[NatureNS] Correction; Fw: Velocity of light

Date: Fri, 21 Sep 2012 20:19:10 -0400
From: Fred Schueler <bckcdb@istar.ca>
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Quoting David & Alison Webster <dwebster@glinx.com>:

> I just dug out my 1st yr Physics (Weber, White & Manning, 1952) and  
> they consistently refer to 'speed of light' as opposed to 'velocity  
> of light'. Four other sources (1941, 1948, ~1965 &1962) have velocity.

* indeed, it would be ineffective to purge society, or even  
literature, of all who misuse speed/velocity or weight/mass. Or, to  
bring it closer to natural history, all who refer to nonhemipterans as  
"bugs."

fred.
===============================================

> ----- Original Message ----- From: "David & Alison Webster"  
> <dwebster@glinx.com>
> To: <NatureNS@chebucto.ns.ca>
> Sent: Friday, September 21, 2012 7:44 PM
> Subject: Velocity of light
>
>
>> Dear All,                        Sept 21, 2012
>>   The recent discussion about transmission of electricity, reading  
>> of HEAT and reading some of Energy... brings to the forefront a  
>> question that has nagged me for decades. Perhaps someone can clarify.
>>
>>   In the typical elementary physics text we are told that velocity  
>> is a vector quantity, and to quote one text "velocity... may be  
>> defined as the rate of change of position in a given direction".  
>> But "In cases where the direction of motion does not require to be  
>> considered , the term speed is employed to express the rate of  
>> travelling."
>>
>>   Based on the above I would think that the rate of movement of  
>> light should be called speed, i.e. speed of light but I think it is  
>> always called velocity.
>> For example, if light from the sun is reflected from two 45o  
>> mirrors then a beam of light could be directed from the earth back  
>> to the sun and, the velocity would then be minus 3 x 10^10 cm/sec.  
>> Or if variously scattered or reflected then the velocity, relative  
>> to the initial sun to earth direction, would always be less than 3  
>> X 10^10 and after several reflections might be zero.
>>
>>   Is there some good reason why the speed of light is termed  
>> velocity of light ? Or is it called velocity because the textbook  
>> authors forget what they said in chapter one by the time they write  
>> chaper eleven ? (And they all copy from each other)
>> Yt, Dave Webster, Kentville
>
>



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          Frederick W. Schueler & Aleta Karstad
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