Submerged antibubbles of air surrounding soapy water

An antibubble is a droplet of water surrounded by a thin film of air, as opposed to an air bubble, which is a sphere of air surrounded by a thin film of water. Antibubbles are formed when water drops or flows turbulently into water. They can either skim across the surface of the liquid, in which case they are also called globules, or they can be completely submerged in the liquid.

Antibubbles are a common but widely unrecognised phenomenon, in part because of their resemblance to air bubbles, and in part because of their typically transient nature. With certain (soapy) solutions, they can be made to last much longer.

The behavior of antibubbles differs from that of air bubbles in three primary ways, and provides a ready means of identification:

• Antibubbles are not held in place by surface tension, and move rapidly across the surface of the water. They can also be seen to ricochet off other objects in the water (such as air bubbles) and off the sides of a container in a manner similar to that of billiard balls.

• Antibubbles can be short-lived. An air bubble with a soap skin may last a minute or two. Antibubbles often have lifetimes of a few seconds or less; however, if the electrical potential between the inner and outer fluid is equalized, antibubbles can last as long, or longer, than air bubbles.

• Antibubbles refract light in a different manner than air bubbles. Because they are water droplets, light entering them is refracted back toward its source in the same manner as rainbows are produced. Because of this refraction, antibubbles have a bright appearance.

Antibubbles are easily created by allowing a tap to drip into a container of water to which a drop or two of soap has been added. The soap reduces the water's surface tension and allows the skin of air surrounding the droplet to remain in place for more than just a fraction of a second.

External link

• Antibubble.org
• Advanced Physics Forums: Antibubble