Light: from the galactic to the earthly

“Gather-Around-Light” is a community in Berlin of people working in various sectors of the lighting industry. The group invited to the Archenhold  Sternwarte in Berlin to an evening to discuss all matters about light. The event started with a very comprehensible presentation about what light is and how it physically behaves. Daniele Leitner presented the physical properties of light within her living area. She explained the blur theory and the electro magnetism using a bunch of socks in her sleeping room. She goes on and explains the theory of relativity in her kitchen, presenting that without the constant of the velocity of light we would not be able to visualize our environment. Because if the velocity of a movement would be added to the velocity of light than we would perceive the movement before the static objects. Daniela presents this phenome pouring a pot of milk into a glass. Would the theory of relativity not exist, we would first see the dropping milk, but neither the glass nor the pot. Why the sun emits light she explains using oranges in glass bowls. The oranges are heated up and thus will move and jump in the glass bowls. But due to  the quantum mechanics an orange can suddenly jump over into the glass bowl of the other orange (the proton has overcome its  electric charge). The light emission is an overflow of this fusion. The radiation needs 100.000 years to travel through the suns’ nucleus, which is denser than lead. From there it travels within eight minutes to earth. Thanks to this long travel time the radiation changes its energy level from gamma radiation to beautiful visible light rays. Daniela went through her whole appartment and at the end of her talk many of us seem for the first time to have understood the physics of light.


From the 230 visitors of the event about 90 percent were lighting planners, but everybody got amazed by the following presentation from Wolfgang Spiess, who presented natural light phenomena at Earths’ darkest spots. Wolfgang Spiess presented auroras and coronas of wonderful colours, from areas, where most of the audience never have nor will visit, like for example Island and Greenland. The presentation built a well suited bridge to the last presentation of the lighting planner Uwe Knappschneider and Sibylle Schroer from STARS4ALL. They presented the impact of artificial light on living organisms on Earth and the challenges for lighting planners to deal with light emission:  to guide it where it is wanted, but not to where it is disturbing.


First, Schroer visualized the increasing extend of light pollution with a rate of over 2% globally and described the changes for the living environment of nocturnal organisms. One third of all described vertebrates and two thirds of all invertebrates live in the night niche and are adapted to the natural dark environment. Artificial light at night has an impact on our nocturnal organisms and thus on our ecosystems. Further she explained that human circadian systems also rely on natural light-dark-rhythms and that we can help our metabolism, when providing darkness at night. She went on to explain what we could do to reduce light pollution. Easy measures can help to avoid light pollution in using:


1.-  light screens to reduce the emission in non-target areas,

2.-  using the lowest light emission needed for the purpose and

3.-  in using blue light emission.


We use light with high blue light emission for maybe energetic reasons, then it could actually be applied in very low intensity, thus decreasing the energy consumption according to the technological potential of the lighting source instead of increasing the brightness.


At this point Uwe Knappschneider stepped in and noted that in praxis lighting planners mostly get not confronted with what they can do against light pollution, but which criteria they have to fulfill for certain illumination tasks. He gave some praxis examples where the lighting criteria are met for the purpose, but where the light emission extends the object, is too bright or causes a lot of up-light emission. As a positive example he explained the light trading concept done in Fulda, Germany. Fulda wants to achieve the certificate of an International Dark Sky Community from the International Dark Sky Association (IDA), as the first European town. Therefore the private business has to decrease the light emission as well from public lighting as from private shopping windows and signs. The town offers the guidance of a lighting planner for accounting the light emission per square meter, an estimate of the energy saving potential and a before-and-after comparison of the visual effect of exemplary shop windows. After a lively discussion, the “Gather-Around-Light” event was concluded in stating that good lighting is efficient, increases visibility, safety and aesthetics and has little impact on ecology and health.


The evening was supported by the cooperation partners, OpTec BB, Deutsche Lichttechnische Gesellschaft e.V.,  Sternenpark Westhavelland e.V., Gather-Around Light and STARS4ALL .


By Sibylle Schroer