Conference noted::sf

    Ah, I was wondering when this topic would surface.  It's one of
    my favorites.
    
    Personally, I consider an FTL drive a perfectly good time machine.
    It's about the most scientifically plausible form of time travel
    available (not that this is saying a great deal).
    
    But you wanted theory first.  Special and general relativity are
    the best available theories on the nature of time.  According to
    them, IF you could time travel (which is possible in some oddball
    models of spacetime from GTR), the past would be rigid.  Go back
    and try to murder your infant grandfather and you WILL be stopped.
    Most of the noters in this file are probably familiar with the paradox
    that would result if you weren't stopped: if you killed your infant
    grandfather, you couldn't then exist so as to kill him, so he lived,
    so you were born to travel back in time to kill him, so can't exist,
    which means you do, which...
    
    Since such a situation is impossible, you can't do it.  Some
    circumstance will always arise (did always arise) to prevent it,
    just as there is always some catch in any attempt to trisect an
    angle with straightedge and compass.
    
    You CAN design a system with a changeable past, but you must go
    beyond current theory and introduce a second dimension of time.
    Asimov did this in "The End of Eternity" and called the second time
    dimension "physio-time" since its main measure was the physiological
    clocks of the time-travelers themselves.  Fritz Leiber was even
    more explicit in his Change War stories, where hyper-time is called
    "The Big Time" and the time we ordinary folk live though is "Small
    Time" or "Little Time."
    
    The reason you need hypertime is that you need something in which
    the past can change.  Change is a thing spread through time.  If
    the contents of time itself changes, then time itself is aging.
    According to what clocks?  Obviously not any clock imbedded in time
    itself.  At what TIME does 1776 have a different contents than it
    does now?  Well, it doesn't have a contents NOW in 1986; it only has
    one in 1776.  There's no room for a second edition of 1776 unless you
    insert some form of hypertime.
    
    Once you do that, you can have a changing spectrum of histories.
    Exact relationship between events in time and events in hypertime
    must be worked out in some detail by the individual SF author.
    
    Now, suppose that someone invents a machine for traveling through
    hypertime.  Is hypertime rigid, or can the whole spectrum of histories
    be changed over a lapse of hyper-hypertime?  (It now becomes convenient
    to label these systems 1-time, 2-time, 3-time..., N-time.)
    
    Personally, I find rigid time more interesting, exactly because
    of the constraints.
    
    By the way, what is the difference betweeen a "linear progression"
    and a "dimension"?  Time is pretty obviously a dimension in the
    physical and mathematical sense, since it can be measured.  By that
    meaning, mass and velocity are dimensions, too.  What did you mean
    by "dimension"?
    
    Getting down to the mechanics, suppose special relativity is
    reasonablly accurate but that we also invent some form of instantaneous
    teleportation or hyperdrive.  Now an "instantaneous" transit is
    one for which arrival and departure times are simultaneous.  And
    simultaneity is notoriously arbitrary in special relativity.
    
    Define a rest frame.  In the frame of a body moving with respect
    to the rest frame, the set of events that are simultaneous with
    the present is "tilted," according to the standards of the rest
    frame.  Some events that the rest frame says lie in the future and in
    front of the moving body are in front but in the PRESENT in the
    moving frame.  Events that are behind the body and in the past,
    in the rest frame, are behind and PRESENT for the moving frame.
    
    So load your teleport or hyperdrive on a near-light-speed ship.
    Head away from the Earth, accelerating until the proper point in
    history is in the rear part of the plane of simultaneity.  Then
    fire off the teleport and arrive on Earth in the past.
    
    You might have to make several such transits to work back to a point
    before you left Earth, but it can be done.  Many people consider
    faster-than-light absurd exactly because it allows for time-travel,
    which they regard as CLEARLY absurd.
    
    Using general relativity, there are tricks you can pull with gigantic
    rotating black holes and such to create Ye Olde Tyme Warpe.  Kurt
    Goedel, author of the famous incompleteness proof, showed that,
    in generat relativity, you can describe a universe that is in absolute
    rotation.  (Relativity disallows absolute position and date, but
    not absolute orientation.)  If you then execute a sufficiently wide
    closed path in this universe, even slower than light, you can return
    before you left.
    
    If you imagine a future technology of gravity control, you might
    be able to time-warp on a smaller scale, without seeking giant black
    holes or hoping that the real universe rotates.  (If it does, it
    does so very, very slowly.)
    
    As I said, both time-travel by hyperdrive and time-travel by time-warp
    take place in a framework of rigid history.  Changeable time requires
    something even more exotic.
    
    Earl Wajenberg

    I mentioned this slightly differently in another notesfile, so,
    based on that experience, I will choose my words very carefully
    here.
    
    The late John W. Campbell, Jr. once proposed the following model
    to help visualize the time _process_:
    
    Consider a nonconductive, infinitely thin, tube or pipe filled with
    water.  Then visualize one end of the tube in intimate contact with
    something cryogenically cold.  The water in the pipe (at the opening)
    freezes instantly, and the freezing process starts up the length
    of the pipe.
    
    In the pipe, there are three conditions: the crystalline ice, the
    semirandomized water molecules, and the interface where the waster
    is becoming ice.  The structure of the ice can be analogously equated
    to the fixed nature of the past; the random structure of the water
    can be equated to the undefined future, and the interface can be
    considered the equivalent of the "moving" present, where events
    gain [temporal] structure.  The velocity of propogation of the
    interface is immaterial (it could be constant, accelerating, or
    decelerating); for our model, it seems constant _in terms of
    crystallization_.  
    
    This model would rule out time travel in both directions (a view
    I rather subscribe to) other than the way we're all "traveling"
    anyway: one second at a time.
    
    That doesn't mean I don't like a good time-travel story.  (Sprague
    deCamp's "Wheels of If" was rather cute that way.)
    
    Steve Kallis, Jr.
    

    	RE. 1
    		331.2 is exactly what I meant by a 'linear progression'.
    That is to say, the theory that time is moving at a not necessarily
    constant, but uni-directional, rate. The theory is nice, but for
    my tastes, too pat. It seems to exclude newer theories ( supersymmetry,
    superstrings, etc. ), that are being upheld daily with further
    experimentation. Supersymmetry especially ( even though I don't
    have the technical background to really understand it ), seems
    to propose added dimensions with increased energy. I basically
    agree with this. For dimension I'm using a *loose* definition
    of another plane in which it is possible to place and move a 
    point. This is bad wording, I know, and I hope I don't get clobbered
    for it. Another way of saying it is a 'direction' beyond the
    length, width and depth we normally move and exist in.
    	
    	Any better? Sorry, have to go. I'll go a little further
    later.
    
    
    ______
       /-/ JASON
    -----

    Re .3
    
    Well, not to clobber you to badly, but I am somewhat familiar with
    the supersymmetry theories, et al., and I'm not aware that they
    posit new dimensions of TIME.  (I *did* posit new dimensions in
    331.1, I'll venture to point out.)  The extra dimensions in the
    new physical theories are spatial ones, and are very small.  That
    is, they posit a proton-sized hypersphere of as many as seven
    dimensions associated with each point of ordinary three-space. 
    
    The sphere may be distorted into various multi-dimensional egg-shapes
    which correspond to the presence of the four fundamental forces
    in their varying intensity.  At least, that's the theory.
    
    Re .2
    
    As in the last time you mentioned this picture of time, I will point
    out that it implies hypertime.  That may be a good, bad, or indifferent
    thing, but it *does* imply it.  You have a given piece of time change
    its state.  At one, uh, time 12:00:00 is "liquid."  At another,
    it is "frozen."  What is the time through which 12:00:00 passes
    as it changes states?  There must be a form of hypertime, 2-time.
    And does 2-time work like a freezing pipe?  Then there must be 3-time,
    and so forth.
    
    Earl Wajenberg

    Going on a little about the freezing-pipe model of time--
    
    There are two novels using it, "Croyd" and "Doctor Orpheus," by
    (I think) Ian Wallace.  The hero, Croyd, is a humanoid alien with
    assorted psychic powers, time-travel being one of them.  If he moves
    into the past, he is phantom-like and can affect nothing.  If he
    moves into the future, he can affect things normally, but the things
    he finds are fuzzy, or appear as multiple exposures, and the blurring
    gets worse the further into the future he goes.  He is, of course,
    interacting with all the different possible futures.
    
    Earl Wajenberg

    re .4:
    
    On hypertime:  Well, I could hypothecate a bilaterally symmetrical
    time state where eaxch time is the other's hypertime.  The model
    is actually a miniaturized way of looking at the whole schmear in
    miniature ("As below, so above," so to speak).
    
    Cheers,
    
    Steve
    

     re .1
    
     I've got five more replies to this to rad, so I may be repeating
    some things already said, but...
    
    One off the wall observation about the killing your grandfather
    paradox.  Why couldn't the resolution of this event oscillate,
    like an amplifier will when you connect its output back to its
    input?  The period of the oscillation would depend on how long
    it took changes to progagate through time.  This would require
    that "second time dimension" for these oscillations to occur
    within.
    
    Regarding the "second time dimension", I used to refer to this as
    "the big clock hidden behind the black velvet curtain".

    len.
    

    Re .7
    
    A temporal oscillation in hypertime sounds logically consistent.
    And just as a piece of pseudo-science rhetoric, it sounds marvelously
    impressive!  I can hear the Doctor using the line now as the TARDIS
    slogs its way through the vortex.
    
    Re .6
    
    A symmetrical pair of time dimensions would probably work.  It would
    certainly allow a marvelous scope for tying one's worldline in temporal
    knots.  Aging through time-B, I travel back in time-A and study
    the Civil War.  Accidentally, I cause and ancestor to step in front
    of a bullet.  Again aging forward through time-B, I return to my
    present in time-A and discover all my family and myself have never
    been heard of.  Put out by this, I can EITHER go back to the Civil
    War and straighten it out with more elapsed time-B, OR change gears
    on the time machine and, aging forward in ordinary time-A move backward
    in time-B and intercept myself while still time-traveling, to warn
    me about killing off Great Grandpa.
    
    Then what happens?  I haven't moved in ordinary time, but I'm back
    at a previous point in time-B.  At this point in time-B, I haven't
    yet altered history.  Hmm.  I can let my previous self go and just
    resume living here.  Nothing has changed.  I will have vanished
    briefly, reappeared with some highly authentic Civil War souvenirs
    and a story about Great Grandpa dying and thus generating a parallel
    history that does not contain myself and my family.
    
    Earl Wajenberg

    I don't mean to turn this topic into a monologue but, as I said,
    time travel is a favorite theme of mine.  Also, I have, as it were,
    some practical experience with it.
    
    Tuesday nights, I play in a fantasy role-playing game.  Our game
    has a Dr. Who flavor to it -- we are batting about the universe
    in a broken-down time-machine.  Theoretically, time is rigid; you
    can't change the past.  But you can subvert it.  As Heinlein remarked
    somewhere, a paradox can be paradoctored.  Example:
    
    In a medieval setting, one of our party was captured and thrown
    into the dungeon of the local castle.  After taking a couple of
    days to re-organize, we used our high tech for special effects and
    tried to pass ourselves off as angels demanding the release of the
    prisoner.  They didn't fall for it and started firing with bows,
    crossbows, and catapults.
    
    We were afraid they would now execute our companion as a
    demon-consorting sorceror.  So we piled back into the time machine
    and fell back a couple of days, materializing inside the castle.
    This sneaky approached worked much better and we sprang our companion
    from durance vile.
    
    But we now realized why the medievals hadn't fallen for our angel
    act.  Angels would know better than to ask for the release of a
    prisoner who had already escaped.  So the angel act failed because
    the prisoner had already escaped, and the prisoner had already escaped
    because the angel act failed.  It ain't quite a paradox, but it
    has a very similar flavor.
    
    Earl Wajenberg

    re .8's Grandpa
    
    You hope!  What if there isn't any "place" for you when you return?
    As you are peddling your "authentic" souvenirs (keeping in mind
    they aren't 100+ yrs. old anymore :-)) I would suggest there were
    some questions you should have asked your grandmother.
    
    Yes, its true; I'm a "Rigid Past" person.  I suppose the thought
    of someone going "back" and messing me up ('course, how would I
    know unless I went along?) disturbs me.  I'll admit a little 
    flexibility regarding changes, but nothing which would change
    a history book or family history.  
    
    I figure (see Trek file) that its already happened so if you go
    back and change something; well, you already did.
    
    Gotta go.  I'll try to give my Time Travel theories next time....

    The system hypothesized in .8 specifically stipulated that time
    travel in either dimension of time was possible, so it would have
    to be the case that you can return to the previous version of history.
    However, there is no evidence for the existence of any extra time
    dimensions.
             
    It could be fairly easy to peddle the souvenirs if the time-trip
    was public knowledge.  Of course, if it were the very first time-trip,
    they'd want to put the specimens in a museum, like with the moon
    rocks.  Only it might be tricky determining which time-trip is relaly
    first....
    
    Earl Wajenberg

The hypothesis went something like:
                                                    
	"In any universe where it is possible to change to past using
	 time travel, you will eventually end up with a history where
	 time travel was never invented."

The reasoning being that sonner or later somebody will maliciously or 
inadvertently make a change where time travel is never invented, and 
then you are stuck.

- CW

    Well, it dependson the nature of changable time.  If the time travelers
    and their machines are snuffed out of existence when they destroy
    their own causes, then he's right.
    
    If they continue to exist, we still have time machines and time
    travelers, and thus the possibility of continued change of history.
    It's just that these time travelers don't have an origin.  "But
    the time machine was invented in Atlantis in 1963!"  "Atlantis blew
    up around 2300 BC."  "Yes, I know, there was this unfortunate accident
    with our sister-craft -- materialized inside the walls of the palace
    and..."
    
    Earl Wajenberg

    So *that's* what happened to it!

Do you really think that "Cause and Effect" operates with regard to time
travel?  What if Time Travel introduces some random factor, so that some
things 'just happen', without any real cause...?

What does this do to all the time travel theories?

Jim.

    Sounds too much like "spontaneous generation".  Remember that concept
    from ancient biology?  Shades of the "hidden variables" that give
    physicists nightmares.
    
    len.
    

    Re .15
    
    Once more, depends on the kind of time-travel you make up.  Using
    the most conservative method, building on relativity, you would
    still have causal systems, although they would (of necessity) allow
    causality to work from future to past as well as the usual past
    to future.
    
    If you throw in quantum mechanics and, say, base your time machine
    on the energy/time version of the Uncertainty Principle, you get
    a cross-time physics with random elements in it, but no more than
    already exist in QM in the real world.
    
    If you make up a new paradigm of physics for the time machine ...
    well, you've made up something new.  It has whatever you decide.
    
    Earl Wajenberg

    
    	Theory:
    
    	I'm no physicist, but, I don't see `Time' as a separate and equal
    dimension. I believe `time' to be an anomaly brought about by the
    convergence of the first three dimensions into physical space. Einstein
    tells us that matter can not be destroyed nor created. Thus, it
    has existed in one form or another and always will, so no measure
    of duration need be applied to it. Objects born of this matter,
    however, are subject to change of form or shape or placement and thus
    we measure its duration in `three dimensional physical space' (TDPS)
    as `time'.
    
    	Being an anomaly of TDPS and not a separate dimension places
    time right at our finger tips. Travel through it, both backwards
    and forward, though not physically, becomes possible and *is* quite
    common.
    
    	The Time Machine:
    
    	The human brain is a powerful machine. At its `core' is that
    wonderful program we call the Mind. With this mind, man has achieved
    some rather phenominal feats, not least of which is mental time
    travel. Perhaps someday man will discover the key to this mind and
    learn to travel, mind and body, through time.
    
    ...Mike...
    

        But relativity *does* require a real and measurable temporal
        dimension, just as much a part of any space-time coordinate
        as X, Y, or Z.
        
        In fact, playing with the relativity equations and the
        theoretical nature of black holes, one can prove that in
        fact "time" becomes a *spatial* dimension within the event
        horizon of a black hole... the axes sort of "rotate" as you
        pass the discontinuity.  In order to leave a black hole,
        you need to travel out of it... and within your frame, that's
        backwards in time.  Which can't be done.
        
        Not, of course, that this problem would be of any great concern
        to someone who actually got beyond the event horizon, of
        course... subatomic particles have a very low capacity for
        worry  :-)
        
        	/dave

    re. 19 and a little .18
    
    	Not to mention (.19) that current theory is leaning toward
    	a 'normal' universe consisting of 10-12 dimensions.

	From 'The Hitch-Hiker's Guide to the Galaxy':

	'One of  the  major  problems  in  time  travel  is  not that of
	accidentally  becoming  your  own  father or mother. There is no
	problem  involved  in  becoming your own father or mother that a
	broadminded and well adjusted family can't cope with.'

	'The major  problem is quite simply one of grammar, and the main
	work  to  consult  in  this  matter  is Dr Dan Streetmentioner's
	Time_Traveller's_Handbook_of_1001_Tense_Formations. It will tell
	you  for  instance  how  to  describe something that was about to
	happen  to you in the past before you avoided it by time-jumping
	forward  two  days  in  order  to  avoid  it.  The event will be
	described differently according to whether you are talking about
	it  from the standpoint of your own natural time, from a time in
	the further future, or a time in the further past and is further
	complicated  by  the  possibility  of  conducting  conversations
	whilst you are actually travelling from one time to another with
	the  intention  of  becoming  your  own  mother  or father. Most
	readers  get  as  far  as the Future Semi-Conditionally Modified
	Subinverted  Plagal  Past  Subjunctive Intentional before giving
	up:  and in fact in later editions of the book all the pages beyond
	this point have been left blank to save on printing costs.'

    Back to the black holes...
    
    As someone mentioned, if you could harness a rotating black hole
    (safely) it would be a dandy time machine because, once inside the
    event horizon, you can move anywhere you like in time.  (However,
    you do not have MUCH time to do it, as you are dragged inexorably
    toward the singularity.)  During your brief life in there, you can
    theoretically meet yourself coming and going several times--
    
    But which one is the real you?
    

    Would it be the case that you could only meet yourself an EVEN
    NUMBER of times (assuming that if A "meets" B, then of course 
    B "meets" A?
    	
    I think this is the case, but I don't really understand the math
    of black holes... yet.

    
    
    R.e Note 1 and others...
    
    I'm not a physicist but I think there may be to much of a leaning
    on Einstein in the discussions on Faster Than Light Travel and the
    like.
    
    The way I've read General Relativity is that the basis of the theory
    is that the speed of light can not be exceeded and this forms the
    basis of Einstein's work.
    
    Thus, if FTL is taken as being possible then Relativity can no
    longet be used to explain the effects as you've just destroyed it's
    basis.
    
    Anyway ,I don't think Relativity has all the answers...........
    
                                   John Browne
                                   [ Amateur Scientist ]

Special relativity, as I recall, is based on the premise that the speed
of light is constant to all viewers in inertial frames of reference.
The consequences of this lead to the conclusion that the speed of light
is insuperable.  Just chip away at the first premise, and the rest of the
model will fall.

- tom]

Re .24

Mr. Powers in .25 has it right; the fundamental assumption in special 
relativity is that the speed of light is the same for all observers, not that 
it is the maximum speed.  General relativity has no special assumptions about 
the speed of light; it takes special relativity as part of its background and 
assumes that accelerations and gravitational fields are the same thing.

There are two mathematical reasons why the speed of light is viewed as an 
upper limit.  First, as you accelerate an object up to the speed of light, its 
apparent mass heads up toward infinity and its apparent length heads down to 
zero.  So trying to accelerate smoothly from one side of the light barrier to 
the other takes you through a nasty singularity in the mathematics.

This is not such a compelling reason in the light of quantum phenomena.  One 
could easily imagine making a quantum jump from one side of the light barrier 
to the other without having to go through the singularlity AT the barrier.

The other reason is harder to get around.  At speeds greater than c, the 
apparent length, mass, and clock rate of an object become imaginary numbers, 
multiples of the square root of -1.  What would that look like?  There's no 
obvious physical interpretation for such answers, so they may be rejected as 
impossible.

There are a few ways out.  One is the one used in tachyon theory.  In this, 
tachyons (particles moving faster than light) have imaginary values in their 
OWN reference frames, so that, when viewed by us, we have an imaginary times 
an imaginary, which is a real number.  But then, what do things look like to 
tachyons?  (I have never seen that question addressed.)

Poul Anderson's "quantum hyperjump" drive spends no time in the FTL state, but 
flicks from one position to another in many tiny jumps per second.  Other 
authors use a hyperjump that takes you from one star system to another in a 
single leap.  In both cases, the ship doesn't spend any TIME in an FTL state, 
so the questions of measurement never arise.

In general relativity, the large-scale architecture of spacetime itself can be 
fiddled with, so that, even though no LOCAL actions take place faster than 
light, the whole ship can get from point A to point B faster than light.  
There are a few worked-out methods for doing this, I understand, involving 
"multiply connected spacetime" around a spinning mass of high density, or the 
more conjectural but better-known method of jumping into a spinning black 
hole.

Earl Wajenberg

    Yesterday, this note will be confusing.
    But I understood it tomorrow...
    
    	Andrew.

Is there any discussion anywhere in this conf. about the (Heinlein?) 
story in which the protagonist is both his own father and his own 
mother?  I only remember the beginning, where he's sitting, rather 
depressed, in a bar, where the barman is also himself ("later on" in 
subjective time), and is just about to compel his earlier self to 
start the sequence of actions necessary to become his own parents.

(Oh, my head.)

That reminds me: does anyone (Earl...) have anything to say about the
good sense or otherwise of using "subjective time" (presumably
physiological aging and subjective memory) as a kind of intuitively
obvious parallel time?  In stories which use it, it is assumed to be
the same for all (or for all time travellers), but that is not obvious
to me.  Whether it is the same or different for each person seems to
me undefined (an under-specified question), in that the physiological
processes are not causes of, but caused by, the passage of time. 

Well, I'm not feeling brilliant today.  Fascinating subject, though.

While we're on the subject, does anybody here remember the words to or the logic
behind the old song "I'm my own grandpa". I've told my kids about it and they
got a kick out of it but I would like to be able to sing the whole song to them.

Dave 

    
    ref .28:
    
    That's "All You Zombies." Great story, but he did it better in
    "By His Bootstraps."
    
    E.    

    Re .28
    
    Since stories are almost always written in a linear fashion, time
    travel stories usually DO treat the protagonist's subjective time
    as a kind of "parallel" or alternative time scale.  These stories
    do not always asume that all time travelers stay in sequence with
    each other, but then most of them only involve a very few time
    travelers, or only one.
    
    In "The Technicolor Time Machine" (aka "The Time-Machined Saga")
    by Harry Harrison, we catch an intriguing glimpse of a cafeteria
    used by time travelers.  One is always in danger of running into
    one's earlier or later self, and the protagonist (who in fact plays
    a practical joke on an earlier self somewhere in the plot) once
    saw five instances of the time machine's inventor gathered around
    the same lunch table, arguing about physics.  (It must be difficult
    to argue with your later self, since you know you're going to change
    your mind and "agree with" him by becoming him.)
    
    In "The End of Eternity," Isaac Asimov gives his time travelers
    (the "Eternals") a kind of instinctive aversion to meeting past
    or future selves.  This helps keep individual world-lines from becoming
    tangled, but does nothing to prevent two time travelers from meeting
    each other in reverse order.  (I met you when I was 30 and you were
    20, then later when I was 33 and you were 18.)
    
    DC Comics recently pulled a trick using this.  Superman and Supergirl
    both occasionally time-traveled.  A while back, they killed off
    Supergirl.  Later on (in our sequence and Superman's), at a moment
    of high drama, Superman has a final, farewell meeting with his "dead"
    cousin Supergirl, who is time-traveling with some folk from the
    far future.  Neither the future-folk nor Superman are so tactless
    as to alude to Supergirl's death, of course.
    
    Earl Wajenberg

    For those of you who care, "By His Bootstraps" is in "The Menace From
    Earth," a rather entertaining collection of random Heinlein short
    stories. 
    
    To hear "I am my Own Grandpa," try calling WEVO (FM 89 in Concord, NH,
    88 in Nashua) during one of their folk music programs - I think there's
    one on Sunday night.  They'll usually play requests.  If you're not in
    NH, check out your local public radio station.
    
    Oh, yes - the request line for WEVO is 224-8989.
    
    Beverly
    

    Re .29:
    
    That sounds somewhat familiar; I think I have seen it in a conference
    somewhere . . .
    
    
    				-- edp

    One of my favorites - "A Sound of Thunder" by Ray Bradbury.
    
    There are others - one in particular by Philip K. Dick, but I don't
    recall the title...
    
    Lisa

    
    I was looking through a pile of old paperbacks at Christmas and
    found a copy of _Empire Star_ by Delaney. It's not quite time
    travel, although that's a part of it. Had a lot of the themes that
    Delaney used later, in _Dahlgren_ and "Time Considered as A Helix
    of Semiprecious Gems." The link between creativity and pain, the
    central character with a musical instrument, the concept of shared
    experiences.
    
    Strange, though--I hadn't noticed before that his female characters 
    are sort of remote and unreal. Only the men seem really THERE. Probably
    wouldn't have noticed if I hadn't read _Stars in My Pocket_...

    A recent series of books that addressed time travel and temporal
    physics in an interesting way (at least to me, I almost understand
    it and it almost even sounds plausible, given the circumstances),
    is the Time Wars series by Simon Hawke.  There's eight of them so
    far, and they are all centered around the basic plotline that in
    the 27th century, time travel into the past has become an everyday
    reality.  
    
    To avoid marring the present with such petty things as international
    conflicts, any grievances between countries are fought in the past,
    using historical battlegrounds and time soldiers plunked into the
    battle as cannon fodder.  Casualities and a complicated point spread
    are used to determine the "outcome" of the "war" and assumably,
    someone wins.  Of course, not everyone likes this and there are
    time terrorist who want to end the Time Wars by purposely created
    timestream splits, which isn't good for anyone and so on....
    
    Hawke integrates some popular literary fiction and characters into
    his series, which makes for interesting plotlines, but the main
    reason I am mentioning the series is that in some of the earlier
    books, he outlines Messinger's Laws of Temporal Physics (or something
    like that).  It is pretty complex, and seems well thought out (at
    least to this highly non technical mind).  One of the main points
    of the all the books is that great care must be taken in time
    travelling and interacting with people of the past because one has
    to be very careful of the timestream and not create anomalies in
    too great of a degree.
    
    The method of travel itself is also discussed often in the books,
    which is through a warp disc and something called an Einstein-Rosen
    Bridge.  (Hey, it all sounds good to me  ;)
    
    Anyway, those of you who really are into temporal physics may want
    to check out one of the books, the first of which is called the
    Ivanhoe Gambit.  It is either this one or one of the first four
    that have the laws outlined in the front of them.  I'm curious to
    hear opinions......
    
                                                      ---kim