My primary goal for my Smart Home was to create a nurturing environment that understands my needs before I do. Recent research has shown the connection between color temperature and the body’s sleep cycle. NASA uses color temperature to help Astronauts on the International Space Station fall asleep, a notoriously difficult place to nod off. Your Smart Home can help you do the same by automating a color temperature schedule that takes full advantage of the science behind sleep.

Before we dive in, it might be useful to cover a few key concepts. If you want to get straight to the tutorial, you can skip ahead to page 3.

Your Circadian Rhythm Impacts Your Health

The circadian rhythm, also known as circadian cycle, is a 24-hour internal clock that drives your sleep/wake cycle. All living things have a circadian rhythm. Melatonin production plays a critical role in circadian rhythm.

Melatonin is a chemical our bodies produce that serves many critical functions. It regulates the female reproductive cycle, it promotes mental health, it triggers the body’s repair mode, it fights cancer, and perhaps most importantly it tells the body when we should go to sleep.

The body produces large quantities of melatonin in the absence of light. It is then consumed while we sleep to perform many restorative tasks so we wake up feeling refreshed and rejuvenated. If you don’t sleep after melatonin is produced, you begin to feel tired and depressed. After a long sleep, melatonin levels have dropped significantly so you wake up feeling alert and ready to tackle the new day.

Color Temperature Controls Circadian Rhythm

The body knows when to encourage or suppress melatonin production based on the color of light to which we are exposed. There are specialized cells in our eyes which don’t aide in visual perception, but regulate our melatonin production. These cells are tuned specifically to blue light, and control pupil dilation as well as our circadian rhythms.

Too much blue light at night or too little blue light during the day are closely related to many mental and physical disorders. Artificial lighting disrupts the signaling of day night cycles and leads to disease. Through the use of color temperature controllable smart lights, we can create lighting schedules that promote health, and induce sleep at desired times.

Color Temperature: literally the color of temperature

Color Temperature gets its name from the color of light emitted by a substance via black body radiation at a given temperature. As it turns out, the red to blue hues of daylight correspond nearly perfectly to the colors emitted by black body radiation. A piece of iron heated to 5,800 K (Kelvin) will emit the same color of light as the Sun in the absence of an atmosphere. For this reason we say that the sun has a color temperature of 5,800 K. The Sun’s light ranges from 5,000 K at sunrise to 6,500 K on a cloudy day.

The atmosphere gives the sky its many colors Color Temperature can be thought of as shorthand for the color of natural light. The Sun emits light through black body radiation. Just like iron in a forge, as the temperature increases the suns color output shifts from red to blue. Radiating bodies like the Sun don’t emit just one color though, they emit a spectrum of colors. The result of the combination of colors is what appears to us as natural daylight.

As seen from space, the Sun emits a very pure white light. As light from the Sun passes through Earth’s atmosphere, the light’s color shifts in Color Temperature to provide the range of possible colors spanning from the deep orange of sunrise and sunset to the bright blue of solar Noon.

These color shifts are due to the different wavelengths of light being reflected off of the various air molecules the light encounters. Blue light is the most susceptible to being reflected in Earth’s atmosphere. This results in less blue light reaching our eyes when the sun is low on the horizon since the light has to travel through more atmosphere. The ratio between the amount of red and blue light reaching our eyes is defined as the Color Temperature.