Probably you don't know

 Remember to look up at the stars not down to your feet-Stephen hawking. Whenever I sat on roof top and look up at the stars in the night sky it looks very beautiful with some cloudy disturbances and recently on mid of October Mars approach at  close to Earth hard night its looks very bright in red-orange colour it's keep on asking me one question that existence of ourselves and it's like keep on telling me that we are just small stuff compare to it but one thing that excites me is the smallest brain in that small stuff has the capability to explore the universe.

  Earth atmosphere wasn't   like that amount of oxygen present today, about 3.5 billion years ago earth atmosphere have only Nitrogen carbon dioxide and methane and oceans full of anaerobic organism including cyanobacteria ,after  cyanobacteria floats in the ocean and able to photosynthesis  with the help of sunlight and carbon dioxide produce their own energy and expelled oxygen to atmospher after the population growth of bacteria increase which leads to oxygen level high which causes death of other organisms around 2.5-2.1  cooling of earth forms ice age and temperature falls and up varied then , aerobic organism comes to play cause decrease the oxygen level so that the level of oxygen rise and fall and finally brings to 21% that we have today after that cyanobacteria swelled by a microbe so that the microbe itself produce energy by the help of cyanobacteria later it's give way to plant cell  Now we are calling this cyanobacteria as chloroplast The d...