Have you ever wonder why bubbles always have spherical shape? It is cause by surface tension. There is always tension on liquid surface so it create a force. To see which direction the force is pulling, let's do an experiment.
Btw, the circle string have nothing to do with the spherical shape of the bubble I am talking about. Also, I just learn thing in school a few days ago so if I made a mistake, please correct me in the comment.
P.S:Sorry if my English is bad.
Step 1: What You Need
- Copper wire
- Super glue
- String or yarn (I use yarn to make it easier for the camera to see
- Soap solution
Step 2: The Frame
Cut a 71cm long copper wire and bend it, making a rectangle which have 20cmx15cm. There will be a small edge which is 1cm long, it will be the joining piece. You can glue it by warp string and apply super glue and make a strong bond
Step 3: The String Holder
Cut two 7cm long copper wire and warp then glue to the frame, it should be in the middle of the edge. After that, you bend the wire up so that the distance between the string and frame is 2,5cm.
The string is a 31,4cm long and tied together. Then warp the copper so that it hold in place.
Step 4: The Experiment
First, you dip the frame in to the soap solution. Then you use a dry, thin object and pop the middle bubble. If you do that, the string will be pull straight out.
So what does this experiment have to do with the spherical bubbles? Well, according to the experiment, tension will always make the surface area of the bubble as smallest as it can. So in the case of a 3D bubble, the tension will try to pull itself inward and the force is apply evenly around the bubble, make it a sphere. And thanks to the atmosphere inside the bubble prevent it from collapsing itself.