9.5.2 Consistency Protection (Relativity and FTL Travel)
Description
This article is from the Relativity and FTL Travel FAQ, by Jason W. Hinson jason@physicsguy.com with numerous contributions by others.
9.5.2 Consistency Protection (Relativity and FTL Travel)
The second provision is what I am calling "consistency protection". The
idea is that the universe contains some sort of built-in mechanism whereby
some event in our list of events would not be allowed to occur.
An example of such a mechanism can be found when we look at the
situation through quantum mechanics. (A theory of Steven Hawking called the
"chronology protection conjecture" (CPC) attempts to do just that--the jury
is still out on this theory, by the way, and will probably be out for a long
time.) In quantum mechanics (QM), we do not think in certain terms of
whether or not an event will occur in the future given everything we can
possibly know about the present. Instead we consider the probability of an
event (or string of events) occurring. One form of consistency protection
would insist that QM prevents the unsolvable paradoxes because the
probability of all the events occurring so as to produce an unsolvable
paradox is identically zero.
Under this explanation using QM, our bullet example would be resolved
through arguments similar to this: It may be that the Op observer is unable
to produce the FTL bullet (perhaps his FTL gun fails), thus averting the
paradox. If he is able to get the FTL bullet on its way, then perhaps the
bullet will end up missing its mark. If it does hit the victim, then perhaps
the victim's friend will be unable to send an FTL signal back to the O
observer (perhaps his FTL message sender fails). If the signal to O gets
sent, it still might not be received by O. If O receives it, he may be
unable to stop Op from firing the bullet. In any case, this particular QM
explanation would insist that one of these events must not occur, because
the quantum mechanics involved forces the probability of all of the events
occurring to be zero.
To sum up, this provision requires that some mechanism exists in the
universe that would prevent at least one of the events from occurring so
that the unsolvable paradox does not come about. This mechanism does not
have to specifically target any of the FTL trips/messages which one might
want to make/send, but it could disallow any of the events which must be
present for the unsolvable paradox to occur. We should also note that this
provision (just like the last) can be apply regardless of the FTL concept
used.
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