Oer Project Big History

# OER Project Big History: A Comprehensive Journey Through 13.8 Billion Years

## Introduction: Understanding Big History

Big History represents a revolutionary approach to understanding the past, present, and future of our universe. This interdisciplinary field synthesizes knowledge from cosmology, physics, chemistry, geology, biology, anthropology, and history to create a unified narrative spanning 13.8 billion years [1]. Co-founded by historian David Christian and philanthropist Bill Gates in 2011, the OER Project’s Big History curriculum has transformed how over one million students worldwide understand their place in the cosmos [2].

Unlike traditional history courses that focus on human civilizations, Big History adopts a panoramic perspective that begins with the Big Bang and extends to the present day and beyond. This approach enables learners to recognize patterns, understand interconnections, and develop critical thinking skills that are essential for navigating the complexities of the twenty-first century. By examining the grand narrative of the universe, students gain insights into the fundamental processes that have shaped our world and continue to influence our future.

The OER Project Big History curriculum is designed for ninth and tenth-grade students but is accessible to lifelong learners of all ages. It is fully aligned with educational standards and provides a comprehensive suite of resources, including lesson plans, videos, activities, and assessments. The course is entirely free and open-source, reflecting the commitment to democratizing education and making world-class learning opportunities available to everyone, regardless of geographic or economic circumstances.

## The Framework: Eight Thresholds of Increasing Complexity

Big History is organized around eight pivotal moments known as “thresholds of increasing complexity.” These thresholds represent critical junctures in the history of the universe when new and more complex phenomena emerged from simpler components. Each threshold is characterized by specific “Goldilocks Conditions”—circumstances that are neither too extreme nor too mild, but just right for new complexity to arise [3].

The eight thresholds are:

1. **The Big Bang** (13.8 billion years ago): The emergence of the universe, time, space, and energy.
2. **The First Stars** (13 billion years ago): The formation of the first stars through gravitational collapse.
3. **New Chemical Elements** (13 billion years ago): The creation of heavier elements in stellar cores and supernova explosions.
4. **The Solar System and Earth** (4.6 billion years ago): The formation of our planetary system.
5. **Life on Earth** (3.8 billion years ago): The emergence of self-replicating organisms.
6. **Collective Learning** (300,000 years ago): The development of language and symbolic thought in *Homo sapiens*.
7. **Agriculture** (10,000 years ago): The domestication of plants and animals, leading to settled civilizations.
8. **The Modern Revolution** (250 years ago): The acceleration of innovation, industrialization, and globalization.

Understanding these thresholds provides a framework for comprehending how increasing complexity has emerged throughout cosmic history, and how each threshold has set the stage for subsequent developments.

## Unit 1: The Big Bang and the Birth of the Universe

### The Moment of Creation

The first threshold of increasing complexity is the Big Bang, the moment when our universe came into existence approximately 13.8 billion years ago. Before this event, there was no time, no space, and no matter—only an infinitesimally small, incredibly hot and dense point known as a singularity. In a fraction of a second, the universe underwent a period of exponential expansion called cosmic inflation, growing from smaller than an atom to astronomical proportions [4].

### The First Moments

In the immediate aftermath of the Big Bang, the universe was an extraordinarily hot and dense plasma of elementary particles, including quarks, electrons, and photons. As the universe expanded, it cooled, allowing quarks to combine and form protons and neutrons. Within the first three minutes, a process called Big Bang nucleosynthesis occurred, during which protons and neutrons fused to create the nuclei of the lightest elements: hydrogen, helium, and trace amounts of lithium [5].

For the next 380,000 years, the universe remained opaque because photons were constantly scattered by free electrons. When the universe cooled to approximately 3,000 Kelvin, electrons combined with nuclei to form neutral atoms in a process called recombination. This allowed photons to travel freely through space for the first time, and the universe became transparent. The light from this era has been traveling through space ever since and is now observed as the Cosmic Microwave Background (CMB) radiation, a faint glow that permeates the entire universe and provides a snapshot of the infant cosmos [6].

### Evidence for the Big Bang

The Big Bang theory is supported by multiple lines of evidence. The discovery of the CMB in 1965 by Arno Penzias and Robert Wilson provided compelling confirmation of the theory, earning them the Nobel Prize in Physics. Additionally, observations of the redshift of distant galaxies demonstrate that the universe is expanding, consistent with the predictions of the Big Bang model. The abundance of light elements in the universe also matches the predictions of Big Bang nucleosynthesis, further validating the theory.

## Unit 2: The Formation of Stars and the Creation of Elements

### The Dark Ages and the First Stars

After recombination, the universe entered a period known as the “Dark Ages,” lasting several hundred million years. During this time, the universe was filled with vast clouds of hydrogen and helium, but no stars had yet formed to illuminate the cosmos. However, gravity was at work, pulling these clouds together and creating regions of higher density.

As these clouds collapsed under their own gravity, the temperature and pressure at their cores increased. When the core temperature reached approximately 10 million Kelvin, nuclear fusion ignited, and the first stars were born. These Population III stars were massive, short-lived, and composed almost entirely of hydrogen and helium. They burned brightly for only a few million years before exhausting their fuel and exploding in spectacular supernova events [7].

### Stellar Nucleosynthesis and the Creation of Heavy Elements

The death of the first stars marked the third threshold of increasing complexity: the creation of new chemical elements. During their lifetimes, stars fuse lighter elements into heavier ones through a process called stellar nucleosynthesis. In the cores of massive stars, hydrogen fuses into helium, helium into carbon and oxygen, and so on, creating elements up to iron. Elements heavier than iron are formed during supernova explosions through rapid neutron capture processes [8].

When massive stars explode as supernovae, they scatter these newly created elements into the surrounding interstellar medium. This enriched material becomes the raw material for the next generation of stars and planets. Without the death of the first stars, the universe would consist only of hydrogen and helium, and the complex chemistry necessary for life would be impossible.

### The Formation of Galaxies

As stars formed and died, they began to cluster together under the influence of gravity, forming the first galaxies. Galaxies are vast collections of stars, gas, dust, and dark matter, bound together by gravitational attraction. Our own galaxy, the Milky Way, contains over 200 billion stars and is just one of an estimated two trillion galaxies in the observable universe [9].

## Unit 3: The Emergence of Our Solar System and Earth

### The Birth of the Solar System

Our solar system formed approximately 4.6 billion years ago from a rotating cloud of gas and dust called the solar nebula. This nebula was the remnant of previous generations of stars that had lived and died, enriching the interstellar medium with heavy elements. As the nebula collapsed under its own gravity, it began to spin faster, flattening into a disk. The Sun formed at the center, where the temperature and pressure were highest, while the remaining material in the disk coalesced to form the planets, moons, asteroids, and comets [10].

### The Formation and Evolution of Earth

Earth, the third planet from the Sun, initially formed as a molten ball of rock through the collision and merger of countless planetesimals. Over hundreds of millions of years, the planet cooled and differentiated, with denser materials like iron and nickel sinking to the core, while lighter materials rose to form the mantle and crust. Volcanic activity released gases that formed the early atmosphere, composed primarily of water vapor, carbon dioxide, nitrogen, and trace amounts of other gases.

Water, delivered to Earth by comets and asteroids, condensed to form the first oceans. The early Earth was a harsh and inhospitable place, bombarded by asteroids and comets, with a toxic atmosphere and no oxygen. However, these conditions set the stage for the next great threshold: the emergence of life.

### The Moon and Its Importance

Earth’s Moon formed approximately 4.5 billion years ago when a Mars-sized object called Theia collided with the young Earth. The debris from this impact coalesced to form the Moon. The Moon plays a crucial role in stabilizing Earth’s axial tilt, which in turn stabilizes our climate and makes the planet more hospitable for life. The Moon also creates tides, which may have played a role in the emergence of life by concentrating organic molecules in tidal pools [11].

## Unit 4: The Origins and Evolution of Life

### The Emergence of Life

The fifth threshold of increasing complexity is the emergence of life on Earth, which occurred around 3.8 billion years ago. The exact origins of life remain one of the greatest mysteries in science, but researchers believe that the first living organisms arose from non-living matter through a process called abiogenesis. The early Earth provided the necessary conditions: liquid water, a source of energy (such as sunlight or chemical energy from hydrothermal vents), and organic molecules.

The first life forms were simple, single-celled microorganisms, likely similar to modern bacteria or archaea. These organisms were able to harness energy from their environment, maintain their internal structure, and reproduce, passing on their genetic information to the next generation. The emergence of life represented a profound increase in complexity, as living organisms are far more intricate and organized than non-living matter.

### The Evolution of Photosynthesis

One of the most significant developments in the history of life was the evolution of photosynthesis, which occurred around 3.5 billion years ago. Photosynthetic organisms, such as cyanobacteria, were able to harness energy from sunlight and use it to convert carbon dioxide and water into organic compounds and oxygen. This process not only provided a new source of energy for life but also transformed Earth’s atmosphere, gradually increasing the concentration of oxygen [12].

The Great Oxidation Event, which occurred around 2.4 billion years ago, marked a turning point in Earth’s history. As oxygen levels rose, it became toxic to many anaerobic organisms, leading to a mass extinction. However, it also paved the way for the evolution of more complex life forms that could use oxygen for respiration, a far more efficient way of generating energy.

### The Cambrian Explosion

For billions of years, life on Earth remained simple and microscopic. Then, around 540 million years ago, a dramatic explosion of new life forms occurred, known as the Cambrian Explosion. During this relatively brief period, most of the major animal phyla that exist today emerged, including arthropods, mollusks, and chordates. The Cambrian Explosion represents a major increase in the complexity and diversity of life, and it set the stage for the evolution of all subsequent animal life [13].

### Mass Extinctions and Evolution

The history of life on Earth has been punctuated by five major mass extinction events, during which a significant proportion of species went extinct. These events were caused by a variety of factors, including asteroid impacts, volcanic eruptions, and climate change. While mass extinctions are catastrophic, they also create opportunities for new species to evolve and diversify. For example, the extinction of the dinosaurs 66 million years ago paved the way for the rise of mammals, including our own ancestors.

## Unit 5: The Rise of Humans and Collective Learning

### Human Evolution

The sixth threshold of increasing complexity is the emergence of our own species, *Homo sapiens*, and our unique capacity for collective learning. Humans evolved in Africa over the last 300,000 years from earlier hominin ancestors. Our evolutionary history is characterized by a gradual increase in brain size, the development of bipedalism, and the refinement of tool-making abilities.

What truly sets humans apart from other species is our ability to communicate using complex language. Language allows us to share detailed information, express abstract concepts, and transmit knowledge across generations. This capacity for collective learning has enabled humans to adapt to a wide range of environments, develop sophisticated technologies, and create rich cultural traditions [14].

### The Spread of Humanity

For most of our history, humans lived as hunter-gatherers, moving from place to place in search of food. Around 70,000 years ago, humans began to migrate out of Africa, eventually spreading to every continent except Antarctica. This global dispersal was facilitated by our ability to adapt to diverse environments, from tropical rainforests to arctic tundra, through the use of tools, clothing, and shelter.

### The Cognitive Revolution

Around 70,000 years ago, humans underwent what some scholars call the “Cognitive Revolution,” a period marked by significant advances in symbolic thought, art, and culture. Evidence of this revolution includes the creation of cave paintings, the production of sophisticated tools, and the development of complex social structures. The Cognitive Revolution represents a major leap in human cognitive abilities and laid the foundation for all subsequent cultural and technological developments.

## Unit 6: The Agricultural Revolution and the Rise of Civilizations

### The Transition to Agriculture

The seventh threshold of increasing complexity is the development of agriculture, which began independently in several regions around the world approximately 10,000 years ago. The shift from hunting and gathering to farming was a gradual process, driven by a combination of factors, including climate change, population pressure, and the availability of domesticable plants and animals.

Agriculture allowed humans to produce surplus food, which in turn supported larger and more sedentary populations. This led to the development of permanent settlements, the rise of cities, and the emergence of complex societies with specialized labor, social hierarchies, and political institutions. The Agricultural Revolution fundamentally transformed human society and set the stage for the development of civilizations [15].

### The Rise of Civilizations

With the advent of agriculture, human societies became more complex and stratified. The first civilizations emerged in river valleys, such as Mesopotamia, Egypt, the Indus Valley, and China, where fertile soil and reliable water sources supported intensive agriculture. These civilizations developed writing systems, monumental architecture, centralized governments, and sophisticated systems of trade and commerce.

The rise of civilizations also brought new challenges, including social inequality, warfare, and environmental degradation. Nevertheless, civilizations have been the primary drivers of cultural and technological innovation throughout recorded history.

## Unit 7: The Modern Revolution and the Anthropocene

### The Industrial Revolution

The eighth and final threshold of increasing complexity is the Modern Revolution, which began in the 18th century with the Industrial Revolution. This period was characterized by the transition from agrarian economies to industrial economies, driven by technological innovations such as the steam engine, mechanized textile production, and the development of railroads. The Industrial Revolution dramatically increased productivity, transformed social structures, and initiated a period of rapid economic growth that continues to this day [16].

### Globalization and Interconnection

The Modern Revolution has also been marked by increasing globalization and interconnection. Advances in transportation and communication technologies have made it possible for people, goods, and ideas to move around the world at unprecedented speeds. This has led to the creation of a truly global economy and culture, but it has also brought new challenges, including environmental degradation, economic inequality, and the spread of infectious diseases.

### The Anthropocene

We are now living in a new geological epoch, the Anthropocene, in which human activity is the dominant force shaping the planet. Human actions have altered the climate, transformed landscapes, and driven countless species to extinction. The Anthropocene presents humanity with profound challenges, including climate change, resource depletion, and biodiversity loss. Addressing these challenges will require unprecedented levels of cooperation, innovation, and collective learning.

## Unit 8: The Future of Humanity and the Universe

### Challenges and Opportunities

Big History not only helps us understand the past but also provides a framework for thinking about the future. What challenges and opportunities lie ahead for humanity? How can we create a sustainable and equitable future for all people? What is the long-term future of our planet, our solar system, and the universe itself?

By understanding the grand narrative of the past, we can make more informed choices about the future we want to create. Big History teaches us that complexity has emerged throughout cosmic history through the interplay of order and chaos, and that new thresholds of complexity are always possible. The future is not predetermined; it is shaped by the choices we make today.

### The Fate of the Universe

Looking even further into the future, cosmologists have developed models for the ultimate fate of the universe. Current evidence suggests that the universe will continue to expand forever, eventually becoming cold, dark, and empty as stars burn out and galaxies drift apart. This scenario, known as the “heat death” of the universe, is trillions of years in the future. However, the universe is full of surprises, and our understanding of its ultimate fate may change as we learn more about dark energy, dark matter, and the fundamental laws of physics.

## Conclusion: The Power of Big History

Big History offers a powerful and transformative way of understanding the world. By integrating insights from multiple disciplines, it provides a comprehensive narrative that spans from the Big Bang to the present day and beyond. This approach helps us recognize the interconnectedness of all things, appreciate the fragility and resilience of life, and understand our place in the cosmos.

The OER Project Big History curriculum is a valuable resource for students, educators, and lifelong learners who seek to develop a deeper understanding of the past, present, and future. By exploring the eight thresholds of increasing complexity, we gain insights into the fundamental processes that have shaped our world and continue to influence our future. As we face the challenges of the twenty-first century, the lessons of Big History can guide us toward a more sustainable, equitable, and hopeful future.

## References

[1] Christian, D. (2019). What is big history? *Journal of Big History*. Retrieved from https://jbh.journals.villanova.edu/article/view/2225

[2] OER Project. (2022). 10 years. 1 million students. A brief history of OER Project. *OER Project Blog*. Retrieved from https://community.oerproject.com/

[3] OER Project. (n.d.). *Big History Project*. Retrieved from https://www.oerproject.com/Big-History

[4] NASA. (2024, October 22). *Cosmic History*. Retrieved from https://science.nasa.gov/universe/overview/

[5] Burles, S., Nollett, K. M., & Turner, M. S. (2001). Big Bang Nucleosynthesis Predictions for Precision Cosmology. *The Astrophysical Journal*, 552(1), L1.

[6] Penzias, A. A., & Wilson, R. W. (1965). A Measurement of Excess Antenna Temperature at 4080 Mc/s. *The Astrophysical Journal*, 142, 419-421.

[7] Bromm, V., & Larson, R. B. (2004). The First Stars. *Annual Review of Astronomy and Astrophysics*, 42, 79-118.

[8] Burbidge, E. M., Burbidge, G. R., Fowler, W. A., & Hoyle, F. (1957). Synthesis of the Elements in Stars. *Reviews of Modern Physics*, 29(4), 547-650.

[9] Conselice, C. J., Wilkinson, A., Duncan, K., & Mortlock, A. (2016). The Evolution of Galaxy Number Density at z < 8 and Its Implications. *The Astrophysical Journal*, 830(2), 83. [10] NASA. (n.d.). *Our Solar System*. Retrieved from https://science.nasa.gov/solar-system/ [11] Canup, R. M., & Asphaug, E. (2001). Origin of the Moon in a giant impact near the end of the Earth's formation. *Nature*, 412(6848), 708-712. [12] Blankenship, R. E. (2010). Early Evolution of Photosynthesis. *Plant Physiology*, 154(2), 434-438. [13] Erwin, D. H., & Valentine, J. W. (2013). *The Cambrian Explosion: The Construction of Animal Biodiversity*. Roberts and Company Publishers. [14] Tomasello, M. (1999). *The Cultural Origins of Human Cognition*. Harvard University Press. [15] Diamond, J. (1997). *Guns, Germs, and Steel: The Fates of Human Societies*. W. W. Norton & Company. [16] Mokyr, J. (2009). *The Enlightened Economy: An Economic History of Britain 1700-1850*. Yale University Press.