In infinite wisdom David Woolley answered:

In article <40A26B94.4030001@somewhere.com>,
"Rich <someone@somewhere.com>" <> wrote:

Energy has momentum, not mass.

There seem to be different ways of interpreting relativistic mass,

You said that...

DW> The limit is actually on the sending of information.  Also,
DW> energy has mass

Energy has no mass, relativistic or newtonian.

but E=mc^2 certainly gives a mass,

Rather it shows the relationship between energy and mass.

and you have used the simple
relativistic mass formula below, so you are not in the school of thought
that says that there is no such thing as relativistic mass.

Energy has no relativistic mass. That is and was my point. If it
did have mass it could not travel at 'c'.

You say that when v=c, m'/m is finite?

Only when m = 0.

Division by zero is undefined. It's a meaningless operation.

Seems to me that it's undefined at 'c' and approaches infinity as
v approaches c.

What have I got wrong?

You've used a non-zero rest mass. 

Energy has no rest mass.

There is an additional constraint,
E=mc^2 that causes the relativistic mass to become well defined.

I have no idea what you are saying.

How would the observer know this? Seems to me that this geometry is
not possible for anyone but a third party observing the transaction.

Because things would happen that were physically impossible in a causal
world.

No causality violations would be visible to either the sender or
the receiver.

Does the phrase 'spooky action at a distance' ring a bell? Physicists
have been saying things like this for decades.

Doesn't convey *real* information.

Note: I think it's totally worthless and I can cut entanglement with
      Occam's razor. But that was not my point.

I'm not so sure that no real information is present. Whether it's a
matter of entanglement, or that the photons were emitted with whatever
polarization, it does allow one to ascertain real information about
something out side your light cone.

In fact it tends to rely on their
being no real information.  As to the decades, that's why I said that
the experiments were based on 50 year old theories.  Whilst the theories
may have upset Einstein, they are not particularly controversial these
days.

I've yet to see any physics experiment which does not simply assume
entanglement. It may not be controversial, but it's never been proven
to exist either.

I believe that you are referring to the fact that a group velocity can
travel faster than 'c'.

There are two classes of experiment:

1) spooky action at a distance[1], popularised as quantum teleportation,    where a conventional communication channel is needed before any
   real information is conveyed (you need to know the state read out of
   the other end of the link before you can do anything with the state
   of your particle, othersise, all you know is that they have opposite
   states - the readout of the other particle can only be communicated
   over a channel limited to c);

Obviously, so even *if* entanglement were real, it could not result in
FTL communications. And you'd have to have your transmitter in the
center, making communications with ET impossible even if entanglement
made FTL communications possible.

Rich

2) anomalous propagation, where refractive index is changing very rapidly
   with frequency and therefore the effect is only possible for very low
   bandwidth signals, which therefore have very long rise times, and
   the start of the rise time propagates at less than c.

This, however, is the sort of subject that leads to stalemates, so I
doubt if I'm going to hang in long on this one.

[1] I'm accepting for the moment that it is possible to show that hidden
   state (i.e. the entangled particles simply go through a sequence of
   opposite states with time) is not a sufficient explanation, although
   it does seem sufficient for at least some of the experiments.