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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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