Condensation nuclei in fizzy drinks???? I know how they work in clouds, but not Champagne.
SciFi - ice isn't just very cold water, it's gone through a physical change from a liquid, to a solid with a crystaline structure. Making that change requires energy, and something to kick off the change. So, if you put no loads whatsoever on a drop of water, and keep cooling it, it hasn't had the initiation to create the use of energy and change form. Give it something to latch onto - like a bit of wing it just hit, and that initiates the state change into crystaline solid, which then transmits itself very quickly through the liquid until it's all changed.
You can demonstrate this at home - have a look at this short video...
https://www.youtube.com/watch?v=kEHdyiBMgAg
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