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    Re: The development of bubble sextants
    From: Bill Morris
    Date: 2009 Aug 14, 02:11 -0700

    In response to hannoix's post:
    
    In a very prelimary experiment I formed an annulus of about 215 mm radius from 
    plastic tubing, bore about 8 mm and filled it with water apart from a bubble 
    about 20 mm long. I just happened to have a circular table top that never got 
    past the embryo and was able to hold the tubing in a more or less true 
    vertical circle by clamping it to the periphery. I was able to squeeze the 
    bottom of the tube by holding it in a small machine vice and could impart 
    acceleration in the horizontal plane by moving it sharply over the bench.
    
    I regret to report that I was not able to get the bubble to do anything but 
    move forward, despite squeezing the tubing from zero to "quite-a-lot", over a 
    length of 100 mm.
    
    At least in very sensitive levels, for example, those of better than 10 
    seconds per 2.5 mm bubble movement sensitivity, the behavious can be quite 
    puzzling and unpredictable. Sometimes just breathing on the vial can set the 
    bubble moving. In  such very sensitive levels it can take well over a minute 
    for the bubble to reach its final position. It seems that swirling in the 
    fluid can affect bubble behaviour in sensitive levels and the physics even of 
    insensitive levels probably needs to take into account fluid dynamics, my 
    knowledge of which would occupy the back of a fairly small postage stamp.
    
    I will repeat the experiment in a few days time taking more care and possibly 
    using alcohol as the fluid. This will allow time for people to explain the 
    null result and to criticise the experimental set up...
    
    Bill Morris
    Pukenui
    New Zealand
    
    
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