56|CUADERNOS lasted longer, made out of branches or resinous wood chips, tied and drenched in tallow for better combustion, were used. The exact origin of the oil lamp is unknown but it was widely used in Greece in the IV century B.C. This “biological clock” starts breaking down at the time that humans control light. They are now capable of carrying out their tasks at nighttime, changing in this way the cycle that had been running for hundreds of thousands years. The changes in the biological clock intensified when electricity became widespread. The working day became longer and the changes in the biological clock appeared. The fact that certain hormones are secreted at night, when the body temperature drops, and not during the day when other aspects, known and unknown, appear, leads us to the conclusion that human beings have adapted their bodies to these two cycles, reacting to them in a different way. A similar effect takes place during the seasons of the year, individuals adapt to these cyclic seasons and adapt their body to the new environment. With the advent of artificial lighting, Project LifeCycle Tower One. Fuente: Zumtobel those natural conditiond changed, making the day longer and with it the opportunity to carry out the day time activities during the night hours. Nowadays, the technological and social evolution that we have gone through during the past century and this one, has brought about a substantial change in the living conditions of human beings to which our bodies have not adapted yet. The body reacts to this changes activating its defense mechanisms. Biological effects of Light Our bodies are regulated by light. Neuroscience states that biodynamic light has a profound effect on the endocrine system and through it, on the rest of the biological systems. The circadian rhythms of light produce a cyclical stimulation of the neurotransmitters which are the information messengers between the neurons. On the other hand, photobiology, which is a science that studies the relationship of living beings with the light, has analyzed how different hormones react to the circadian cycles. Melatonin the hormone that regulates sleep, increases in the absence of the stimulus of light. Cortisol which is the hormone responsible of keeping us “alert” has a cycle in reverse of that of Melatonin. Another parameter used is body temperature that has a cycle in reverse to Melatonin. When we stray away from the circadian rhythms our biological clock gets altered. One of the most common disorders that occur is a mood disorder that comes about when autumn comes along. Some people notice that their mood goes down, their vital energy diminishes, they start to crave sweets, especially chocolate, they lose interest in social contacts and they become irritable. The cloudy and wintery days accentuate and maintain these feelings but as soon as spring comes they begin to fade away until normality is regained. This disorder is called SAD (Seasonal Affective Disorder). The most important symptoms of SAD are: depression, irritability, loss of energy, hypersomnia or increased need of sleep, increase in appetite for carbohydrates, weight gain, decrease of sexual desire, avoidance of social and family contacts, and a decrease in daily activity. It is estimated that 20 per cent of the population suffers from this disorder: 6 “We should try to design our environment in a manner that would be less agressive to our body and light is an important part of it”. Project LifeCycle Tower One. Fuente: Zumtobel