Re: FTL communication


"Randy Poe" <poespam-trap@xxxxxxxxx> wrote in message news:1138656113.432876.282120@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> Spaceman wrote:
> > <snipped from http://en.wikipedia.org/wiki/speed of light >
> >
> > It has long been known theoretically that it is possible for the group
> > velocity of light to exceed c. One recent experiment made the group velocity
> > of laser beams travel for extremely short distances through caesium atoms at
> > 300 times c.
> >
> > If such is true,
> > a group velocity travels 300 times FTL.
> > It is simple to send info FTL
> >
> > simply use 2 setups
> > 1 turned on only if by land,
> > 2 turned on if by sea.
>
> Nope. The information that it is turned on can't get there any
> faster than c.
>
> There used to be a nice online simulation of the 300c experiment.
> It showed pretty clearly the difference between phase velocity
> and group velocity. It let you turn the pulse train on and
> off. When you first flip the switch, the information travels
> at c. It is only after that change propagates through the
> channel that you start seeing pulses "propagating" at
> 300c.
>
> Turn the switch off and again the information travels
> to the other end at c.

http://gregegan.customer.netspace.net.au/APPLETS/20/20.html
http://www2.ee.mu.oz.au/staff/summer/applets/group_velocity.html
http://webphysics.davidson.edu/Applets/superposition/GroupVelocity.html
http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/sines/GroupVelocity.html

I think you had the first one in mind?

Dirk Vdm


.

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