X-Message-Number: 5289
Date: Tue, 28 Nov 1995 21:07:42 -0800
From: John K Clark <>
Subject: Signal Speed


In #5275    On  Mon, 27 Nov 1995 Wrote:         

                >For an analogy, imagine a long train, and ask yourself how
                >long it takes, after the engine begins to move, before the
                >caboose begins to  move. The speed of the cars has very
                >little to do with it; it is the tightness of the coupling
                                >that counts.                   
In your example, the time it takes the longitudinal wave to go from one end  
of the train to the other, that is, the time it takes for the caboose to move 
depends on the amount of force the engine provides, the number of boxcars, 
the amount of slack between boxcars, and the MASS of the individual boxcars. 
If everything else is the same, the lighter the boxcars the sooner the 
caboose will move.                                          

                >(You don't have to have charged particles moving to get
                >electric current; you only need changing magnetic fields,
                                >as in Maxwell's equations.) 

According to Maxwell, a changing magnetic field is caused by a changing 
electric field, ( as in a capacitor), and the way to generate that is to  
accelerate or decelerate an electric  charge. The lighter the charge the  
easier it is to accelerate, and you will never find a lighter charge than  
an electron. If want to send information, if you want to send a signal, you 
need modulation, something must change and the lighter the better.

                                        John K Clark     

Version: 2.6.i


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