Galaxies are Born
Galaxies formed early in cosmic history, within a few hundred million years of the Big Bang.
Big-Bang-Timeline
The Big Bang Timeline
Nucleosynthesis Period
Leaving the highly speculative first second, and skipping to a few minutes later, the Nucleosynthesis period accurred about 3 to 20 minutes after the Big Bang. During this period, the universe had cooled enough for protons and neutrons to come together to form simple nuclei, but not yet atoms, as the universe remained too hot
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Electroweak Era
In the first fraction of a second, the universe cooled enough for the electromagnetic and weak forces to split, setting the stage for stable particles.
Inflationary Epoch
The Inflationary Epoch was from about 10−36 seconds to 10−32 or so seconds. Notice the duration label change from “era” to “epoch” and from a narrow time to a range. However, also note that we are still within the first millisecond of the Big Bang. This was a period of extremely rapid expansion driven by
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Grand Unification Era
The speculative Grand Unification Era ends around 10−36 seconds after the Big Bang. During this era, the strong force is believed to have separated from the other three fundamental forces. The universe was still incredibly hot and dense, and it’s during this period that the first subatomic particles, including quarks and leptons, could have begun
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Planck Era
The Plank Era occurred in the first part of the first millisecond after the singularity. Current estimated put it at up to 10−43 seconds after the Big Bang. The term “era” is used for this micro-duration as a sort of tip of the hat to Einstein’s Relativity. It reflects a conceptual approach to time that
Earth is Born
The Earth and the other planets formed 4.5 billion years ago from the same cosmic cloud—the primordial material which gave birth to the Sun. The dust and comets—the rocks—were composed largely of hydrogen, ice, carbon, and nitrogen.
Population I Stars: Like our Sun
Population I stars likely started forming around 8 to 10 billion years ago, with the process continuing to the present day as new star-forming regions develop in galaxies. These third generation stars are composed of the remnants of Population II stars. The majority of the stars adorning the Milky Way today belong to this third
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Birth of the Sun
4.6 billion years ago, a cloud of gas and dust collapsed under the force of its own gravity to form our solar system.With the Sun at its center, glowing, the planets had not yet formed. The Sun, a G-type Population 1 star, shines brightly with a surface temperature of about 9,400 degrees, 5,500 Kelvin, and
Population II Stars: Heavy Element Synthesis
Legacy: Began enriching the interstellar medium with heavier elements, including carbon, necessary for organic chemistry From the ashes of Population III stars, celestial giants, rose a new generation of stars, the Population II stars. These stars contained a higher proportion of the heavier elements, granting them a longer lifespan, and likely the company of planets.
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Population III Stars: Heavier Elements
Legacy: First 26 elements of the periodic table of elements. After a few hundred million years, gravity continued to play its part, drawing atoms into an intimate collapse, giving birth to the very first stars and galaxies. These first stars, known as Population III stars, were stellar giants: massive, hot, and short-lived; they burned for
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First Atoms
The image of the early universe that we see in the CMB reveals a time shrouded in darkness. During this era, the 17 known particles first started to combine to form the universe’s first atoms. Electrons, protons, and neutrons came together to create neutral hydrogen atoms, a process that allowed photons—or light—to traverse the cosmos
RCW 86 Supernova
This supernova was observed by Chinese astronomers in 185 CE. The Chinese kept meticulous astronomical records for centuries, including observations of what modern scientists interpret as supernovae. Chinese astronomical records from 185 AD describe the appearance of a “guest star” in the constellation now known as Circinus. This guest star matches the expected location and
Death of the Sun
The death of our Sun is estimated to occur in about 5 billion years. Around this point, life on Earth will become uninhabitable. There will likely be life here right up until there’s not. Most humans will have left the planet many millions of years prior to this point. Also, the merging of the Andromeda
Singularity
When we trace the universe backward, our equations point to an unimaginably hot, dense beginning — not a confirmed object, but the mysterious edge where current physics breaks down.
Oldest Known Fossil-Microorganisms
The earliest known life on Earth are fossilized microorganisms found in hydrothermal vent precipitates. Currently dated to about 3.42 billion BCE. These microorganisms were prokaryote cells. Single celled organisms with no nucleus and had early simple DNA. More complex DNA in a nucleus evolved about 1.5 billion years later in Eukaryotic cells, circa 2 billion
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South America Splits from Africa
Over millions of years, the modern-day South America and Africa separated during the breakup of the supercontinent Pangaea.
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Opening of the North Atlantic Ocean
North America splits from Europe causing diverging evolutionary lines. Over millions of years, the modern-day Europe (Eurasian plate) and North America (North American Plate) separated during the final breakup of Pangaea in the early Cenozoic Era. This split is a later part of that breakup and created the North Atlantic Ocean.
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Plate Tectonics
By dating rocks and fossils scientists can document the movement of the continents over time. To confirm and refine this science, geologists study rocks, paleontologists study fossils, and anthropologists study human societies, cultures, and relics. The location and dating of rocks, fossils, and relics allow us to understand the distant past. Cynognathus, circa 242 million
Pangaea Splitting Starts Splitting Evolution
The breakup of Pangaea did not just reshape geography. It reshaped evolution by isolating populations, limiting movement, and allowing different branches of life to follow different paths.
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