Question

There are several forces in nature that work to move water. Gravity is one force we are familiar with. Another less familiar one is "capillary action." Please describe capillary action.

Answer

Capillary action is the movement of water (and other liquids) due to the interacting forces of adhesion, cohesion, and surface tension. It has to do with the "stickiness" of the liquid — how much water molecules stick to each other compared with how much they stick to other substances, such as glass, cloth, organic materials, and soil. Capillary action occurs when the adhesive forces holding the liquid to the other substance are stronger than the cohesive forces within the liquid.

If you dip a paper towel in a glass of water, the water will "climb" up the towel through capillary action. It will climb up to the point where capillary action can no longer overcome the downward force of gravity on the water.