That your stomach waits for lunch at noon with increased activity and that you reach your lowest point of performance during the subsequent digestion, you will may have noticed in yourselve for a long time. But did you also know that in the morning your heart has to do quite a lot to get you on your toes and therefore here is the time of the highest failure rate, e.g. in the form of a heart attack? Or the late afternoon is good for recreational sports and the time after that is best for one (!) beer after work?

The body is a merciless creature of habit. From the age of 12 years on, it develops a day/night sleep pattern. Children and especially babies have a different rhythm. Doctors call the above-mentioned peculiarities of humans genetically conditioned. This also means certain differences, e.g. those of so-called day and night people. Both types would like to keep their peculiarities during the working week as well as on weekends.

One has the impression that not necessarily as much wealth as possible should be one of the desirable goals, but rather the free determination of waking and sleeping times, if one really uses them to pay more attention to one's body. In addition to all this, the seasons are a determining factor. Weight gain and the greater need for sleep in winter and its reversal in summer seem to be more widespread than expected.

And if we now also mention the sleeping behaviour of the body, which becomes more and more problematic with age, and thus awake and active phases that are more difficult to determine beforehand, we can finally lead to our topic, namely how to change such phases positively with light, for example. So what do you do if you have eight hours, but wake up after four hours and find it hard to falls asleep again. Get up somehow and go to the toilet for example, but do everything as far as possible without switching on a lot of light.

This influences your melatonin balance, which is responsible for the most continuous sleep possible during the night. White-blue, short-wave and perhaps even bright light would be very harmful. So less is more here. Just think of the inhumane interrogation methods, which often kept test persons under light for days, i.e. the body constantly under slight stress. Conversely, the body also maintains its rhythm in the darkroom for days on end.

And you've probably also heard about the higher suicide rate in winter in Nordic countries like Finland. And what does that have to do with car lights? For example. Audi has created a completely new term, namely 'human- centric lighting concepts'. The aim is to investigate how light affects people 'visually, emotionally and biologically'. No, that has probably not only brought us the increasing ambience lighting, but is probably once again meant as such a harbinger of autonomous driving.

Of course, research here is first directed at the workplace in order to produce light for the most beneficial effect on performance. Audi has announced that the HCL concept will soon be installed in the car as a ceiling light, probably creating a certain atmosphere even in broad daylight. So you don't want to wait until you can drive fully autonomously, for example to support the driver's ability to concentrate.

And all the theories about the changing needs of people throughout the day, for example the invigorating effect of cold white light and a soothing one of warm white and reddish light are then to be put into action depending on the time of day. Of course you will probably be able to readjust illuminance and colour temperature according to your own mood. It can also be, that the observation by a camera is reinstated and that if, for example, the driver does not respond to the offer of a cup of coffee, at least suitable lighting is provided conjured up.