[![在这里输入图像描述][1]][1]银河近20年(每个星系= 2.3亿年太阳能年)通过太阳的诞生以来,和三个银河年已经过去了自从地球上生命的形成当大气中的氧气浓度显著增加(在时间期间,我们有环绕银河系的三倍)。根据大气中氧气的浓度和地球上的生命改变,几乎每个银河年可分为常规每年“三季”,与氧气在第一和第二季增加在不同的斜坡和减少在第三。当太阳围绕银河系,它进入和退出银河武器在某个特定时间,这可能是这些near-regular事件“可能”导致的大规模物种灭绝和地球上的大气气体浓度的变化在每个星系,由于通量显著增加的宇宙射线。有一些主要的银河系,阳光穿过周游星系的中心。当地球进入一个星系的手臂,持续的大雨宇宙射线(大功率)撞击地球大气层接近光速。很高能宇宙射线打破股DNA分子,破坏基因和杀死细胞(导致细胞突变,死亡和灭绝)。宇宙射线也打破空气分子高我们的大气层,与原子和分子相撞(主要是氧和氮),甚至分裂分子,并将原子和亚原子粒子降临到地球上,所谓的二次辐射空气簇射。传入的宇宙射线通过与氮分子碰撞,7的过程取代一个质子氮包含额外的中子。由此产生的原子,现在包含6 8质子和中子,是碳14之一。 As result, nitrogen in the atmosphere changes to Carbon-14 by cosmic rays.The generated Carbon-14 (radioactive) then reacts with oxygen in the atmosphere and forms CO2 (as result of this process also, concentration of oxygen is reduced). The CO2 from Carbon-14 is then absorbed by the plants. In addition, earth temperature may have also rised by increased flux of incoming cosmic rays, increasing water evaporation from oceans into atmosphere (air) that results in higher number of water molecules being spilt by the cosmic rays. All these events changed the atmospheric gases concentration and life conditions on earth during traveling of sun into each arm of the galaxy. However, future research will provide a more accurate answer to this question. More information can be found here: 1- https://www.researchgate.net/publication/256762257_Mass_Extinction_And_The_Structure_Of_The_Milky_Way 2- https://www.space.com/19915-milky-way-galaxy.html 3- https://www.radioactivity.eu.com/site/pages/RadioCarbon.htm [1]: https://i.stack.imgur.com/noNa8.png