Chapter 1
The Universe

Where did everything come from? Where are we heading? Big History tells the story of the Universe starting from the Big Bang, the formation of stars, planets, life on Earth, modern civilization — and what might exist in the future.

Chapter at a Glance

50 Minutes

3 Thresholds

6 Videos

1 Gallery

In the Beginning

Understanding Thresholds of Increasing Complexity

To grasp the entirety of the Universe we divide Big History into eight "thresholds." You may consider a threshold a transition point. It's an event that creates something completely new.

Where to begin? It's up to you. You may proceed through the thresholds in consecutive order, from the Big Bang to the Future, or skip around bouncing from protostar to Pangaea, from Silica to the Silk Road. Make your own connections between thresholds and test your knowledge as you go. Complete quizzes, earn badges, and become a "Big Historian."

Let's get started.

Not too hot, not too cold

The Universe is a simple place. Vast stretches of space filled with nothingness. Yet as it developed over billions of years, it grew increasingly complex. This is a central concept Big History will emphasize — the ever-increasing complexity of the Universe.

Another central theme in Big History is "Goldilocks Conditions." Big History uses this concept to describe when the right conditions occur at precisely the right time to trigger a form of fundamental change.

Taking a look at these changes through the widest possible lens, Big History offers an understanding of where we came from, where we're going, and the complexity and fragility of our world.

Adopted from the story of Goldilocks and the Three Bears, Goldilocks Conditions are when conditions are "just right" for something new and more complex to emerge.

Origin Stories

Where did everything come from?

Every culture has its own origin story. They may be very short anecdotes. Or they might be elaborate narratives that help explain the mysteries of our existence.

Big History is an origin story like many others. But, instead of being rooted in a specific culture or geography, Big History aims to account for everything we know and that which we have yet to discover. Contributors include philosophers, scientists, scholars, adventurers, and curious learners of all stripes who weave a story of enormous scale.

And like all origin stories below, the Big History story has developed over time, and will continue to evolve.

From Many Beginnings, Many Stories

Pan Gu and the Egg of the World

According to Chinese mythology, in the beginning a huge egg contained chaos. The giant Pan Gu emerged from the egg and gave order to that Chaos. As he grew to 48,000 kilometers high, his skull separated the sky while his feet remained planted on the Earth. When he died, his eyes became the Sun and the Moon, his breath the wind, his voice thunder, his limbs mountains, and his blood the roaring water.

Ancient Greeks: The Titans and the Gods of Olympus — © Bettmann/CORBIS

Titans and Gods of Olympus

From Chaos emerged Gaia and Uranus who gave birth to the Titans. Two of the Titans, Cronus and Rhea, had many children. Fearing they would overthrow him, Cronus tried to destroy them. Zeus challenged his father and with the help of his siblings defeated Cronus and became ruler of Mount Olympus and all the gods. Prometheus shaped humans from clay while Athena blew life into them.

The Great Turtle's Island

The Iroquois believed all the world was water. A woman fell from the sky and was saved from drowning by two white swans. The ruler of water animals, Great Turtle, dispatched creatures to the depths — otter, muskrat, beaver — to bring up mud. Old lady Toad brought a mouthful of mud and placed it on Great Turtle's back. This mud grew into the world island, and offered a home for the woman who fell from the sky.

Genesis

In the Judeo-Christian tradition, God created the heavens and Earth, sky and water, land masses, seed-bearing trees, and living creatures. "Let us make mankind in our image, in our likeness," God said, to rule over all living things. A second story tells how humans are created first, followed by plants and animals.

Popul Vuh

In Maya origin stories, the makers in the water, the Plumed Serpent, and the makers in the sky, the Heart of the Sky, created Earth and the animals. The animals did not show proper respect to the makers, so they were hunted. Then, the makers created creatures from wood. Thoughtless and without emotions, they did not show respect. They too were killed. Finally, humans — respectful and thoughtful — were created out of corn.

Modern Scientific

Suddenly, 13.8 billion years ago, all the energy in the Universe burst. Gradually this energy became matter, combining to bear the stars. These too exploded, creating galaxies and the Earth. Water was able to form, which contained the chemicals to give life to single-cell living organisms, then creatures with many cells, such as plants, and later animals. These creatures became more complex and aware, until about 100,000 years ago when humans evolved from a shared ancestor with apes.

The Big Bang

In an Instant, Everything Happens

Try to imagine something unimaginably tiny, unimaginably dense, and unimaginably hot. Then instantaneously, bang! — space, time, and all molecular material explode in a manner far beyond what words can describe.

What is known is that, within a few millionths of a second, the Universe expanded at an inconceivable speed. From that expansion, some recognizable subatomic particles and fundamental forces formed. Then the Universe cooled dramatically — to about 1 billion degrees Celsius, allowing energy, and then matter, to appear. Much later, after dropping to a cool 1,650 degrees, the first hydrogen and helium atoms formed.

A cosmic "Dark Ages" set in for the next 200 million years. This quiet expansion spread more complex atoms and other materials throughout the Universe. The tiny particles drifted apart like a dense puff of smoke, but not uniformly. Those little inconsistencies of distance set the stage for gravity, creating something very complex out of something very simple.

A Mysterious Hiss from the Heavens

It took decades from the time a few scientists proposed that the Universe was expanding until the point where the Big Bang hypothesis was generally accepted. More proof was needed. In Big History, we call this process of gathering evidence that supports a theory or idea "claim testing."

When the theory of an expanding Universe was first proposed by Georges Lemaître in the 1920s even the great physicist Einstein did not believe it. In 1929, astronomer Edwin Hubble made observations from a powerful telescope showing that galaxies sped away from each other at an ever-increasing velocity. Still, many scientists refuted the idea.

In 1964, two scientists in New Jersey, Arno Penzias and Robert Wilson, aimed a new, extra-sensitive radio antenna at outer space to discover what they could hear. They were surprised to hear the same low, static hiss wherever they aimed it. They were baffled.

Finally, a colleague at Princeton suggested the hiss might have something to do with the start of the Universe. He pointed them to mathematical calculations by astrophysicists that showed if the Universe did, in fact, begin with a Big Bang, it would have released a huge amount of energy in just the same frequency as this low, static hiss. In this way, scientists discovered evidence and claim tested the Big Bang.

Scale

Whether stargazing distant galaxies with the naked eye, viewing protons under powerful magnification, or listening to the beginning of time and space, thinking about how different things appear from different viewpoints is key to understanding Big History.

Changing scale impacts what we can understand and how we fit in with the Universe. This classic video is a great study of these magnitudes.

Quiz: Threshold 1

The Big Bang

Ingredients
Goldilocks Conditions
New Complexity

What key ingredient contributed to the Big Bang?
- Energy Incorrect, Try again
- Matter Incorrect, Try again
- We can only speculate Correct
What Goldilocks Conditions led to the Big Bang?
- Dramatic pressure imbalances Incorrect, Try again
- Extremely high temperatures Incorrect, Try again
- We honestly don't know Correct
The Big Bang led to which form of "new complexity?"
- Matter and energy Correct
- Organic life Incorrect, Try again
- Our Sun and Solar System Incorrect, Try again

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Star Formation

When stars are born in nebulae, lighting up in fusion, they will race through life. Some will be lucky to reach a few billion or trillion years of age. The heaviest and densest of these will die in massive supernova explosions. Others, like our Sun, will burn more slowly, and probably expire less dramatically. Upon a star's death, matter will spill out into space in the form of new elements, creating new star-forming nebulae, continuing its circle of life.

Tiny imperfections. Little knots, wrinkles, and flaws will begin attracting nearby particles of matter. The clumps will grow, becoming more massive, and attracting more particles.

As these compacted clumps of hydrogen and helium grow in density, they'll also heat up. Eventually, the clumps heat and compact to form a "plasma," sort of a hot, swirling soup made up of free-floating atomic nuclei. This will form into giant balls called "protostars."

Gravity squeezes the center of the protostars tighter and tighter. Their temperature rockets until they reach a flash point. And they "light up" as free-floating nuclei, slamming together with such intensity that they fuse into a new element. This process of "nuclear fusion" releases a tremendous amount of energy, presenting the Universe with a new complexity that is critical to the formation of galaxies, larger clusters, and superclusters.

Tiny knots and wrinkles in the young Universe

Climb on board for a deeper dive into the Goldilocks Conditions of star formation.

Gravity

Three centuries after Isaac Newton watched an apple fall from a tree to the earth, we are still trying to completely comprehend the nature of gravity.

Essentially, as Newton's equation put it, two masses — whether apple and Earth, Moon and Earth, or two tiny particles that happen to be near each other — exert an attractive gravitational force on each other.

Also, the larger and denser an object is, the stronger the gravitational pull it exerts on another object. The massive Earth pulls your smaller body mass to it. This gravitational pull prevents you from floating off into space. At the same time, the mass of your body, as Newton described, is actually exerting a tiny gravitational pull on Earth.

A fundamental force in the Universe

In his great scientific work, Newton asserted the three Laws of Motion, elaborated on Johannes Kepler's Laws of Motion, and stated the Law of Universal Gravitation — all of which were giant leaps in human understanding of Earth and the cosmos.

Universal Gravity — Isaac Newton / © CORBIS

Newton's Mathematical Principles of Natural Philosophy

The Lifecycle of Stars

The Birth of Matter and Elements

The Universe is so big, we don't actually know how big it is. But we do know it's beige. John and Hank Green explain the huge scale of the Universe, why chemistry is so important to understanding Big History, and how we're all made of stars.

The Life Cycle of Stars — © The Big History Project

Space, time, matter, and energy. It all came from the stars.

Quiz: Threshold 2