Siphoning

I needed to separate my fermented wine mix from the yeast. The yeast had been poisoned once the alcohol content was high enough and sank to the bottom. The method of extraction is siphoning. A large tube goes from the wine down to an empty demijohn on the floor. You get it started like a big straw by sucking on the lower end. This reduces the pressure at the lower end so that atmospheric pressure on the surface of the wine pushes it up the tube and out of the upper demijohn. The theory then says that the pressure difference is maintained by the falling liquid. I started thinking about whether it could happen with gases. I concluded that it might only work in liquids because of the cohesion of particles because they are touching in a liquid. This doesn't work in a gas. It turns out that cohesion is the rival theory to pressure for explaining siphoning. Both theories have counter examples. Siphoning works if you have a vacuum above the wine, apparently, so there is no pressure pushing the wine. And apparently it works with carbon dioxide gas. https://en.wikipedia.org/wiki/Siphon