Big Hisory Project
by: mary esquilin
Big history, is all the history, and science that had ever happened since the beginning of time.
In the Beginning
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.
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.
The Big Bang
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 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."
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.
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.
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.
The Lifecycle of Stars
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.
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.
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.
Our Solar System
Ever since the Big Bang, the Universe has been drifting and expanding. The birth and death of stars leave an aftermath of galaxies, planets, and even living organisms
The Birth of the Sun
It was five billion years ago. A giant cloud of matter in our own galaxy, the Milky Way, condensed under its gravity, exploding in nuclear fusion.
The lifecycle of our Sun
The Sun is currently stable, about halfway through its lifecycle. It's estimated it will live for about another five billion years before consuming all the hydrogen in its core and transforming into a red giant.
How Did the Planets Form?
New elements, combined with the just-right Goldilocks Conditions came together and formed our Solar System.
The Earth got so hot, it began melting. Heavier material sank to the bottom, lighter stuff rose to the top. Some elements evaporated. This transformation created the Earth's layered core and mantle, crust, and atmosphere.
It took billions of years for the Earth to form and settle into orbit around the Sun. But how do we know that? What makes it so? These questions burned and plagued astronomers for millennia.
Going out to the stars, Astronomers know that by studying Cepheid variables, the fluctuation in brightness of certain stars, we can calculate the star's distance from Earth. The longer the period of fluctuation, the brighter the star. So even though a star might appear extremely dim, if it had a long period it must actually be extremely large. The star appeared dim only because it was extremely far away. By calculating how bright it appeared from Earth and comparing this to its intrinsic brightness, Astronomers could estimate how much of the star's light had been lost while reaching Earth, and how far away the star actually was.
The rise of oxygen formed a protective layer around the Earth and also helped cool the Earth, eventually encasing the planet with ice in a series of "Snowball Earths" 2.4 to 2.2 billion years ago. Some life forms survived, some proliferated, pushing oxygen levels higher. This enabled a greater diversity of life.
As knowledge of life on Earth evolves, thinking about it as a biosphere helps explain the entire intertwined network of life. Here's an early look at how the Earth warmed, cooled, and built its biosphere over time.
Along the edges where the continental and oceanic crust plates meet, all sorts of crazy things happen. These massive plates scrape past each other sideways. They dive under each other. And in places, they get snagged, causing tremendous pressures to build. When this tension suddenly releases things happen much, much faster than two centimeters per year.
While other scientists put forth the theory that the Earth's landmasses had once been connected by land bridges that had since sunk into the ocean, and had always been located where they are today, a few renegade scientists postulated that the Earth once contained one huge supercontinent. In 1858, Austrian geologist Eduard Suess postulated a supercontinent called Gondwanaland, and American astronomer William Henry Pickering suggested in 1907 that the continents broke up when the Moon was separated from the Earth.
As the Earth formed, it posed opportunities for new complexities not yet seen in the Universe. The prevailing hypothesis is that volcanic vents deep under the sea were spewing very hot, chemically rich compounds into the ocean, which led to the first microbial organisms that spread throughout the oceans — setting the stage for life to inhabit the Earth.
The great oxidation event
A huge number of prokaryotes rose from the ocean and flooded the atmosphere with oxygen, a by-product of photosynthesis. While poisonous for many species, new life forms thrived in the oxygen-rich atmosphere, which also protected life forms from the Sun's harmful ultraviolet rays.
As new complexities start to populate the air, sea, and land, it might be a good time to ask, "What's the difference between non-life and life?" What is the difference between a mountain and a whale? Both are made of molecules. Both engage in chemistry. And both change through time.
Since the 1980s geologists and paleontologists have agreed upon five major extinction events. And today, many biologists agree that a sixth major extinction is currently underway. This one is unique — the result of humans degrading and destroying the habitats of other life forms. This extinction apparently began about 50,000 years ago when humans moved into Australia and then the Americas, causing the disappearance of many species.
Layers of History
The history of our planet along with clues about its future is written in the layers of rock. Rock detectives or as they prefer to be called, geologists study these clues about the past and can also observe Earth's current changes firsthand.
The crater of doom
in 1950, oil geologists had noted the unusual features of a crater in the sea off of Mexico's Yucatán Peninsula. They thought it was a buried volcano. When the K-T boundary geologists learned about it, they were able to prove it was their meteor impact site.
In 1953, three English biochemists were racing to determine the double helix structure of the DNA molecule. They collected knowledge from Linus Pauling, an American biochemist, who was using X-ray technology and had already successfully shown that the general shape of DNA must be a helix, or spiral.
Chromosomes in a cell
In human cells, long sequences of DNA are contained in chromosomes. These chromosomes are packed inside the nucleus of the cell, protecting this important genetic information. DNA is so tightly wound within a chromosome that the 51 million to 245 million base pairs in one human chromosome are estimated to be up to two meters long unraveled.
Tree of Life
It was first believed that humans represented the pinnacle of evolution. But as biologists continue to study life on Earth, and as new species are discovered and more evidence comes in, the Tree of Life will continue to grow.
At its center is LUCA, or the Last Universal Common Ancestor. It's believed it was a single-celled organism born more than 3.5 billion years ago. From there, the Tree of Life separates into more than 190 different species and three domains of life. Eukaryota, all the plants, animals, fungi, and some single-celled organisms Bacteria, single-celled organisms functioning without a membrane-enclosed cell nucleus Archaea, single-celled organisms often living in extreme environmental conditions
About 200,000 years ago, we evolved to become the most important force for change on the planet. Our knack for collective learning — preserving information, sharing it with one another, and passing it to the next generation — helps us create entirely new forms of complexity.
Crash Course Big History takes a look at Humans, one of the weirdest examples of change in the Universe. Around for only 250,000 years, we are truly one of the most complex things in the cosmos.
Writing and Saving Knowledge
Writing likely originated as a system of accounting as elites and power brokers who were accumulating more and more resources tried to keep track of their wealth. Eventually, the symbols used for accounting evolved to convey all the nuances of everyday languages and generate literature, history, and proper writing.
At the end of the last Ice Age, many humans decided to stay put instead of migrating any further. Communities grew denser and they had to draw more resources from a smaller area. Using their learned knowledge from the environment, humans began to experiment with agriculture, which became a revolution. Farming produced a surplus of food, allowing others to take up new work. Societies became diverse, populations exploded, and collective learning thrived.
The greatest places to eat, 11,000 years ago
Once people learned how to plant crops and domesticate and raise livestock, they no longer had to move around to follow their food. They were able to generate powerful networks of collective learning — civilizations.
As humans abandoned foraging, farming claims the vast majority of credit in explaining the birth of civilizations. But what if it wasn't farming at all? A recent discovery in the limestone pillar ruins at Göbekli Tepe, Turkey, archaeological evidence suggests that this was a temple. Almost 12,000 years ago nomadic tribes made the pilgrimage here to worship, share community, or perhaps to simply stand in awe.