To: WSFAlist at keithlynch.net
Date: Sun, 17 Mar 2002 05:21:56 -0500
Subject: [WSFA] Waste of "Time Machine"
From: ronkean at juno.com
Reply-To: WSFA members <WSFAlist at keithlynch.net>

On Sun, 17 Mar 2002 00:52:09 -0500 (EST) "Keith F. Lynch"
<kfl at keithlynch.net> writes:

> I'm aware of five major self-consistent approaches to dealing with
> the
> classic "grandfather paradox" of time travel (i.e. what if you go
> back
> and kill your grandfather before your father was conceived):
>
> * Backward time travel is impossible.  This is the most widely
>   believed both among laymen and scientists, but has the serious
>   flaw that it doesn't lead to interesting time travel stories.

Time travel stories would still be possible, as fantasy, but they would
not qualify as good science fiction, even if they are entertaining.

>
> * Events will somehow conspire to remain consistent.  If you go
> back
>   to the Battle of Gettysburg, you will have been there the first
> time.
>   Heinlein uses this approach in several books.

But if a time traveler goes back into the past and performs some action
which had not been performed in history, as history existed before the
traveler acted, then at least that one act would be inconsistent with the
original history.  Unless, of course, the time traveler finds it
impossible to act with effect, but can only observe, when 'visiting' the
past.  If events somehow conspire to negate the change which would have
been expected to result from the time traveler's action, then we have the
odd situation wherein some events change, and some do not.  That, in
turn, implies that some events are more 'important' than other events, in
that the 'important' things may not change, while the 'unimportant' ones
may change.  That does not make much sense, given that 'importance' is
not a physical quality, but is rather a psychological quality.

A kind of backward time travel would be possible by flying out into space
faster than light (assuming FTL travel is possible), and intercepting the
light rays from past events.  But that would be _observing_ the past, not
changing it.  Of course we already know how to observe the past (using a
video camera/recorder), if we plan ahead by making a recording of what we
wish to later observe.

>
> * History branches.  Change the past, and you simply create a new
>   timeline.  L. Neil Smith prefers this approach.  James Hogan
>   (_The Proteus Operation_) has also used it to good effect.  Some
>   physicists think history branches anyway, even without the aid of
>   meddling time travelers.  Some stories describe "sideways" time
>   travel in which one can travel into parallel time-streams, but
>   not into the past or future.  H. Beam Piper (_Lord Kalvan of
>   Otherwhen_), F.M. Busby (_All These Earths_), Isaac Asimov
> (_Earth
>   is Room Enough_), and Murray Leinster ("Sidewise in Time") are
>   good examples.
>

There are enormous number of ways in which the universe changes
unpredictably from instant to instant, on a quantum level.  Let's say
that's at least 10^80 choices, based on the number of nucleons in the
universe, and let's say that each instant is the Planck time.  That's an
awful lot of new universes popping up each second.  It's not economical,
and it seems like it might require a lot of extra dimensions.  And if
many branching histories were true, how would we ever know?  If there is
no way to know whether a proposition like that is true, perhaps the
proposition is not meaningful.

> * The stack theory:  Change the past and history starts over from
> that
>   point.  The previous future is erased, except for whatever parts
> of
>   it the time traveler brought back with him.  James Hogan (_Thrice
>   Upon a Time_), John Cramer (_Einstein's Bridge_), and Orson Scott
>   Card (_Pastwatch: The Redemption of Christopher Columbus_) have
>   used this to good effect.
>

This sounds like a more economical variant of the many branching
histories hypothesis.  So I suppose the grandfather paradox is solved by
the traveler somehow becoming someone else, someone who was born, when he
kills the grandfather; in other words, when he tries to kill his
grandfather, the man he kills is not his grandfather, if he in fact
succeeds in killing that man.

> * Niven's law:  Time machines will never be invented since use of
> time
>   machines would repeatedly alter the past until it was altered to
>   cause the time machine not to have been invented.  In one of
> Larry
>   Niven's short stories with a long title, one side in an
> interstellar
>   war invents a time machine, but, believing in this law, decides
> to
>   leak the information to their opponents instead of trying to
> build
>   one, expecting that this will cause their civilization to
> collapse.
>

Another perspective is that if time machines are invented in the future,
time travelers could visit the past and teach their ancestors how to make
a time machine, or simply provide them a time machine.  So if backward
time machines exist at anytime in the future, they should exist now, but
they don't, so they won't.

> > But suppose we ask whether it is possible to simply _look_ into
> the
> > past, without actually 'being there', ...
>
> It's true that this wouldn't lead to paradox.  It could lead to
> social
> problems, as in Isaac Asimov's classic novella "The Dead Past".
> Clarke
> and Baxter's _The Light of Other Days_ is a good recent treatment.
>

If we had a Big Brother-type surveillance society, with many events of
human interest being recorded and archived continuously, we could
approximate the ability to observe the past, at least as far back as the
recording began.

> > Suppose there were a webcam on a planet orbiting a nearby star,
> > say, 5 light years away.  The camera and the computer to which it
> > is connected would record events as they happen, and, assuming we
> > had an internet connection to that computer, we could watch those
> > events, but we would see them 5 years after they actually
> happened,
> > because the internet transfers data at roughly the speed of
> light.
>
> Yes, this could work, if they had a *really* strong telescope, and
> if
> you didn't mind waiting ten years for the web page to load.

It sounds like you thought I was talking about the camera on the other
planet observing events on Earth through a telescope.  I was thinking of
the camera observing local events on the other planet.

>
> A simpler approach is to have an earth-sized flat mirror a few
> light
> years away, and aim a nearby telescope at it.
>
> More practical would be lots of cameras in low earth orbit, and
> lots
> of videotapes.

Watching an old 'I Love Lucy' rerun, we can see events which happened
half a century ago.  When we look at a star 50 light years away, we see
light that left the star 50 years ago.  What's the difference?
Fundamentally, I don't think there is a difference.  In each case, light
from events has been recorded and played back, only the methods of
recording and playback are different.

> We're already starting to get video cameras everywhere.  I have no
> great objection to this (so long as they don't start peeking into
> houses), but I think access to this should be available to
> everyone,
> not just to the government.  Imagine being able to key in a
> location
> and a date and time on your PC, and being shown what was visible
> then
> and there (assuming a camera was there at the time).
>

I see problems with the system being open to access by anyone.
Suspicious girlfriends would be tracking their possibly unfaithful
boyfriends.  Stalkers would have a field day.  Burglars could stake out
buildings efficiently, watching for when the occupants are not present.
Of course would-be victims of burglary could watch their buildings from a
distance, but there is anther related problem which could arise.  If
ubiquitous surveillance became a reality, it might become fashionable for
people to wear masks and disguises in public.  Then there might be
demands for people to implanted with ID tracking chips.  But like it or
not, cameras and data storage are becoming so cheap that we may well soon
have cameras in many more public places than now.

> > But suppose we had an internet connection which was many times
> > faster than the speed of light, ...
>
> Unless there are major flaws in special relativity (which seems
> unlikely) faster than light communication implies an easy way to
> also
> get back through time communication, which leads back to the
> classic
> paradox.  Imagine being able to enter a location and a *future*
> date
> and time on your PC and being shown what will appear then and
> there.
> --

It does not make sense to me that it could be possible to view the
future.  Suppose that Enron stockholders could have found out last summer
that Enron would collapse in December.  They would have sold their stock
last summer, and Enron would have collapsed last summer.

Is it now possible to communicate instanteously across space, using
quantum entanglement?  If so (or even if not), how is that different from
communicating faster than light?

Ron Kean

.

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