Re: Quantum Time Travel

From: <>
Date: Mon, 21 Feb 2000 19:08:25 EST

In a message dated 02/18/2000 8:19:15 PM Pacific Standard Time, writes:

> I've been considering time travel in the context of quantum mechanics and
> parallel universes, and have come up with some thoughts and ideas about
> subject. This might be a little off-topic, but it does have to do with
> theory of parallel universes, which seems to be a large part of the
> discussion on this newsgroup. I'm interested to know what you think of my
> thoughts/ideas.
> Most scientists agree that time travel is theoretically possible.
> the task seems monumentous, many scientists also agree that it will
> eventually be possible. Using MW theory, the paradoxes are resolved.
> are some of my observations/ideas/theories behind quantum time travel.
> I know from some of the research I did (and some reasonable assumptions)
> that travelling back in time would put you back to the branch in which you
> set your "time machine" to travel back to, and from there you would branch
> into a universe in which you suddenly appear from the future. From there,
> probability would remain as you expect it to using the SE, but since
> are initially different in this branch (you are there), things would turn
> out differently in that universe than in one in which you didn't appear.
> But how exactly is probability affected during time travel? I assume one
> two possibilities:
> 1. Travelling back in time actually affects the probability of the people
> from that time suddenly seeing you appear from the future. So, if
> the probability of you appearing would be nil, then because in the future
> you decided to travel back to that time, you actually made their
> of seeing you appear significant. Perhaps those people actually have a
> 50/50 chance of seeing you appear. Those who end up in the universe in
> which you didn't appear would eventually end up at the point in which you
> decide to go back in time. Those who end up in the universe in which you
> did appear would probably follow an entirely different path.
> 2. Travelling back in time does not affect the probability of the people
> from that time suddenly seeing you appear from the future. The only way
> they would see you appearing is if molecules from their universe suddenly,
> by pure chance, arranged themselves to create you. Of course, you know
> this universe was very likely to be YOUR universe, but at the same time
> know that everyone else you see in it is in a universe that they had an
> absolutely nil chance of being in. They are justified in claiming that
> appearing in their universe was an absolute miracle and fluke of nature,
> while at the same time you are justified in claiming that this universe
> very likely for you, and was not a miracle or a fluke of nature at all.
> other words, by time travelling you have managed to put yourself with
> virtual certainty into a virtually impossible universe. If this was the
> case, then for us to see beings from the future visiting us would be no
> special, and in fact no different, than me suddenly appearing on the moon
> pure chance. This would give an answer to Stephen Hawking's argument
> against time travel, which was that if time travel were possible, we
> be seeing visitors from the future.

Somehow Proposition #1 does not satisfy me. I believe that time is a first
person experience, which is the result of the linkage between points in the
plenitude. This linkage is perceived only when it is antropically allowed and
results in the rationality of our consciousness exactly matching the
rationality of the physical laws. Proposition #1 according to which time
travel can change the probability of the world we travel to, implies a third
person (objective) effect which I find difficult to accept.

Proposition #2 implies that the world we travel to is very highly improbable
and therefore you discount it.

To put things into perspective, let me ask a question. How probable is your
world? How likely is it that a sentient creature called Fritz Griffith with
precisely the right height, weight, birth date, correct number of freckles
and wrinkles, number of tooth cavities and hair on the head, profession,
parents, siblings, nationality, number of chromosomes living on a planet with
one moon, a solar system with nine planets,... exists anywhere in the
universe? Isn't this a miracle just as unlikely as being transported to the
moon? In fact I could come up with a scenario that could make being suddenly
transported to the moon a *relatively* very likely event: imagine a race of
extragalactic creatures, the %$&nicks, who just set up a zoo on the far side
of the moon to provide a cast for their movie "Monster from Planet Earth," in
which you, Fritz, will be the star. They descend on the Earth in their ultra
compact insect like space vehicle and shoot you with their amnesia producing
sting. A larger radar-invisible vehicle then transport you to the moon where
you suddenly wake up, not being aware of your little interplanetary trip. You
are then given your role in the movie in which you manage to survive long
enough to eat, out of hunger, a large number of baby %$&nicks until you
encounter your nemesis when you meet their mother.

I won't go into the math to prove that such a scenario is more likely than
you existing in the first place for the following reason:

Even though our world seems to be quantized (discrete), I believe that the
variations from world to world in the MW follow a continuum. This is
something I cannot prove. However this appears to be the maximalist model in
keeping with the idea of the plenitude and any other (finite or discrete)
model would have to be justified. Because the MW is a continuum it should be
possible to renormalize the measure at every point in the MW, and therefore
the assertion that a probability is "low" is ambiguous and possibly

George Levy
Received on Mon Feb 21 2000 - 16:12:10 PST

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