Extinct contain power and can absorb many things, it can cause growing for some composing. Thus some of microbes, viruses and alive cells can grow at darkness and cause many illnesses at body and those who live at dull medium would suffer kinds of diseases. When light strikes at a thing, it reflects at darkness and this energy cause many functions. Many substances can live or even can get alive in darkness and cause many disorders. Alive animals such as turtles, some snakes and others can remain more in dark medium and underground. When use of electric lamps increases on earth and the globe became lighter, length of life gets short and limited but those who benefit from light more, lesser can live on earth and those who benefit from extinct, can live more on earth. We must have darkness nearly equal to lightness while electric power cause higher brightness more than darkness. Earth and life on it needs to the extinct and when we decrease the extinct of earth we can live shorter and living on earth becomes limited. It is different between sleep and extinct. Extinct is necessary for many other causes and those who want sleep well, can benefit from it.