Final answer:
The universe's timeline spans from the Big Bang approximately 13.8 billion years ago to the appearance of early human ancestors about 4 million years ago. Significant events include the formation of galaxies, solar system, and the accumulation of oxygen in the atmosphere after the emergence of cyanobacteria. The K-T extinction event was a critical turning point that allowed for the rise of mammals.
Step-by-step explanation:
The history of the universe and Earth is a long and complex one, marked by several significant events:
- The Big Bang, which occurred around 13.8 billion years ago, marks the beginning of the universe and kick-started the expansion of space.
- Formation of galaxies began to take place within the first billion years after the Big Bang as matter started to clump together due to gravity.
- Our solar system, including the sun and Earth, formed approximately 4.6 billion years ago, which corresponds to around September 10 in a cosmic calendar where the Big Bang happens on January 1.
- By about 3.8 to 4.0 billion years ago, primitive life on Earth began to appear, likely around hydrothermal vents or shallow marine pools.
- Cyanobacteria emerged and were responsible for the production of oxygen, which began to accumulate in Earth's atmosphere around 2.7 billion years ago. This event was crucial for the development of aerobic life forms.
- The K-T extinction event, which occurred approximately 65 million years ago, is characterized by the end of the dinosaurs and most other species, paving the way for the rise of mammals.
- Early human ancestors, known as australopithecines, appeared on the scene around 4 million years ago, marking the emergence of hominids that would eventually lead to modern humans.