In Russian two concepts designate by a word "day". The first are an astronomical day lasting 24 hours, the second is a time of day, along with night, in the morning and in the evening. In the second case "day" understand time as a word from 12:00 to 16:00. But there is also separate concept "light day", it is used most often, when it comes to biological rhythms to which all submits live on Earth.
Duration of light day
Light day is time from rising and till the sunset. Depending on in what point of the orbit there is Earth rotating around the Sun also duration of light day changes. The longest light day – on June 21, this day its duration makes 16 hours. The shortest day which lasts only 8 hours drops out for December 21 or 22, depending on whether year is leap. In the fall on September 21 and in the spring on March 21 the nature celebrates days of the autumn and vernal equinox when duration of light day is equal to duration of night – time from calling till the sunrise.
The annual cycle to which all submits live on the planet Earth depends on duration of light day. At the same time, as length of light day changes, at one time another changes years: after spring the summer, fall, winter and again spring follows. Especially visually this dependence is traced on the example of plants. In the spring as duration of light day increases, in them the sokodvizheniye begins, in the summer you can observe their blossoming, in the fall – withering, and in the winter – the anabiosis, a dream similar to death. But, perhaps, not in such obvious form, but duration of light day influences also the person.
Influence of duration of light day on the person
The person as a part of the biosphere of the planet is also sensitive to how light day lasts long in spite of the fact that the mode of his life is subordinated to a daily working rhythm. Nevertheless the conducted medical researches confirmed that in the winter the intensity of a metabolism in a human body decreases, the increased drowsiness and emergence of excess weight is a consequence of what.
The lack of enough natural light affects also a psychoemotional state. In winter time and also at the beginning of spring many complain of depressions, bad mood, headaches, insomnias and irritability. Violation of functions of nervous system provokes failures in functioning and other bodies and systems. In an organism the synthesis of natural vitamin D decreases that involves decrease in protective properties of the immune system therefore total number of diseases and aggravations of chronic pathological processes at this time the highest. Physicians advise at the end of winter - the beginning of spring at least on the weekend to get out to the nature, to spend more time in the afternoon in the fresh air, it will help to cope with bad mood and to improve the general health.