[WylieE (OP)]

Hi,

I see there have already been some posts on sonoluminescence, and an explanation of what it is, but I didn't see an explanation about why it occurs. Is there a consensus about what causes this? Are there any practical applications yet?  Or is it just still a cool phenomenon?

Thanks, Colleen

[Soul Surfer]

When high intensity sound waves pass through a liquid they may cause cavitation where the negative pressure in the wave is low enough to disrupt the liquid and form a bubble containing vapour.  These bubbles are very small and almost perfectly spherical.  When the sound wave goes into the pressure part of its cycle these spherical bubbles are forced to collapse very rapidly and symmetrically.  This causes a peak of extreme pressure and temperature at the centre of the bubble. This emits light. It has been suggested that temperature can rise briefly to tens of thousands of degrees C,  maybe even millions, and could be a way of instigating cold fusion.

[WylieE (OP)]

Thanks Soul Surfer,
  Nice explanation, that was easy to understand.
  What brought up this question was a discussion I had where someone mentioned this as a possible source to initiate (?is this the right word)cold  fusion as you said.  During the conversation, they mentioned they had heard that a lab had detected extra neutrons (suggesting there was fusion occurring?).  So I went back and caught up on the story, I think they are referring to the 2002 article in Science from Taleyarkhan (Oak Ridge Labs).  I can get a very crude grasp of the article, and understand that the review, also in Science, also from Oak Ridge (wow, friendly place to work) is very critical of the paper.  However, I don't see anything really since then. . .

So, I was wondering if it has been shown to not work, or if it has just not been long enough and these experiments take time?
I am guessing from your answer that this is still thought of as a serious possibility- am I correct? 
Thanks,
Colleen

[Soul Surfer]

The excess neutron observations may be ok and a minute amount of cold fusion may be occurring in this and other electrolysing experiments but it seems very unlikely that an energetically useful amount of fusion could ever be caused.