The soap molecule has two ends: one is hydrophilic or water loving and the other is hydrophobic, repelled by water. These liquid ribbons are actually a laminate: soap, water in the middle, then soap again.
Bubbles do not form due to strong surface tension. If this substance were pure water, they would break up into droplets. Soap lowers the surface tension of water to about 1/3 of its original elastic strength. It measures in at about 1 grain per inch.
When the bubbles are first blown in the sculpture, each arc is a section of a circle. Scientists calculate the convex or concave arcs and determine the pressure of each air cell relative to the one next to it. Eventually surface tension pulls all the air cells into equilibrium, balancing the pressure. Then all membranes take the shortest distance between points, a straight line.
Whether the bubbles are curved or straight, the angles where they meet are always 120 degrees. When the bubbles are heavily curved it doesnít seem that this could be so, but at close examination, the angles are still 120 degrees.
It would be surprising if it were not the symmetrical 120. Each of the three bubbles that creates this angle has exactly the same amount of surface tension. The length of each bubble does not matter; they are liquid. It is not like a rubber band where the more it's pulled the longer and more full of energy it gets. It's only the surface tension that matters. It has a specific force. The thickness of each bubble also does not matter. Each has two surfaces and two surface tensions; whatís in the middle has no surface, no force. Each bubble has two surfaces. Everything is equal. The angles must be equal. It must be symmetrical. It must be 120 degrees.
Although they look thicker where the liquid flanges to the glass, but these liquid ribbons of color are extremely thin. Between the distance of the hills and valleys of your fingerprints, you could fit 1,000 walls of a bright blue bubble.
The liquid is clear. The color comes as the surface becomes thinner.
Light is composed of waves. These waves have a crest, a valley, a crest and so on. The distance from crest to crest is called the wave length. A whole series of these wave lengths is called a wave train. When the liquid of a soap bubble is about half a wave length thick, the light reflecting off of the rear surface back through to the front travels one full wave length within the liquid. Another wave train is reflected directly off the front surface. When they meet, both wave trains match up; they are ďin phaseĒ or ďin constructive interference.Ē
This makes the color very bright. It makes them iridescent.
The bubbles start out thick. Gravity and surface tension thin them to where they act as tiny resonance chambers for light. There is a time when, due to gravity, they are slightly thinner at the top and thicker at the bottom. This is when the colors align in bands. The difference of thickness, from one color to the same color in the same bubble, is equal to one extra wave length the light travels within the liquid.
The wave length for red is slightly more than twice the length for violet. Their numbers donít add up neatly. Therefore, there is an overlapping of colors. So, in thicker bubbles, colors are mixed. They are not the pure colors of the rainbow, but different blends. In thick bubbles, 50 millionths of an inch thick or so, all the wave lengths are thoroughly mixed, making them appear white.
In old bubbles, when the walls are thin and have a uniform thickness, they are all blue or all red. At this point, all the other colors pass through. For example, the other side of a blue bubble will be everything except that blue which has been reflected away. It will be a pastel. It will be the complementary color of blue: orange.
Some older bubbles are very thin. They are less than half a wave of ultraviolet thick. They are totally clear to us. To insects, which see a different spectrum than we do, the bubbles still appear brightly colored. But since they reflect no visible wave to us, scientists call these Black Bubbles.
Look at all the colors and remember that the liquid used has no color of its own; it is clear. The color appears as the bubble thins. Itís due to constructive interference. Iím not sure, but I think itís due to the mathematics of the universe. Iím not sure, but I think itís due to God. However, I do know itís due to a miracle. And that miracle is due to the smile and joy of Mother Nature.
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