From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Spin
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Fri, 2 Oct 92 04:57:40 GMT

In article <1992Oct1.004921.9474@sjsumcs.sjsu.edu> b5249-23@mathcs.sjsu.edu (Kurt Stocklmeir) writes:
>From Baez
> his articles
>
>You do not get it, and I do not think you are going to.  Only fools
>talk when they do not know what they are talking about.  You are
>1 of them.
>
>That is what I like about sci.physics.  A person can ask 1 simple question on
>sci.physics, and get 400 different answers,  all wrong.  As each
>fool is giving their wrong answer they are doing everything they
>can to insult another person.  Most articles on sci.physics are
>written by the same small group of people.  Most people in the
>world who read sci.physics, will not put an article on it, because
>they know sci.physics is a joke.  But they read it if they have
>nothing else do to see fools give the wrong answers and insult
>each other.  
>Putting an article on sci.physics makes me a fool also. 

I'm sorry if I hurt your feelings.  I was rather annoyed at how you
twisted the meaning of Misner, Thorne and Wheeler in your first post,
so I reacted rather strongly.  Let me try to be extra nice and simply
address some of your points. 

>Gravity observed moves faster than the speed of light.

Give us some evidence, please?  Simply repeating this statement is
not very convincing.

>This also applies to the
>other forces.  But you do not get it because you are always talking.
>and you do not have anytime to think.  

I used to be very shy as a youth and I'm making up for it now.
Luckily I spent a lot of time thinking back then so I don't need
to much anymore.  :-)

>There is not anything wrong with something moving faster than
>the speed of light.  Tachyons are an example.  But you still can not figure
>that out and I do not think it is because you have done a lot of
>homework.  Collisions with gravitions and other particles that create
>forces cause attraction, and that may mean negative momentum.  Tachyons can
>have negative momentum.  But you can not figure out even something that
>simple. 

Alas, if you read my book with Segal and Zhou, Algebraic and 
Constructive Quantum Field Theory, you will see that I agree completely
that the quantum field theory of free tachyons is consistent.  There
are two problems, though: 1) it seems impossible to develop a theory
of interacting tachyons, because their energy will be unbounded below,
and 2) tachyons have not been observed.  Of course these are related; 
we could have plenty of free tachyons around but, being free, we would
never observe them.  In short, the example of tachyons is far from an
example of an *observed* case of something moving faster than light.

>I hate trying to get you to think, something you can not do, but all
>forces are attractive when the force collides with a particle.  You do not
>need to tell me, you still can not figure it out.  Even if relativity
>could cause gravitons to have an infinite velocity, it still can not
>explain negative momentum of gravitons.

Hmm.  I agree that I have some trouble making sense of the above.  If
anyone else on sci.physics *does* understand it, could they post an
explanation?  

>In 1 of your normal articles you state that electric fields do not move
>faster that the speed of light.  If you knew anything what you were talking
>about, you would have known in QED that electric fields are virtual photons
>and they have an infinite velocity.  But if that is true, then all positive
>electric fields, negative electric fields, north magnetic fields, and south
>magnetic fields are made up of virtual photons.  

But again, while virtual
particles do not have to lie "on shell" (as they say), and can have any
(even infinite) velocity, one cannot use them to transmit information.
In other words, they aren't real particles; they are just bookkeeping
devices arise when you calculate things perturbatively using Feynman
integrals.  So if your point is that static gravitational fields can be
regarded in terms of virtual gravitons, fine, but no information is
being propagated faster than lightspeed.

For folks who read my earlier posts, what I'm saying here is that
Einstein's equation is causal.  Of course this is trickier to define
than for other fields, because gravity *is* the metric, the same metric
whose lightcones appear in the definition of causality (the "diamond
property").  Nonetheless one can make sense of causality in this case
and prove that gravity is causal.  

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