All the Light we Cannot See

Daylight is by far our most prominent form of natural illumination, and it is essential for life on Earth. It is made up of visible and invisible components both of which play important roles in our health and wellbeing.

White Light can be defined as - apparently colourless light, such as ordinary daylight.  It contains all the wavelengths of the visible spectrum at equal intensity - however there is nothing ordinary about ordinary daylight, there is something quite magical about natural light.

Visible light is the part of daylight that we can see, and we see it when it is reflected off objects. It is made up of a range of different colours, including red, orange, yellow, green, blue, indigo, and violet. These colours have different wavelengths and frequencies, red has the longest wavelength and violet has the shortest, and they interact with our eyes and brains to create the colours that we see in the world around us. Exposure to visible light is important for regulating our circadian rhythm, which helps to govern our sleep-wake cycles as well as other biological processes.

In addition to visible light, daylight also contains invisible components, Ultraviolet (UV) radiation and Infrared (IR) radiation. UV radiation is responsible for causing sunburn and skin damage, and it is also a major risk factor for skin cancer. However, UV radiation also plays an important role in the production of vitamin D, a component that is essential for healthy bones and a healthy immune function. Vitamin D can function as both a vitamin and a hormone in the body, depending on its form and how it is obtained.

1. As a Vitamin:

- Vitamin D is often referred to as a vitamin because it is essential for the proper functioning of the body, and it must be obtained through diet or sunlight exposure.

- There are two primary forms of vitamin D that are important for humans: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).

2. As a Hormone:

- Once the body has obtained vitamin D, it undergoes a series of conversions, particularly in the liver and kidneys, to become an active hormone.

- The active form of vitamin D is known as calcitriol, and it acts as a hormone that plays a crucial role in regulating calcium and phosphorus metabolism.

- Calcitriol acts on various tissues and organs, such as the intestines, bones, and kidneys, to ensure proper absorption and utilisation of calcium and phosphorus.

In summary, vitamin D is initially obtained through diet or sunlight exposure as a vitamin, but it undergoes transformations in the body to become an active hormone (calcitriol) that is involved in various physiological processes, particularly in maintaining calcium homeostasis.

Infrared radiation, on the other hand, is responsible for the heat that we feel when we are outside on a sunny day. It can penetrate deep into the skin, promoting circulation and stimulating the production of collagen and elastin, two proteins that are essential for healthy skin. Infrared radiation has also been shown to have therapeutic benefits for a range of health conditions, including pain, inflammation, and wound healing.

When looking at the three constituent parts of visible and invisible light, 7% is Ultraviolet Light, 39% is Visible Light, and 54% is Infrared Light, the clear majority being Infrared. These three components of light interact with our skin and each one drives a different physiological response as a result of their wavelengths. Ultraviolet light is a relatively short wavelength by comparison to Infrared, and wavelength is a measure of how far the light can travel. The way in which light interacts with our skin is shown in the image below.

In the image above we see that Ultraviolet light is essentially skin deep, only just penetrating the Eperdermis, visible blue, green and red travel deeper respectively. Infrared light penetrates inches deep and can travel through our bones.

Light has been used as a form of therapy and this concept is not new and I was recently reminded of Heliotherapy by a LinkedIn post by Chris Lowe . Heliotherapy, also known as light therapy or phototherapy, is a form of medical treatment that uses sunlight or artificial light to promote healing and improve health. The use of sunlight for medicinal purposes has a long history dating back to ancient times.

In ancient Egypt, Greece, and Rome, sunlight was used to treat a range of medical conditions, including tuberculosis, leprosy, and rheumatism. In the 19th century, physicians began to use sunlight to treat tuberculosis, a disease that was prevalent at the time and had few effective treatments. Sunlight was thought to kill the tuberculosis bacteria and promote healing in the lungs.

The use of sunlight as a treatment for tuberculosis became increasingly popular in the early 20th century, and specialised sanatoriums were built in sunny locations such as the Swiss Alps and the American Southwest to treat patients. The treatment involved spending long periods of time outdoors, often in specially designed sunrooms or on sun decks. Patients were also advised to eat a healthy diet and get plenty of rest to aid in their recovery.

My father contracted TB as a child and it was thought in a wider context that recovery in dark spaces was the best way to tackle TB. In fact the opposite was true, however the availability of such knowledge and information was not as easily shared as it is today, there was no internet back then.

As the use of antibiotics became more widespread in the mid-20th century, the popularity of heliotherapy declined, and maybe so did our general understanding of the importance of natural light as a force for health and wellbeing. Maybe the combination of antibiotics and our ability to control of artificial light has led us away from thinking of light as a source of good whilst at the same time taking light for granted. Have we commoditised light so much that we've forgotten it's powerful effect on living things?

The history of heliotherapy is a long and rich one, with a legacy that continues to this day in the form of modern light therapy treatments and the growing interest in the benefits of natural light for health and wellness. In the background the use of light therapy has continued to evolve and expand, and today it is used to treat a wide range of conditions, including seasonal affective disorder (SAD), psoriasis, acne, and sleep disorders. Research has shown that exposure to sunlight can have a range of benefits, including promoting the synthesis of vitamin D, regulating our circadian rhythms, and improving mood and cognitive function. Vitamin D is recognised as a key component for brain health, whilst IR stimulates our mitochondria, in our brains and all over our bodies, to produce energy, both of these elements are directly connected to natural light.

Reports suggest that we spend on average 90% of our time indoors and whilst current artificial light sources contain little to no UV or IR it is critically important for our industry to continuously push for the highest quality of light into projects. Collectively we need to push back on the cheap alternatives that come flooding into the market through the value engineering process. Not all LEDs were born equal! Light is Life!

Disclaimer moment....

Daylight is a complex and multifaceted form of natural light that is essential for our health and wellbeing. While visible light is the most well-known component of daylight, it is important to be aware of the potential risks and benefits of the invisible components, including Ultraviolet radiation and Infrared radiation, and to take appropriate steps to protect ourselves from harm while giving ourselves the opportunities in our every day lives to enjoy the many benefits that come from both the visible and the invisible elements of daylight.