(Excerpts of Chapter 3 from "Healthy Lighting of your Homes - Guiding principles to health efficient lighting of homes". The book is available for purchase at http://www.amazon.com/dp/B00TKSLSK4)

Natural day light is part of the electromagnetic spectrum of the sun. EM spectrum is the energy behind our modern day life style. Everything from radio, television, mobile phones, laptops, internet to oven, x-ray, and infrared cameras work on EM spectrum. EM radiation is available naturally from sunlight or artificially created by exciting atoms. Non ionizing radiation are low energy radiation which does not affect the atom’s structure. This extends from the radio waves to the visible light part of the spectrum. Micro waves are harmful to human beings even though, they are of low energy. Ionizing radiation are high energy radiation which can affect an atom’s structure. This extends from the ultraviolet to the gamma waves part of the spectrum. Controlled exposure to some of these radiations are used in medical analysis and treatment. But most part of the EM spectrum is absorbed by our atmosphere except for visible light, short radio waves and some infra-red and UV wavelengths.

The relevant portion of EM spectrum for our discussions, are the visible light and the invisible portions of light, namely the Ultra violet and Infra-red radiations. Every light source, natural or artificial, contain specific percentages of these two radiations. UV radiation is lowest before sunrise and after sunset and highest from 11 A.M to 3 P.M. While our eye detects the visible light radiation, our skin can detect the UV radiation and produce vitamin D. This is important for healthy bones, healthy immune systems and healthy hearts. Our skin is not completely opaque and visible light can penetrate to the inside of our body. Recollect that earlier forms of light harvesting was from light sensitive skin pigments. Not only visible light, but even the variations of intensities in UV radiations can signal the time of the day. This is how our internal systems sense daybreak even when our eyelids are closed.

Light and Dark Energy

Presence of light is for energy absorption. Presence of darkness is for energy utilization.

Light enters our eyes at a speed of 299,792,458 m/s. Still, light energy is subtler than a faint whiff of air that we do not sense it physically. Imagine a gust of wind at the speed of light. But the energy potential of light can be visualized when we think about a Fresnel lens focusing the light burning even metals. Even the example of powerful laser lights which can burn metals are proof of that energy. Solar panels convert light energy in to electricity or heat and hold an immense potential for our future.

Fig 3.1 – Light Energy

Light photons bouncing off surfaces exert a subtle pressure on those surfaces which are not perceived in our atmosphere but in space, pressure of light photons hitting on the surface of solar sails, can be used to propel satellites. It would be like tortoise and hare story, where the rocket fuelled satellites being the hare, can accelerate faster but eventually run out of fuel. The light propelled satellites being the tortoise, would be slow to accelerate as it is subtler energy but, as it gathers momentum in space, they can travel many times faster than the rocket fuelled satellites and even return back to earth.

Light creates subtler energy transformations in our body that we do not perceive. As the light of the day finds its way in to our eyes, it creates electrochemical reactions in our retinal cells which is similar to an engine start. The process is so efficient that we do not hear any whirring sound or see fumes. The subtle energy of photons hitting our photosensors in the retina, is amplified manifold through a cascade of electrochemical reactions like a snowball effect and transmitted to the daytime circuitry in the brain through the optic nerve. Darkness or absence of light also produces a similarly powerful snowball effect but triggers a different set of electrochemical reactions and is transmitted to the night time circuitry in the brain. The absence of light also fills us up with energy but targeted at restoration and rejuvenation efforts in our body and not for activity. Imagine the energy from 120 million rods actively releasing transmitters in the night compared to 6 million cones active in the day. Imagine getting used to these high energy levels, in the night, for millions of years and suddenly being denied these high energy levels. It is quite natural for the human body to struggle to function as normal and react adversely.

It has been entrained in to our system for years that our body clock respond to light by producing the hormones like cortisol, adrenaline and serotonin. As the morning wears on, the body clock signals the cortisol levels to drop, while continuing to increase the levels of serotonin and adrenaline. As the levels of serotonin and adrenaline keep increasing, our body temperature increases and so does our metabolism. By midday, we start to feel hungry as the body clock signals the liver, stomach and other organs to process the nutrients. By mid-afternoon, our body has reached its peak metabolism and best suited for physical activity and conversion of fat in to energy. By evening, with fading daylight, our body clock reduces its output of active, energetic hormones. Body temperature starts to fall, metabolism slows down and in the absence of light cues, serotonin gets converted to melatonin. This induces sleep, during which cell repair and many other important functions like fat metabolism, synthesis of proteins and strengthening of bones happen. All this energy for activation and inhibition of these various physiological functions is provided by light and darkness.

In the recent centuries, even daylight has been maligned by associating it with a plethora of fancy cancer types, slowly, but steadily confining us to the interiors. Farming communities of every skin type have been out and about under these lighting conditions for millions of years, healthily, without any side effects. Their healthy sleeping habit seems to have repaired any kind of cellular damage, if any, due to UV exposure in the day. A new economy of coffee, energy drinks, vitamin D supplements, antidepressants, sunglasses, sunscreens, tanning salons have emerged to heal our generation. Even many items in our food chain like fruits, vegetables, poultry, cattle, egg etc. are grown and reared in the interiors, depleted of precious solar energy. Even they are given supplements for vitamin D deficiency. It is the unnatural exposure of light at night (LAN) which is a probable cause of breast cancer than safe exposure to natural daylight. Probably healthy sleeping habits can heal our cancers than any other product or treatment.

Much like the many subconscious activities like heartbeat, breathing, blinking, blood flow, etc. varying periodic oscillations of presence of light and absence of light could subconsciously regulate and heal many of our physical and psychological conditions.

Zeitgebers (Time givers)

Similar to the lighting requirements for “visual” efficiency, we now realize that there are some lighting requirements for “biological” efficiency. Greater than all the social cues and of all the characteristics of light, human circadian cycle seems to have been entrained more, by these two basic factors of light, namely:

- Lighting levels

- Color temperature

LIGHTING LEVELS: Light and darkness are as important as other oscillating cycles like, inhalation of oxygen and exhalation of carbon dioxide, for nourishing and sustaining our life. Any imbalance in their frequencies of oscillation, impact our health and longevity. Even worse than imbalance is the reversal of sorts from their natural states. How long can we survive on inhaling carbon di oxide and exhaling oxygen? Unfortunately, there are not only imbalances, there is also a reversal of sorts in the light and darkness cycle. Sunshine from a clear sky, provides around 100,000 lux at noon time. On a cloudy day, we could have 25000 lux and even under an overcast sky the average lighting levels are around 2000 lux. Under the shade of a tree, it would be 10,000 lux, near a window, it would be around 1000 lux and inside a room the lighting level would be around 100 lux. Being exposed to outdoor environments for centuries, we are used to, at least an average of 10000 lux for most part of a typical day. People are found to be more happy and lively under these higher lighting conditions. Lighting levels anywhere from 1000 lux to 2000 lux from daylight is generally accepted for interiors. From these lighting levels, we have downgraded to around 200 to 300 lux, nowadays, within our interior work spaces. And still lower lighting levels in our homes during the day.

Fig 3.2 – Wave Fundamentals

The lighting levels or the number of photons striking the rods and cones determine the strength of the electrochemical reactions in the retinal circuity and this strength is an indicator of the time of the day. The increasing and decreasing strengths of the electrochemical reactions indicate the onset of day and night respectively. Brightness/intensity of a light source depends on its amplitude or power of the wave. Wavelength/color of a light source can influence brightness to a certain extent. Yellow light tends to appear brighter than red or blue. Short wavelengths of light have higher frequency and long wavelengths of light have lower frequency. Complexity/Saturation of a light source depends on the mix of different wavelengths in a light source (fig 3.2). Typically, naturally occurring light is a mix of different wavelengths. With LED light sources, highly saturated single wavelength sources of red, green, blue and amber are available. By mixing these individual wavelengths and phosphor coatings and UV radiation, white light and various other colors are made possible.

Have a look at the comparison of low brightness light wave and a high brightness light wave which is brighter by 10 times (fig 3.3). This is like comparing 1000 lux against 10000 lux or 1 lux against 10 lux.

Fig 3.3 – Low power and high power light wave

But what if, the factor is 100 instead of 10? It is difficult to show a legible scaled drawing in a page. We are receiving only one hundredth of light we should be receiving in the day time and receiving 100 times more light in the night than we should be receiving.

We know that cones are highly active under high lighting levels and also that the rods are inactive in high lighting levels. But inactivity of rods also trigger neurochemical reactions in the retinal circuitry which activate melanopsin producing ganglion cells, the SCN and pineal gland circuitry to signal daytime hormone secretion, like, serotonin, adrenaline etc. Only when bright sunshine washes these light sensors, serotonin secretion is possible, thereby improving our productivity and happiness. Only with enough serotonin levels, can enough melatonin can be generated, promoting healthy rest. From working under 10000 lux to 100,000 lux for most part of the day, we are now exposed to only 200 lux to 300 lux for most part of the day. That is a factor of 0.003. We are receiving only 0.3% of energy that we are normally accustomed to, on a typical day.

Now coming to the other side of the day, as night falls, rods become activated at low lighting levels. Now, active rods trigger different neurochemical reactions in the retinal circuitry which activate the ganglion cells, the SCN and the pineal gland circuitry to start conversion of serotonin to melatonin. We find that the lighting levels under a clear sky full moon night is around 0.1 lux. Our eye has this amazing ability to adapt to this huge range of lighting levels with the help of rods and cones. Typically, bedside lamps or other lamps used, nowadays, in our houses provide more than 100 lux. From relaxing under 0.1 lux to 1 lux in the night, we are now exposed to more than 100 lux in the night. Even considering 1 lux, that is a factor of 100. We are receiving more than 10000% of energy than we are normally accustomed to, on a typical night.

As, we can see, improper use of artificial lighting has actually reversed our light and dark cycle entrainment, which is creating a lot of troubles to our health. Our energy for restoration and growth is missing from our lives. It is no surprise then, that our generation and possibly future generations are facing the biggest risk of lifestyle diseases.

COLOR TEMPERATURE: White light is a combination of colors commonly referred to as ViBGYOR or ROY G BiV referring to Violet, Indigo, Blue, Green, Yellow, Orange and Red. Violet is higher energy and Red is lower energy. When we see Violet light, around 700,000,000,000,000 (Seven hundred trillion) waves enter our eyes per second. When we see orange light, around five hundred trillion waves enter our eyes per second. The entire visible light ranges from 380 trillion hertz in the violet region to 830 trillion hertz in the red region.

Natural light has a dynamic hue of colors (color temperature) from dawn to dusk, altered by the latitude, time of day, cloud cover, season etc. But, typically, it starts with a rich bluish color (>12000 K) in the morning and changes to cool bluish white (5000 K to 8000K) during the day which gradually transforms in to a warm orange to red color (2000 K to 3000K) in the evening and in the night, moon and stars provide us with a dim glow of cool bluish white (5000 K to 8000 K), as it reflects the light from the sun on the other side. Millions of years of exposure to these colors seem to have tuned the light sensitive ganglion cells (ipRGC). They are highly sensitive to the bluish light and least sensitive to the warm orange to red color. They are spread all around the retina like the rods but in a different layer. Compared to the rods, they are even slower to respond. Hence an hour or two under high intensity bluish light seems necessary for complete activation of the light sensitive ganglion cells.

It is the high intensity bluish light in the morning that is detected by melanopsin producing retinal ganglion cell (ipRGC) and transmitted as signal to the pineal gland through SCN. This resets the master clock and the secondary clocks in our body. And if the signal is missing, then the body clock has a free run and results in sleep, metabolism and endocrine disorders etc. The worst thing that is happening nowadays, is that this high intensity bluish light is available in the night time from artificial light sources, laptops, smartphones and tablets. Imagine the master clock getting reset every 8 hours or 10 hours or 12 hours instead of 24 hours. Imagine the plight of the secondary clocks in our body organs and the stress levels that our internal organs should be subjected to.

We have seen that energy level increases as we go from the red to the violet region of the spectrum (VIBGYOR).

The three types of cone photoreceptors in the retina help us to absorb these different wavelengths of the natural spectrum of light. There are about 60% of Long (Red) type cones, 30% of Medium (Green) and 10% of Short (Blue) type cones distributed mainly in the fovea area, where fine detail vision happens. But we also know that in the next layer, light sensitive retinal ganglion cells are spread all around the retina and can sense the short wavelength bluish light. Not only does higher intensity light can give us energy, even shorter wavelengths also can give us energy, meaning, color light even with lower lighting levels can energise our retinal circuits. The key is to expose ourselves to this high energy short wavelength in the daytime and avoid it completely after sunset. Similar to the varying lighting levels influencing the strength of electro chemical reactions, varying color temperatures in a typical day also influence the strength of the electro chemical reactions. 

What do you think? Share your comments below.

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I aim to spread awareness on the subject of Healthy Lighting designs to facilitate co-creation of healthy lighting at home, work and other social spaces. My posts can be accessed at Archinect  and Linkedin Group. I also have a self published book "Healthy Lighting of your Homes" at Amazon.