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Disorganized packets of air molecules

Article 1 Module 1

The primary reason objects in nature are white is that light hits disorganized packets of air molecules. 

These bounce the light photons all over the place. It is like being in a chaotic, nano-sized pinball game. The light is scattered. Much of it is reflected back to us. 


White polar bear


The hairs that make up the bear's fur are transparent and hollow; this fur covers a black skin!

However, when sunlight hits a polar bear's fur, the light scatters from the air mass within the straw-like strands of hair. The result is a white coat.

 

A cumulonimbus cloud develops  as a hot air mass pushes upwards into a towering cloud. 

It is as if a giant were standing on Earth with a large bicycle pump, injecting warm, moist air into the troposphere. 

White clouds - cumulonimbus
White air bubbles beer


Fermentation proteins of beer forming the “head” of a pint of beer.  The gas that produces the "head" in a pint of beer is carbon dioxide, though nitrogen is sometimes added to produce a longer lasting, less acidic taste. 

Uneven air masses create white color; Keep in mind that it is the air bubbles that reflect the white light back. It is not water bubbles. Light refracts at different angles between the air bubbles and the water holding the bubbles in place.

This chaotic bouncing around of light prevents light from going through. The light is reflected back to us, making the bubbles appear white.

Air bubbles while diving

It's not only dogs and cats that foam at the mouth. Even crabs - forcing air out of their gills - will produce foam when out of the water

The image shows a sputtering crab.

Spitting crab
Transparent glass with air bubbles


Even glass  can trap air bubbles.  

Disorganized and different-sized air bubbles reflect white light back to us.  


Sea foam forms for the same reason that a beer head forms. Long lasting cohesive molecules hold the air bubbles in place

Adding cohesive molecules to whipped cream (like gelatin or non-fat powdered milk)  will help make longer lasting whipped cream.  The cream will have stiffer peaks that keep their shape for days.

Lake foam - Algae
Soapy foam on man's hand

Have you heard the expression "foaming at the mouth" or "spluttering" or "frothing".

Colorless saliva turns white as breath is forced through the liquid in the mouth.

The result is white foam bubbling or spluttering out.

Similarly, soap forms a foamy liquid when lathered.


It depends on how you freeze the cubes. Household ice cube trays often freeze water relatively quickly.

This entraps the air bubbles in the center of the cube - the last place to freeze. 

The ice cubes shown look as if they have clouds trapped in their center. 

ice cubes with central white cloud
white snow on deck

Whereas snowflakes seen individually are colorless, a mass of snowflakes with entrapped air bubbles will appear white. When snowflakes fall and collect on the ground, they glue to other flakes through frozen bonds. In doing this, they entrap pockets of air.  

The chaotic arrangement of air bubbles within snow will bounce (refract) light all over the place. Enough light is reflected back to us from the surface of the snow as white light.

Water splashes - white water

Liquid water is white at the interfaces of water and air when there is turbulence.

Wave crests, breaking waves, waterfalls, the wake of ships and boats, river whitewater, water splashes, and water jets are all examples of turbulent water/air interfaces.

Agitated water at the air interface encourages aeration of liquid water with air bubbles.


Pockets of air are not only encompassed with water. Other natural materials hold air bubbles hostage. For example, molecules such as protein, fats, and soaps are really good at this.  Egg white proteins help form whipped meringue.

Whipped egg whites


 Mynah bird feathers are not white: the feathers of the Bali Mynah bird tend to be hollow entrapping pockets of air. 

White snow/white Mynah bird

Since air's oxygen and nitrogen molecules do not absorb any of the light, totally white light is reflected back to us. 

This is different from, for example, Chlorine gas that absorbs higher frequency wavelengths of light. It reflects back lower frequency lightwaves; Chlorine gas looks greenish yellow.

The common thread through those elements is that the disorganized masses of air molecules have to be held in place to act as a reflecting surface. Furthermore, what holds them in place must be transparent to allow the lightwaves to hit the packets of air molecules.

In the next lesson, we go over the different molecular nettings that  encase masses of air molecules.  

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