by S. Prasad Ganti

Most of us are curious about how it all started. We study history of specific countries and periods like European history during the medieval ages or American history since the civil war, but not about everything in one stretch. The concept of Big History was started by Prof. David Christian as a multi-disciplinary study involving cosmology, physics, chemistry and biology from the Big Bang to the formation of simple elements like hydrogen, to stars and galaxies, to heavier elements, to our Sun and Earth and to the evolution of life up to the present.

Christian came up with the concept of how it all started in a very simple way and through eight thresholds increasing in complexity to our present state. He offered it as a one-semester course at the University in Australia. His course became popular enough to be sold through the Great Courses web site. He also gave a talk on TED (http://www.ted.com/talks/david_christian_big_history). Bill Gates was very impressed by this concept to the extent of sponsoring a simplified version of the course in middle and high schools across the US.

I was impressed when the New York Times covered it in their Sunday magazine a few weeks back. I saw the TED talk, took a five hour free mini course online and also got the DVDs from The Great Courses to view in detail. Each of the eight thresholds involves certain ingredients and certain Goldilocks conditions resulting in a new level of complexity. The next threshold then builds on this level of complexity. Goldilocks conditions involve considerations like not too far, not too close, not too hot, not too cold, not too big, not too small, etc.

The first threshold was the Big Bang itself. No one knows the ingredients nor the Goldilocks conditions. It led to protons and electrons forming the simple element hydrogen. Hydrogen and gravity formed the ingredients for the second threshold. The Goldilocks conditions were the tiny variations in density of matter. The Universe was not uniform all across. These variations led to star formation 200 million years after the Big Bang.

The third threshold involved very high temperatures and dying stars, leading to the formation of elements heavier than hydrogen like helium, carbon and oxygen. Threshold four led to creation of astronomical bodies like the Earth that are chemically richer than the stars. Nickel, iron and other heavy radioactive elements sank to the center of the Earth, while lighter ones like silicon floated. This led to the creation of a magnetic field. The comets brought water vapor to fill the oceans.

Threshold five led to creation of life on the Earth. Complex chemicals like DNA with the right amount of energy and liquids like water led to single-celled organisms at first. This was life in its simplest form. The evolution of life led to threshold six resulting from powerful brains producing symbolic language and shared ideas. Homo sapiens evolved to use collective learning and passed information to the next generation thereby creating the ability to adapt speedily without any genetic changes.

Threshold seven led to domestication of plants and animals and the agrarian civilization that resulted in increasingly dense human communities with knowledge about the environment. The last threshold utilizing the new energy resources like coal, oil and electricity led to the globally connected human society.

This is the gist of the eight thresholds, but many more details lies behind each of them. A very interesting set of concepts for those who want to know all about everything!