Episode Details

Daniel looks out the window at snow and asks why it's white. Water isn't white. Ice isn't really white. So why is snow?

The answer starts with a correction.

A single ice crystal is transparent. See-through, like glass. Light passes right through it. So a snowflake -- which is essentially a tiny, complex ice crystal -- isn't white either.

But when millions of them pile up together, something happens. Light enters the snow, hits a surface, and bounces. Then hits another surface, and bounces again. And again. After bouncing over and over through all those crystals and air pockets, it comes back out in every direction at once. And sunlight contains all the colors -- red, orange, yellow, green, blue, violet -- all mixed together. Snow scatters all of those colors equally. When all the colors reach your eye at once, that is what we see as white.

Snow doesn't have a white pigment. It looks white because of what it does to light. It is showing you whatever light hits it.

Which is why deep snow and glaciers can look blue. The further light travels through ice before bouncing back out, the more red light gets absorbed along the way -- leaving more blue. And at sunrise or sunset, snow can look pink or orange, because the incoming light is those colors. The snow just shows you what it receives.

And fresh snow on a sunny day can be almost painful to look at. Because snow reflects a tremendous amount of sunlight -- including ultraviolet light. Without sunglasses, that reflected UV can damage the surface of your eyes. Snow blindness is real. Most people don't think about needing sunglasses in snow -- but the reflection makes it more important, not less.

Then Daniel asks the question that opens the second half of the episode.

If snow is white because it reflects light -- mirrors also reflect light -- why isn't a mirror white?

The answer is about how the light bounces. Snow has millions of tiny surfaces pointing in every random direction. Light scatters everywhere. No image. Just brightness. Just white. A mirror's surface is almost perfectly flat and smooth. Every ray reflects at the same angle it arrived -- one precise direction -- so the scene is preserved exactly. Every detail, every color, right back at your eye.

Snow scatters. Mirrors preserve. Both are reflecting light. Completely different results.

Daniel figures out the difference himself before Mom names it. The technical terms for what he described are diffuse reflection and specular reflection. Worth hearing how he gets there.

What you will find in this episode:

• Why a single snowflake is transparent but a pile of snow looks white
• What is actually happening to light inside snow
• Why deep snow and glaciers can appear blue
• Why snow can look pink or orange at sunrise and sunset
• Why fresh snow can cause snow blindness -- and why UV matters
• Why mirrors aren't white even though they also reflect light
• The difference between diffuse and specular reflection -- and how Daniel explains it before hearing the names

Short, surprising, and the kind of episode that makes every snowy day look completely different.

Listen, wonder, and learn.

Find us @smilewithDaniel everywhere.