A bubble will always try to make itself as small as possible. The smallest shape is usually a sphere, unless the bubble is trapped between some other objects.
In this activity, the giant bubble is trapped between two rings. When you pull the rings apart you make a tunnel-shaped bubble, with a ring at the top and a ring at the bottom.
You might think the bubble will make a cylinder, but a cylinder is not the smallest possible shape for this bubble. Instead, the bubble curves inwards at the middle. This shape has a smaller surface area than a cylinder and is called a catenoid.
The curve of a catenoid is called a catenary, and is the shape made by a freely hanging rope or chain.
The shape of a bubble trapped between two rings is called a catenoid. In 1744, Swiss mathematician Leonard Euler confirmed that the catenoid is the shape between two rings with the smallest surface area.
The curve of the catenoid is called a catenary. The word catenary comes from the Latin word for chain because it is the shape made by a freely hanging rope or chain. In 1671, English scientist Robert Hooke, determined that the strongest possible arch was a catenary, and this shape can often be found in architecture.
The catenary is the shape of a freely hanging rope or chain and can often be seen in nature, from power lines to the web of a spider.
When turned upside down, the catenary is the strongest arch. This was proven in the 17th century, but there are many earlier examples of arches that approximate the catenary.
Maths at Home
Make your own super bubble solution with this recipe:
How big of a bubble can you make? How many bubbles can you make in one breath?