Approximately 13.7 billion years ago, the universe went from a singularity state of infinite curvature and energy to a rapidly expanding chaotic state, the Big Bang. During the first pico and nano seconds of this period of rapid expansion, the types and behavior of particles that existed rapidly change as the energy levels dropped. Within a few nanoseconds, the kinds of matter and the ways they behave settled into, more or less, the sorts of material constituents we find today. At this point, only hydrogen, helium, and lithium exist. The matter continues to expand outward and eventually, several billion years later, gravitational pull congregates clumps of matter together to form stars. These heat and energy at the cores of these stars cook the early forms of matter, transforming it and creating many of the other, heavier elements on the periodic table. Some of these stars are of sufficient mass to ultimately collapse on themselves, exploding outward and spraying the new elements formed in their cores out into space. That matter eventually coalesces into smaller stars, planets and moons like our own.
Only very recently have one of the hominid species--homo sapiens--on the planet developed cognitive faculties that were sophisticated enough to be able to discover these various facts about the universe. Some of those discoveries are landmarks of vast significance in our develop, although not in a cosmic scale: Darwin’s The Origin of Species is published in 1859. In 1929, Edwin Hubble published his paper, “A Relation Between Distance and Radial Velocity Among Extra-Galactic Nebulae,” in which he showed that the universe is expanding. Extrapolating backward from its rate of expansion made it possible to date the explosive beginning of the universe at approximately 13.7 billion years ago. In 1953, James D. Watson and Francis Crick published their discovery of DNA in Nature: “A Structure of Deoxyrobose Nucleic Acid.”
- The Big Bang occurred 13.7 billion years ago.
- Only hydrogen, helium, and lithium exist for millions of years until large stars form and create many of the other, heavier elements on the periodic table.
- Some of these stars go supernova and distribute these new elements into space.
- That matter eventually coalesces into smaller stars, planets and moons like our own.
- The Earth formed about 4.5 billion years ago.
- Life in the form of the simplest, self-replicating molecules occurs on Earth around 4 billion years ago.
- Once there is replication, natural selection and random mutations over billions of years lead to the evolution of more and more life forms, many of them of increasing levels of complexity.
- Dinosaurs live from about 208 million years ago to 65 million years ago.
- Life on the planet goes through several mass extinctions.
- The Cambrian explosion—a rapid proliferation of the kinds and numbers of living organisms on the planet, occurs about 540 million years ago.
- Mammals begin to expand and diversify significantly about 54 million years ago.
- Modern humans (homo sapiens) originated in Africa about 200,000 years ago.
- Human religious behavior starts approximately 300,000 years ago.