stuart@BMS-AT.UUCP (Stuart D. Gathman) (10/12/86)
Well, Gathman channels have generated some interesting discussion. All
the proposed paradoxes so far have missed the point. The usual misunder-
standing revolves around the usual definition of 'simultaneous' in
relativity. Since I didn't invent "Gathman channels", it is amusing
to see my name attached. All the flames have prodded me to do some
more thinking about them myself, however. The examples offered so far
have assumed that the world lines of points 'connected' by channels
are parallel. This is not necessarily the case. My own paradox
depends on this.
First, the "throop" diagram doesn't prove anything (or the equations
supplied at no extra charge). This diagram shows events that are
'simultaneous' under the usual definition: i.e. light from the
events would have met half way. What is missed is that nothing new
is learned by sneaking a view of 'z' through B's frame of reference:
the observer will experience the event himself before the light arrives
at 'y'! Clearly, 'simultaneous' needs to be redefined when Gathman
channels are in use. My first inclination is to define the first
observation of an event to be the 'original'. Notice that with
channels, an event can be observed many times (like with mirrors).
With nice, constant velocity channel endpoints, I still maintain
that causality is not violated (but of course channels could never
have been created unless the endpoints accelerated).
The real problems occur when the channel endpoints accelerate, as they
must to create channels in the first place. First consider non-
parallel world lines for the endpoints. This would be the case as
you hold one endpoint and your friend carries the other to a distant
planet. The faster your friend travels, the greater the time dilation.
As you watch your friend through the channel, he appears to be in
suspended animation. As he watches you, you appear to be an indistinct
blur of activity. Does this situation violate causality? What happens
to light as it crosses over the channel? Could a macroscopic object,
such as a human survive a trip through the channel? When he was half-
way through, the time rate difference between the two halves would, I
believe, kill him. This 'time well' effect is similar to what happens
when observing an object in a gravity field. Does this mean that a
Gathman channel has a gravity effect tending to pull matter through
the door?
NOTE: "Gathman channels" are *not* FTL travel.
--
Stuart D. Gathman <..!seismo!{vrdxhq|dgis}!BMS-AT!stuart>throopw@dg_rtp.UUCP (Wayne Throop) (10/21/86)
> stuart@BMS-AT.UUCP (Stuart D. Gathman) > Since I didn't invent "Gathman channels", it is amusing to see my name > attached. You didn't say who did invent them, nor provide references to where we could read about them. Lacking that, I've been going by what you say here, and what you have said here is dead wrong. > The examples offered so far have assumed that the world lines of points > 'connected' by channels are parallel. This is not necessarily the case. This certainly doesn't help your case any, since allowing one endpoint to move with respect to the other one makes the situation worse, not better, and all the time paradoxes remain. > First, the "throop" diagram doesn't prove anything I never said it did. I try not to claim to "prove" things, since the term has specific meaning in mathematics that I don't often intend. So what *does* the diagram do? It is a construction of a paradox using the starting rules of 1) special relativity and 2) Gathman channels. This is something Stuart said couldn't be done. Nevertheless, it *was* done, and Stuart has failed to point out any flaw in the construction. While not a proof in any formal sense, it is strong indication that either 1) SR is wrong after all, or 2) Gathman channels cannot work as Stuart says they can, or 3) events can indeed "preceed" their causes. I simply consider (2) most likely. > What is missed is that nothing new is learned by sneaking a view of 'z' > through B's frame of reference: the observer will experience the event > himself before the light arrives at 'y'! Blatantly, obviously, trivially, clearly *WRONG*. News of event z reaches event x. Event x preceeds event z on A's timeline. This is a time paradox. The fact that Stuart thinks that light from some unspecified event will reach y before some observer "experiences" z is *COMPLETELY* *IRRELEVANT* to this paradox. In fact, every point Stuart has brought up is *IRRELEVANT* to the paradox. Some of Stuart's points are true, some are false, but all (so far) have been *IRRELEVANT*... their truth or falsity doesn't have *ANY* *BEARING* *WHATSOEVER* on the existance or nature of the paradox I diagrammed. (And did I say Stuart's points were *IRRELEVANT*??? I did? good! :-) "The endpoints could accelerate." Fine. But they aren't accelerating in the diagram, so it DOESN'T MATTER. "A could see the message over C's shoulder." Fine. But this is still transfer of information, so this point DOESN'T MATTER. "I didn't invent Gathman channels." Fine. Wonderful. SO WHAT? What does it matter what you call them? They *STILL* violate causality under special relativity. (Gee, all this shouting takes it outa ya. I'll try to do less... :-) Please either admit you were wrong, or come up with some relevant point that has something to do with the assertion you are claiming, that is, that instant message channels do not violate causality under SR. I have shown a violation using IMCs and the assumptions of SR. Show where I went wrong, or please shut up. > Clearly, 'simultaneous' needs to be redefined when Gathman channels are > in use. AAAAUUUUGGGGHHHH!!!! (Calm, calm, I said I'd try to shout less.) This is precisely what I've been claiming all along... have you now changed your mind? I said that either SR's notions of space and time and "simultaneity" and "instantness" are wrong, or IMCs violate causality. Now you seem to agree with this, by saying that notions of spacetime need to be reformed when IMCs are "in use". What are you claiming here? Or are you claiming anything coherent at all? Do you even *know* what what you are saying means? (Feh!) > My first inclination is to define the first > observation of an event to be the 'original'. First with respect to what? Please remember that SR claims that there is no such thing as a unique "first observation" when two observations are separated by a spacelike interval. > I still maintain that causality is not violated And you are still wrong. > As you watch your friend through the channel, he appears to be in > suspended animation. As he watches you, you appear to be an indistinct > blur of activity. Does this situation violate causality? What happens > to light as it crosses over the channel? Utter nonsense. Stuart doesn't seem to know the first thing about how time dilation occurs. > NOTE: "Gathman channels" are *not* FTL travel. Yet more utter nonsense. With IMCs, a signal or object can move between events separated by a a spacelike interval. This is FTL travel. Period. -- ...You got the most in you and use the least. Got a million in you and spend pennies. Got a genius in you and think crazies. --- Gully Foyle in The Stars My Destination -- Wayne Throop <the-known-world>!mcnc!rti-sel!dg_rtp!throopw