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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Transatlantic cable
From: Alexandre Eremenko
Date: 2005 Jun 2, 04:20 -0500
From: Alexandre Eremenko
Date: 2005 Jun 2, 04:20 -0500
This topic is out of the scope of the list but I want to correct some statements. First of all, Thomson's name was William (not David!) and this is the same Thomson who later became Lord Kelvin. After the first cable failed, the scientific consultant was replaced by Thomson. The main reason of the first cable poor characteristics was its design. Physicists and engineers of that time poorly understood physical and mathematical principles involved, and even Faraday supported the wrong views on this cable design. The necessary theory contained in the book of Joseph Fourier, published around 1830. W. Thomson was one of the few physicists/applied mathematicians who read and understood this book. I do not want to include mathematics here, but a good sorce for the whole story (of the transatlantic cable design) is the book of T. Korner on Fourier Analysis. I lecture on this from time to time to my students and plan to add this lecture to my web site sometimes. Alex. On Wed, 1 Jun 2005, Lu Abel wrote: > Gentlemen: > > The first cable was plagued with inadequate insulation, resulting in > frequent bouts of not quite short circuits but signal losses so great > that telegraphic characters were often simply not received at the far > end. It was this that led to it requiring "several hours" to transmit a > telegram. > > "Spreading" of electrical signals takes place when a medium (such as a > cable) can not transmit the high frequency portion of a signal. An > on-off pulse, such as a telegraphic character, theoretically includes > signal components of very high (indeed, infinite) frequencies. But the > speed of transmission is still the speed of light. Thus a nice sharp > pulse transmitted on one end of the cable might arrive as a smeared-out, > possibly unrecognizable mess -- but it would travel across the Atlantic > (and therefore arrive) in a fraction of a second. >