🚀 go-pugleaf

u894793@bruny.cc.utas.edu.au (Timothy D Little) writes:
> 
> >1. What's the shape of it? Is it a perfect semi-sphere?
> 
> It can't be a perfect semi-sphere due to the effect of surface tension at
> the edges.  Furthermore, the internal pressure of the bubble would make
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> the 'flat' bottom slightly curved.
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  
  I've tried to calculate that "curve", assuming the pressure deference
between inside and outside is balanced by the surface tension on the 
'flat bottom'.

 
> >2. Why does it break? And what's the machanism of it's breaking?
> 
> I read once that it was evaporation of the bubble film.  I don't know
> how much weight to give this, since it was a 'popular science' book and
> not a technical one.
> 
  But water also condense, so you have predicted that if the air is wet
enough, the bubble won't break. :)
  Some said it is because the density ( or width of the film) is not 
uniform, and the bubble starts its breaking at the thinest point. There 
are two problems in this point of view:
  1. Why not uniform? If the only reason is gravity, there should be 
     simply a vertical variation, and the thinest point is at the top
     center. So the bubble should always break at its top, this should
     be checked.
  2. How does it break at that point? I think the thick surrounding film
     has a larger tension to pull apart the water molecules in between.
     Once there is a hole, it can't stop breaking. Is this true?

> Fairly much.  I'm more interested in the 'antibubbles' you get by skimming
> small droplets of water across the surface, consisting of a glob of water
> separated from the main mass by a thin film of air (I assume).

  Your "antibubbles" is awful interesting, I wonder can it live on water 
surface. ( That is, a film of water, and a film of air containing a glob 
of water. The water film seperate the "antibubble" from the air). And how
can you identify an antibubble floating in the water? The bubbles always
float to the surface, is it also true for an antibubble? Hmm...perhaps
slower ;-)  Would antibubbles "break"? (in water) 

Dragon
clwu@Uz.nthu.edu.tw