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RE: Is Time Travel is Possible?



I’d like to come back on just two of my points, perhaps the more contentious, and therefore more fruitful lines of enquiry.

 

The first point, in summary, is that if time travel exists, then the mass of the universe will fluctuate over time. I use the phrase “over time” to get around any semantic discussion on whether the mass of the universe can be considered outside the context of time.

 

Now, I have noticed that much of the debate on this thread has included a high content of scientific argument, which suppresses contributions from those without a scientific bent, so I’ll keep my content science light. If time travel does exist, then I’d expect this to occur to some degree in the natural world. My reasoning is that if something is possible, then we usually see it occurring in nature. I’m thinking here about matter moving through time – elementary particles, black holes, light, car keys etc. Now, with the exception of car keys, which may have another explanation, we don’t normally experience things disappearing or appearing. My argument, in basic philosophical terms is

-          if time travel is possible it would occur in the natural world

-          time travel in the natural world would be observable

-          there is no evidence for time travel occurring in the natural world

-          ergo – time travel is not possible

 

The next point is over the claim that neither the past nor the future exist. We need to ground ourselves on what existence means, and without wishing to regress to Descartes I would suggest that for something to exist it needs some element of tangibility, or a potential for interaction with other things that exist. OK, the past is important in that it has some bearing on the present, but it cannot be said to interact with the present. I cannot weigh an object in the past, or eat a cheese sandwich that was made in 1837, or speak to my great, great, great granddaughter who will not be born until 2075. Therefore, in the normal context of the semantics, the past and the future do not exist. If they do not exist, I cannot go there. You might argue that this is a circular argument – if time travel did exist, then the past and the future must also exist. I would not say this is circular, but the two statements must either both be true, or both be false.

 

Any thoughts …?

 

Bernie Doeser

Sandiway, Cheshire, UK.

 

-----Original Message-----
From: owner-bups-dis@purplepancake.com [mailto:owner-bups-dis@purplepancake.com]On Behalf Of andrew stephenson
Sent: 10 November 2005 00:15
To: bups
Subject: Re: Is Time Travel is Possible?

 

hi Bernie,

 

in reply to your first point: The fact that object was travelling from time A
 to time B does not mean that it somehow steps outside the universe, thus reducing the overall matter of that universe. Such an idea would indeed result in a breaking of Einstein's (thought it was Newton's?) laws because it presupposes that it is possible for there to be something outside (or other than) the universe, which Einstein's theory does not and cannot account for or accept. Time travel, if we are to look at it from within an Einsteinian universe, would occur by travelling diferently through curved spacetime, not by leaving it.

 

to your second point: i entirely agree that what was talked about does not cohere with what most people think of when they think of time travel, but this is because we have a certain concept of time. Perhaps exemplified best by Kant in the trascendental aesthetic of his first crit, where he offers arguments for the apriority of time (and space) and also when he argues for the pure concept of causality, it is very tempting and intuitively correct to thinkof time as linear, successive etc, like this ---------------------------,or ABCDEFGHIJKLM... But our traditional view of space and time has been challenged precisely by relativity theory (not to mention Quantum theory). And therefore, if we are trying to discuss time travel with reference to science, as i think we must, we should of course try to disregard what we think are our intuitions (not, this time, in the kantian sense). Particularly if they have been formed, or have their primary refence to Spielberg Films. ! This delimiting may of course be more boring, but then isn't everything more boring without Doc Brown and a flux capacitor thingy?!

 

to your third bit: i think this is the most common and most difficult problem. it is easy to come up with loads of paradoxes, but again, only if we take a Doc Brown view of time travel. But for the moment i will accept this, just incase my second reply (just above) is detrimentally faulted. But now i dont precisly know if i have an answer. Perhaps if we take an extreme relativist stance which denies a reality that is independent, then time travel would not involve moving yourself, but instead moving reality so that the past simply became part of the present (your present which is on this view the present). the same applies for travel into the future. hmmm, i never thought i would find myself arguing for the possiblity of time travel from an anti-realist point of view.

 

to the fourth and final point: lots of things happened that are not documented ( how do i know this if they are not in some way documented, by pen or memory etc?). i personally, and i have an incling that Alice might agree with me, have now wish to by out microsoft, if the implication was that it would be to make money, lot and lots of it...

 

there we go, what you tink?

cheers,

andy

 


Bernie Doeser <bernie@doeser.org> wrote:

To reply to this message or start a new topic please email: BUPS-DIS@bups.org


There are a number of problems and paradoxes with the concept of time
travel, which favour the argument against it, which I don't think have been
raised so far.

Firstly - if an object, with mass, travelled from time A to time B, then the
mass of the universe would be reduced by the mass of the object for the
period of time between A and B. This would seem to contradict one of
Einstein's theories that matter cannot be created or destroyed.

Secondly - there are no known mechanisms for time travel. Accepting that
your internal time slows the nearer you get to the speed of light, it is
theoretically possible that you could fly in a rocket and return in eighty
years time, with only five years on "your" clock. But is that time travel ?
I think it is not ! what most people mean by time travel, which is what
happened in the "Back to the Future" films. Dial a date, press a button, and
fall in love with your long dead great great grandmother. Time travel in
it's common understanding involves a discontinuous travel backwards or
forwards in time. No mechanistic theories come close to explaining how this
might happen.

Thirdly - for time travel to be possible the past and the future have to
exist. We know that the past existed - we remember it, but we do not know
that it continued to exist after we experienced it. There is an inherent
assumption in time travel that the past and the future exist continuously,
and we are merely passing through it. The determinists will argue that the
future already exists, that it is unchangeable, and that we have merely to
experience it. As philosophers we know this poses problems for free-will,
personal responsibility etc etc. So therefore time travel is inconsistent!
with free-will. There is an interesting twist when you extend this thought
experiment. If the future already exists and we travel to it we would be
changing it (by our presence) which would mean that it exists in a different
form after we travelled to it than before. Therefore the future changed and
so could not have existed.

Finally - If the past does exist, and someone has travelled back there, then
someone has already time travelled, and there is a record of it in the past.
But as there isn't, we haven't. The conspiracy theorists would say that time
travellers would be ultra discreet. Personally I think they'd have bought
out IBM, Standard Oil and Microsoft.

Bernie Doeser
Sandiway, Cheshire, UK.






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