What causes the bursting of a spherical air bubble?

[jobsism]

What actually causes the bursting of a spherical air bubble? Is it because of the random collisions of air molecules with the bubble? But if that's the case, shouldn't the collision effects be symmetrical? I mean, if air molecules are colliding at one point of the spherical bubble, it's diametrically opposite point also experiences collision effects from air molecules, so as to cancel any imbalance.

Or is the bubble collapse due to the drying of the water layer? But I've seen bubbles lasting weeks, if not months!

 

[Simon Bridge]

You mean a soap bubble in air?

A spherical bubble is an unstable shape - small pressure changes disrupt it.
Small collisions around the bubble are never exactly symmetrical.
The shell does dry out ... also, in a soap bubble, the soapy film gets dragged to the bottom of the bubble - eventually the top is too thin to support itself.

I believe the record is held by James Dewar, who did a lot of research on surface tension in soap bubbles. His longest lasted 108 days. It's all in how you make the film.

Technically, if a bubble is a volume of air trapped in a spherical membrain of any kind - then you can blow bubbles in glass that last a very long time ... more generally, you get bubbles in things like ceramics and concrete. I've seen bubbles of air trapped underwater last for years. But I suspect you are thinking of soap bubbles.

 

[jobsism]

You mean a soap bubble in air?

A spherical bubble is an unstable shape - small pressure changes disrupt it.
Small collisions around the bubble are never exactly symmetrical.
The shell does dry out ... also, in a soap bubble, the soapy film gets dragged to the bottom of the bubble - eventually the top is too thin to support itself.

I believe the record is held by James Dewar, who did a lot of research on surface tension in soap bubbles. His longest lasted 108 days. It's all in how you make the film.

Technically, if a bubble is a volume of air trapped in a spherical membrain of any kind - then you can blow bubbles in glass that last a very long time ... more generally, you get bubbles in things like ceramics and concrete. I've seen bubbles of air trapped underwater last for years. But I suspect you are thinking of soap bubbles.

Oh yes, I indeed meant a soap bubble! Sorry about the poor wording.

Thank you so much for the explanation! I was under the impression that random collisions with air molecules could be considered symmetrical. And I overlooked the downward drag of the soap film too.

I just started this bubble-blowing hobby, and was just researching ways to improve their longetivity. Well, it seems I won't be beating Dewar in a long time, hehe!