RE: Is Time Travel is Possible?

["Bernie Doeser" <bernie@doeser.org>]

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Does the time shift phenomenon that James describes constitute time travel? If so, then me bouncing up and down on my chair constitutes geographical travel. I think that what we truly mean by time travel is what is described in science fiction. That is, flick a switch and go out for a drive in a hansom cab with your great great grandmother.

I agree that my postulation that if time travel were to exist, then it would exist in the natural world, is purely an argument by analogy. Gravity, electromagnetism, condensation, osmosis are several of the many phenomena which exist in the natural world. Their study has formed the basis of scientific research. We can duplicate them in the laboratory and the factory. I struggle to think of any physical phenomenon that man has produced in the laboratory that cannot be or have not been found in nature. Fission, fusion, x-rays.....

To respond to the implied question  "if time travel exists in the natural world how would it show itself?" I guess we would expect to see duplicates of objects, one older than the other. One of these objects would just appear out of nowhere. We would also see objects disappearing. As there are no verified recorded instances of such events, then I postulate that they don't happen, and if they don't happen, then time travel doesn't happen in the natural world. To say that if time travel only occurred out of our universe and into another universe or part of space we cannot observe, then we would not observe it, is true, but is it reasonable? Why should time travel only occur in such ways that we cannot observe them. These arguments are reminiscent of creationist justifications, or for some of the arguments in favour of life after death.
To move on to the really interesting postulate, that the past does not exist, is, I agree, very difficult to conceive, but I do not think I am alone, or the first, to suggest such a notion. I would contend that it is indeed possible to eat a cheese sandwich on Sirius B, as geographical travel is possible. We could put James and his sandwich in a rocket and send him to Sirius B and if he were still alive, then he could eat his cheese sandwich there. The issue would be whether he could keep alive for the journey, not whether or not he could get there. 
There is a view, which I think is one borne out of hope rather than rationality, that our past is preserved, as if in aspic, so that in the future we could return to it should we crack the minor technical problem of time travel. In one of the Back to the Future films Dr Emmet Brown draws a series of time lines, with bifurcations at key decision points. It all seems so logical.
My real problem with this thesis is that if the past still exists somewhere, then the inhabitants of it will think of it as the present, their present. So the past would be tangible, it would be real. For time travel to be possible there must be a present to travel from and a past to travel to, therefore one needs at least two copies of the universe. Everything has mass, even in the past. Mass requires energy. So every second when a tangible "copy" of the universe is left in the past, there has to be enough energy found from somewhere to duplicate the entire universe. But why take a copy every second? Why not every nanosecond? Far more copies. But really the copies should be continuous - for that we need infinite amounts of energy. Am I getting any converts yet ?
Ah, I hear you say, but all of the past and all of the future already exist. No energy will be required. Then we need to look at the deterministic arguments. A pre-exisiting future denies the possibility of free will, therefore all of these debates we will continue having have already happened in the future. If you think that this is the case, then you must also agree with the tenet that we are not responsible for our actions as we have no free will, therefore incarceration is unjust. We don't need to try to do anything as our future is already planned out in detail. This is a very dangerous path to follow.
Can I challenge the believers in time travel to try and prove, not that "time travel is not impossible", but either that "time travel is possible", or "time travel happens", or perhaps even "time travel is necessary" ? An alternative attack might be to show that time travel is not inconsistent with free will.
I might assume that should no one rise to this challenge, then my argument has found widespread favour.
Ps. If anti-matter is matter moving backwards through time, and if anti-matter explodes on contact with matter, then doesn't this make time travel rather dangerous?

Bernie Doeser
Sandiway, Cheshire, UK.

-----Original Message-----
From: owner-bups-dis@purplepancake.com [mailto:owner-bups-dis@purplepancake.com]On Behalf Of James Alexander Cunningham
Sent: 07 December 2005 11:14
To: BUPS-DIS@bups.org
Subject: RE: Is Time Travel is Possible?

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


Better late than never, here are my thoughts. Firstly, time travel, in the sense of sending of a spaceship, having it return eighty Earth years later to find that only five years have passed for the crew of the ship, happens. Granted, not on such a dramatic scale, but the effect has been observed. A few years ago, on the Royal Society Christmas Lectures an atomic clock was placed on an airliner and flown around for a week or so. When it returned it was something like 0.0000002 seconds out of sync with a similar clock that remained on Earth. If this is considered to be time travel then we are all travelling through time constantly.
The argument that Bernie gives for supposing that if time travel were possible it would occur in the natural world is very suspect. Allow me to re-iterate the argument with my comments:

-If time travel were possible it would occur in the natural world.
Firstly, it may. One explanation for anti-matter is that it is matter moving backwards in time. Secondly not everything that is possible is observed in the natural world (the synthisization of certain elements for example, or even certain chemicals). Thirdly, it presupposes that everything that is possible (at least in some sense) has happened. Any argument following this line would need further explanation.
-Time travel in the natural world would be observable.
Not necessarily. This would suppose that either a) Time travelling objects only moved to within the observable universe, within recorded history (including fossil records, archaeological data, written sources etc.) or b) That the observer is omniscient. Denial of both poses no problem for the supporter of time travel.
-There is no evidence that time travel has occurred in the actual world.
-Ergo, time travel is not possible.
In fact all this argument proves is that there have been no recorded examples of time travel within the observed universe. To claim from this that time travel is impossible requires the claim that everything that is non-actual is impossible (which you may wish to argue for, but most would shy away from it).

Bernie then goes on to deny that the past exists, claiming that it cannot exist because we cannot interact with it. The example given is that I cannot eat a cheese sandwich in 1837. This is very true, but equally I cannot eat a cheese sandwich on Sirius B. The reason is very simple. I cannot eat a cheese sandwich on Sirius B because I am not there. Equally I cannot eat a cheese sandwich in 1837 because I am not there (or then) either. The fact that I (or Bernie) am not present does not mean that either Sirius B or 1837 do not exist. Just a couple of thoughts. People who are interested in this sort of thing might like to check out Time, Change, Cause and Effect in issue 1 of the British Journal of Undergraduate Philosophy, a superb article that I really cannot praise highly enough (if only because I wrote it).

When I get a moment I'll knock out a few of my own ideas on this subject but I'm busy busy, and tend to change my mind on a daily basis anyway.

Love you

James




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