Human beings evolved with natural light patterns. Our bodies respond differently to the rising sun, the light at full noon and the darkness of night. For some time, researchers have known that our internal circadian rhythms are modified by the eye’s exposure to light, whether it comes from the sun or from LED lighting.

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LED lights have been used in a variety of applications since their invention in 1961. From inexpensive appliance display lighting to automobile daytime headlamps, light-emitting diodes seem to be everywhere. Indeed, LED lighting could even change air travel as we know it. The 787 Dreamliner, Boeing’s new jetliner, includes LED lighting designed to positively influence passengers’ circadian rhythms.

How could LED lights possibly affect the body’s diurnal rhythms? The answer hinges on the fact that LEDs are “programmable.” Unlike filament-heating incandescent bulbs, LEDs are tiny semi-conductors, fueled by electricity-stimulated electrons crossing a field to fill electron holes. The chemistry here is pretty complex, but suffice it to say that engineers can affect the light wavelengths an LED produces by changing the semi-conductor material. Zinc selenide, for instance, is used to produce blue LED lighting.

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