Formation and evolution of the Solar System impact event, the Tunguska event, the Chelyabinsk meteor and the impact feature Meteor Crater in Arizona. The process of accretion, therefore, is not complete, and may still pose a threat to life on Earth. Over the course of the Solar System's evolution, comets were ejected out of the inner Solar System by the gravity of the giant planets, and sent thousands of AU outward to form the Oort cloud, a spherical outer swarm of cometary nuclei at the farthest extent of the Sun's gravitational pull. Eventually, after about 800 million years, the gravitational disruption caused by galactic tides, passing stars
Chinese sun and moon mirrors "fangzhu" mirrors "jiàn" 見 "seeing" the sun and moon. The Way of Heaven is called the Round; the Way of Earth is called the Square. The square governs the obscure; the circular governs the bright. The bright emits "qi", and for this reason fire is the external brilliance of the sun. The obscure sucks in "qi", and for this reason water is the internal luminosity of the moon. Emitted "qi" endows; retained "qi" transforms. Thus yang endows and yin transforms. The unbalanced "qi" of Heaven and Earth, becoming perturbed, causes wind; the harmonious "qi" of Heaven and Earth, becoming calm,