🚀 go-pugleaf

In article <25362@dog.ee.lbl.gov> sichase@csa1.lbl.gov writes:
>In article <1992Aug10.174709.18689@nevada.edu>, rbond@nevada.edu (RICHARD BOND) writes...
>>In article <1992Aug7.165808.1391@visus.com> jml@visus.com (Jim Large) writes:
>>>  "The intersection of a pair of scissors"
>>>		-- Cool idea, though I doubt that we'll ever make the 
>>>		   the scissors which are perfect enough to actually 
>>>		   do this experiment.
>>  
>>   Dumb idea; if you would review your relativity theory, you will see
>>   that it points out that there is no such thing as a perfectly rigid
>>   structure. No matter how long you made your scissors, the far end 
>>   would not get the signal that the near end was moving any faster than
>>   the speed of light. Or do I just not get the joke?
>
>It's not a joke, but you didn't get it.  You are correct about the 
>limiting speed of the tips of the scissors.  But Jim was referring to the
>point of contact between the two blades, which speeds off towards the tips
>at much faster than the speed of light if the two blades are long enough.
>Imagine a pair of scissors with each blade two light-seconds long. They
>are open at the far end by only 1 inch.  Now close the scissors.  The 
>tips move 1 inch in, say, one second.  But the leading point of contact
>travels down 2 light-seconds of blade in the same one second.
>
>-Scott
>--------------------
>Scott I. Chase			"The question seems to be of such a character
>SICHASE@CSA2.LBL.GOV		that if I should come to life after my death
>				and some mathematician were to tell me that it
>				had been definitely settled, I think I would
>				immediately drop dead again."      - Vandiver

It seems to me that Richard Bond was refering to the fact that
no point along either scissor blade will begin to move in reaction
to the closing of the scissors until the E/M signal propagates
from the end of the scissors (where you are closing them)
to that point.

Consider your own example.  Close the scissors.  One second later
an observer at the tip of the scissors knows that you did so.
But that observer is stationed two light-seconds away from you.
-- 
at Bell-Northern Research
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