dat surface tension. so hydrophobic.

Extra info from YT : "Helpers were bubbling air from compressed air bottles into the pool to ease surface tension. Yet, he failed in hitting that spot but went away without injury. It is reported that at a first glance they suspected a pelvis displacement which luckly couldn't be confirmed."

It's not only the sting of the slap, it's the raw concussive force of a large surface area (ie. nape to ass) meeting strong surface tension. The best way to land is to break the surface tension with the smallest area possible (ie. fingertips, toes etc) allowing the body to slide in to the water.

My physics lab prof in college said:

"If you ever see a question about 'why does water do x while {insert other liquid here} does y', the answer is always 'because it's polar'".

Expanding when frozen? Polar.
Strong surface tension, adhesion and cohesion? Polar.
Complex molecules dissolving in water? Because the water AND the dissolving molecules are polar. Non-polar things *won't* dissolve in water, for the reverse reason.
...
And I guess this can be thrown on the list also, although just saying "polar" misses some of the details/nuance that Sagemind covered.

Ok, so here is a very good point.
Because of strength and density, squeezing the air out of the sponge, while submerged under the mercury..., where is that air supposed to go?

Displacement. for the mercury to fill the sponge, the air must be pushed out and displace mercury while submerged, Can air, displace the Mercury in this instance? that's another interesting factor here.

Surface tension sounds plausible, but with the pressure of squeezing the sponge, I would think that tension would break even a little.

Adhesion. Water is polar, its why you get surface tension and I think that's why it sticks to most surfaces. Mercury adheres to itself pretty good but for different reasons. You'll notice it runs off surfaces in a similar way water runs of a hydrophobic surface - it doesn't streak because it doesn't stick.

Now, perhaps if it were an aluminium sponge...

I suggest that it's most importantly to do with the surface tension of mercury. When the mercury covers any of the sponge's holes it forms a new little surface where the strong surface tension matters. You can tell this by looking at any transparent container of mercury such as old barometers and such. The meniscus bends down at the edge rather than the equivalent container of water where it bends up a little. If you pour out a bunch of mercury on a flat surface it will spread out so it's about half a centimeter deep iirc, i used to play a bit with some as a kid. (sometimes in a vac chamber, but not always!)

Here's a thought though. Unfortunately he had parts of the sponge poking out (possibly because of the limits of his container/supply of mercury) and so air could refill the holes in the sponge and allow it to retake its preferred shape. But if it was entirely submerged in the mercury and squeezed, which would be stronger? The springiness of the sponge to want to return to its shape sucking mercury in, or the surface tension of the mercury and the sponge just stays squashed. And i know that packing material is more springy than a bath sponge (or a natural sponge).

With the fruit flies... Another trick is to fill a bottle with apple cider vinegar and then put a little soapy water in there. When the flies land on the surface the fly breaks the surface tension and falls in.

Its caused by breakdown of biological products mixing in with water rather violently. Usually when a large algal bloom dies, the breakdown of the matter acts like a surfactant (destroyer of surface tensions!!!), which causes the foam.

Not usually all that harmful.

I imagine it's a result of various forces and circumstances (I don't think it's a coincidence that the droplets were soapy water which would increase it's surface tension/bubble strength).

Also keep in mind that a droplets surface would be a mesh of the outermost water molecules held together by their polar attraction. As the sphere bounces and moves its surface would have mini waves and ripples along it that would push against and then move away from the molecules on the water surface below it as the kinetic and polar forces acted.

If you imagine that every sphere of water had portions of its surface moving away from the water surface below and then oscillating back towards the surface while the molecules on the spheres surface that had been touching the water surface below would begin to oscillate back into the sphere.

This would create many points of contact oscillating against and away from the water surface below and thus there might not be enough contact/pressure between the 2 surfaces for it to coalesce at any given time. Imagine bugs whose feet are tiny enough for them to "stand" on water due to surface tension and the principle would be the same. It'd be like an infinite number of these bugs legs jumping up and down on the water at a microscopic level.

Also I'm not familiar enough with how water molecules align themselves while at the surface of something so perhaps the alignment of their atoms helps as well?

Thats all a guess though I'm sure you could google the real answer.

I can imagine that a flat surface meeting the curve of the droplet makes for a smaller surface area of contact than if the convex curve of the droplet meets a concave curve of the vibrating water. Maybe the weight of the droplet ensures that it will always be in a concave part of the vibrating surface. I don't know enough about surface tension at an atomic level to really have any good ideas on this.

But why? Why does vibration create larger surface tension (assuming that surface tension is what keeps the bubbles bubbly)? You would expect the opposite.

Oh, now I will not be able to sleep tonight.

Apropos comic from a self proclaimed Apple fanboi:

http://hijinksensue.com/2012/06/19/surface-tension/

Apparently, adding oil to the water reduces surface tension, preventing the water from boiling over.

The chemist in me thinks that it doesn't make a huge difference.

>> ^quantumushroom:

It's easier to type WITCHCRAFT! Also acceptable: SORCERY!
>> ^juliovega914:
For those of you interested in the actual mechanics of the superhydrophobicity, I direct you to this wiki:
http://en.wikipedia.org/wiki/Lotus_effect
Basically, the reason its so repellent isn't due to a hydrophobic coating, but rather the development of a surface nanostructure that has sharp angles and points in such a way that the surface tension of water binding to the surface is less than the attraction of the dipoles of the water molecule to other water molecules. As a result of this, the water forms globules on the surface rather than running off the side.


Don't forget the ever popular "God did it", Jesus probably coated his feet with this shit.