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I.1 Timeline: From the Big Bang to Modernity |
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Major Cosmic and Earthly Events |
Years Since First Known Appearance |
| Birth of the universe, the Big Bang, starts the conversion of primal energy into matter. E.g., massless photons into elementary particles. | 13,700,000,000 |
| Elementary particles form mainly hydrogen and helium atoms. The four basic forces of the universe appear: gravity, electromagnetism, weak and strong nuclear force. | Within a few minutes after the Big Bang |
| Gigantic clouds disperse in all direction forming galaxies and the first stars from hydrogen and helium. | 300,000,000 past Big Bang |
| Stars fuse all other elements and eject them into space. These nebulas contain most elements and form many compounds and solid rock. The Milky Way Galaxy forms. | 8,000,000,000 |
| Our solar system is born when one nebula forms a disk and breaks up. | 4,650,000,000 |
| The moon formed when a planet or asteroid plowed into Earth. | 4,500,000,000 |
| The surface of the Earth cools down enough for the crust to solidify. The atmosphere and the oceans form. | 4,100,000,000 |
| Vigorous chemical action turns elements into the molecular building blocks of life. Cells resembling prokaryotes appear. | 3,900,000,000 |
| The first life appears, microbial cells with no true nucleus. | 3,700,000,000 |
| Complex (eukaryotic) cells with true nuclei | 2,000,000,000 |
| Algae | 700,000,000 |
| Cambrian period (about 100 million years): Plant and animal life radically diversifies in the oceans. Vertebrates (simple fishes) appear. | 550,000,000 |
| Vascular land plants (conduct water and synthesize food) | 430,000,000 |
| Amphibians and insects | 380,000,000 |
| Fern forests and reptiles (the reptilian brain) | 330,000,000 |
| Dinosaurs and mammals (the mammalian brain with a neocortex) | 225,000,000 |
| Birds appear. Pangaea, meaning "All-Earth," breaks up and divides into land masses that look like our modern-day continents. | 195,000,000 |
| Plants evolve flowers. | 136,000,000 |
| Nonhuman primates--flexible hands and feet with five digits. | 65,000,000 |
| Grazing and carnivorous mammals | 50,000,000 |
| Earliest apes such as Proconsul Africanus | 23,000,000 |
| Human ancestors split from now-extinct African apes, evolved, and spread over the planet (see diagram) | 5,000,000 |
| Australopithecines upright walking ancestors of humans | 4,000,000 |
| Modern humans in whom the universe becomes conscious of itself . Their ability for self-determination partly unshackles them from the chains of natural causation, genes, instincts, and the environment. | 200,000 |
| Plants, and later animals, were domesticated. This agricultural revolution facilitated larger communities and the division of labor. | 12,000 |
| First known civilization, the Sumerian, appears ca. 4,000 BCE. It was a high order social organization with writing, full-time rulers, and priests. | 6,000 |
| Western culture peaks with the Greek and Roman civilizations. | 900 BCE to 476 CE |
| The Dark Middle Ages, a European period of cultural decay/regression. | 476 to 18th century |
| Modernity begins with the revival of Greco-Roman learning and results in scientific, political, and industrial revolutions. | ca. 1400 to present |
