All About Bubbles

Bubbles have entertained and fascinated children and adults alike for eternities;  they evoke carefree childhood memories and bring on pure nostalgia. The elegance and whimsicalness of a delicate bubble levitating and jetting around on a current of air is a sight to behold. Yet the simple, timeless appearance belies the fact that they encapsulate fundamental scientific concepts such as elasticity, surface tension, chemistry, light, and even geometry. For these reasons, I will be studying bubbles for my ISP.

In this first blog post, I will be providing some prerequisite information about bubbles to lay the groundwork for my future posts. 

Bubble Composition:

A bubble is a thin layer of water enclosed by two layers of soap. This layer is then stretched out to form a sphere after  air is blown into it. Soap is a critical ingredient to bubbles since without the soap, the bubble would not form, as the surface tension (see below) would be too strong and cause the bubble to collapse in on itself, in the same way as a very stiff balloon which is nearly impossible to inflate. Soap works by weakening the surface tension of water thus making it possible to form a bubble. A good way to understand this is to think about the slipperiness of soap making it more difficult for water molecules to grasp onto each other.  

Surface Tension: 

Surface tension is the intermolecular force that pulls water molecules together. It’s similar to the stretch of a balloon.

Bubble Shape:

The most ubiquitous shape of a bubble is a sphere because the surface tension of the bubble pulls it into the smallest shape possible for the air enclosed inside. Out of all geometric shapes, the sphere has the smallest ratio of its surface area to volume. 

However, this is only true for isolated bubbles; when bubbles cluster together, a multitude of shapes (some quite unexpected!) can be formed (foreshadowing a future blog post!) ranging from a two-dimensional flat plane to a dodecahedron. 

In fact, Dr. Karen Uhlenbeck, a former professor at UT Austin and the first female winner of the Abel Prize, a prestigious award given to outstanding mathematicians, performed research on minimal surfaces, which are epitomized by bubbles; bubbles, as previously mentioned, will always strive to minimize their surface area.  Minimal surfaces pop (pun intended) up in nature a lot as nature is always looking to do the most in exchange for the least energy. In the case of a soap bubble, nature tries to maximize the volume while minimizing the energy it has to expend (stretch to a certain surface area). 

Bubble Color:

The color of a bubble is hard to describe, as the color changes depending on how you look at it. Even though bubbles do not have a set color, the shimmery, iridescence of an unassuming soap bubble is one of the most beautiful things in nature. What’s even more puzzling, however, is the origin of the bubbles: the bubble is made from clear liquids, so where do the colors come from? The answer lies in how light behaves when passing through different substances; this will be the subject of a future blog post as it is astoundingly intricate. 

Different States of Matter in Bubbles:

For the most part, bubbles are formed of a liquid film. However, in cold locations, it is possible to freeze the bubble into a solid shell, but it must be extremely cold (not Austin) as otherwise the bubble will not freeze in time before it pops. 

Popping Bubbles:

When the water in the film evaporates, the bubble will pop. This is a major concern for large bubbles, as there is much more surface area for the water to evaporate from. Thus, to keep bubbles from popping (for as long as possible), most large-bubble recipes will have some sort of hydrophilic, or water attracting, chemical such as glycerin or corn syrup in them. 

World Record Bubble:

On July 20th, 2015, Gary Pearlman (from USA) was able to blow a free-floating bubble 96.27 cubic meters in size. To put this in perspective, this is equivalent to 25 thousand gallons of water.  

Later in my ISP, I will attempt to (unofficially) break this record! 

Bubbles in Nature and the World

The concept of minimal surfaces is everywhere in nature. For example, one recently discovered shape, a scutoid, which is essentially a prism formed by any two parallel shapes, is essential to the development of epithelial cells (skin cells), as it takes the least energy to form and is the most efficient at packing together (thus maximizing work done).  

In 2008, the Beijing National Aquatics Center was erected.

It took inspiration from nature; namely, the concept of minimal energy makes an appearance again. The stacks of bubbles that comprise the building are representative of the best way to pack spheres into a box. The structure had one surprising side effect: the building is especially resilient to earthquakes as the minimum-energy configuration makes it very good at absorbing energy – the total energy has lots of room to go up! 

In conclusion: bubbles are cool/sick/dope/whatever you want to call them.