in time to join its earlier self. Nothing in PEP says two particles can't exist near each other while being in the same state.

For one, PEP applies to particles in the same atom. No one says an atom traveling backward in time somehow overlaps itself physically.

You are reading far too much of PEP into this scenario.

 

[Ash Small]

Nothing in PEP addresses a particle moving backward in time to join its earlier self. Nothing in PEP says two particles can't exist near each other while being in the same state.

For one, PEP applies to particles in the same atom. No one says an atom traveling backward in time somehow overlaps itself physically.

You are reading far too much of PEP into this scenario.

Dave, If two particles were in the same state they would be super-imposed, PEP excludes this. They can be identical in all other respects, but they cannot occupy the same space at the same time.

They are each associated with their own unique state in 'space-time'.

 

[DaveC426913]

Dave, If two particles were in the same state they would be super-imposed, PEP excludes this.

Show what this has to do with what we're talking about.

They can be identical in all other respects, but they cannot occupy the same space at the same time.

Nobody said they have to.


These are both red herrings. Who claimed the particle traveling backward in time must occupy the same space as its younger self?

I have an atom in a beaker on my desk. I send it backward in time; it appears in another beaker a foot to the left of the first one. Show how PEP disallows this.

 

[Ash Small]

Show what this has to do with what we're talking about.



Nobody said they have to.


These are both red herrings. Who claimed the particle traveling backward in time must occupy the same space as its younger self?

I have an atom in a beaker on my desk. I send it backward in time; it appears in another beaker a foot to the left of the first one. Show how PEP disallows this.

PEP states that each fermion has it's own unique state associated with it in space-time (singular).

You show me where it says otherwise, and says a fermion can exist in two states in space-time.

 

[DaveC426913]

PEP states that each fermion has it's own unique state associated with it in space-time (singular).

You show me where it says otherwise, and says a fermion can exist in two states in space-time.

I don't disagree.

Now you show me how my two atoms, a foot apart, are in the same place.

 

[Ash Small]

I don't disagree.

Now you show me how my two atoms, a foot apart, are in the same place.

They are not in the same place, but they violate the space-time component of PEP.

PEP states that each fermion occupies it's own unique state in space-time (singular)

(if A occupies x, then B occupies y, A cannot occupy y if it occupies x anymore than A and B can occupy x at the same time.)

 

[DaveC426913]

They are not in the same place, but they violate the space-time component of PEP.

PEP states that each fermion occupies it's own unique state in space-time (singular)

The two atoms (actually, particles) do not violate this.

One particle is at [x y z t] while the other is at [x' y z t]. Those are, indeed, unique places in spacetime (singular). I'm really not sure why you are not getting this.

 

[pallidin]

Uh, I would assume that going back-in-time violates a whole host of contemporary theories.

 

[pallidin]

Look, we have a clue in reality.
The past is observationally possible, but NOT interactive.

 

[Time Machine]

Yes there is. Occam's Razor and the Scientific Method.

We don't suppose faeries and unicorns for the same reason.

Aren't parallel universes in the same realm as faeries and unicorns. I'm sure a clever mathematician could conjour some ammusing calculations. The only reason it was mentioned by me was to do with an earlier comment in the thread that made a humerous remark relating to parallel universe. It was quite a long time ago.

Any-one got anything to say about my comment that did involve time travel?

 

[JaredJames]

Am I the only one who can see the logic in DaveC's view?

The PEP may say that two particles cannot occupy the same space-time, but if particle A was at [x,y,z,t] and also at [x',y,z,t] it isn't in the same space-time location. So it doesn't violate the rule.

I literally know nothing regarding this topic, but I can see what DaveC is saying. So far, none of the counter-arguments address this and simply restate the same point over and over.

 

[DaveC426913]

So far, none of the counter-arguments address this and simply restate the same point over and over.

Yyyep.

 

[DaveC426913]

Uh, I would assume that going back-in-time violates a whole host of contemporary theories.

I don' t think so, no. None that I can think of.

I mean, time travel might end up violating some theories, and thus may finally not work, but I don't know of any theories that a priori rule it out.

 

[Time Machine]

I had actually been following the dialogue about fermions but having nothing to add to this conversation about "particle physics" apart from perhaps making the suggestion that you guys are in the wrong thread or pointing out the fact that whilst the Big Bang Theory is wildly popular it is to all intents and purposes only a concept in itself and an abstract one at that.
Not an input that would have been welcomed too much no doubt.

Dave, you have complained that input has been off-track concerning this thread yet you continue to talk to me about a flip parallel universe comment that I have repeatedly told you was not serious, have no interest in and has nothing to do with this thread other than some-one else had brought it up, when the choice was there to respond to comment that I made that is related to this thread of "time travel".
Dave, I do realize that my approach to physics is unconventional and that my use of language is unusual. I see no reason that this should invalidate my input. I can assure you that I have extremely valid reasons behind this fact. If you care to contact me privately then I would be happy to explain.

Getting back to time travel, incase any-one visiting this thread is interested in my input! It occurs to me that if a potential time traveler used slow time/gravity variables to travel through faster time/gravity variables, that it actually would indeed be possible to arrive back at the place of your journey's start in your own past. Obviously it is debatable as to whether or not this is physically possible. If not then potential time travelers would probably avoid such occurances happening in their calculations when mapping out their journey.
The benefits of the time travelers time going slow whilst time outside the craft is going quicker, apart from getting to your destination in less time, would mean that engine revs could be kept down in slower speeds affording a more fuel efficient journey.
The difficulties that I mentioned before concerning containing a gravity field:
Perhaps somewhere in the work of Thompson Townsend Brown there lies a clue to the answer. If the walls of the craft were electrically charged: in an inward direction with slow time/gravity variables, in an outward direction with fast time/gravity variables and cancelling out charges were directed at each other between the inside and the outside of the walls that stopped each field leaking into the other, then perhaps this problem could be overcome.

Any comment on time travel?

 

[ZapperZ]

At some point, a thread on this topic inevitably leads to posts that are highly speculative and violates our https://www.physicsforums.com/showthread.php?t=414380" that everyone had agreed to. If this thread does not get back to discussion using valid physics AND back up unusual claims with proper citation, this thread (and this topic) will be closed.

Zz.

 

[Ash Small]

The two atoms (actually, particles) do not violate this.

One particle is at [x y z t] while the other is at [x' y z t]. Those are, indeed, unique places in spacetime (singular). I'm really not sure why you are not getting this.

Ok Dave, one last time, If fermion A is at point (x,y,z) at time t it can't also be at point (x',y,z) at time t. PEP states that each fermion has it's own unique state at anyone point in time.

Please show me where you think PEP says that a fermion can occupy TWO STATES AT THE SAME TIME?

I have read and re-read PEP and and all it says is that each fermion has it's own unique state (singular) at anyone point in time.

 

[Time Machine]

It's a long time since we heard from the OP.

Perhaps he really meant that a Time Machine will not be invented because he is a Time Lord and has already invented one.

No doubt this is one of posts you are referring to Zapper Z. There is nothing in mine that violates any rules and there are no "Holy Cows" in theoretical physics.

 

[DaveC426913]

I had actually been following the dialogue about fermions but having nothing to add to this conversation about "particle physics" apart from perhaps making the suggestion that you guys are in the wrong thread...

It is highly relevant. The claim is that time travel of any form, would violate PEP. If true, this thread topic is stopped in its tracks. But Ash has not made his case on this one.

or pointing out the fact that... whilst the Big Bang Theory is wildly popular it is to all intents and purposes only a concept in itself and an abstract one at that.

This is not true. It is a well-established and accepted theory that is virtually uncontested by any competent scientist except in the details. Make no mistake, we understand the formation of our universe back to within microsceconds of its creation.

Dave, you have complained that input has been off-track concerning this thread yet you continue to talk to me about a flip parallel universe comment that I have repeatedly told you was not serious, have no interest in and has nothing to do with this thread other than some-one else had brought it up, when the choice was there to respond to comment that I made that is related to this thread of "time travel".

All right. Consider it dropped then.

Dave, I do realize that my approach to physics is unconventional and that my use of language is unusual. I see no reason that this should invalidate my input.

I can assure you that I have extremely valid reasons behind this fact. If you care to contact me privately then I would be happy to explain.

If you didn't want it discussed, you wouldn't have put it out there. By ptuting it out there, you are expecting it to be challenged. I'll assume you'ree retracting it. No prob.

Getting back to time travel, incase any-one visiting this thread is interested in my input! It occurs to me that if a potential time traveler used slow time/gravity variables to travel through faster time/gravity variables, that it actually would indeed be possible to arrive back at the place of your journey's start in your own past.

No. No matter how much you slow a car down, it will never be slow enough to arrive back home.

Time travel, OTOH, is a reversal of direction.

The benefits of the time travelers time going slow whilst time outside the craft is going quicker, apart from getting to your destination in less time, would mean that engine revs could be kept down in slower speeds affording a more fuel efficient journey.

...despite the fact that it's a one-way trip in time.

If you let 100 years go by while you take only 6 years to travel to Gliese 581, all your loved ones are dead forever.

The difficulties that I mentioned before concerning containing a gravity field:
Perhaps somewhere in the work of Thompson Townsend Brown there lies a clue to the answer. If the walls of the craft were electrically charged: in an inward direction with slow time/gravity variables, in an outward direction with fast time/gravity variables and cancelling out charges were directed at each other between the inside and the outside of the walls that stopped each field leaking into the other, then perhaps this problem could be overcome.

Any comment on time travel?

It is important to keep in mind that there is dilation in only one direction. You can slow time via GR but you cannot speed it up. Free space, away from massive bodies is the fastest time is going to travel. Moving into a gravity well will slow time for you, but there'e no counterpart. There is no flatter space or negative curvature.

 

[DaveC426913]

Ok Dave, one last time, If fermion A is at point (x,y,z) at time t it can't also be at point (x',y,z) at time t. PEP states that each fermion has it's own unique state at anyone point in time.

Please show me where you think PEP says that a fermion can occupy TWO STATES AT THE SAME TIME?

Boy, you just really don't get this time travel concept do you?


Please show me how any object can be in two places at the same time. It can't. Right?


Your argument really has nothing to do with PEP. Look, I'll use the exact same argument on a macroscopic object.

By the definition of person - a person cannot be in two places at once. Right? That doesn't require PEP; it is just common sense. In every way meaningful, one object cannot be in two places at once. Period. PEP is smply a specious argument that applies to atomic particles and their states.

The point here is that PEP does not add anything to the discussion about uniqueness of objects. If an object cannot be in two places the same time, then it can't be in two places at the same time, PEP or no PEP. Full stop.



Now we add time travel into the mix. As soon as we allow the possibility of time travel it becomes obvious how one person can be in two places at the same time. It also becomes obvious how any particles can be in two places at the same time - if we allow for time travel. It also becomes obvious that PEP has nothing to say about - this because PEP - like all our other sans-time-travel statements - doesn't account for time travel. PEP (like all the rest of physics) assumes that one particle exists only once at any point in time.

But with the advent of time travel, that is now a false assumption. PEP is now inadequate to describe our new situation.

 

[Ash Small]

I had actually been following the dialogue about fermions but having nothing to add to this conversation about "particle physics" apart from perhaps making the suggestion that you guys are in the wrong thread or pointing out the fact that whilst the Big Bang Theory is wildly popular it is to all intents and purposes only a concept in itself and an abstract one at that.
Not an input that would have been welcomed too much no doubt.

Dave, you have complained that input has been off-track concerning this thread yet you continue to talk to me about a flip parallel universe comment that I have repeatedly told you was not serious, have no interest in and has nothing to do with this thread other than some-one else had brought it up, when the choice was there to respond to comment that I made that is related to this thread of "time travel".
Dave, I do realize that my approach to physics is unconventional and that my use of language is unusual. I see no reason that this should invalidate my input. I can assure you that I have extremely valid reasons behind this fact. If you care to contact me privately then I would be happy to explain.

Getting back to time travel, incase any-one visiting this thread is interested in my input! It occurs to me that if a potential time traveler used slow time/gravity variables to travel through faster time/gravity variables, that it actually would indeed be possible to arrive back at the place of your journey's start in your own past. Obviously it is debatable as to whether or not this is physically possible. If not then potential time travelers would probably avoid such occurances happening in their calculations when mapping out their journey.
The benefits of the time travelers time going slow whilst time outside the craft is going quicker, apart from getting to your destination in less time, would mean that engine revs could be kept down in slower speeds affording a more fuel efficient journey.
The difficulties that I mentioned before concerning containing a gravity field:
Perhaps somewhere in the work of Thompson Townsend Brown there lies a clue to the answer. If the walls of the craft were electrically charged: in an inward direction with slow time/gravity variables, in an outward direction with fast time/gravity variables and cancelling out charges were directed at each other between the inside and the outside of the walls that stopped each field leaking into the other, then perhaps this problem could be overcome.

Any comment on time travel?

i agree that using relative speeds and gravity it is possible to slow time down, but this is not the same as time travel.

There is an argument that anti-matter travels backwards through time, but when it meets it's corresponding matter both are annialated, releasing energy.

While you could, theoretically, set out in a spacecraft on a ten year trip and arrive back here after 50 years had passed here, essentially traveling into the future (or your own future relative to others who stayed here) you could not arrive back here before you left.

It could possibly be argued that 'anything that travels backwards through time is antimatter' and will therefore be annhialated as soon as it comes into contact with matter, which travels forwards in time.

(All the above is based on accepted scientific theory)

 

[DaveC426913]

There is an argument that anti-matter travels backwards through time...

An argument, yes. For virtual particles.

It could possibly be argued that 'anything that travels backwards through time is antimatter'

This does not follow. If all dogs are mammals, are all mammals dogs?

(All the above is based on accepted scientific theory)

Please reference this accepted scientific theory.

 

[Ash Small]

Boy, you just really don't get this time travel concept do you?


Please show me how any object can be in two places at the same time. It can't. Right?


Your argument really has nothing to do with PEP. Look, I'll use the exact same argument on a macroscopic object.

By the definition of person - a person cannot be in two places at once. Right? That doesn't require PEP; it is just common sense. In every way meaningful, one object cannot be in two places at once. Period. PEP is smply a specious argument that applies to atomic particles and their states.

The point here is that PEP does not add anything to the discussion about uniqueness of objects. If an object cannot be in two places the same time, then it can't be in two places at the same time, PEP or no PEP. Full stop.



Now we add time travel into the mix. As soon as we allow the possibility of time travel it becomes obvious how one person can be in two places at the same time. It also becomes obvious how any particles can be in two places at the same time - if we allow for time travel. It also becomes obvious that PEP has nothing to say about - this because PEP - like all our other sans-time-travel statements - doesn't account for time travel. PEP (like all the rest of physics) assumes that one particle exists only once at any point in time.

But with the advent of time travel, that is now a false assumption. PEP is now inadequate to describe our new situation.

Dave, you macroscopic analogy of PEP does hols, as we are comprised mostly of fermions ourselves (per unit mass), therefore PEP is relevant.

If we were to travel back in time, the point that we travel back to (and all points that we pass through on the way) would already contain fermions (even space isn't a complete vacuum).

We would be violating PEP for a second time if our fermions were occupying the same space as other fermions.

The only way to avoid this would be to move those other fermions (the other 'matter') out of the way first, which would involve 'changing the past'.

Before you can argue that time travel may be possible, you first have to suggest a viable mechanism, based on scientificly sound principles, by which we can achieve this, and change history after the event.

How would you attemt to overcome these obstacles?

 

[Ash Small]

An argument, yes. For virtual particles.


This does not follow. If all dogs are mammals, are all mammals dogs?



Please reference this accepted scientific theory.

Dave, I'll leave aside the points we seem unable to agree on for now, and stick to the 'common ground'.

(BTW, antimatter isn't 'virtual particles', it has been observed and is real)

If the only thing we know of that travels bacwards in time is anti-matter, then it follows that any time machine capable of traveling into the past MUST be constructed purely from anti-matter.

While this may be theoretically possible, in practice, for obvious reasons, it is impractical/impossible, as it would be annhialated, along with any matter it came into contact with.

 

[DaveC426913]

Dave, you macroscopic analogy of PEP does hols, as we are comprised mostly of fermions ourselves (per unit mass), therefore PEP is relevant.

That's kind of my point. It's not that PEP rules out things being in two places at once, it's simply our conventional non-time-traveling physics. Once we posit time travel, we have to re-examine these assumptions about two places at once.

If we were to travel back in time, the point that we travel back to (and all points that we pass through on the way) would already contain fermions (even space isn't a complete vacuum).

We would be violating PEP for a second time if our fermions were occupying the same space as other fermions.

This argument is silly. By your logic, no atom can ever move, since to do so, it might "occupy the same space" as an adjacent atom.

Again, you do not understand PEP. PEP means that two electrons in the same atoms cannot both occupy the same state. It does not say that one whole atom pushing another atom out of its way somehow constitutes these two atoms occupying the same space and being in the same state.

You're really going off the reservation now.

Before you can argue that time travel may be possible, you first have to suggest a viable mechanism, based on scientificly sound principles

No I don't. That is an engineering issue, far down the road. We first posit that time travel may be possible in pirinciple. We then try to determine if there are any existing laws that prohibit it (the is where we are in the discussion right now). So far, we know of none.

 

[Ash Small]

That's kind of my point. It's not that PEP rules out things being in two places at once, it's simply our conventional non-time-traveling physics. Once we posit time travel, we have to re-examine these assumptions about two places at once.


This argument is silly. By your logic, no atom can ever move, since to do so, it might "occupy the same space" as an adjacent atom.

Again, you do not understand PEP. PEP means that two electrons in the same atoms cannot both occupy the same state. It does not say that one whole atom pushing another atom out of its way somehow constitutes these two atoms occupying the same space and being in the same state.

You're really going off the reservation now.



No I don't. That is an engineering issue, far down the road. We first posit that time travel may be possible in pirinciple. We then try to determine if there are any existing laws that prohibit it (the is where we are in the discussion right now). So far, we know of none.

Dave, here is a quote from the wikipedia article on PEP. This conclusively proves that I am correct here.

"In one dimension, not only fermions, but also bosons can obey the exclusion principle. A one dimensional Bose gas with delta function repulsive interactions of infinite strength is equivalent to a gas of free fermions. The reason for this is that in one dimension, exchange of particles requires that they pass through each other, and for infinitely strong repulsion, this cannot happen."

Time is one dimensional, so nothing can travel through time. Pauli clearly states that.

PEP clearly states that time travel is impossible.

The full article is here:

http://en.wikipedia.org/wiki/Pauli_exclusion_principle

(I've already provided this link in my first post on the subject, If you'd read it you would already be aware of the above quote.)

 

[DaveC426913]

Dave, here is a quote from the wikipedia article on PEP. This conclusively proves that I am correct here.

"In one dimension... bosons can obey the exclusion principle. A one dimensional Bose gas with delta function repulsive interactions of infinite strength is equivalent to a gas of free fermions. The reason for this is that in one dimension, exchange of particles requires that they pass through each other, and for infinitely strong repulsion, this cannot happen."

Time is one dimensional, so nothing can travel through time. Pauli clearly states that.

Nonsense. It says absolutely nothing of the sort.

Once again you are using an "all dogs are mammals therefore all mammals are dogs" argument. There is no way you could understand what the quote was saying and still come to that conclusion logically.

x (of xyz) is only one dimension too. Next you'll be telling me that objects cannot travel through x. The whole point of spacetime is that it is freedom in all 4 dimensions simultaneously. Two particles at the same x coordinate can certainly coexist if they are not at the same y coordinate. For two particles to be "in the same place at the same time" all four coodinates must be the same.

You are really burning credibility now. You should have quit while you were ahead.

 

[Ash Small]

Nonsense. It says absolutely nothing of the sort.

Once again you are using an "all dogs are mammals therefore all mammals are dogs" argument. There is no way you could understand what the quote was saying and still come to that conclusion logically.

x (of xyz) is only one dimension too. Next you'll be telling me that objects cannot travel through x. The whole point of spacetime is that it is freedom in all 4 dimensions simultaneously. Two particles at the same x coordinate can certainly coexist if they are not at the same y coordinate. For two particles to be "in the same place at the same time" all four coodinates must be the same.

You are really burning credibility now. You should have quit while you were ahead.

Dave, One question.

How do you ensure that nothing else is at point (x,y,z) at the time you arrive in the past?

(Or, for that matter, at any point in time en-route)

Unless you can ensure this, my reasoning above still holds.

 

[DaveC426913]

Dave, One question.

How do you ensure that nothing else is at point (x,y,z) at the time you arrive in the past?

How do you ensure that nothing else is at point xyz when you arrive at the cottage in your car?

Or are you going to insist that it is impossible for your car to move into the space occupied by other atoms near your cottage? Are your car atoms and the air atoms going to threaten to be co-incident in spacetime, meaning your car will not move? (No, you're not.)

Unless you can ensure this, my reasoning above still holds.

Your reasoning was about PEP. I'm glad you've finally abandoned this, it was fruitless.


Now we are simply down to an engineering aspect as to how time travel might be implemented, and how we might insert an object in a past time. Who knows?

The point was simply that - whether or not there are loads of implementation issues - we have yet to find a principle that excludes time travel.

 

[Ash Small]

How do you ensure that nothing else is at point xyz when you arrive at the cottage in your car?

The simple answer to that is that my car doesn't travel through time.

I will concede that my car will push air molecules, insects, rabbits, etc. out of the way, but it won't push larger vehicles, trees, buildings out of the way.

OK, Dave, I guess I'll have to concede that you can't (hypothetically) travel backwards in time without altering the past, because whatever was at (x,y,z) before you travel there will have to be pushed out of the way.

If you change the past you change the present, so by traveling into the past you will alter reality at the time you left the present.

This raises a different set of problems.

 

[Magnethos]

Possibly not, but there are some theories to look at first.

Possibly time travel won't be invented never. But I've read some different theories about "pseudoscience".

I think to travel into time, you don't need to go faster than light. Time travel means to dematerialize into this space-time continuum, travel in the hyperspace and materialize in the selected time, and in the selected physical reality.
The first thing to understand is to know how to materialize/dematerialize matter. That means that you need to understand alchemy (unconventional chemistry). Once you understand how to do this, then you can alter finite matter in a specific space-time continuum. In some texts have been documented the possibility to do this using some kind of non-hertzian waves (not electromagnetic energy). In pseudoscience texts it's very know that other kind of electrical manifestation exists. With that non electromagnetic waves you need to know how to interact with matter.

This thing can be proved with a simple idea. You can build a device to measure the resonance properties of materials, and then place a material between an electrical arc. After discharging some electrical energy, then you can "Scan" the material and look if some change has been made (some "transmutation").

Once you understand how to affect matter via electrical waves, you need to understand about time. You need to know that the space-time is a continuum, not an emptiness. All the universe is full of a non-electromagnetic energy. That kind of energy is electron deficient, it means that there is not electron flow. There is a sub-electronic particle that have very different names.
I have some books of an Italian man that build a device to read the acoustic phenomena recorded in materials. He explains that all matter has memory to record past events. He used some electrical equipment and demonstrated that he can "play" the information that was recorded in that stone (or other materials). So, if the physical matter has memory... Why not the ether has memory too? The ether is a chemical compound that is electron deficient. It means that he has not electrons, and it's a gas lighter than Hydrogen, because its atomic number is less than 1. For that reason it's called "Virtual Chemical Compound", since virtual means "massless".

So, if we would able to read the data that was recorded in the ether... we can materialize matter in other time, since we can read and affect time at a distance.

Of course, all this theory is pure hypothesis and it's non proven. But it's only a suggestion...

 

[JaredJames]

If you change the past you change the present, so by traveling into the past you will alter reality at the time you left the present.

There are a number of theories which negate this possibility.

Multiple dimensions and the whole "everything has already happened so whatever you do doesn't change anything" (can't remember the name for that one).

 

[Magnethos]

There are a number of theories which negate this possibility.

Multiple dimensions and the whole "everything has already happened so whatever you do doesn't change anything" (can't remember the name for that one).

I think the same. There are multiple spaces, so anyone can travel through time or through present but in different realities. The universe is running an extremely large amount of multiple realities at the same time.
It's like a world of possibilities. In the present, we're affecting the direction of each reality we're traveling to.
I mean, each little change in this present, affects the next "space frame" we're traveling to.

We're living in a space-reference but we can travel to other space-references, in the present and in other times. Only if the correct characteristics are given and you travel to an exact past space-reference, then could be possible that you affect this space-reference. But if you travel to other past space-reference, then nothing will happen in this space-present.

 

[Time Machine]

The original question was:

"Time machine will not be invented. we will never travel in time, not future, not past.

Why?
Etc.."

I will concur that in your present avenue of approach to time travel that it is highly relevant whether a fermion can be in two places at the same time.
I do believe that with a slight perspective adjustment in the way of thinking about time travel itself, that other methods can be considered and that even if Ash proves (good luck with that) a violation of PEP, that perhaps time can be traveled without the need for anyone to be in two places at the same time...

I agree that the Big Bang Theory is the best theory on the market and also very well funded.

Other not so well funded projects are probably not acceptably cited and therefore shall not be mentioned again. However on the basis that time travel itself is a purely speculative topic, I feel that I am not out of line in speculating that if gravity could be manipulated, that a time travel of sorts may be theoretically possible.

Your concerns, Dave, for the return journey are logical. I'm not seeing a way round this actually. Perhaps this is what puts off the OP's theoretical potential time traveling visitors from making the journey.

Thank you Ash for agreeing that it is (I think he did actually mean) "theoretically" possible to slow time using relative speeds and gravity.

Read your hypothesis Mognethos. Thinking on that...

 

[Brin]

While I'm done arguing since I wanted to pull my hair out (I <3 DaveC), I thought ANYONE interested in a serious and reasonable discussion of time travel might find the following philosophy of physics article interesting:
http://plato.stanford.edu/entries/time-travel-phys/

The Stanford Encyclopedia of Philosophy is a brilliant source for discussions about these kinds of things. These guys are the experts.