’Light is a powerful clock for our body’

Light creates safety through street lighting, enables us to work at night or illuminates our city centers at Christmas time - and thus affects almost all’areas of our daily lives. At the same time, artificial light can be harmful to our health and the environment. On the International Day of Light, Dr. Cornelia Vandahl, scientific staff member at the Lighting Engineering Group at TU Ilmenau, explains which technological solutions can provide a remedy and gives everyday tips for a more conscious, healthier use of light.

Hello Dr. Vandahl, on the occasion of today’s Day of Light, UNESCO is drawing attention to the importance of light in all’areas of life. Why is this topic so relevant to us?

Light is a fascinating and interdisciplinary topic. It affects almost all’areas of life: from medicine and biology to ecology, architecture, physics, technical lighting design and LED development. Our research shows that light not only has a visual function, but also has profound effects on the environment, health and social interaction. It influences biological rhythms, quality of life and the cityscape. And the topic of light is discussed in many disciplines.

Light pollution in particular is a controversial topic. Why is that?

The discussion about light pollution is so controversial because different interests and points of view are opposed to each other. On the one hand, there is light as a cultural asset and technical achievement: it creates safety, enables mobility, night-time activities, creative lighting in city centers, e.g. at Christmas time, and social participation. On the other hand, nature suffers from artificial lighting: Insects, birds, plants - they all depend on darkness. Humans also need darkness to relax. The contradiction cannot be resolved by extremes, but only by differentiated, intelligent solutions that take both sides into account.

What technical solutions are there for using light in a more resource-saving and environmentally friendly way?

Today, there are a wide range of technical options for designing lighting that is both needs-based and environmentally friendly. Luminaires can be designed in such a way that they only illuminate the areas that actually need light. Control technologies allow light to be switched on only when it is needed - for example by sensor or time control. Color temperatures can be adjusted, for example to make them more insect-friendly. It is important that lighting design is carried out by experts - many problems arise due to poorly planned or incorrectly installed luminaires.

In your area of expertise, you deal with measurement technology and lighting control, among other things.

Yes, department focuses on two areas: On the one hand, we investigate how light must be designed so that it meets people’s visual and biological requirements and does not disturb them - keywords are glare, light flicker, color temperature. On the other hand, we measure light and develop methods with which real lighting conditions can be precisely recorded. To do this, we use camera technology, classic light sensors and also virtual sensors - for example, weather data, location information or calendar data to estimate light requirements. In the "Chronolite" research project, we use the technology in mobility scenarios such as train compartments. There, the lighting can be adjusted specifically for individual user groups.

You mentioned earlier that people need darkness to relax. To what extent does light affect our health?

Light is a powerful clock generator for our bodies. In addition to visual performance, it also has biological effects: It regulates our internal clock. Our body needs bright light during the day to be active and darkness at night to regenerate. Too little daylight or too much artificial light in the evening can lead to sleep disorders, exhaustion and, in the long term, health problems. People in care facilities or shift workers in particular often do not have a stable day-night rhythm. In our Chronolite project, we are investigating how this rhythm can be supported by technology-supported lighting control - for example via apps or sensor data. The aim is individualized light management that compensates for a lack of daylight and sensibly doses artificial light.

What recommendations do you give people for a healthy approach to light?

Basically, we should be guided by natural daylight. In the morning, bright, daylight-like light is ideal for waking up. In the evening, light should be reduced, especially the blue component. This can also be controlled via apps. If you can, you should spend one to two hours outside during the day - this stabilizes your internal clock. In the evening, it is important to dim the light. The following applies outdoors: light only where it is needed - and preferably not towards the sky or bedroom windows. Many small measures can also be implemented in everyday life: Shield light sources, dim them, use motion detectors.