maze
- 661
- 4
Could a tiny sugar ant walk on a soap bubble? Would the bubble burst? Would the ant be able to locomote along the surface or would it get stuck?
The discussion centers on the feasibility of a sugar ant walking on a soap bubble. Participants concluded that while an ant's weight could theoretically be supported by the bubble due to the pressure dynamics involved, practical attempts revealed that the ant becomes immobilized in the foam. The ant's body geometry affects its interaction with the bubble's surface, leading to a lack of traction and eventual sinking into the foam layers. Ultimately, one participant reported that their attempt resulted in the ant's death, highlighting ethical concerns regarding such experiments.
PREREQUISITESBiologists, entomologists, educators conducting experiments in fluid dynamics, and anyone interested in the interaction between small organisms and their environments.
maze said:Usually I have to keep things super clean or else ants will take over, but now that I'm actually looking for sugar ants to drop on a soap bubble, I can't find any.
:/
Andy Resnick said:People are not considering the fact that soap bubbles have *two* interfaces; the soapy water is a thin film.
Given that the interfacial energy of pure water in air is about 70 dyn/cm (70 erg/cm^2), say the interfacial energy of soapy water about 10 dyn/cm.
An ant weighs about 3 mg, so each 'foot' has 0.5 mg spread over (say) 0.1 mm^2. 'g' ~ 1000 cm/s^2, so each foot exerts about 0.5 dyn/mm^2 (5*10^-3 dyn/cm^2) pressure.
The pressure jump across one interface of a 5 cm diameter soap bubble is 2* 10 dyn/cm * (2/2.5 cm) = 16*dyn/cm^2. This is much higher than the foot pressure of an ant, so the ant's weight should be supported by the bubble.

maze said:Ok, I found an ant and dropped it on a soap foam. The bubbles were about 1/2 the size of the ant (ie: 2 bubbles = 1 ant).
The ant basically got stuck in the top layer of foam, immobilized. I believe its body geometry was serving as boundary conditions for the foam surface. After about a second of just sitting there, it spazzed out kicking its legs every way, which caused it to sink slightly to the 2nd or 3rd layer, and then after a couple seconds it stopped moving so I took it out. I think it died, which I didn't expect to happen (especially not after only a few seconds). I don't think I will be trying again since it seems a pretty cruel way to go.