The article outlines the statistical history of Earth’s existence, which is estimated to have formed around 4.5 billion years ago. Chemist Clair Patterson's 1956 research on the isotopes of lead in meteorites provided significant insights into the age of the Earth and its formation alongside the solar system. This scientific foundation remains crucial in understanding Earth’s age today. Following the formation of Earth, life is believed to have emerged with microorganisms appearing approximately 3.5 billion years ago, and life activities starting around 3.8 billion years ago, as evidenced by the carbon isotopes found in sedimentary rocks in Greenland.

The narrative then transitions to discuss major mass extinction events that have shaped Earth’s biodiversity, highlighting six notable events, including the Ordovician-Silurian extinction about 444 million years ago and the Cretaceous-Paleogene extinction that wiped out the dinosaurs around 66 million years ago. Mass extinctions are characterized by rapid global environmental changes that occur in relatively short geological time frames. These profound shifts may be triggered by volcanic activity, asteroid impacts, and other cataclysmic events, leading to an inability of many species to adapt and subsequently their extinction.

In particular, the article references the widely accepted view that the mass extinction of dinosaurs 66 million years ago was linked to an asteroid strike, illustrated by the discovery of the Chicxulub crater in Mexico and the abnormal high levels of iridium in global rock layers from the same period. This iridium is typically scarce in Earth's crust but prevalent in asteroids, thus providing compelling evidence of an external cosmic factor contributing to massive extinction events and suggesting that the solar system's galactic orbit could be influencing these catastrophic changes on Earth.