X-Message-Number: 22164
Date: Tue, 08 Jul 2003 23:06:02 -0700
From: Mike Perry <>
Subject: Time Travel

Alan Mole, #22156, and my responses:
...
>In fifty years we'll probably have intelligence genes and very-high-IQ
>offspring, thousands or millions of clones of our brightest scientists,
>man-machine interfaces to augment our wetware, strong AI, and 
>nanotechnology.  What
>will come of that we cannot imagine.  What will come of that in a thousand
>years, or a million, is utterly unknowable.  But it could well include time
>travel and mind harvesting.  Why *wouldn't*  it?

In particular, you are asking why wouldn't time travel be among the 
accomplishments of beings of higher intelligence that could develop out of 
our civilization. You lump this in with "mind harvesting" but here I will 
focus just on time travel alone. A good reason that time travel may be 
impossible regardless of how much intelligence and effort you throw at it 
is that it would involve a logical contradiction. If "time travel" is to 
include travel into one's own past, it seems such a contradiction would be 
unavoidable, since you could look up your father, mother, grandparents, or 
some other ancestors, and *interfere* in such a way as to prevent the chain 
of events that resulted in your own presence in the world. However, you 
*did* come into existence (contradiction!). This is called the grandfather 
paradox. Could a superintelligent being "find a way around it"? I suppose 
it is possible (such as a discovery that one might travel into the past and 
gather information but one's ability to influence past events would be 
limited or nonexistent). This however is far from guaranteed. And you are 
asking for reasons why time travel *might not* be possible, not why it 
might be. Think of the problem of squaring the circle with ruler and 
compass (that is to say, using mathematical idealizations of these tools). 
An ancient might have argued that some day we would have knowledge, 
intelligence, and so forth such that surely we would know how to do this. 
But we know now that we never will. True, our knowledge did increase, but 
knowledge can cut different ways. In this case, in 1882 a mathematician 
named Lindemann proved that the problem could not be solved. Intelligence 
can sometimes find a path to a goal that was heretofore unknown. But it may 
also be able to show, contrary to previous hopes or expectations, that all 
paths to a goal are blocked. Returning to time travel again, the one 
problem of the grandfather paradox already makes the case for it look, 
maybe not absolutely hopeless, but still very doubtful.

Mike Perry

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