HDTenEightyP/NetNews huggingface dataset:
From: pksuk@mothra.syr.EDU (Peter K. Suk)
Subject: Re: Time Travel and Causality Violation
Organization: Syracuse University, Syracuse, NY
Date: Mon, 14 Dec 92 11:03:09 EST

In article <BCR.92Dec12023142@hfl3sn02.cern.ch> 
bcr@cernapo.cern.ch (Bill Riemers) writes:

>In article <8895@lee.SEAS.UCLA.EDU> 
>leonardo@mills.seas.ucla.edu (Leonardo E. Blanco De Freitas) writes:
>
>>   1) Forget time travel: it is impossible (I would guess that faster-
>>      -than-light travel goes as well, for reasons I won't care to
>>      mention...)
>
>>   or
>
>>   2) Allow more than one dimension of time. If you don't want all uni-
>>      verses existing at the same time, that's fine. However, you can't
>>      resolve certain paradoxes with one single timeline if time travel
>>      is allowed (see a previous posting by someone else; sorry I don't
>>      have the reference... :(  ).
>
>You forgot two other possabilities possabilities:
>
>    3)  Predestiny...[deleted]
>
>    4)  Limited predestiny...[deleted]

We dealt with this in the previous discussion.  If the entire history of
the universe is predetermined, such that no paradoxes occur, the simplest
configuration for this universe would be:

	There is no time travel.

If the time continuum heals itself by changing history such that no paradoxes
occur, the simplest change would be:

	There is no time travel.

So if time travel were possible in a single-timeline universe, then 
things would happen to insure that no one invented and successfully
operated a time machine.  (And if time machines are at all complicated,
one could easily see how this would happen.)

	--Peter Kwangjun Suk
Newsgroups: rec.arts.sf.science
From: greg@huia.canterbury.ac.nz (Greg Ewing)
Subject: Re: Teleport Gate Paradox (New?)
Reply-To: greg@huia.canterbury.ac.nz (Greg Ewing)
Organization: University of Canterbury, Christchurch, New Zealand
Date: Mon, 14 Dec 1992 22:52:55 GMT

In article <Yf_rT2m00gpIQQoUhs@andrew.cmu.edu>, "Andrew C. Plotkin"
<ap1i+@andrew.cmu.edu> writes:
|> Excerpts from netnews.rec.arts.sf.science: 11-Dec-92 Teleport Gate
|> Paradox (New?) Sean Morgan@arc.ab.ca (1465)
|> 
|> Now do the old trick of putting the receiver gate above the transmitter.
|> Put a rock in between and let it fall. Now conservation goes all to hell
|> -- the rock will continually gain kinetic energy from nowhere. *This* is
|> why I think such gates can never exist.

I think conservation laws can be preserved in this case if the rock
feels an upward force as it tries to pass through the lower gate,
due to the difference in gravitational potential between the two gates.

The force is just enough so that by the time the rock has passed through
the lower gate, the force x distance is equal to the energy needed
to raise the rock from the lower to the upper gate through the
gravitational field.

So when the rock emerges from the upper gate, it will be moving slower
than when it entered the bottom one - by the same amount it sped up
while it was falling.

This could have interesting implications if you were using these
things for space travel. You'd have to take into account the
relative velocities of the two gates, and the difference in
gravitational potential between them. Just sticking one on each
planet would be highly inadvisable - step into one and you'd
probably come flying out of the other at some thousands of
km per hour!

Greg Ewing, Computer Science Dept, Canterbury Univ., Christchurch, New Zealand
Internet: greg@cosc.canterbury.ac.nz	+--------------------------------------
Spearnet: greg@nz.ac.canterbury.cosc	| A citizen of NewZealandCorp, a
Telecom:  +64 3 667 001 x6367  		| wholly-owned subsidiary of Japan Inc.
Newsgroups: rec.arts.sf.science,alt.folklore.science
From: frank@rover.uchicago.edu (Frank - Hardware Hacker - Borger)
Subject: Re: The Marching Morons (was Re: Cindy the Disco Queen)
News-Software: VAX/VMS VNEWS 1.41    
Reply-To: frank@rover.uchicago.edu
Organization: Joint Center for Radiation Therapy
Date: Thu, 17 Dec 1992 18:08:00 GMT

In article <1992Dec16.183357.3186@colorado.edu>, juola@bruno.cs.colorado.edu (Patrick Juola) writes...
>In article <1gnr5vINNik@gap.caltech.edu> carl@SOL1.GPS.CALTECH.EDU writes:
>Why is universal education important?  And *particularly*, why should everyone

	The other day I picked up some chicken from the Colonel on the way
	home, and the bill came up to something like $13.52. I keep only a
	few bucks in my pants pocket, the rest stashed in an inside vest
	pocket, so I reached inside my vest, took out the folder, and put
	a 10 on the counter, put my folder back in my vest and was reaching
	for some singles out of my pocket.

	The person behind the register rang up my 10, saw the $3.52 balance
	remaining, and was going to give me $3.52 in change.

	When we fail to educate people to the point where they can comprehend
	that $13.52 is more than $10.00, they will be functionally unemployable,
	and will end up being supported by my taxes.

	'nuff said!

   Frank R. Borger - Physicist    __       Internet:  Frank@rover.uchicago.edu
Michael Reese - Univ. of Chicago |___      Phone : 312-791-8075 fax : 567-7455
  Center for Radiation Therapy   | |_) _   In the first place God made idiots.
                                   | \|_)  That was for practice. Then he made
    "Birthplace of Softball"          |_)  school boards. - Mark Twain
Newsgroups: rec.arts.sf.science
From: pciszek@nyx.cs.du.edu (Paul Ciszek)
Subject: Re: The Marching Morons (was Re: Cindy the Disco Queen)
Organization: University of Denver, Dept. of Math & Comp. Sci.
Date: Sun, 13 Dec 92 20:08:27 GMT

It is my understanding that the population growth of the US is mostly due 
to immigration.

Xref: sparky rec.arts.sf.science:3733 rec.arts.sf.misc:3447
From: dave@cs.arizona.edu (Dave Schaumann)
Newsgroups: rec.arts.sf.science,rec.arts.sf.misc
Subject: Re: Territorial Disputes
Date: 12 Dec 92 02:50:19 GMT
Reply-To: dave@cs.arizona.edu (Dave Schaumann)
Followup-To: rec.arts.sf.science
Organization: University of Arizona

In article <1992Dec9.114933.14903@newstand.syr.edu>, pksuk@mothra (Peter K. Suk) writes:
[lots of discussion about why terratories are a Bad Thing deleted]
>I would claim that this is a severe drawback to the whole concept of
>'territory'

Territory and protecting the same is a natural outgrowth (at least
for humans) of the need for protecting one's accumulated wealth
and other possessions.

To suppose that we would abandon the "right of territory" pre-supposes
a fundamental and enormous shift in human nature.

>and that a truly enlightened interstellar civilization
>would abandon the concept entirely.  

"and they all lived happily ever after... The End"

-- 
What I've learned from reading net news #2:
  Surely the most ignored phrase to be posted to the net is "'nuff said".
Newsgroups: rec.arts.sf.science
From: bcr@cernapo.cern.ch (Bill Riemers)
Subject: Re: Time Travel and Causality Violation
Organization: CERN, European Research Center for High Energy Physics
	<1992Dec6.173452.10058@newstand.syr.edu> <8895@lee.SEAS.UCLA.EDU>
	<Bz9pw5.Csn@newcastle.ac.uk> <1632@tdat.teradata.COM>
Date: Thu, 17 Dec 1992 20:45:40 GMT

>>>>> On 17 Dec 92 19:00:34 GMT, swf@tools3teradata.com (Stan Friesen) said:

	Stan> Actually the greatest argument against the existance of time travel was brought
	Stan> to my attention by my brother:

	Stan> If it is possible why aren't we up to our ears in temporal archaeologists and
	Stan> time tourists?

You might also add temporal terrorists to your list.  However, if personal
time travel is much harder to obtain than personal 5 Megaton bombs (forexample)
then this wouldn't really be a problem.  Any culture with a significant
terrorism problem, would destroy itself long before developing personal
time travel.  

Along the same lines, we can also argue that any culture that doesn't develope
a high respect for the environment will also destroy itself.  So it is not
unreasonable to expect future cultures will also protect the past with environ-
mental laws long before temporal tourists or temporal archaelogists become a
problem.  Both might still exist, but they would be required not to harm the
past.  This means they would have to try to fit in like normal people and hide
any evidence that they are from the future.  (Probably under the penalty of very
stiff fines or worse if they fail.)

So, I'll agree this argument does severly limit when, and what sort of time
travel will be possible.  (So if you plans for a personal time machine listed
in the back of the next issue of Popular Science, don't buy them!)  However,
your brother's argument far from eliminates the possability of time travel.


                                       Bill


--
"Yeti!  Saw them in the London Underground twenty years ago.  Ghosts!
A headless woman used to walk through my bedroom at midnight.  Mermaids?
Grandpa was rescued from the Marie Celeste by one.  Vampires?  I always
wondered where my dad went to at night.  Telepathy?  Right now you're
thinking that I'm talking crap.  So what can you tell me that I won't
believe in?" - Andrew Hunt, "CAT'S CRADLE: WITCH MARK"
Newsgroups: rec.arts.sf.science,alt.folklore.science
From: flatline@uni-paderborn.de (Michael Wehking)
Newsgroups: rec.arts.sf.science
Subject: Re: Do starships collapse when flying near c?
Date: 15 Dec 1992 13:01:05 GMT
Organization: Uni-GH Paderborn, Germany
Distribution: world
NNTP-Posting-Host: dublin.uni-paderborn.de

In article <sH1JVB6w165w@west.darkside.com>, max@west.darkside.com (Erik Max Francis) writes:
|> flatline@uni-paderborn.de (Michael Wehking) writes:
|> 
|> > Starships flying near c accumulate mass from the energy of their 'stardrive'.
|> > So imagine a starship, perhaps one of Larry Niven's Bussard type ramscoops,
|> > flying with that speed. Is there a point where the ship has accumulated
|> > enough mass to collapse (to a black hole :-) or do I make a serious mistake?
|> > (Plaese excuse my terrible English.)
|> 
|> This is a good question and I wondered about it as well.  The answer is 
|> that, no, you won't turn into a black hole if you go too fast.  The 
|> motivation for believing this goes like this:  Yes, if someone looks at 
|> you while you zip by at relativistic speeds, your mass appears to be 
|> greater.  However, from your point of view, it's the rest of the Universe 
|> that's moving (and thus more massive); you're the same mass you've always 
|> been (your rest mass).  Thus it doesn't make sense for you to suddenly 
|> blink into a black hole when, from your frame of reference, you've only 
|> got your rest mass.  All the frames of reference would have to agree for 
|> something like that to happen.
|> 
|> ----------
|> Erik Max Francis   Omnia quia sunt, lumina sunt.  Coming soon:  UNIVERSE _ | _
|> USmail:  1070 Oakmont Dr. #1 San Jose CA 95117  ICBM:  37 20 N  121 53 W _>|<_
|> UUCP:  ..!apple!uuwest!max   Usenet:  max@west.darkside.com   464E4F5244   |

Does this mean that starships flying with the 'right' speed will fall into a 
black hole anyway (the rest of the universe)?

Michael
-- 
-------------------------------------------------------------------------------
Eine hinreichend fortgeschrittene Technologie laesst sich von Magie nicht
unterscheiden.
                                                       Clarke's 3. Gesetz
-------------------------------------------------------------------------------
Newsgroups: rec.arts.sf.science
From: bucknerb@bnr.ca (Brent Buckner)
Subject: Re: Time Travel and Causality Violation
Organization: Bell-Northern Research, Ontario, Canada
Date: Fri, 18 Dec 1992 19:40:07 GMT

In article <1992Dec18.182141.18256@porthos.cc.bellcore.com> ccw@prefect.cc.bellcore.com (wood,christopher) writes:
>In article <1992Dec18.165816.25061@bnr.ca> bucknerb@bnr.ca (Brent Buckner) writes:
>>In article <1992Dec18.154730.15628@porthos.cc.bellcore.com> ccw@prefect.cc.bellcore.com (wood,christopher) writes:
>
>>>[if you receive, then don't send; if you don't receive, then send
>>>paradox description deleted]
>
>>In the parallel universes scheme, there are two resulting universes.
>>In Universe 1, at 7:30 you received no object, so you put the
>>object into the time machine.  In Universe 2, at 7:30 you received
>>an object, so you destroy the time machine and the object.
>
>Where does the object in universe 1 go?  Where did the object I received
>in universe 2 come from?  Could I use this as a duplicator?  Does this
>teleport the object from one universe to the other?
>

You can regard the object as being sent from Universe 1 to Universe 2.
Universe 2 then has two copies of a previously unique item, and
Universe 1 does not have the item.

>What happens if the object I declare that I am going to put through the
>time machine is a Gold Brick?  If I get one, I take both bricks and
>leave.  The next night, I do the same thing with two bricks. After 64
>nights, I have enough bricks to cover california to quite a depth.

Yes.  However, there are alternate versions of you who spent
money on gold bricks and received nothing.

>
>>In the single-universe no-paradox scheme, you do not receive
>>the object at 7:30.  When you try to send the object at
>>8:00 you fail.   
>
>Since this is true no matter how the time machine works, then I have a
>proof that in the single-universe no-paradox scheme, no time machine
>could work....
>

A time machine could work, but only when its operation would not
result in a paradox.  Sending something as complex as a brick
would be unlikely to work.  Sending a photon could be fine.
if you receive a photon at 7:30, send one back at 8:00.

[Aside to Ray Ingles:  Say, do you have an updated copy of your
series on temporal travel and communication?  I hesitate to
go through all this again....]

-- 
at Bell-Northern Research
voice:        (613) 765-2739
Canada Post:  P.O. Box 3511, Station C, Ottawa, Canada, K1Y 4H7
I do not claim that BNR holds these views.  
Newsgroups: rec.arts.sf.science
From: dietz@cs.rochester.edu (Paul Dietz)
Subject: Re: Territorial Disputes
Organization: University of Rochester
Date: Wed, 16 Dec 1992 12:38:53 GMT

In article <1992Dec15.171048.27281@newstand.syr.edu> pksuk@mothra.syr.EDU (Peter K. Suk) writes:

>However, Bussard Ramjets are just not practical, at least not at this
>speed.  The amount of hydrogen fuel -- assuming total conversion --
>needed to get a 10000 kg spacecraft to 0.99c is something like the
>number of atoms in the known universe.


Um, how do you compute this?  The kinetic energy of an object
moving at 99% c is about 7 times its rest mass.

	Paul F. Dietz
	dietz@cs.rochester.edu
From: jaskew@spam.ua.oz (Joseph Askew)
Newsgroups: rec.arts.sf.science
Subject: Re: Territorial Disputes
Summary: And technology too
Date: 17 Dec 92 02:22:01 GMT
Followup-To: rec.arts.sf.science
Organization: Statistics, Pure & Applied Mathematics, University of Adelaide

In article <1992Dec15.141750.2877@cs.rochester.edu> dietz@cs.rochester.edu (Paul Dietz) writes:

>All this talk about galactic empires shows a typical blind spot that
>occurs in a lot of science fiction.  Specifically: it ignores the role
>of time.
>
>Here on earth, empires collided because they became possible at about
>the same time.  Fundamentally, this is because everyone is of the same
>species, the evolution and spread of which synchronized the clocks, so
>to speak.  In the galaxy, however, different empires will start at
>wildly different times.  Stories that assume everyone is at a low
>level, or is expanding all at once, are just too implausible.  There
>is no longer any good excuse to ignore the Fermi Paradox.

Also it ignores the technological time process too! The chances of their
actually being a fight between two similar civilisations is roughly nil.
Look at the fighting between Syrian and Israeli jets over the Beka'a
Valley! The Russian built MIG's were only 10 years or so behind the US
built planes (and that is an exaggeration) but still Israel got 32 for 0
Any meeting between interplanetary civilisations etc is likely to be
between cultures that are more than 10 years apart. And this is an upward
trend too. Planes built in the 60's were closer than planes built in the
80's. In 100 years time you will not be albe to fall 1 year behind in
advanced electronics, stealth technology etc. If two such Empires met
one would so outclass the other that there would be no fighting worth
mentioning at all. Like the British in the Sudan or in China. No amount
of fighting will help in the face of craft that blow you up before you
see them or out class you to any great extent.


Joseph Askew


-- 
Joseph Askew, Gauche and Proud  Barbarian horns draw out the northern wind;
jaskew@spam.maths.adelaide.edu  Paler than water lies the Thistle Pass;
Disclaimer? Sue, see if I care  Sky swallows up the road to Kokonor;
One China One Korea One Eire32  Moonlight, a thousand miles along the Wall.
Newsgroups: rec.arts.sf.science
From: ingles@engin.umich.edu (Ray Ingles)
Subject: Re: Time Travel and Causality Violation
Date: Fri, 18 Dec 92 12:56:37 EST
Organization: University of Michigan Engineering, Ann Arbor

In article <1992Dec18.165816.25061@bnr.ca> bucknerb@bnr.ca (Brent Buckner) writes:
>In article <1992Dec18.154730.15628@porthos.cc.bellcore.com> ccw@prefect.cc.bellcore.com (wood,christopher) writes:

['if you send it back, you don't, and if you don't, you do' paradox deleted]

>In the parallel universes scheme, there are two resulting universes.
>In Universe 1, at 7:30 you received no object, so you put the
>object into the time machine.  In Universe 2, at 7:30 you received
>an object, so you destroy the time machine and the object.

>In the single-universe no-paradox scheme, you do not receive
>the object at 7:30.  When you try to send the object at
>8:00 you fail.   

 (Or, you send it, but decide that you can't bear to destroy such a unique
object, and then you send it back knowing you won't destroy it.)

 Of course, some stories let you make paradoxes indiscriminately...
For example, in the Back_To_The_Future series, you would destroy it,
ensuring that Biff became ruler of ann the known and unknown universe,
and then Marty McFly would go back and rescue it. :->

Sincerely,
Ray Ingles
ingles@engin.umich.edu

 They said there'd be snow at Christmas; They said there'd be peace on Earth.
 Halelujah Noel, be it Heaven or Hell; The Christmas we get we deserve.
      -ELP, "I Believe in Father Christmas"
Newsgroups: rec.arts.sf.science
From: colin@callisto.pas.rochester.edu (Colin Roald)
Newsgroups: rec.arts.sf.science
Subject: Re: Still WASTE HEAT? (actually, it's more about sentinels now)
Keywords: surveillance stealth detectors computers aesthetics
Date: 20 Dec 92 00:12:36 GMT
Organization: U(r) AstroTheory Group

jdunning@phoenix.Princeton.EDU (John Alan Dunning) writes:
>
>But the sentinels will inevitably occlude stars, and perhaps you can
>catch them then.

Actually, not inevitably.  If they're small enough a distant star will
have a substantially larger apparent size. For example, assume a sentinel
about 2 m across (no problem, right?), and an intruder 100 AU (=10^13m) away.
Also assume a star the size of the sun (10^9 m) at an average distance of the 
centre of the galaxy (10^20 m).  Quick fractions show the star appears about
five times larger than the sentinel, and so there is no occlusion.

Plus, the sentinel is still indistinguishable from a random rock, and there
are *lots* of random rocks out there.

I'd be tempted to rule a silent sentinel undetectable.

>The more I'm thinking about it, the more I'm realizing how difficult
>it would be to deliver exactly the same number and wavelength of
>photons from exactly the same point, without interruption, that the
>sentinel is expecting.  If you don't, the sentinel is going to see the
>star twinkling, or change in brightness.

Although stars *do* vary some in brightness anyway.  I'm sceptical of
this as a viable detection scheme.  

As an attacker I'd be more tempted to send something like a hypervelocity
ISBM (interstellar ballistic missile :-)--it's stealth factor would be c.
Your warning of its approach becomes arbitrarily small as it's velocity
approaches c, and given adequate guidance (I think less of a problem than
getting arbitrarily close to c), it could easily hammer a planet badly.

(I'm sorry for joining this discussion in the middle. I hope I'm not 
bringing up an old topic.)



colin roald rational |  he opened up his mind and snapped out of the groove
   romantic mystic   |  he saw both sides of everything and found he could
  cynical idealist   |    not move.                    -- james mcmurtry
Xref: sparky rec.arts.sf.science:3735 rec.arts.sf.misc:3449
From: mt90dac@brunel.ac.uk (Del Cotter)
Newsgroups: rec.arts.sf.science,rec.arts.sf.misc
Subject: Re: Territorial Disputes
Date: 12 Dec 92 15:15:16 GMT
Organization: Brunel University, West London, UK

In article <1992Dec9.114933.14903@newstand.syr.edu> pksuk@mothra.syr.EDU (Peter K. Suk) writes:
>There is a certain type of geometrical problem which comes up when one
>thinks about starfaring empires/federations settling border disputes.  
>
>[Problem where one species gets boxed in]
>
>I would claim that this is a severe drawback to the whole concept of
>'territory' and that a truly enlightened interstellar civilization
>would abandon the concept entirely.  

Want to bet the 'Kzinti' get 'enlightened' well before the other two?

 'What is a Communist?
  One who has yearnings
  for equal possession
  of unequal earnings'
-- 
 ',' ' ',','  |                                                  |  ',' ' ',','
   ', ,','    |       Del Cotter       mt90dac@brunel.ac.uk      |    ', ,','  
     ','      |                                                  |      ','    
Newsgroups: rec.arts.sf.science
From: kasprj@isaac.its.rpi.edu (Jim Kasprzak)
Subject: Re: The Marching Morons (was Re: Cindy the Disco Queen)
Reply-To: kasprj@rpi.edu
Organization: The Big Wedge 
Date: Mon, 14 Dec 1992 13:03:43 GMT

In article <1992Dec13.200827.25088@mnemosyne.cs.du.edu>, pciszek@nyx.cs.du.edu (Paul Ciszek) writes:
|> It is my understanding that the population growth of the US is mostly due 
|> to immigration.
 
 It was my understanding as well, until this month. However, that turns out
not to be the case.
 
 The Census Bureau data which predicted zero population growth, or close to
it, for the US was based on the assumption that sometime in this decade the
birth rates of the black and Hispanic populations would level off to about 
the same rates as the white and Asian populations. This has not happened, 
and based on current trends, is not likely to happen any time soon. Throw 
out your old theories; the new data cometh.
------------------------------------------------------------------
     __  Live from Capitaland, heart of the Empire State...
 ___/  | Jim Kasprzak, computer operator @ RPI, Troy, NY, USA
/____ *| Sam Adams,Spaten# Life is too short #Hudson Lager,Beck's 
     \_| Pilsener Urquell#to drink cheap beer#Pete's Wicked Ale
      ====  e-mail: kasprj@rpi.edu or kasprzak@mts.rpi.edu 

Newsgroups: rec.arts.sf.science