The True Story of Light


The holiday season is often referred to as the season of lights. Light represents many things to different people — everything from hope to rebirth to knowledge and goodness.

Candle light. Photo: Sander van der Wel from Netherlands, cc-by-sa 2.0

Legend has it that in the 16th century, Martin Luther wired candles to an evergreen tree after a walk through a starry night in the woods, creating the first illuminated Christmas tree. Beginning Sunday, candles are lit on menorahs as they have for millennia as those of the Jewish faith celebrate light over darkness. Like Hanukkah, Diwali is known as the “festival of lights” and is celebrated by Hindus, Buddhists and many others around the world.

We feel a deep connection to light. It represents the opposite of darkness, both literally and as a metaphor for knowledge. But, in fact, visible light, as it’s called, is just one chapter in the entire book of light’s story.

Setting Sun in Moorea-Maiao, Windward Islands, French Polynesia. Photo: J L Spaulding, creative commons license.

The light that we can see with our eyes is just a small fraction of all of the light that exists. If the full range of light were a piano keyboard, visible light would be represented by just a few keys around middle C. But, there is a vast spectrum of invisible forms of light, known as the electromagnetic spectrum, that extends beyond this middle key, from radio waves at one end of the spectrum to gamma rays at the other. We use and interact with all types of light, visible and invisible, in our everyday lives.

The electromagnetic spectrum. Illustration: NASA/CXC/M.Weiss

Our ability to see light depends on a key property: its wavelength. Light is —> Read More