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.

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Chapter at a Glance
50 Minutes
3 Thresholds
6 Videos
1 Gallery

In the Beginning

Understanding Thresholds of Increasing Complexity

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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.

Goldilocks Conditions

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

The Big Bang

In an Instant, Everything Happens

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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

Holmdel Horn Antenna

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.

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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?

  • What Goldilocks Conditions led to the Big Bang?

  • The Big Bang led to which form of "new complexity?"

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Unlock your badges and begin your journey towards becoming a Big Historian.

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Big Historian

You've correctly completed all eight thresholds of complexity.

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Big History never ends. Explore the Classroom site to make further connections.

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Star Formation

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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.

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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

Newton's Mathematical Principles of Natural Philosophy

The Lifecycle of Stars

The Birth of Matter and Elements

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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

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

Quiz: Threshold 2

Star Formation

  • Ingredients
  • Goldilocks Conditions
  • New Complexity
  • To form a star, you need gravity, hydrogen and what one other element?

  • Which of the following is NOT a Goldilocks Condition for the formation of stars?

  • Which of the following is an example of why stars are considered to be "increasingly complex?"

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You've earned the STAR FORMATION badge

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That Was Awesome

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Congratulations, You're a

Big Historian

You've correctly completed all eight thresholds of complexity.

Get your official Big Historian sticker showing off your success.

I've Earned It

Big History never ends. Explore the Classroom site to make further connections.

Visit the Online Classroom

Get timely updates and connect with Big History

New Elements

Complexity Explodes into the Universe

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2:39

Stars are very hungry. Burning at incredible levels, cranked to the extreme, a star will eventually consume all the hydrogen that powers its nuclear fusion. Then the star changes dramatically. The hot center shrinks. It grows even hotter. This intense heat and pressure creates other nuclear reactions, producing new, heavier elements — carbon, silicon, oxygen, and others, until it creates iron. Iron is heavy, highly stable, and cannot be fused further.

A catastrophic event begins. Lacking the outpouring of energy from its core, the star collapses. Its many outer layers fall inwards, in an enormous unbelievable avalanche of matter crumbling due to the pull of gravity from the dense core. They slam with unimaginable force into the star's iron center, creating new elements. These new elements bounce off the iron core, hurtling outwards into space.

This is, in effect, the massive explosion and death of a star — a supernova — and the birth of new elements out into the cosmos.

Collective Learning

New stars shining in the Universe did not happen overnight. It would take many elements coming together, over time, building until they could prove their light in the darkness of space. In many ways, our collective learning follows a similar pattern.

Ideas and knowledge accumulate. Generation after generation, humans build upon the information on hand. First, Chinese astronomers in 185 BCE and Islamic astronomers in 1006 had recorded sudden, bright stars that lasted for a brief time and faded away. Weather observers in Italy, China, and Korea observed another of these brilliant objects In 1604. Then after a yearlong observation, Johannes Kepler, an astronomer in Prague, would publish a treatise, undermining an age-old theory of the Universe — and also proving crucial to the development of modern chemistry.

The Periodic Table

Hank Green takes us on a deeper dive into the formation of the Periodic Table of Elements and examines the genius of Russian chemist Dmitri Mendeleev, whose theories were so brilliant he gets credit for elements that aren't even discovered yet.

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11:21
Aristotle's table of the elements

The Aristotelian model of basic elements

Aristotle believed the Earth resided at the center of the Universe and that all matter was composed of four basic "elements" — earth, water, air, fire. A fifth element, called aether, did not interact with the other four, but instead formed the heavenly bodies.

Activity

Periodic Table

Find the two types of matter which are most abundant in the Universe

  • Li

    Lithium

    Incorrect

    Lithium is believed to be one of three elements synthesized in the Big Bang.

  • Ne

    Neon

    Incorrect

    Neon is a colorless, odorless, inert noble gas.

  • Au

    Gold

    Incorrect

    Gold is a highly valuable precious metal.

  • O

    Oxygen

    Incorrect

    We have enough on Earth, but it's not one of the most abundant in the universe.

  • Kr

    Krypton

    Incorrect

    Krypton is a colorless, odorless noble gas occurring in trace amounts in the atmosphere.

  • W

    Tungsten

    Incorrect

    Tungsten is only found naturally on Earth in chemical compounds.

  • H

    Hydrogen

    Correct

    Hydrogen is the most abundant element in the Universe and the simplest known atom.

  • Si

    Silicon

    Incorrect

    Silicon is mostly found throughout the Universe in dusts, sands, planetoids, and planets.

  • He

    Helium

    Correct

    Helium is the second most abundant element in the Universe, comprising about 24% of the total elemental mass.

  • I

    Iodine

    Incorrect

    Iodine is rare throughout the Solar System and in the Earth's crust.

Quiz: Threshold 3

New Chemical Elements

  • Ingredients
  • Goldilocks Conditions
  • New Complexity
  • Which of the following is a key ingredient in the creation of new elements?

  • What is a key part of the process within a star to create new elements?

  • Why do elements represent a new form of complexity?

Congratulations!

You've earned the NEW CHEMICAL ELEMENTS badge

You have unlocked 0 of 8 badges. You're on your way to becoming a Big Historian!

That Was Awesome

Unlock your badges and begin your journey towards becoming a Big Historian.

Congratulations, You're a

Big Historian

You've correctly completed all eight thresholds of complexity.

Get your official Big Historian sticker showing off your success.

I've Earned It

Big History never ends. Explore the Classroom site to make further connections.

Visit the Online Classroom

Get timely updates and connect with Big History

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