Douglas Krantz - Technical Writer - Describing How It Works
Go to the Writer Home Page of Douglas Krantz -- Describing How It Works
Go to the Fire Alarm Operation Map Page of Douglas Krantz - Technical Writer
Go to the General Electrical Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Description Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Installing Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Maintaining Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Testing Map Page of Douglas Krantz - Technical Writer
Go to the Fire Suppression Map Page of Douglas Krantz - Technical Writer

Trivia

The sun is yellow, the snow is white, and the sky is blue.
If snow reflects all light, how does it get white when the sun is yellowish?
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer






Why is Snow White?

By Douglas Krantz

Question: If the sun is yellow, why is snow white?
Answer: Because the Sky is Blue.


Um, the riddle seems to be nonsense, but really, it does hold a scientific truth.

The light from the bluish white sun has the blue removed and scattered in the atmosphere, making the sunlight appear yellowish.
As the light from the sun travels through the atmosphere, the blue value light is scattered by the moisture. This gives us the yellowish light from the sun we see.

White Snow - Yellow Sun

The snow, indeed, does look to be white. Whereas the real sun doesn't look as yellow as these drawings show, it does have a definite yellow tinge to it, especially when compared to real snow.

Sunlight Above the Atmosphere

Above the atmosphere, the sunlight starts out with a blueish white color. As the light from the sun pierces the atmosphere, it is modified; some of the blue light from the sun is diverted so it no longer comes down to the earth in a straight line.

Blue Sky

Moisture in the atmosphere scatters the blue light, and re-scatters the blue light again and again
Yellow sunlight and blue sky light is combined by the snow to make white snow.
The snow takes all this light, the yellowish light from the sun and the bluish light from the sky, and recombines it to make white light.
so it seems to come from all directions of the sky. Some of the blue light from the sun is scattered back into space, a little is absorbed by the atmosphere, and in what we observe as blue sky, much of it does get to earth.

What's left of the original white light from the sun is white, minus some of the blue component. To us it looks yellowish.

Size Ratios

The sun is very intense, but it's also a very small portion of the sky.

On the other hand, the blue of the sky isn't all that intense. However, to make up for the lack of intensity, it takes up most of the sky. Added together, all that blue light from all over the sky equals a lot of blue.

This means that as a whole, when added together, the light from the yellow sun and the light from the blue sky provides a total of white light.

The Snow Combines the Light

Snow, of course, is what adds the light together. The light is reflected and refracted by the snow, which makes the snow a combiner of the white light we see.





Popular Articles

What is a Stair Pressurization Fan (SPF)? -- In case of fire in a high rise building, an SPF uses clean outside air to pressurize the air in stairwells. The pressurized air helps people escape... Read More

How Does Class A Fire Alarm Wiring Work?-- Fire alarm systems save lives and protect property. Fire alarm systems also break down because... Read More

What's the Difference Between Class A and Class B? -- The Fire Alarm System is a Life Safety System - so the occupants of a building can escape quickly, the idea behind a Fire Alarm System is that it will provide a warning that there is a fire. The trouble is, if something is wrong with the system, like a wire is broken somewhere in the building, the Fire Alarm System... Read More

What is a Flyback Diode? -- Someone Thinks the Flyback Diode is Important. Manufacturers all over the world spend good money installing these diodes, they must think they're ... Read More

What is a Waterflow Switch? -- The fire alarm waterflow switch, a delayed action mechanical/electrical assembly, is a conventionally wired fire alarm device. The fire department reacts... Read More

What Should I Do When the Fire Alarm Sounds? -- When the alarm sounds, as caretaker for an apartment building, what should you be doing? "I would never suggest turning off the fire alarms, or in any way... Read More

What is a Fire Alarm System? -- Long ago, as earliest method of spreading the word of fire danger, people shouted "Fire!" Depending on the circumstances, people would run... Read More

What Does E=IR Really Mean? -- If it isn't just a word, and it isn't really something to be memorized in order to pass a test, what do the letters in Ohm's Law really mean?... Read More