such energy flows survive and prosper, while other systems adversely affected by too much or too little energy are non-randomly eliminated. Fred Spier is foremost among those big historians who have found the concept of energy flows useful, suggesting that Big History is the rise and demise of complexity on all scales, from sub-microscopic particles to vast galaxy clusters, and not least many biological and cultural systems in between. David Christian, in an 18-minute TED talk, described some of the basics of the Big History course. Christian describes each stage in the progression towards greater complexity as a "threshold moment" when things become more complex, but they also become more fragile and mobile. Some of Christian's threshold stages are: The universe appears, incredibly hot, busting, expanding, within a second. Stars are born. Stars die, creating temperatures hot enough to make complex chemicals, as well as rocks, asteroids, planets, moons, and our solar system. Earth is created. Life appears on Earth, with molecules growing from the Goldilocks conditions, with neither too much nor too little energy. Humans appear, language, collective learning. Christian elaborated that more complex systems are more fragile, and that while collective learning is a powerful force to advance humanity in general, it is not clear that humans are in charge of it, and it is possible in his view for humans to destroy the biosphere with the powerful weapons that have been invented. In the 2008 lecture series through The Teaching Company's Great Courses entitled Big History: The Big Bang, Life on Earth, and the Rise of Humanity, Christian explains Big History in terms of eight thresholds of increasing complexity: The Big Bang and the creation of the Universe about roughly 14 billion years ago The creation of the first complex objects, stars, about 12 billion years ago The creation of chemical elements inside dying stars required for chemically complex objects, including plants and animals The formation of planets, such as our Earth, which are more chemically complex than the Sun The origin and evolution of life from roughly about 4.2 billion years ago, including the evolution of our hominine ancestors The development of our species, Homo sapiens, about 300,000 years ago, covering the Paleolithic era of human history The appearance of agriculture about 11,000 years ago in the Neolithic era, allowing for larger, more complex societies The "modern revolution", or the vast social, economic, and cultural transformations