Full transcript of formulation scientist Li Wei Tan’s TED Talk: The Fascinating Science of Bubbles, from Soap to Champagne.
Li Wei Tan – formulation scientist
Some years ago, I was visiting Paris and walking along the Seine River during a beautiful summer afternoon. I saw giant bubbles floating on the riverbank, like this one.
The next moment, it popped and was gone.
Making them were two street performers surrounded by a crowd. They visibly make a living by asking for donations and by selling pairs of sticks tied with two strings.
When I was there, a man bought a pair of sticks for 10 euros, which surprised me.
I am a scientist who is passionate about bubbles. I know the right trick to make the giant bubbles is the right soapy water mixture itself — not the sticks, which may be needed, but you can easily make them at home.
Focusing on the sticks makes us not see that the real tool is the bubble itself. Bubbles might seem like something just children make while playing, but sometimes it can be really stunning.
However, there are more fascinating science to bubbles, such as problem-solving tools. So I would like to share with you a few stories about the science of creating bubbles and the science of eliminating the microscopic ones.
Since it’s up on the screen, let’s start with the soap bubble. It is made from very common substances: air, water, soap, in the right mixture. You can see soap bubbles constantly changing their colors.
This is due to the interaction with light at various directions and the changes of their thickness. One of the common substances, water molecules, are formed by two atoms of hydrogen and one atom of oxygen — H2O.
On most surfaces, water droplets tend to curve inwards, forming a semihemisphere shape. This is because the water droplet’s surface is like an elastic sheet. The water molecule on the surface is constantly being pulled inwards by the molecule at the center.
And the quality of the elasticity is what we call “surface tension.”
Now by adding soap, what happens is the soap molecule reduces the surface tension of water, making it more elastic and easier to form bubbles. You can think of a bubble as a mathematical problem-solver.
You see it relentlessly trying to achieve geometry perfection. For instance, a sphere is the shape with the least surface area for a given volume. That’s why a single bubble is always in the shape of a sphere. Let me show you. Check it out.
This is a single bubble. When two bubbles touch each other, they can save materials by sharing a common wall. When more and more bubbles are added together, their geometry changes. These four bubbles are added together. They meet at one point at the center.
When six bubbles are added together, a magical cube appears at the center. That is surface tension at work, trying to find the most effective geometry arrangement.
Now, let me give you another example. This is a very simple prop. This is made from two layers of plastic with four pins connected to each other.
Imagine these four pins represent four cities that are equally apart, and we would like to make roads to connect these four cities.
My question is: What is the shortest length to connect these four cities? Let’s find out the answer by dipping it into the soapy water.
Remember, the soap bubble forms will always try to minimize their surface area with a perfect geometry arrangement. So the solution might not be something you expected.
The shortest length to connect these four cities is 273 times the distance between these two cities.
Now you’ve got the idea. The soap bubble forms will always try to minimize their surface area with a perfect geometry arrangement.