Why aren't these streams of liquid merging?

These streams are all the same thing — silicone oil — and they are engaged in a beautiful, yet baffling, display of fluid dynamics. Perhaps if the liquids were like oil and water, this photo would make sense, but these streams are both five-hundred-micrometer-wide streams of silicon oil. Clearly each stream has some internal cohesion, and the same chemical properties. They should be clinging together perfectly, but they aren't.

The reason they stay solidly separate because they're not actually touching. The molecules are separated by a tiny stream of air; the air lubricates their movement, so as they rush past each other, more air rushes in to keep the separation going. As long as they don't actually touch, they don't blend, and we see a group of separate structures rather than a merging liquid.

Image: Navish Wadhwa and Sunghwan Jung; Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Via APS.